# Horizontal Air Cooled Engine



## Brian Rupnow (Oct 31, 2021)

Yesterday I finished designing a welding fixture for one of my old customers. Earlier this week I redesigned one of the cylinder heads for my opposed twin engine, seeing how I could relocate the sparkplug up near the top of the cylinder head. I don't really want to mess with a finished engine, so I decided to design a new engine to go with my redesigned cylinder head today. Of course this leads me right down the garden path, and seven or eight hours after I think of it, I've designed it. This engine will be air cooled, and will have two valves and a throttled carburetor. I've put a 2" diameter fan on it, and even designed a fancy fan shroud to support and guard the fan blades. I'm not sure when I will get around to building this one, but  winters coming and I will need something to do----


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## Brian Rupnow (Oct 31, 2021)

And a couple more views so you can see where this one is going---


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## Brian Rupnow (Nov 1, 2021)

Today I made the first part for this engine, the cylinder mounting plate. I used my new bandsaw, and what a wonderful bandsaw it is. It zipped thru the aluminum as if it was butter. This is the first part I have made using the new bandsaw, and all I can say is, I wish I'd bought it ten years ago!!!


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## coulsea (Nov 1, 2021)

I don't like the carb mount. a plug in the current hole and a new hole through the side might look better. Of course the right angle path would not be good for efficiency.


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## Brian Rupnow (Nov 1, 2021)

Coulsea--I'm not a huge fan of the carb mount either, but the trick with engines like this is being able to keep the carburetor above the fuel tank. I did consider putting the carb straight out to the side, but that makes the carburetor so low that it makes an even lower gas tank look goofy.---Brian


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## Nerd1000 (Nov 1, 2021)

Why not a downdraft carb?


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## Brian Rupnow (Nov 1, 2021)

Coulsea---When you're right, you're right!!! The more I looked at it the uglier it looked. I haven't built anything on the head yet, so I was able to go in and change it---carb comes straight out the side now. I left that big air horn that was on the front of the carburetor off too.---Thank you.


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## Zeb (Nov 2, 2021)

Looks really cool. With the gearing, that fan looks like it's gonna need thrust bearings to keep it from flying off! Should run nice and cool, though I'm wondering if it'll need baffles to direct airflow around? That way the cooling wouldn't have a sharp gradient. It'd look better without for sure though.


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## awake (Nov 2, 2021)

Brian, in the first and second pictures in your first post, it looks like one of the push rods intersects with the muffler. Maybe just an effect of the angle / rendering ... ?


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## Brian Rupnow (Nov 2, 2021)

It misses. Not by much, but it does miss.


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## gddecker (Nov 2, 2021)

Nice looking machined piece!


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## Steamchick (Nov 2, 2021)

Hi Brian. I'm already thinking of making this one... Do let us know when plans are completed.?
K2


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## Brian Rupnow (Nov 2, 2021)

Today was spent making sideplates. They are finished except for tapping a bunch of holes. I have used up my entire day machining these parts, and will do the tapping tomorrow.


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## gddecker (Nov 2, 2021)

Nice work! You must have a CNC mill.


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## Brian Rupnow (Nov 2, 2021)

No, all of my machinery is manual. Pretty well all of the stuff I do is 'One of'.


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## Fireguy976 (Nov 3, 2021)

Brian Rupnow said:


> Coulsea---When you're right, you're right!!! The more I looked at it the uglier it looked. I haven't built anything on the head yet, so I was able to go in and change it---carb comes straight out the side now. I left that big air horn that was on the front of the carburetor off too.---Thank you.



Hi Brian,
Just a thought from someone very new to this,,,
My first reaction is running the fan off the large part of the flywheel just looks off, to me of course.
What about running it off a slightly smaller step down channel or groove just in the inside of the flywheel,,,
The reasons I’m thinking why,,,,
   A small ”groove” on the inside of the flywheel puts the belt off the surface face of the flywheel and gives a better look of symmetry. (I’m a big believer of symmetry when it can be done.) And having it slightly smaller on the inside it won’t reduce your fan speed all that much, and with the groove, would it help keep the belt running true??
You won’t have to worry about belt wonder and adjustment screws like you do with belt grinders and keeping the sanding belts running true.
   And the fan looks to be supported only from the one side, and the bracket just looks “off”, to me of course. What if the fan was supported from the bottom with a small pedestal on both sides and a split bearing and top cap. And either leave the fan blades completely exposed, or have the fan included as part of a small flywheel as you typically see on compressors. It has more of the traditional look of stationary engines or steam engines with the flywheel fan design, or a wow factor if you leave the blades exposed. I don’t think OHSA will be after you.
The flywheel fan idea ”may” help with evening out the speed and timing pulses because of the added mass.
Just my less than 2 cents. Love your work.
Cheers,
Ken


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## Fireguy976 (Nov 3, 2021)

Sorry another idea,,,,
It appears now that the one side flywheel is offset a “significant“ amount in order to provide alignment for the fan pulley and the flywheel belt.
If you run the fan off a small stepped down groove on either the inside or outside of the flywheel, you should be able to keep the fan and the flywheel in the same plane of movement if that makes sense.
cheers,
Ken


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## Jasonb (Nov 3, 2021)

It looks quite symmetrical to me the offset fan drive flywheel is no further away from the frame than the other which has to clear the timing gears and was often even further out on hit and miss engines to allow room for the governor spool. I expect Brian will squeeze his ignition points into that space anyway.

As for running off the flywheel and having the fan on a stub axleif it was good enough for the likes of IHC it will be good enough for Brians engine


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## Fireguy976 (Nov 3, 2021)

Hi Jason,
I hope my previous comments didn’t sound negative, because they were not meant to be.
I was just tossing out some of thoughts that popped into my head.
Good enough for IHC doesn’t mean we can’t entertain other concepts. I am always looking at drawings, and pictures trying to see what I would do different if I was designing it.
Your picture does however present the idea I was talking about regarding the fan not being caged.
Regards,
KJ


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## Brian Rupnow (Nov 3, 2021)

Jason---thank you for the great picture---Brian


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## Brian Rupnow (Nov 3, 2021)

I had a stroke of good luck this morning. After tapping something like 20 holes, and assembling things, I discovered a length of 01 steel with two cams cut on it. The last time I set up to cut cams I decided to cut over-length while I was in the set-up for use on a potential future engine. The future has arrived!!!


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## Jasonb (Nov 3, 2021)

Ken, the fan bracket does look a bit heavy to my eyes too but I think its all part of Brian's style of building that differs to mine but at the end of the day he does seem to get a good running engine and anyone building one of his designs can always add their own touch so long as the critical sizes remain the same.

I suspect Brian will be cutting the finned cylinder from Aluminium so not too easy to join to and as it won't be painted you can't hide JBWeld. One option you might want to think about Brian is not cutting one of the fin grooves which would leave you with a thick fin of about 3/8". Id you then set up the cylinder on the rotary table you could use a 1/8" cutter to form the missing grove but don't go full circle, leave a bit so you can drill & tap for a stud to mount the fan on.


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## Brian Rupnow (Nov 3, 2021)

Jasonb----I like your idea. I'm not sure I will use it, but I do like it.---Brian


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## Brian Rupnow (Nov 3, 2021)

--I picked up my cast iron today to make the cylinder. The only material that my supplier had in stock was 2.1" diameter ($25 for 4"). I haven't made the cylinder yet, but this gave me an idea. Without changing anything, I can make it look like this if I want to. This shape harkens back to some of the early model two cycle airplane engines that were made in the 1930's to 1950's. I kind of like it.


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## Steamchick (Nov 4, 2021)

Hi Brian,
This barrel shape (for 2-strokes) was to keep the "top-of-the-stroke" Hot, for better combustion, but cooling where the exhaust gases heat the lower part of the barrel during the exhaust port open phase. - Or anyway, that's what I understood. 
4-stroke engines e.g. motorcycles, that were without fans and housings) always had a taper so the bottom of the cylinder wasn't cooled too much, but the top was cooled MUCH more 3~5 times more fin area? (The taper can be a curve - like a half barrel?).
Cheers!
Love the work,
K2


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## Steamchick (Nov 4, 2021)

I like the simplicity of the cam drive and push-rods.... But I would have a cover (maybe even clear acrylic?) over the rockers. - Just personal preference...
K2


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## Steamchick (Nov 4, 2021)

I also noticed the "levitation" facility - as shown on the CAD drawing. How does that work? I'm fascinated....
K2


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## Donnyo65 (Nov 4, 2021)

Hi Brian, I'm fairly new to all this and i am currently building the Nemmet 15cc four stroke engine. Just a question from your earlier post, you mentioned cutting part in aluminium on a band saw. What type of bandsaw do you use? i have a portable (ish) metal bandsaw that I have used to cut up to 5" En8 steel but it won't work in vertical mode and has no fitting for a table even if I could get it vertical. Is yours a dedicated metal saw or just a wood saw with a metal cutting blade? Im after a wood cutting bandsaw anyway and if this can be used successfully for metal that would be great.


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## Jasonb (Nov 4, 2021)

Same as a Mirror, if you stand an item on a mirror it is not the top of the glass that the reflection is in but the silvered backing which will be some distance from the top surface depending on thickness of glass


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## Thommo (Nov 4, 2021)

Hey Brian, I had to laugh. A couple of weeks ago you were saying that you were over building engines for awhile. Haha so much for that. Once the bug has you, it won’t let go in a hurry. Love the new engine btw.


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## Brian Rupnow (Nov 4, 2021)

Up until very recently. I used an upright wood cutting bandsaw, to which I had added a second shaft and pulley set, to get the blade speed down to 175 foot per minute, which works well on steel or aluminum. I used this for ten or twelve years and just last month I bought a huge industrial metal cutting  bandsaw from a used industrial equipment seller.


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## Gordon (Nov 4, 2021)

I have converted a few wood band saws to cut metal and always used a gear reducer which eliminated the belt slip. Used gear reducers can be rather cheap, at least in my area.


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## Brian Rupnow (Nov 4, 2021)

This morning I made up the main baseplate. This plate has an interesting feature in it. In order to keep everything small, a scallop was cut from the baseplate to clear the 40 tooth cam gear.


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## Brian Rupnow (Nov 4, 2021)

This afternoon I machined a cast iron cylinder. I like that shape a lot. I've got a temporary clamp on there right now, because I haven't drilled any bolt holes yet. I'll do that tomorrow.


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## Ghosty (Nov 4, 2021)

Brian,
Looks like the top cap head screw needs to go a bit deeper in the case. Still following your work.
Cheers
Andrew


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## Brian Rupnow (Nov 4, 2021)

Since I have to build a complete cylinder head, I may as well get crazy and make a finned cylinder head. It isn't a lot more work to do this. It just means the overall height of the cylinder head increases by 1/4". The valves get 1/4" longer, and the blue rocker arm support gets 1/4" taller, and the pushrods get 1/4" longer.


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## Richard-Vanderpol (Nov 5, 2021)

it looks like a hit and miss engine


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## Robsmith (Nov 5, 2021)

Steamchick said:


> Hi Brian,
> This barrel shape (for 2-strokes) was to keep the "top-of-the-stroke" Hot, for better combustion, but cooling where the exhaust gases heat the lower part of the barrel during the exhaust port open phase. - Or anyway, that's what I understood.
> 4-stroke engines e.g. motorcycles, that were without fans and housings) always had a taper so the bottom of the cylinder wasn't cooled too much, but the top was cooled MUCH more 3~5 times more fin area? (The taper can be a curve - like a half barrel?).
> Cheers!
> ...


Two stroke engines were also cooled by the fuel.


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## Steamchick (Nov 5, 2021)

Robsmith said:


> Two stroke engines were also cooled by the fuel.


Hi Rob, yes I heard that about some Kawasakis, etc in the 1970s... I.E. A rich mixture "to avoid overheating". But from my and friends' experience, as long as the ignition timing is Not too far advanced, the mixture Stoichiometric, and the engine properly set-up, the rich mixture was just a myth for helping the engine.... soot developed in the wrong places that caused pre-ignition and consequential overheating failures. My last 2-stroke was a prod, racer LC350 with stage 3 tuning... needed 105 octane fuel, but correct mixture... I also knew a reliable Prod racer Kawasaki 500 triple in the 70s. Mixture critical,  it had to be right, not rich. As did all the winning Yamahas when I used to Marshall  at race meetings.
Myth proven by reality in my book....
K2


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## Zeb (Nov 5, 2021)

Aircraft engines (fuel injected) are often run "lean of peak" using change in exhaust gas temperatures (EGTs) to conserve fuel. Carbureted engines have uneven mixture distribution between cylinders, but I guess if you ran just one it wouldn't matter. I've had to change out a few cooked jugs from aggressive leaning. Would be neat to see the all the nice looking engines on this forum react to mixture and cooling under a FLIR camera.
Gradient eye candy!


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## Brian Rupnow (Nov 5, 2021)

Today I drilled clearance holes in the cylinder base flange and drilled and tapped holes in the other end of the cylinder, and attached the cylinder to the frame. I really suffered getting the cylinder bolted to the chassis, and I'm going to change the design drawings of this to give a bit more wrench clearance. I also made the fan housing and installed it. I'm not really sure of how the finished fan and bearings are going to be attached, but for now I will just call it a work in progress.


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## Robsmith (Nov 6, 2021)

Steamchick said:


> Hi Rob, yes I heard that about some Kawasakis, etc in the 1970s... I.E. A rich mixture "to avoid overheating". But from my and friends' experience, as long as the ignition timing is Not too far advanced, the mixture Stoichiometric, and the engine properly set-up, the rich mixture was just a myth for helping the engine.... soot developed in the wrong places that caused pre-ignition and consequential overheating failures. My last 2-stroke was a prod, racer LC350 with stage 3 tuning... needed 105 octane fuel, but correct mixture... I also knew a reliable Prod racer Kawasaki 500 triple in the 70s. Mixture critical,  it had to be right, not rich. As did all the winning Yamahas when I used to Marshall  at race meetings.
> Myth proven by reality in my book....
> K2


Yep.  My mate raced go karts and was pretty successful in his class.  I noticed all the racers putting their hands over the carby intake when braking into a corner. 
I asked why and they explained that it sucks a lot of fuel into the engine and cools it rapidly.   Most of the fuel went raw out the exhaust and they carried on with a tiny bit of "boost" coming out of the corner with the throttle wide open.   Simply put down as a "race trick "


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## Brian Rupnow (Nov 6, 2021)

This cylinder head is a complex little guy to machine. None of the individual steps are difficult by themselves, but the hard part is having something to hold onto while you do them.---And if you don't do things in the correct sequence, you can easily "paint yourself into a corner". I do have a plan, and the first part of my plan is using my four jawed chuck in the lathe to turn a "stem" to hold onto with the chuck mounted on my rotary table for all of the following steps.


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## Steamchick (Nov 8, 2021)

Robsmith said:


> Yep.  My mate raced go karts and was pretty successful in his class.  I noticed all the racers putting their hands over the carby intake when braking into a corner.
> I asked why and they explained that it sucks a lot of fuel into the engine and cools it rapidly.   Most of the fuel went raw out the exhaust and they carried on with a tiny bit of "boost" coming out of the corner with the throttle wide open.   Simply put down as a "race trick "


Hi Rob, maybe they were also aware that many seizures occur under severe braking on racing bikes fuel by petrol-oil mix for crank and bore lubrication. The carbs are set to shut off fuel completely, when the oil in the engine is pumped out (naturally) during engine braking, leading to seizures. The "choking" of carbs sucks some fuel-oil mix through due to the high vacuum, thus maintaining the oiling of parts that could otherwise seize.
Possibly on the carts the engines were higher tuned than bikes? (short races and easier to swap motors between races?). Also a wide ope carb choked so it cannot run will give more air charge - hence more braking from the engine, and will fire immediately the hand is removed and mixture is "leaned-out" back to stoichiometric? I guess this also turns-on the power faster than the milliseconds of opening and closing the throttle...? (Many carbs suffer on a highly tuned engine when the throttle is opened quickly and the vacuum drops rapidly between induction strokes. Fuel pumps were added even to production car carburretors to eliminate this issue!).
This process is of course completely different to a constant running condition of running a poorly cooled engine set rich at WOT (a truly "hot" engine) so that the rich mixture runs cooler than the stoichiometric mix and keeps the engine from over-heating - a real "petrol-cooled" engine. Just poor tuning! (A lack of "total engineering"!). I was aware that those guys never won races but often broke-down... Too much tuning, too little understanding... Deep wallets for the petrol pump attendants! I knew of a production racing Kawasaki 500 triple, tuned so highly it could get as low as 5 MPG! - We reckoned more than half the mixture was pumped out of the exhaust due to the highly tuned porting! It was sold (many times) as a road bike, as it didn't finish the longer races in its class! (races more than 17 miles long for the fuel it could carry!) The best on-road consumption was around 20 MPG. But it went like stink! I reached the speed limit (70MPH) in 3rd gear before 6000rpm... when the front wheel started to lift as it hit the power-band! - That was 1975...
Nostalgia ain't what it used to be...
Sorry Brian, I seem to have wandered from your engine making.
K2


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## Brian Rupnow (Nov 8, 2021)

There is a lot of work to this cylinder head, and I am only about half done with it. However, it's a beautiful day here, sunny and 64 degrees F, so I'm going to put my tools away and take my good wife somewhere for lunch. This is probably one of the nicer days that November will offer, before we have snow up to our armpits. The slots were cut with a slitting saw.


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## Gordon (Nov 8, 2021)

Brian: You are making the rest of us look bad. Taking on paying work. Taking your wife out for lunch. Fortunately my wife does not look at this forum.


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## Brian Rupnow (Nov 8, 2021)

So here we have most of a days work. I took good wife out for lunch, then came back and started laying out, drilling, and tapping holes and the main 1" counterbore in the cylinder head. So far, so good. I am rather amazed at how small this thing is. That's a standard size pocket calculator laying in the foreground to give you some ides of a size comparison.


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## Brian Rupnow (Nov 8, 2021)

Gordon--I like the paying work thing. That way I don't feel guilty spending the grocery money on  tools and material. I wouldn't want to be doing it all the time (I did it for 50 years full time). Now I just take a contract once in a while from one of my old customers.


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## Steamchick (Nov 9, 2021)

Brian, I followed your fine example and took my wife out in the car to see some ships arriving in the river Tyne. Escorted by 3 tugs. The ship that is, not my wife, she only had me for escort. Pub was closed so we came home without a glass or 2 or our favourite refreshment.
Then I re-tuned the carbs on the motorbike, after shaving 0.5mm (0.020in.) off the air slides this morning with the miller. (Precise to a 50th of a mm). Checked with colour-tune plug and a little less rich than before. When it is dry I propose a few trips around town to check the slow running, where I have changed the carbs. Models are just so much easier than bikes!
K2


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## Brian Rupnow (Nov 9, 2021)

Today I finished and mounted the bracket which supports the rocker arms, and finished and mounted the bar which the cooling fan will mount to. The cylinder head is finished except for some cosmetic work.


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## Brian Rupnow (Nov 9, 2021)

I have scrapped the old "Rupnow Engine" that I built about 10 years ago, and am gradually salvaging the parts. I have two bronze flywheels that are the right diameter, and I'm thinking of salvaging the outer rims  and turning new aluminum centers. I have never made solid flywheels with no holes in them, and I'm thinking of doing that. Many of the old hit and miss water cooled engines had solid webs in the flywheels---I remember. If I don't like them I can always add holes in the webs later. What do you think?


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## Ghosty (Nov 9, 2021)

Brian,
Try it with the solid flywheels, and if too heavy, you can lighten them, bit harder to put the weight back on after
Still watching.
Cheers
Andrew


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## Steamchick (Nov 10, 2021)

Hi Brian, I think your illogical, design it as you go, methodology is crazy! But you are brilliant in how you create unusual and very good models that way. Shows the depth of your skill and understanding. 
Go for the plain flywheels, that can have very thin webs, as stresses are spread around so uniformly. But with thin webs, you can't fit a belt drive onto the outer rim... That needs a thicker web to cope with the bending stresses, or spokes.... will the flywheel rims drive fans or generators or pumps?
K2


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## Brian Rupnow (Nov 10, 2021)

I've decided I don't care that much for the solid flywheel web. I have an idea that is easy to machine and makes the flywheel action more visible as they turn. I think this will be what the finished flywheels look like.


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## Brian Rupnow (Nov 10, 2021)

Today was intake and exhaust day. I had just enough brass around the shop to make these two assemblies. I have to go buy some more 1/2" diameter brass rod to make tappet guides and valve cages with. All or at least most of the brass will get polished as I get deeper into this engine.


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## Layne Leinster (Nov 10, 2021)

Brian,
Have been following your work, please continue to update. Looking forward to seeing what it looks like in the end. Great engine.
Cheers
Layne


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## Gordon (Nov 11, 2021)

I looked at your picture which showed the brass rocker arm pivot and my first thought that you were designing it to plug into an electrical outlet.


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## ddmckee54 (Nov 11, 2021)

Brian:

If you want to get really ambitious when you make the flywheels, you could always add a pair of self-folding handles to make "Hand" cranking the engine easier.  At this scale they probably be next to useless, but it's the thought that counts right?

Don


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## Brian Rupnow (Nov 11, 2021)

The morning was spent cutting out the centers of the brass flywheels on the old Rupnow Engine to give me two nice outer rims for my new flywheels, and cutting two aluminum centers from a piece of 3 1/2" diameter aluminum that I had left over from another project. I still have miles to go before I sleep, but so far things are looking good.


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## LorenOtto (Nov 11, 2021)

Brian Rupnow said:


> I've decided I don't care that much for the solid flywheel web. I have an idea that is easy to machine and makes the flywheel action more visible as they turn. I think this will be what the finished flywheels look like.


I am sure this has been done somewhere, sometime, but I have never seen it and I like it.


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## Brian Rupnow (Nov 11, 2021)

Today I did something for the very first time!!! Those reliefs in the face of each flywheel are 3/16" deep, and they have a 1/8" radius in the corners. I have always known that there should be  radius there. I know the whole tune about sharp inside corners causing stress risers and are more apt to fracture in use. It's just that I never actually did it before. I have about 40 engines running just fine without a radius in the corners of the flywheels. Today I actually ground an HSS tool and machined the radius.  The outer brass rims are loctited to the inner aluminum flywheel body (That's why they look dirty--that dirt will all come off with a "clean up" pass in the lathe.) Drilling and reaming the center hole for the shaft is one of the last things I will do.


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## Brian Rupnow (Nov 12, 2021)

The flywheels are finished except for keyways, and I like this new variation on round holes cut in the webs. This gives the flywheels an interesting look, and it will still make it highly visible when they are rotating under power.


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## GreenTwin (Nov 12, 2021)

Brian Rupnow was one of the folks who inspired me to learn 3D modeling, back in 2012.
Great work Brian !
Its always interesting to follow your builds.
.


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## Brian Rupnow (Nov 12, 2021)

Thanks for saying Hi, Green Twin.---Brian


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## Brian Rupnow (Nov 13, 2021)

I spent yesterday afternoon and this morning preparing blanks for my 20 and 40 tooth gears, and sawing a slab of 1144 stress-proof steel from the round to make a crankshaft. These are all somewhat brainless operations, but they have to be done, and they take time. The gear blanks are finished outside diameter, thickness, hub diameter and bore, but the hub is a couple of inches too long, which gives me something to grip in the 3 jaw chuck on my rotary table while the teeth are being cut. This over-length hub will be cut off after all of the gear teeth are cut.


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## Brian Rupnow (Nov 13, 2021)

Now I've got to ask---Is that a beautiful thing, or is that a beautiful thing!! Both gears turned out fine, the large gear fits into the cavity prepared for it in the base, and they mesh just the way they are supposed to. I always feel good when I've cut a pair of gears and they turn out the way I had hoped for.


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## Brian Rupnow (Nov 14, 2021)

Today, since I had to take the sideplates off to fit the crankshaft and camshaft, I decided to go full ball bearings on the crank and camshafts. I was originally going to run the camshaft in bronze bushings, but decided that since I had the correct size of sealed ball bearing, I might as well add the counterbores to the sideplates and go full ball bearing.


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## Brian Rupnow (Nov 14, 2021)

So, at the end of a long and hard fought day, I have a one piece crankshaft and a cam shaft. It's been a long day!!


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## Brian Rupnow (Nov 15, 2021)

And here we have a video of all the bits and pieces I machined yesterday, working in harmony. This is my horizontal air cooled engine, 7/8" bore. The cylinder is not mounted in this video, although it is finished.


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## Brian Rupnow (Nov 16, 2021)

This morning I machined a con rod. My digital camera shows up things I missed when sanding the finish.--Oh well, I'll sand it a bit more to take out those tool marks. I always have trouble getting a perfect fit between the big end of the con rod and the crank journal. When I bore the big end of he con rod, my biggest fear is that I will go oversize, and there really is no good fix for that except to make another con rod. So, I end up marginally undersize and then have to screw around for an hour with emery paper and lapping compound to get the fit exactly what I want it to be.


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## Brian Rupnow (Nov 16, 2021)

I am rapidly approaching the point where I have to finish the cylinder and make a piston. When I first designed this engine, I never noticed that I couldn't remove the sideplates without first removing the cylinder, which is a giant PITA. I am going to modify the cylinder flange where the grey arrow is pointing, by putting in a couple of clearance holes in the flange, which will then let me remove the bolt which was previously trapped under the edge of the cylinder flange.


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## Brian Rupnow (Nov 16, 2021)

This afternoon I managed to machine a piston. I'm tired, and suppers ready.---Enough work for one day!!!


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## Steamchick (Nov 17, 2021)

Brian Rupnow said:


> Today I did something for the very first time!!! Those reliefs in the face of each flywheel are 3/16" deep, and they have a 1/8" radius in the corners. I have always known that there should be  radius there. I know the whole tune about sharp inside corners causing stress risers and are more apt to fracture in use. It's just that I never actually did it before. I have about 40 engines running just fine without a radius in the corners of the flywheels. Today I actually ground an HSS tool and machined the radius.  The outer brass rims are loctited to the inner aluminum flywheel body (That's why they look dirty--that dirt will all come off with a "clean up" pass in the lathe.) Drilling and reaming the center hole for the shaft is one of the last things I will do.


Hi Brian, and interesting process sequence. I should have made the centre hole first, then mounted the flywheel on an arbour to machine everything concentric to the shaft centre. But I guess you have done it your way so the loads on the arbour are minimal with only finishing cuts to clean-up the flywheel and true it to the centre?
K2


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## Steamchick (Nov 17, 2021)

Hope your piston ring process works well for you this time. I recall you had a big learning curve on a previous engine?
Enjoy you modelling  Brian. We all enjoy your posts!
K2


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## Brian Rupnow (Nov 17, 2021)

The engine is completely assembled except for the cylinder head. Everything  has a coat of 10w 30 lubricating oil, and the rod cap bolts are snugged up. It is currently out on my workbench being "ran in" at about 450 rpm driven by my electric motor via v-belt. Every 10 minutes I will go out and snug up the con rod bolts a little more. I will let it run for about half an hour and by the end of that time the rod bolts will be fully tightened.


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## Brian Rupnow (Nov 17, 2021)

And here we have one more step in the evolution of an engine. This video was made after the engine was "ran in" for about half an hour, and the rod bolts were progressively tightened after each ten minutes of running in until they were cinched down tight and everything ran freely with no binding. There are no rings on the piston yet.


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## Brian Rupnow (Nov 17, 2021)

Earlier in this thread I mentioned that I had some cams left over from some other engine build. At the time I made those cams, I remember thinking "Since I have to go thru all the motions to make these cams, I'll cut the stock long enough to get a second pair of cams from." The time has come!! ---and I can't be happier. These cams were bored for a 3/8" shaft, and since I had 1/4" sealed ball bearings on hand, the camshaft is 1/4" diameter on both ends but 3/8" diameter where the cams will fit on. Things are very tight where they have to go, but my computer tells me there is just enough room for the cams to fit in there  with enough gap between them to let the con-rod swing thru between them. The cam without a hub (for the exhaust) will be pinned to the shaft, the one with a hub will have set screws to hold it in place rotationally.


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## Steamchick (Nov 18, 2021)

Hi Brian - Love it! Excellent work. But how about some counterbalance for the primary piston/rod/big-end imbalance? - Maybe some weights added to the flywheels? - Now would be a good time to balance the engine, as it is all so free without rings, cams, valve-gear... etc. I'm sure you have approximate weights for the con-rod, piston, etc. from the CAD? - Does that have a balance calculation thrown on the side? Or do you have to do the engineering separately, and just draw stuff with CAD? - Being a pencil n paper Luddite my paper drawings don't do calculations.
Cheers!
K2


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## Steamchick (Nov 18, 2021)

P.S. When I have tried to weigh pistons, rods, etc. I cannot get enough weight to move the kitchen scales! - So I have to take bits to the Post-Office (in a poly bag - with a story about needing to weigh them before packaging). But sometimes I just tape a small weight on the flywheel and see how it goes! - Usually that does it well! Needs the cylinder vertical though, so when you turn the crank to 1/2 stroke both ways it neither drops nor lifts against the bearing friction. Makes slow running really smooth!
K2


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## Brian Rupnow (Nov 18, 2021)

Steamchick--at the speed I run my engines, the counterweights make very little difference to the smooth running of the engine. If I ran at higher speeds, then I would need counterweights. One thing about the engines I design/build---If someone wants to alter the design a bit and add bolt on counterweights, it is very simple to do.---Brian


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## Brian Rupnow (Nov 18, 2021)

No real work accomplished today, other than mounting the cams where they will go on the camshaft and taking a picture of it with one sideplate removed. I have to pick up some 1/2" diameter brass tomorrow to make valve cages and tappet guides from, and a piece of 1/16" diameter drill rod to cross-pin the cam to the camshaft. The woman who runs BusyBee tools in Barrie called and told me about an old fellow in town who built "Steam engines and things" but was too old to work in his shop anymore. I called him and arranged a visit this afternoon and went to see what I might want to buy. He was a nice old fellow of 90, but was selling off all his shop toys. unfortunately, I have everything he has, only bigger and better. I did buy eight small cast steel C-clamps for $25, but that was all I bought.


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## Brian Rupnow (Nov 19, 2021)

This morning I went down street and bought my ignition points and condenser. I machined an ignition cam and fitted it in between the sideplate and the flywheel on the side opposite from the timing gears. I flame hardened and quenched my cams in oil, and after clean up got them mounted on the camshaft. The con rod clears the cams when it rotates, by about a gnats hair. (That's about .001"-.003").


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## Brian Rupnow (Nov 19, 2021)

And at the closing of the day---I have tappet guide bushings made and installed, and valve cages made and installed. Setting out by itself on the end of the engine baseplate, is one lonely valve cage that ended up being too short. I thought it looked too short when I made it (it was the first one) and after doing some checking I found that I had modelled it too short. Ahh poop!!!--Thats why, when you buy a set of drawings from me, the mistakes have already been found and corrected. My original plan was to make the rocker arms out of steel, but I found an offcut of brass that might work for me. I'll figure that one out tomorrow.


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## Brian Rupnow (Nov 19, 2021)

One step forward, two steps back. I realized after loctiting the valve cages into the cylinder head that I hadn't put the counterbores in the cylinder head for the valve cage flanges to fit down into. I don't have a great deal of free room in the combustion chamber, so it's pretty important that the flange sets down into a counterbore. Sparky asked me about that, and I thought about it to the point where I pulled the valve cages out of the cylinder head before the Loctite had a chance to set up. What I really need is a 13/32" diameter reamer with no chamfer on the end, with the end drilled and tapped for a pilot. If I put a counterbore in, I have to do the main hole and the counterbore all in one set-up, otherwise I can never get the counterbore concentric with the main hole. After doing some frantic Googling, I find that there are reamers with pilots available, but the reamers all have a chamfer on the end. I need a reamer with no chamfer on the end and with the end drilled and tapped so I can put different size pilots on it. Does anyone know of a commercial source for such a thing? I do have a guy near Barrie who sharpens endmills and drills and can make a custom cutter for me, but he's not cheap.---Brian


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## Gordon (Nov 19, 2021)

Brian Rupnow said:


> One step forward, two steps back. I realized after loctiting the valve cages into the cylinder head that I hadn't put the counterbores in the cylinder head for the valve cage flanges to fit down into. I don't have a great deal of free room in the combustion chamber, so it's pretty important that the flange sets down into a counterbore. Sparky asked me about that, and I thought about it to the point where I pulled the valve cages out of the cylinder head before the Loctite had a chance to set up. What I really need is a 13/32" diameter reamer with no chamfer on the end, with the end drilled and tapped for a pilot. If I put a counterbore in, I have to do the main hole and the counterbore all in one set-up, otherwise I can never get the counterbore concentric with the main hole. After doing some frantic Googling, I find that there are reamers with pilots available, but the reamers all have a chamfer on the end. I need a reamer with no chamfer on the end and with the end drilled and tapped so I can put different size pilots on it. Does anyone know of a commercial source for such a thing? I do have a guy near Barrie who sharpens endmills and drills and can make a custom cutter for me, but he's not cheap.---Brian


Why not just make your own from drill rod. I have made counterbores for cap screws. It is the same process as making the valve seat tool.



			Making Counter-bores on the Taig Lathe and Mill


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## Brian Rupnow (Nov 20, 2021)

Gordon--Thank you. That is a great article.  Yesterday I was chasing all over the internet trying to find what I wanted but had no luck.---I was calling it the wrong thing!!!  This morning I woke up realizing that I should have been searching for a "piloted counterbore". Ran downstairs and checked the internet again and found out that everybody and their dog is selling "piloted counterbores"!!! I started phoning around and then realized that this is Saturday and all the shops are closed. This is a tool I could make but would rather buy. ---Will find out more on Monday.---Brian


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## Gordon (Nov 20, 2021)

You obviously are a better man than I am. I would have a problem with waiting for two days and then waiting for shipping. I would be in the shop making one. Making your own allows whatever size you want and it would probably not even have to be heat treated for only two cuts but I would do so if I thought that I would ever need it again


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## Brian Rupnow (Nov 20, 2021)

Nothing big or fabulous machined today. Just a pair of brass rocker arms and axles and hardened 01 steel round contact pads on the end that touches the end of the valves.


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## perko7 (Nov 21, 2021)

Probably a bit late to respond to previous posts, but I made a successful counterbore out of a broken drill of the required size. I ground the end flat first, then ground some relief on the cutting edges. I already had a pilot hole, so I started the counterbore recess with a regular drill to make sure the counterbore ran true, then drilled the remainder with the counterbore to the required depth. Worked a treat. It didn't need to be a high precision job but when I screwed the capscrews in the clearance around the perimeter seemed pretty consistent.


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## Brian Rupnow (Nov 22, 2021)

These two little guys that look like tubes are actually the tappets. They have a short counterbore in the end you can see and are solid at the other end where they rub against the cams. The counterbore which is about 0.350" deep holds the end of the pushrods for the valves. The cams have been flame hardened and quenched, and the tappets have also been flame hardened and quenched. They are made from 01 steel and quenched in old motor oil. Once the engine is fully assembled, you won't see these tappets anymore, as they are mostly contained in the tappet guides.


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## Brian Rupnow (Nov 22, 2021)

At this point, I don't know exactly how long the pushrods are going to be. I can get a length from my 3D model, but in situations like this I just make the pushrods 1/2" longer than what the computer said and will trim them to length on finished assembly.


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## Brian Rupnow (Nov 22, 2021)

This afternoon I finished all of the fan mechanical parts except the fan blade. The fan is represented by the disc of cardboard, 2 1/4" diameter.---I don't know why it isn't centered in the shroud, but I can move the hole in that brass strap enough to center the fan, and nobody'll know. There is a lot going on in that fan hub. There are two 3/16" diameter ball bearings in there that were originally intended for a router, and a spacer between them.---I like it.


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## CFLBob (Nov 22, 2021)

Brian Rupnow said:


> I don't know why it isn't centered in the shroud, but I can move the hole in that brass strap enough to center the fan, and nobody'll know.



Making a crude measurement in a drawing program, it looks like that hole isn't centered in the brass strap.  The left side of the nut is over air while the right side is on the brass with room to spare.

Move it to the right about half the diameter of that threaded part and it centers the fan?


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## Brian Rupnow (Nov 22, 2021)

Yep


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## L98fiero (Nov 23, 2021)

CFLBob said:


> Making a crude measurement in a drawing program, it looks like that hole isn't centered in the brass strap.  The left side of the nut is over air while the right side is on the brass with room to spare.
> 
> Move it to the right about half the diameter of that threaded part and it centers the fan?


Been there, done that, sucks when you read your own drawing wrong!


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## Brian Rupnow (Nov 23, 2021)

This morning I cut keyways in both flywheels and the crankshaft. I fabricated a fan, silver soldered it to the fan hub, and installed the fan and hub in the fan housing. (It is now centered in the housing). We got about 8" of new snow last night in Barrie.


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## Brian Rupnow (Nov 23, 2021)

And I think this is it!! I machined the valves this afternoon and I  don't think there is anything left to machine. I'm waiting for a piloted counterbore to come in from my supplier so I can finish up the valve cage counterbores in the cylinder head. I have to build some kind of starter hub, and maybe some kind of take-off pulley to attach to the offside flywheel. I have left the "handles" on the valves so I have something to grip when I lap the valve faces into the valve cages.---and oh Yes---I have to make rings.---Cast iron rings.


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## Brian Rupnow (Nov 24, 2021)

Today was not one of my stellar days. I machined the drive hub and the power take off pulley, and they turned out well. They are held onto the flywheels by four #4-40 socket head capscrews. Drilling the four holes in the starter side flywheel went well. Tapping the first flywheel hole went well. Tapping the second hole didn't. I broke the tap off flush with the surface of the flywheel. After repeated tries to get the broken tap out, I went across town to my tool shop and bought two new taps, two new drills and two 1/16" diameter center cutting carbide endmills. On arriving home, I discovered that my newest Diana Gabbeldon book had arrived, so I made an executive decision to read for the rest of the day. Something of interest--that #4 hand tap and it's drill are about 13 years old, and gets used fairly often. I measured the drill, and it measures at 0.088" diameter. the man who sold me the new taps and drills said that the standard tap drill for a #4-40 bolt is 0.094" diameter.---Who knew--


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## L98fiero (Nov 24, 2021)

Brian Rupnow said:


> Today was not one of my stellar days. I machined the drive hub and the power take off pulley, and they turned out well. They are held onto the flywheels by four #4-40 socket head capscrews. Drilling the four holes in the starter side flywheel went well. Tapping the first flywheel hole went well. Tapping the second hole didn't. I broke the tap off flush with the surface of the flywheel. After repeated tries to get the broken tap out, I went across town to my tool shop and bought two new taps, two new drills and two 1/16" diameter center cutting carbide endmills. On arriving home, I discovered that my newest Diana Gabbeldon book had arrived, so I made an executive decision to read for the rest of the day. Something of interest--that #4 hand tap and it's drill are about 13 years old, and gets used fairly often. I measured the drill, and it measures at 0.088" diameter. the man who sold me the new taps and drills said that the standard tap drill for a #4-40 bolt is 0.094" diameter.---Who knew--


Don't know where he got that dimension, if you use the nominal size - the pitch the tap drill should be 0.087 and a #43 drill which is 0.002 oversize will produce a 70% thread. IF a 3/32 drill, drills on size it will produce a 56% thread which really isn't 'standard' though if you're going more than 6 or 7 threads deep in anything but aluminum you won't loose a large amount of holding force.


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## Brian Rupnow (Nov 25, 2021)

Once again the old and arthritic have defeated the powers of darkness. It cost me a 13 year old #4-40 tap and a new 1/16" carbide endmill, but in the end the broken tap was removed and the hole was rethreaded at the correct size. (on #4 taps, that trick actually works about one time out of three for me.) So, the engine now has a starter hub on one side and a power take-off pulley on the other.


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## Brian Rupnow (Nov 27, 2021)

The engine is almost fully assembled. I had trouble with the first cylinder head, so had to machine a second one. The engine is pretty well finished except for "tidy up" and cosmetic stuff. I'm not sure you can see it, but the camshaft gear ended up hanging below the baseplate by about 0.020", so I've had to epoxy a pair of filler plates on the bottom of the base to raise everything so the gear doesn't rub on the table top. This was an easy change to the engine plans, I just made the base out of 5/8" stock rather than 3/8" thick. I didn't want to remake the baseplate, so the filler plates will do for me---I have to tidy them up to match the contours of the engine base. The only remaining things to be made are the cast iron piston rings.


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## Brian Rupnow (Nov 28, 2021)

Does anyone have a source for 1/4"-32 Helicoils? I've managed to bugger up the threads in my sparkplug hole in the aluminum cylinder head. There is a considerable amount of time and work involved in making these heads, and I don't want to scrap this one. My options are #1--Find someone who manufactures a sparkplug with a 5/16" thread---(That would be my absolute best option)---Or find a source for 1/4"-32 Helicoils,----Or ---Make my own sparkplug with a 5/16" thread. I have made my own sparkplug before, but I don't really want to. Thank You----Brian


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## Brian Rupnow (Nov 28, 2021)

Something more--There are manufacturers of M8 metric sparkplugs, which are very close to 5/16".  M8 is 0.315" diameter.  5/16" is 0.312" diameter. Perhaps my easiest fix here is to buy an M8 sparkplug and an M8 tap. They seem to be readily available on the internet.


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## Mike1 (Nov 28, 2021)

Brian, Have you room to bore out your spark plug hole, and make a mild steel insert/bush bored and threaded to suit your original plug thread, and press fit into the head or fix with loctite, even JB Weld.

Mike


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## Brian Rupnow (Nov 28, 2021)

Mike--I have considered it, in fact, I came down to my shop intending to do just that. The cylinder head gets hot.--Hot enough to loosen the bond of Loctite, and even possibly J.B. Weld. It's Sunday here today, but tomorrow when the shops are open I intend to pursue the M8 sparkplug option.----Brian


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## dsage (Nov 28, 2021)

JB weld will be fine on it's own for any temperature your engine will achieve.
But, depending on how much room you have you can make the suggested bushing thread into the head instead of just a press fit.
That, along with JB weld will be fine. Been there, done that.


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## Jasonb (Nov 28, 2021)

Brian, do you really have room to go upto an M8 plug, it looks like your existing plug hole comes quite close to the recess in the head and a larger one will leave very little if any area to seal against the raised edge of the cylinder.

Might be OK if you bore it out by plunging a 7mm milling cutter with the ctr slightly closer to the valve

If you do buy a tap make sure you get M8 x 1 which is finer pitch than the common metric coarse of 1.25mm pitch


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## Brian Rupnow (Nov 28, 2021)

Yes, I do have room for an m8 plug. I'm not sure of the thread specs are on the M8 marine sparkplug Amazon sells, but I will find out more tomorrow.


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## Brian Rupnow (Nov 28, 2021)

Having a very wimpy day here in the great white north. It has snowed here all day and I haven't been outside. I did a little tidy up work on the cylinder head and the rocker arms, and added a screw to the base to mount the condenser. Other than chasing down an 8mm sparkplug and making rings, the engine is completely "built". I have successfully made and ran cast iron rings in my last two or three i.c. engines, and now I will pull out all the notes I made with respect to 1" diameter pistons and see if there are any real changes to make rings for a 7/8" bore engine.


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## johwen (Nov 29, 2021)

Brian Rupnow said:


> Does anyone have a source for 1/4"-32 Helicoils? I've managed to bugger up the threads in my sparkplug hole in the aluminum cylinder head. There is a considerable amount of time and work involved in making these heads, and I don't want to scrap this one. My options are #1--Find someone who manufactures a sparkplug with a 5/16" thread---(That would be my absolute best option)---Or find a source for 1/4"-32 Helicoils,----Or ---Make my own sparkplug with a 5/16" thread. I have made my own sparkplug before, but I don't really want to. Thank You----Brian


Hi Brian,
Make an aluminium plug 5/16 -40tpi an Loctite in place and when set drill and tap for you 1/4 32 spark plug Cheers. John


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## aka9950202 (Nov 29, 2021)

I discovered that the spark plug thread is not normal M8. It has an 1mm pitch. 

Cheers, 

Andrew in Melbourne


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## Brian Rupnow (Nov 29, 2021)

I ordered an M8 A.C. Delco sparkplug this morning. Cost $14 delivered. I will post a picture when it comes.---Brian


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## awake (Nov 29, 2021)

Brian, from what I am seeing, M8 appears to be a model number rather than a size; everything I am seeing describes that plug as having a 10mm diameter. Hopefully I have it wrong, and you will be good to go ...


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## Jasonb (Nov 29, 2021)

M8 is the thread dia just like a CM-6 has a M10 thead both 1.0mm pitch.

8mm sparkplug is liekly to have an "E" prefix which indicates M8 thread and 13mm A/F body with a 1mm pitch. C is the prefix for M10 threaded plugs eg CM-6

Typical details of an "8mm" plug, click the technical tab but ignore the way off imperial conversions in brackets









						NGK ER8EH-N (5606) - Standard Spark Plug
					

The UK's largest independent supplier of automotive oils, fluid and parts. We've products to suit any vehicle, from full blown Race / Track weapons, to Daily Drivers looking to save money. Plus FREE expert advice & recommendations - OPIE KNOW OILS



					www.opieoils.co.uk
				




Plug code chart


			https://www.ngk.com/ngk-spark-plug-numbering-systems


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## awake (Nov 29, 2021)

I agree that M8 sounds like a thread diameter ... but when I search for "AC Delco M8 spark plug specification," I get links such as the following - which all consistently say that the diameter is 10mm, not 8:



			https://www.oreillyauto.com/detail/c/acdelco/ignition---tune-up/spark-plugs/b14eb31b13d7/acdelco-spark-plug/acd0/m8
		



			https://www.summitracing.com/parts/acf-m8
		









						M8, AC Delco Spark Plug (10mm) - The Brillman Company
					

#M8, AC Delco Spark Plug 10mm Thread 1/4" Reach




					brillman.com
				




Based on these links, I am thinking that M8 happens to be a misleading part number rather than an indication of size ... and that Brian is going to be disappointed with the actual size of the plug.


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## Jasonb (Nov 29, 2021)

M is used on premium and performance plugs, see the third chart in my link which as M10 x 1 thread. Standard would be E with M8 x 1 generally referred to as 8mm plugs

Maybe Brian can link to what he has bought


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## Ghosty (Nov 29, 2021)

NGK ME8  1/4-32 thread


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## Brian Lawrence (Nov 29, 2021)

Hey Brian, I just typed 1/4' X 32 Helicoil insert  and this web site pooped up. Hopes this helps.
www.rivetsonline.com/uniquespecial-size-thread-repair-kits-unef-size-14-32/rc-34040-32  doesn't look overly cheap though.

Brian


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## Brian Rupnow (Nov 29, 2021)

Brian--Thank you for that. I have almost wore out the internet looking for sparkplugs with a 5/16" thread, but haven't found any in the world. I have ordered what I thought was an 8mm sparkplug on line, but Sparky has cast doubt on that. My cheapest route by far is to machine another cylinder head, but I really don't want to do that. I just got word today about designing some light automation for a company in Toronto, so I'll probably just spend the money and buy the thread repair kit.---Brian


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## dsage (Nov 30, 2021)

I guess you've rejected the suggestions of making an insert (threaded or not) and JB weld (or loctited) in place??

Threaded and JB weleded worked for me on a much more detailed head that I definitely did not want to re-machine.
Just saying. Nothing to lose.


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## Brian Rupnow (Nov 30, 2021)

I have not reached a decision yet. I am waiting for the sparkplug I ordered to show up. If the sparkplug isn't 8 mm thread, I perhaps can turn the threads off, leaving a 5/16" or 8 mm plain end that I can then thread to 5/16".  I have also thought about j.b. weld, and a dozen other things, but I'll get the sparkplug I ordered first.


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## Zeb (Nov 30, 2021)

Something to add to the insert plug option mentioned might be to make it an interference fit. Similar to how valve guides go in with some heat and dry ice.


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## Steamchick (Dec 1, 2021)

IMHO I don't think JBweld or other epoxies can be anything other than a bodge job. Not of the standard of your workmanship. If there is insignificant room to over-bore thread and fit an insert, then the simple repair for aluminium is a blow-lamp ally weld rod. I used to you the heavily zinc based rods, but there are now some very cheap (€&@y) alloy rods that are 90+% aluminium, but melt flow and take to your aluminium below the melting point of your aluminium. 
I have used it as a solder on 1mm thick aluminium, 3mm thick, and other small jobs. I have used the zinc-aluminium mixtures to fill holes in thicker ally. 
But try an insert first if possible. Least risk to your existing job.
K2


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## dsage (Dec 1, 2021)

If you thread the insert, the JB weld is just a permanent thread sealant. You don't even see it when it's done. Except for a very fine ring the diameter of the insert. Same for loctite.


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## Brian Rupnow (Dec 1, 2021)

I have spent the last two days designing some light automation for an old customer. My new sparkplug will be here on Saturday, and if it doesn't have an 8mm thread I am going to buy a 1/4"-32 helicoil kit from a source provided by Brian Lawrence from Calgary. Tomorrow I will begin the task of making rings for a 7/8" diameter piston. I have the grey cast iron material, but will have to build a new heat treat fixture to accommodate the new ring size. The rings will have the same cross section as the ones I made earlier this year for my T-head engine.


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## minh-thanh (Dec 2, 2021)

Hi Brian !
Why don't you make spark plugs with 8 x 1 mm or 8 x 1.25 mm ?


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## johwen (Dec 2, 2021)

Very Easy to make as I have described before John


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## Brian Rupnow (Dec 2, 2021)

Todays job was to make a whole armada of 7/8" rings. The material is fine grained grey cast iron, same as I made my other 1" rings from. The o.d. of the ring is turned to 0.875" diameter and polished with 200 grit aluminum oxide strip and a fine India stone, to the best finish I can get. The i.d. is drilled and bored out to leave the rings 0.038" wide axially, which is what I was aiming for.  The rings are then parted off, and with some luck will all be slightly greater than 0.045" width, which is the width of the ring grooves in my piston. They will be finished on both sides with some 600 grit aluminum oxide paste on a sheet of glass, rubbing round and round until they are a sliding fit into the ring grooves in the piston. After they are "sized" for width, I will break them in my bench vise. I don't like the fancy fixture which I made to split them because it has a tendency to bend the rings. The last rings I made were cut with a sharp cold chisel, but I felt that doing that deformed the ring on both sides of the cut.


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## Brian Rupnow (Dec 2, 2021)

Okay---Just to set the record straight---My rings came off the lathe about 0.003" to 0.004" too wide (as I had planned). I tried polishing that 0.003" to 0.004" off using 600 grit compound on a piece of glass, but it took so long I thought I might not live long enough to get all the rings done.---So---I used a sheet of 600 grit paper laying on a finished cast iron surface, and my handy dandy piece of steel with a 0.875" dia. x 0.025" deep hole in it to hang onto the rings with while I polished them. That went more quickly, but even so it took a lot of scrubbing in circles before the rings came down to 0.044" thick and would fit into the 0.045" grooves in my piston.


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## MRA (Dec 2, 2021)

I am intrigued how you are going to snap them 'just so'.  Hope you show that bit!


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## Brian Rupnow (Dec 2, 2021)

MRA--I misled you. 
This was something new---The material didn't want to break in the vice. Damn stuff wanted to bend, which is unusual. When I seen that it didn't just snap quickly like other rings  have made, I sharpened up my big cold chisel and cut them with the chisel and a pall peen hammer. Whack---and it was done. All the rings in this picture are finished, deburred, and split. Tomorrow I will machine a heat treat fixture and into the heat treat oven they go.---Brian


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## Nerd1000 (Dec 2, 2021)

Brian Rupnow said:


> MRA--I misled you.
> This was something new---The material didn't want to break in the vice. Damn stuff wanted to bend, which is unusual. When I seen that it didn't just snap quickly like other rings  have made, I sharpened up my big cold chisel and cut them with the chisel and a pall peen hammer. Whack---and it was done. All the rings in this picture are finished, deburred, and split. Tomorrow I will machine a heat treat fixture and into the heat treat oven they go.---Brian


Is it possible that you got ductile iron rather than grey cast iron? It would be more inclined to bend than snap.


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## Jasonb (Dec 3, 2021)

I was thinking the same when I saw that swarf from drilling out the waste, looks more like ductile iron.

If it is the same bar you used for the others that may also explain why the Trimble cutter was deforming the ring around the split.


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## Brian Rupnow (Dec 3, 2021)

Could very well be. I've broken rings in my vice in the past, and they always cracked under light sideways pressure. I have never n one bend before.


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## Brian Rupnow (Dec 3, 2021)

A couple of picture worthy things going on here. One picture shows a good way of filing the ends of the ring at the ring gap. That is an ignition points file gripped in the vice, and a ring spread over it. I grip the ring with thumb and forefinger of each hand and slide it back and forth on the file, keeping it "square" to the file. Give it 20 strokes and try it for fit in the cylinder--You are aiming for a gap of 0.004" between the ring ends when the ring is slid into the cylinder. Keep track of the number of strokes you take, because whatever it took for that first ring will work for all the rest of the rings. The other picture shows the heat treat fixture I machined this morning, made specifically for 7/8" rings. The drawing I am working from specifies a 0.131" diameter spreader rod. Closest I had was an 0.135" drill, so thats what I used, and the drill will be sacrificed as my spreader rod. Once the cap is bolted on, compressing all of the rings to ensure that they are all laying flat and tight next to each other, the fixture and rings go into my heat treat furnace for 4 hours.


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## CFLBob (Dec 3, 2021)

Brian Rupnow said:


> The drawing I am working from specifies a 0.131" diameter spreader rod. Closest I had was an 0.035" drill, so thats what I used, and the drill will be sacrificed as my spreader rod.



Is that a typo? Those are a tenth of an inch different?  I mean is it supposed to be 0.131 and 0.135 or .031 and .035?


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## Brian Rupnow (Dec 3, 2021)

That was a typo Bob.--thanks. I fixed it.---Brian


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## Brian Rupnow (Dec 4, 2021)

Bad on me---I ordered an M8 sparkplug from A.C. Delco, assuming it would have an M8 thread on it.---it doesn't. It has a 10 mm thread on it. However, all is not lost. As we speak, Stephen Hucks is making me a "one of" sparkplug with a 5/16"-24 threaded end. As luck would have it, I do have a 5/16"-24 tap and die as part of a set I inherited from my dad.


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## Brian Rupnow (Dec 4, 2021)

After four hours at 1100 degrees F and then an overnight cooling off period, the fixture comes out of the oven looking like this. There is a lot of black crud on the outside of the fixture (Don't know what it is) but it cleans off very easily. When the fixture is taken apart, the rings come off easily, but they are all stuck together. A bit of finessing with a jacknife gets them apart, and as you can see in the picture they have all taken a set to the new gap of 0.135".


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## Nerd1000 (Dec 4, 2021)

The black stuff is probably mill scale, a mixture of iron oxides formed at high temperatures.


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## Gordon (Dec 4, 2021)

I have always used Brownell anti oxide paste. Others seem to get by without it just fine. I am not sure if I am doing something good or just wasting time and money.

I have always used some good quality end cutters to cleave the rings which should work like Trimble's cleaver. When I end up with a bad ring it is usually right at the break but I am not sure if making his cleaver would improve results. Brian did not have much luck with his. Trimble said that he had trouble making good rings until he made his. Anyone have any thoughts?


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## Brian Rupnow (Dec 4, 2021)

The rings are on the piston and the piston is back in the engine, and everything goes round and round and up and down like it's supposed to. Out of 8 rings four were damaged, two are on the engine, and I have two left over for some other project.---I would not recommend  putting new rings on a new piston to anyone who was looking for a way to pass a tranquil afternoon. There is no cylinder head on the engine right now, but it does have lots of "suck" when I put my hand over the cylinder and turn the engine over with the flywheels.----thats a good thing!!!!


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## Brian Rupnow (Dec 5, 2021)

The engine is basically finished. I'm just waiting for a new sparkplug from Steve Hucks. In the meantime, this things needs a gas tank. I've built about a zillion round gas tanks, but this time I decided to try something a bit different. I went out into my "junk steel closet" and found a piece of 1 1/2" square tube. It will be the basis for my new rectangular tank, and I have a piece of 3 1/2" x 1/2" aluminum flat bar that will make a good sub base to hold the engine and the gas tank.


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## Brian Rupnow (Dec 5, 2021)

Got this far today, and just run out of ambition. Tomorrow I will finish the gas tank and the sub base.


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## stevehuckss396 (Dec 5, 2021)

That plug will be in the mail Monday morning.


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## Brian Rupnow (Dec 5, 2021)

Thank you----Brian


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## Brian Rupnow (Dec 6, 2021)

Today the gas tank was assembled. There is a lot going on here that you can't see, but the ends of the tank are assembled to the body using J.B. Weld. The tank assembly is bolted down to the sub base, and the big vice grip clamp is on there as  secondary means of clamping things tight for the next 24 hours. The sub base has had all of the holes added to hold the engine and the gas tank. Tomorrow I will leak test the gas tank, and if all is well I will paint the gas tank and the fan assembly.


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## Brian Rupnow (Dec 7, 2021)

Every day I do a little bit more (gas tank out spout), but I'm almost out of little things to do. That red gas cap is "borrowed" from another engine, so I still have to make one of them for this tank. The filler spout is made from a 1/2" standard pipe nipple and the cap is machined from a 1/2" standard pipe plug. This is the best solution I have found for a nice big filler spout that has a cap that screws on tight---and yes, there is a one mm hole in that cap.


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## Brian Rupnow (Dec 8, 2021)

This morning was "Leaktest morning". I sat the gas tank on a sheet of white printer paper, plugged the outspout, and very carefully filled the tank with naptha gas. Almost immediately my white paper started showing evidence of a leak.---CRAP!!!---Closer investigation showed that it wasn't any of the j.b. welded joints that were leaking. It was leaking where outspout #1 was brazed to outspout #2. Dumped the gas back into the bottle, ran out to my main garage and re-brazed that joint. Second leaktest went fine---No leaks. Then I went to grab a can of dark blue enamel to paint the tank and fan assembly, and sure enough--I have every color under the rainbow, but not dark blue.  Wife has gone out to a spa with daughter, and I am baby setting our Grand-dog. I'm not sure what kind of dog it is, but it just looks like a larger version of the old pit bull we had for many years. She's very quiet and well mannered so I talk to her while I'm working and take her out to pee every hour.


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## Brian Rupnow (Dec 8, 2021)

At noon I went out and bought a can of Tremclad blue spray enamel and some brass pipe caps to turn into gas tank caps. I machined both gas caps and screwed one onto an engine which I had robbed the cap off and screwed the other onto the tank for this engine. Both tank and fan assembly have been painted, and I see as I posed them for this camera shot that the cap on this current tank needs a bit more paint on it. That was my work for today. My new sparkplug from Steve Hucks should be here this week, and if I have lived a clean and useful life I may have a running engine by this time next week.


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## Brian Rupnow (Dec 9, 2021)

Time to stop and consider---What is left to do? My new sparkplug will be here this week. Head has to be bolted in place and a head gasket made. Valve lash has to be adjusted and valve timing set up with a degree wheel. Ignition timing has to be set. Painted gas tank and fan have to be bolted back into position. I find that with these spray cans of enamel, it is much safer to not handle the painted parts for about three days so as not to get marks all over them during handling them. I have to make a special wrench. It is very, very tight where the base of the cylinder bolts to the vertical frame plate. I can get the bolts started with a ball end Allen wrench, but I'm going to have to fabricate a special wrench to actually get in there and tighten them properly. I will post a picture of the wrench I'm going to have to build-----it's quite simple.


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## Brian Rupnow (Dec 10, 2021)

In this picture you can see both valves after they have been lapped using 600 grit aluminum oxide paste. The valves have the contacting surface of the face smeared with 600 grit paste and then (while the handles are still attached) they are placed into the respective valve cages and spun back and forth against the valve seats under slight pressure. This is not done with any kind of power tool---fingers only. I hold the handle between thumb and finger and spin them back and forth 10 times--Then lift up. Turn about 30 to 40 degrees then repeat. After a total of 100 "back and forths" they are finished.  Then the "handles" are parted off in the lathe. Beyond this point, the valves must go back into the valve cage in which they were lapped. Don't mix them up. Normally, at this point they are finished, but to make it clear for the picture, I put some blue machinists die on the valves, and using the pin vice in the foreground I gave each valve 50 additional turns in their cages with 600 grit. This clearly shows the contact area on the face of the valves, because all the machinists die is worn away at this point.


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## mayhugh1 (Dec 10, 2021)

When QC'ing a valve's contact area with bluing, it's important to not spin the valve. You should drop the valve into the seat, and rotate it just a few degrees plus and minus. If your seat has a single tiny leak-creating high spot, and if you spin the valve 360 degrees over this high spot, a contact ring will show up on the valve due to this high spot rubbing on it, and you'll get a false indication of full contact. - Terry


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## Brian Rupnow (Dec 10, 2021)

I can buy that Mayhugh. These valves are only 5/16" diameter and have been lapped before they were blued. The only reason for bluing them was to show people where the valve contacted the seat in order to seal.


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## Nikhil Bhale (Dec 11, 2021)

For marine engines when we lap valves in their seat, we draw lines on valve seating area with a pencil. 
The valve is then rotated on the seat. If all the pencil lines disappear after one rotation the valves are seating perfectly.
This was for old engines.
In new engines the valve and seat are at different angles, so no lapping only grinding in a valve grinding machine.

Regards
Nikhil


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## Brian Rupnow (Dec 12, 2021)

I have reached a point where I can not go any farther with this engine until I receive my new sparkplug. This morning I pulled both flywheels off and set the engine's ignition timing. (I realized after the fact that I didn't have to remove the flywheel from the side with the timing gears on it). Basically, the way I do this is loosen off the set screws in the ignition cam then turn the crankshaft in it's normal rotation until the piston is about 1/16" before top dead center. At this point, without moving the crankshaft, I rotate the cam in it's normal direction until I get a big fat spark from the sparkplug laying out on top of the engine. Then I tighten the setscrews in the cam to lock it in place. After that I turn the engine over by hand a few times just to assure that the spark will come every time the piston reaches that spot 1/16" before top dead center. On my engines I run the ignition points off the crankshaft, so it is a "waste spark system". I get spark every time the piston comes up to top dead center, but it only ignites a charge of fuel every other revolution of the crankshaft.


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## Brian Rupnow (Dec 14, 2021)

Today I received a new mail order piloted counterbore from Travers. I have a set of counterbores for all of the different socket head cap screws that I have, but this one is a bit different. This one was purchased for the sole use of putting counterbores into aluminum cylinder heads where the flanged end of a valve cage goes, so that the face of the cage sets down flush with the inside of the cylinder head. I have found, by experience, that when I drill and ream these holes, then change to an unpiloted counterbore in the same set-up , that the unpiloted counterbore always pulls a bit to one side and is never totally concentric with the 0.375" reamed hole which the cage body sets into. For this first shot, I have made my own pilot, which sets inside the 7/16" counterbore tool and is held in place with a pair of set screws. I wanted to have the capability of using different size pilots, that's why I didn't buy a one piece counterbore with a pilot ground onto the end of it. It's not too often that I buy a new piece of tooling, so figured it was worth posting about. I'm still waiting for my new sparkplug to arrive, so I can go ahead and finish up the horizontal i.c. that I have been working on.


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## ShopShoe (Dec 15, 2021)

That counterbore looks like it will do the trick. I applaud your skills again. I myself would not have thought of making a pilot, but would have been a slave to the tool vendors again. The pilot looks like something easily made to solve a user's problem.

...Always watching and waiting for the engine to run,

--ShopShoe


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## Gordon (Dec 15, 2021)

Brian:
What difference does it make if the counterbore/mill cutter cuts a little bit oversize? It will not leak around that part of the valve seat. The seal is in the stem of the valve seat, not that short shoulder. Actually why do you need a shoulder at all? The seat is either a press fit or locktite in place and once it is in place it will not move.


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## Brian Rupnow (Dec 15, 2021)

Gordon---the flange on the valve guide is there because---I have this terrible fear that without a flange, the Loctiite would heat up from the engine running, and as I hover over the engine running it, the engine will fire and shoot valve guide with valve attached out and hit me in the eye. Shopshoe---These piloted counterbores and different size pilots are readily available from toolshop suppliers.---Brian


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## Gordon (Dec 15, 2021)

Brian Rupnow said:


> Gordon---the flange on the valve guide is there because---I have this terrible fear that without a flange, the Loctiite would heat up from the engine running, and as I hover over the engine running it, the engine will fire and shoot valve guide with valve attached out and hit me in the eye. Shopshoe---These piloted counterbores and different size pilots are readily available from toolshop suppliers.---Brian


You could accomplish that even if the counterbore was a few thousands oversize.


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## Brian Rupnow (Dec 15, 2021)

HURAYYYY-My sparkplugs came in the mail today from Steve Huck--And what beautiful sparkplugs they are!!! I had only ordered one with a 5/16"-24 thread, because I buggered up the threads for 1/4"-32 in my aluminum cylinder head. There was too much work in that cylinder head for me to scrap it, so I decided to go up to the next larger thread size and re-tap it. Steve has sent me what I needed and also samples of his "standard" plug with a 1/4"-32 thread on them to show me the quality of his work. I think the quality is excellent, and Steve's business card is in the picture for anyone who wants to order spark plugs for their project.  Thank You Steve Huck!!---Brian Rupnow


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## Brian Rupnow (Dec 15, 2021)

And here we are, head rethreaded and new sparkplug installed.  Engine build can now resume.


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## CFLBob (Dec 15, 2021)

Yay!!


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## Brian Rupnow (Dec 15, 2021)

Thrilled to announce that the engine is back together, valves and pushrods are installed, head and head gasket are installed, and flywheels do seem to have "bounce back" when given a flick by hand (which is a sure sign of compression). Valve timing and valve gap (between pushrods and shcs has not been set yet. I don't need the fan housing and fan on there yet. Also still have to make a gasket to fit between intake manifold and cylinder head. Tomorrow---tomorrow---


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## awake (Dec 16, 2021)

Can't wait to hear it run!


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## Brian Rupnow (Dec 16, 2021)

Everything is buttoned up and I am just at the point of setting the valve timing with a degree wheel. You can see that I have a pointer attached to the crankshaft, and by loosening the set screws on the small crankshaft gear and loosening the set screws on the intake cam, I am able to move things around until the intake and exhaust valve begin to open at the correct time in the cycle. This particular degree wheel was originally designed for a vertical cylinder engine. It still works for me here, even though the "0" degree marker is at the top of the dial.


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## Gordon (Dec 17, 2021)

Brian: I have a question for you. If I have read your posts correctly you obtain final cylinder bore size by drilling and reaming and then finishing with a brake hone. Is that correct? I have tried a reamer for final bore size and I have not had good results. My understanding is that if the drilled hole is not perfectly round the reamer will follow the egg shaped hole.


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## Brian Rupnow (Dec 17, 2021)

I've never had issues with a reamer. As long as the drill is at least 0.020" smaller than the reamer. The reamer will make an oval hole become round. But--If you drill wanders a bit, the reamer will follow it.


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## Brian Rupnow (Dec 17, 2021)

Yesterday afternoon I tried everything I can think of to start the engine. Not happening. Valves lash and valve timing is set "by the book" and ignition timing is correct. Tried a fresh can of fuel, made no difference. After about 4 hours messing with things, I thought "Everything is set perfectly but the engine won't fire.--Maybe it's my new cast iron rings." I squirted 30 weight oil down the sparkplug hole, and compression rose a great deal---that must be it---my c.i. rings are no good. So---today I made a new piston and put a Viton ring on it. Changed pistons about half an hour ago---and---it didn't make any difference. Engine refuses to fire with cast iron rings and with Viton ring. Sparkplug from Steve Huck is firing fine when removed from sparkplug hole and laid out on top of the cylinder head. But when cranking it over, not a pop, not a fart----nothing. I haven't seen an engine act like this before. Both intake and exhaust valves are sealing very well. If I choke it with my finger over the carb air intake while cranking it over with my electric drill, it will pull fuel up from the tank, and spit it out the exhaust pipe. But not firing at all. Thinking---thinking---


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## Brian Rupnow (Dec 17, 2021)

Before I take anything apart, or change any settings, there is one more thing I will try. That is to try using automotive gasoline instead of Coleman fuel. I'm not sure why that sometimes works, and it probably has to do with the volatility of automotive gasoline. This gets a bit too scary for me to do on my side-desk in my office. Tomorrow I will move operations out to my main garage, where there is more of a chance to put out any catastrophic unexpected fire disasters.


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## johwen (Dec 17, 2021)

What I have noticed Brian is on your degree wheel Your pointer is not parallel with the degree line emanating from the centre and is at considerable angle. This would throw the valve and ignition timing way off. Looks from the photo to be way of by as much as 25 degrees. Correct me if I'm wrong.
John


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## Brian Rupnow (Dec 18, 2021)

Jonwen--The pointer wasn't pointing at anything in particular during that shot. That was simply a picture of the degree plate.---Brian


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## dsage (Dec 18, 2021)

Try starting fluid with no liquid fuel. That will eliminate issues with the engine possibly flooding or starving.
Also
If the plug fires properly (across the gap) when it's out of the cylinder, put  the plug in the cylinder and put a spark gap in line with the plug wire. If you get a spark at the gap it will also be firing at the plug in the cylinder. It's unlikely but compression might be high enough (or your spark too weak) to fire under compression.


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## Brian Rupnow (Dec 19, 2021)

Yesterday was a complete write off, machine wise. Spent half the day designing something for a customer and half the day doing pre-Christmas things.  Today however, I got really bold and tried to start the engine with automotive gasoline in the tank.  No difference at all!! Engine will not fire. It is definitely sucking gas up to carburetor but not igniting it in the cylinder. Engine has good compression. Even if timing is out of whack, I should be getting some pops and farts while turning engine over with drill, but it's not happening. Can it possibly be the sparkplugs?---surely not. Steve Huck sent me two new sparkplugs and they both fire like crazy when laying out on the cylinder body. It has to be something deeper. I will now pull the cylinder head off and see if something is funky with the head gasket.


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## Brian Rupnow (Dec 19, 2021)

Okay---Just pulled the head off. This is a view of the inside of the cylinder head. There was nothing funky about the head gasket. There was nothing funky about the position of the sparkplug relative to the valves. The only thing I can see is that the spark from the center electrode to the side of the plug is happening on the side away from the valves. If I put a small brass washer between the sparkplug and the cylinder head, I hope to be able to re-tighten the sparkplug and have it so that the spark jumps to the valve side of the sparkplug. It seems highly improbable that this would cause a "no fire" situation, but when everything else has been checked, we start to seek out the improbable and correct it.


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## johwen (Dec 19, 2021)

Hi Brian, If you crank over the engine with your drill and then pull the plug out is it wet with fuel. If it is it has to be ignition. Is the spark blue or yellow? Yellow being not very hot and under compression not firing.   John


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## Brian Rupnow (Dec 19, 2021)

Jonwen--I'm not coordinated enough to take a picture of the spark the same time it is happening. However, it is a good spark, not weak at all.---Brian


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## Brian Rupnow (Dec 19, 2021)

YES!!!!--That did it. Engine is now finally firing. Turning the sparkplug 180 degrees so that the spark was occurring closest to the valves done the trick.---I'm happy--happy--happy. Next amazing stunt will be getting an extended run and making a video.


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## Gordon (Dec 19, 2021)

Since the only real difference in this engine over others is the spark plug I would think that is the most likely problem. Perhaps the arc is following down the outside of the plug or jumping from the cap to the head or some other metal part like. I have had that problem and I had one engine which would only run with a longer plug.


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## Richard Hed (Dec 20, 2021)

Brian Rupnow said:


> Okay---Just pulled the head off. This is a view of the inside of the cylinder head. There was nothing funky about the head gasket. There was nothing funky about the position of the sparkplug relative to the valves. The only thing I can see is that the spark from the center electrode to the side of the plug is happening on the side away from the valves. If I put a small brass washer between the sparkplug and the cylinder head, I hope to be able to re-tighten the sparkplug and have it so that the spark jumps to the valve side of the sparkplug. It seems highly improbable that this would cause a "no fire" situation, but when everything else has been checked, we start to seek out the improbable and correct it.


Actually, your conjecture does not sound all that improbable at all.  Can you make a washer that is the thickness of half a thread?  That would turn that plug around half a turn.


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## Steamchick (Dec 20, 2021)

Brian Rupnow said:


> YES!!!!--That did it. Engine is now finally firing. Turning the sparkplug 180 degrees so that the spark was occurring closest to the valves done the trick.---I'm happy--happy--happy. Next amazing stunt will be getting an extended run and making a video.


Hi Brian, Clever you! - for deducing the spark location has an influence on running! - I would have reduced the spark gap by a few thou... as sometimes that enables a good spark to be obtained when the spark is otherwise too weak (strung-out) to fire the mixture. 
In HV circuit breakers (a part of my life's apprenticeship), the intent is to "extend the arc" so it can be "blown-out" (I.E. cooled, so the ionisation fails within the electic field strength), as short fat arcs take a lot more puff to extinguish!  (A near spherical zone of ionised gas is much hotter and a better conductor than a long narrow "cylinder" of ionised gas). As an ignition source, the spark between the contacts of the spark plug is intended to be "near spherical", not long and drawn-out, with some "turbulent flow" of the fuel gas between the electrodes. The ionisation voltage at the electrodes ionises and heats the fuel molecules and air molecules, so that they combine and exothermally release their chemical energy to initiate the combustion... The field strength between the electrodes has to be high enough to strip electrons from the fuel and O2 molecules in order to do this. A gap that is "too large" will not have the field strength required, but a shorted gap will, for the same voltage.  (A Champion Spark-plug designer taught me the details - which I have mostly forgotten - so this explanation may be imperfect!).
All good Engineering!
Well done Sir!
K2


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## Brian Rupnow (Dec 21, 2021)

And since we last spoke---things have went off the rails. I had reached a point in my trouble shooting where I had discovered that the engine WOULD fire if I rotated the sparkplug 180 degrees to bring the spark closer to the valves. And immediately after I discovered that it would fire, I started loosing head gaskets. Multiple fixes were tried, but sadly there was no good way to fix it. Ultimately, I have decided to make a new cylinder and cylinder head. And yes, we're going to try something different. All of my previous i.c. engines have worked just fine using head gaskets made of 0.031" thick general purpose water pump gasket material. Now we're going to go away from conventional head gaskets and try our luck with a Viton o-ring head gasket. The two highlighted areas in this model indicate where the o-ring is going to go. These 1/16" o-rings actually measure 0.070" in cross section. The annular groove will be plunge cut with an 0.094" wide  cut-off tool and will be cut 0.018" deep in both the cylinder and the cylinder head. This will give me 0.034" of "squeeze" when the head is bolted to the cylinder. The fact that the groove is 0.094" wide will give the o-ring material somewhere to be displaced into when the head is fully tightened down on the cylinder. A day will make me a new cylinder, and the new cylinder design will leave more clearance between the base flange and the first "cooling fin" (I had a horrible time getting the bolts in that hold the cylinder to the vertical plate). There won't be much visual difference in the new design, except the top ring on the cylinder will be slightly larger in diameter, as will the head. I can probably make a new cylinder head in a day, but with Christmas it will probably be more like two days.


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## Gordon (Dec 21, 2021)

That means that you can go back to your original spark plug too.


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## mayhugh1 (Dec 21, 2021)

If you haven't already done it, I'd do some research on o-ring 'compression set'. Fifty percent compression is off the charts. - Terry


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## minh-thanh (Dec 21, 2021)

Hi Brian !


Brian Rupnow said:


>



I have a question :
Why don't you flatten the cylinder surface and cylinder head and use paper or similar as gasket ?


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## dsage (Dec 21, 2021)

I ditto what Terry has stated. You'll probably strip the bolts before you get the head fastened down. 
You'll want the head to fasten down until it touches the cylinder to get heat transfer.
10% of the material diameter (.07 x .1 = .007) squish would be plenty for a seal and even that much for a ring that diameter might be too much to compress easily.
As suggested, have a look at some charts on an O-ring manufacturer website for that usage case.


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## johwen (Dec 22, 2021)

Hi Brian, back in my early days as a Motor mechanic 50s 9I'm an old geezer). A make of English car with poorly designed cylinder head bolt spacing, they blew head gaskets frequently.
We removed the head and replaced the gasket but before installing same we painted the gasket both side with silver paint and never had one blow after that. Why not give that a try on your original head and cylinder. I would get some 5 thou thick copper shim and make a gasket out of that, some silver paint and I would be very surprised if that would leak. I personally do not use gaskets on small engines just some gasket cement (shellac)


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## mayhugh1 (Dec 22, 2021)

Brian Rupnow said:


> YES!!!!--That did it. Engine is now finally firing. Turning the sparkplug 180 degrees so that the spark was occurring closest to the valves done the trick.---I'm happy--happy--happy. Next amazing stunt will be getting an extended run and making a video.


Are you sure it was really a rotation of the plug gap? The brass washer might actually have sealed a leak between the plug and the head. If combustion really is sensitive to the rotation of the plug gap, that might be caused by the valve seats sitting so high in the combustion chamber. Also it looks like your head bolts are too close to the edge of the combustion chamber for a viable head gasket. One threaded hole looks like it may even have broken through. You may be leaking into the head bolts. If you haven't actually measured leak down or compression, the no-start problem may be due to a basic lack of sufficient compression. - Terry


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## Jasonb (Dec 22, 2021)

Could you not have just redone the head as it was originally drawn with the shallow recess. That way like many other engines the seal is on the narrow raised "ring" around the top of the cylinder or liner not the flat area beyond with the risk of pressure escaping up the screw holes as on yours now there is no seal from combustion chamber to these holes.

You don't even need a gasket with the head sealing against the narrow "ring" at least mine run that way, I think Keep it Simple is what they say.


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## werowance (Dec 22, 2021)

johwen said:


> Hi Brian, back in my early days as a Motor mechanic 50s 9I'm an old geezer). A make of English car with poorly designed cylinder head bolt spacing, they blew head gaskets frequently.
> We removed the head and replaced the gasket but before installing same we painted the gasket both side with silver paint and never had one blow after that. Why not give that a try on your original head and cylinder. I would get some 5 thou thick copper shim and make a gasket out of that, some silver paint and I would be very surprised if that would leak. I personally do not use gaskets on small engines just some gasket cement (shellac)



you can also pick up copper head gasket spray.  i use it on the non coated metal head gaskets on farmall super a and cultivision a tractors, else they leak every time.  but spray both sides of the gasket with that copper spray and let it "tack" up a bit then drop it on and bolt the head down and 0 leaks.  i get it at Napa Auto parts


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## Brian Rupnow (Dec 22, 2021)

So, here is the new assembly.--Looks just like the old assembly. The only difference is that the cylinder head and the very top of the cylinder are slightly larger than the previous version.


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## Brian Rupnow (Dec 23, 2021)

So, here we go. Out with the old cylinder and in with the new cylinder. You will notice that the new cylinder has a much wider "land" at the cylinder head end. This is to allow for the o-ring seal and so that the counterbored holes in the cylinder head don't break out past the edges of the cylinder head. You will also note that I have left much greater space between the bottom cooling fin and the mounting flange to make it easier to get that ring of bolts in place.


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## Brian Rupnow (Dec 23, 2021)

The new cylinder is finished and the o-ring groove is cut into it's mating face. I probably would have liked it better if the o-ring groove had ended up concentric with the bore, but when it's all buttoned up, nobody will see that. It won't have any effect on the way the o-ring seals.  That ring was machined in there with a 3/32" endmill while the cylinder was held in the chuck mounted on the rotary table. I might have ended up with a truer set-up if the cylinder had been mounted on a four jaw chuck in the lathe, but I'll remember that for next time.


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## stevehuckss396 (Dec 23, 2021)

Just asking Brian but shouldn't the width of the groove be about the same as the width of the oring? Seems like any leak in compression would force the oring to the outer diameter of the groove and possibly damage it by over stretching it. Maybe use an oring that fits the outer diameter of the groove? Am I over thinking?


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## Steamchick (Dec 24, 2021)

Hi SteveH... I agree, in principle, but the friction of clamping the O-ring may be adequate to prevent the combustion pressure forcing the o-ring out - to cause a leak. Brian will find out, and probably make a backing ring to prevent this if necessary?
Perhaps another "worry" is that the increased volume (at Top-dead centre  or compression at the ignition point) may well be considerably reduced by the extra volume created if the o-ring is permitted to expand so far, leaving an inner annulus of volume connected to the combustion chamber. May be a simple (if temporary?) fix would be to fill the gap outside the o-ring with Silicon Seal? - Cures to solid, remains elastomeric, manages relatively high heat, easy to clean-off afterwards, etc. - Just a thought...
K2


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## Jasonb (Dec 24, 2021)

Something not right with the sizes stated, if that is a 1/16" nominal ring then it is actually 0.070" wide in which case there is no way that groove is 3/32", looks more like 5/32"

Hopefully if the groove in the mating head gets cut to the stated sizes that may stop the ring moving about


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## Gordon (Dec 24, 2021)

Why do you need a groove in both the cylinder and the head? It would seem like full depth groove in either the cylinder or the head would work.


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## Brian Rupnow (Dec 24, 2021)

Gordon--You are right. A full depth groove in the cylinder or in the head would do, in fact that is what o-ring book suggests. However, since the ring is sealing against compression, I think that it would work best if the groove is partially in both. I haven't done this before, so I'm aiming for 50% compression of the o-ring when both surfaces of head and cylinder touch each other with the bolts torqued down. I will let you know how this works out.----Brian


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## Brian Rupnow (Dec 25, 2021)

Okay!!!---Christmas is over. Santa did come. Second son showed up for Christmas dinner and brought his new Ojibway girlfriend. (she is a very nice girl). Everybody else stayed home and "Christmassed" with their families---Too much Covid around for big family get togethers. When I put that o-ring groove in the top of the cylinder, I grabbed the wrong size endmill.---Poop!!! It has been fixed with a steel back-up ring to fill up the extra space, and now the groove is 3/32" wide to accept the 1/16" o-ring.. Work is proceeding on the engine. New cylinder is finished. New cylinder head is 3/4 finished.


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## Richard Hed (Dec 26, 2021)

Brian Rupnow said:


> Okay!!!---Christmas is over. Santa did come. Second son showed up for Christmas dinner and brought his new Ojibway girlfriend. (she is a very nice girl). Everybody else stayed home and "Christmassed" with their families---Too much Covid around for big family get togethers. When I put that o-ring groove in the top of the cylinder, I grabbed the wrong size endmill.---Poop!!! It has been fixed with a steel back-up ring to fill up the extra space, and now the groove is 3/32" wide to accept the 1/16" o-ring.. Work is proceeding on the engine. New cylinder is finished. New cylinder head is 3/4 finished.


I was reading about Ojibway and related languages.  Does she speak Ojibway?


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## Brian Rupnow (Dec 26, 2021)

I'm not sure Richard.  We are putting on our best face for her, and not asking too many personal questions. She is very pleasant and the relationship is still very new.


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## Richard Hed (Dec 26, 2021)

Brian Rupnow said:


> I'm not sure Richard.  We are putting on our best face for her, and not asking too many personal questions. She is very pleasant and the relationship is still very new.


My son speaks a bundle of languages which he, himself, took the initiative to learn.  I encourage him to learn one of the local Indigenous languages (most likely Colville or Spokane) but the problem is that the languages are not easy to get materials for unless one lives near a Jr. college that teaches that language which is basically near the tribes that originally spoke that language.   The Indians that at one time existed in Grant County, the great bend of the Columbia, no longer exist, not even on the res.  So there are no indigenous languages here.  He would have to travel 2 hrs each way to learn at a Jr. college.  What I would REALLY like him to learn is Navaho or Hopi as I like their cultural ideas.

The Algonkian group is your area which extends down to about Colorado, but is quite different at that place.  My local group are known as Salish.  It is a shame that we have lost those languages out of ignorance and the attempt to assimilate the Native Americans.  Had the Americas Known 150 years ago what we know now, this would not have happened.  At least there is an attempt to bring back the languages.  There is a lot of resentment amongst the tribes for this, and yet there are many who also realize it is not all bad.

I was reading about the tribes of Quebec demonsstrating a few years ago about their rights.  That information was kept out of the United States very effectively.  I might have gone myself.


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## Steamchick (Dec 27, 2021)

I grew up in a county whichhas been argued about since 1604. A Welsh bishop and Engish bishop both wanted tithes from Monmouthshire, so both argued and claimed the money! Currently the land is in Wales, but I was born when it was in England. I was in school when it was moved - for the 10th time? - so they decided to find someone to teach us the Welsh National anthem - in Welsh. Only 1 person knew a relative that could speak Welsh, so they got a tape recording and we learnt the Anthem. But now at Wales v anyone Rugby matches, they sing a different version, as I was taught "old" Welsh, not 1970s modernised Welsh!
So why do we try to resurrect "old" languages? Even the English of today is different from the 1950s and 1960s language I learned... 16th century English would be unintelligable to me now....
Of course, where languages have not been erased by history, the current (if radically changed) version is still valid. And it is good to raise children as bi-lingual, as they have a better ability to learn new languages later in life.
K2


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## Richard Hed (Dec 27, 2021)

Steamchick said:


> I grew up in a county whichhas been argued about since 1604. A Welsh bishop and Engish bishop both wanted tithes from Monmouthshire, so both argued and claimed the money! Currently the land is in Wales, but I was born when it was in England. I was in school when it was moved - for the 10th time? - so they decided to find someone to teach us the Welsh National anthem - in Welsh. Only 1 person knew a relative that could speak Welsh, so they got a tape recording and we learnt the Anthem. But now at Wales v anyone Rugby matches, they sing a different version, as I was taught "old" Welsh, not 1970s modernised Welsh!
> So why do we try to resurrect "old" languages? Even the English of today is different from the 1950s and 1960s language I learned... 16th century English would be unintelligable to me now....
> Of course, where languages have not been erased by history, the current (if radically changed) version is still valid. And it is good to raise children as bi-lingual, as they have a better ability to learn new languages later in life.
> K2


In the case of Britain, it is much like any other place,: stamp out a language, suppress a home rule movement.  That is very much the same reason it was done in this country.  But . . . native languages contained methods--in built in the language--for survival on the hunter gatherer level.  Information that is surely lost.  However, the pharmaceutical companies would certainly like to have at least one part of that language preserved.  When I was a kid (last week) there was a small bush across the road from our house which had little berries in clusters.  I asked my dad if we could eat them.  No, they were poison.  Well, it turned out these berries are related to all those fruits with pits that we know: peaches, cherries and most of all plums.  These little fruits have at least three names:  June Plum, Indian Plum and Osoberry.  Look up Oso berry and you will see it.  Turns out to be quite edible and tastes like cantaloupe, of all things. 

There are hundreds of fruits and plants and medical stuff if not more that their uses have been lost.  All across the Americas, I'm sure this is in the thousands of plants.  Don't forget the animals either.  You can eat crow if you forget.  The thing is, that the Indians would have been assimilated sooner or later anyway without being forced to learn English writing and ways.  It is quite the opposite way to do things.  We should have taught them writing--yes, but THEIR language.  Look what happened with we Cherokees when we learned to read and write Cherokee which ended in TWO trails of tears. 

This is an awful chapter of general/president jackson that is quite kept out of the history books.  I'm sure you would like to read about Chief Sequoia and what he accomplished and why we were crushed for no good reason.

Languages inherently have methods to thimpfk in different ways.  It is impossible to explain to those who know only one language, like what is he taste of the color blue (just joking, explain the colors to a blind person).  I could bore you with a couple hundred more pages, but then I's get spanked for being off topic.

Anyway, what's wrong with being taxed by two or three different authorities?  We get taxed in this country for everything we do except breathe.  They'll figure out a way to tax that too.  We get national tax, state tax, county tax, city tax, and because of all that, heart-a-tax.


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## Brian Rupnow (Dec 27, 2021)

The engine has been reassembled with a new cylinder, a new cylinder head, and a Viton o-ring head gasket. I'm not going to try and start it today, as I've just Loctited the carburetor into the brass adapter and I want it to set up good before I start messing with it. Somebody on one of the forums I post on has recently built a multi cylindered radial engine, and he said that he didn't put any angle on the valve seats, just left them sharp cornered, and that he got great compression with no lapping.  This didn't seem reasonable to me, but I thought "If it worked for him, maybe it would work for me."---It doesn't. Tomorrow I will pull the head off and use my magic George Britnell tool to put an angle on the valve seats the way I usually do. I'm getting awfully good at pulling the head of this engine.


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## stevehuckss396 (Dec 27, 2021)

So did you drop down to the 1/4-32 spark plug and save the 5/16 (rescue plug) for another time?


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## Brian Rupnow (Dec 27, 2021)

No, I am using the "rescue plug". I did pull the head off and used my George Britnell tool to put a chamfer on the valve cages, and then lapped the valves as per usual since my last post. Compression came up fine after doing that. New o-ring head gasket seems to be working fine. I've just came downstairs from eating dinner, and expected the engine to start . It didn't, and I'm not sure why. Valve and ignition timing are set right, lots of spark at the sparkplug when it's laying out on the deck, and it's getting lots of gas. I may have to pull the head off and see if the end of the sparkplug is too shrouded by the aluminum head material. I'll have to sleep on that one. I can counterbore the deck to let the plug intrude a bit more into the cylinder, or I can take some material out on the inside of the head. There isn't an awful lot of material with threads in it, and I have to be careful about what material I take out.


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## Steamchick (Dec 28, 2021)

On valve seats... Stick with what works for you.
You have so much experience, you know what makes sense. Otherwise I can't suggest what may be causing the lack of bangs... A richer mixture will often get things going, so then it is just a matter of tuning...?
K2.


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## Steamchick (Dec 28, 2021)

Or can you retard the ignition a bit until it fires? That does 2 things, It sparks when the compressed gas is more compressed and hotter, as often the cranking speed is lower than idle. And gives a better chance for running without kick-back. If you have an electronic trigger, it may not be getting a signal for the spark at cranking speed, with the plug in and proper compression slowing the cranking speed compared to when the plug is on the bench..?
K2


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## Brian Rupnow (Dec 28, 2021)

I'm using the 5/16"-24 that was made for me. Last night I lay in bed thinking---I don't want to mess with the head. That is the third head that I have made, it's a lot of work, and I don't want to make a fourth head. I have came up with a third way to get that sparkplug deeper into the combustion area without touching the cylinder head. If I can run the thread up another 0.100" on the plug body, that accomplishes what I want to do. That way I don't have to do anything to the cylinder head nor to the cylinder.


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## awake (Dec 28, 2021)

Brian Rupnow said:


> I'm getting awfully good at pulling the head of this engine.



Well, that's one way to get ahead ...


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## dsage (Dec 28, 2021)

Try starting fluid. It'll rule out quite a few things and get you going in the right direction quickly.


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## Brian Rupnow (Dec 28, 2021)

I ran a die all the way up to the hex shape on the sparkplug, which gained me about 0.100". That didn't help---engine still won't fire. Tried advancing the spark timing a little---engine won't fire. tried indexing the plug--engine wouldn't fire. Tried retarding the spark a little----engine won't fire. Got really, really desperate and tried some ether---engine won't fire. Took out piston with cast iron rings and put in a piston with viton o-ring---engine won't fire. Tried holding a spare finger over the carb air horn to choke it while spinning engine with my "starter-drill"---choked it until raw gas was coming out the exhaust.---engine didn't fire. I'm just about out of tricks. If I pull the plug and lay it out on the deck, plug fires like crazy while engine is being cranked. My sparkplug boot is transparent, and I can see fire jumping like crazy from the end of the wire to the top end of the plug when engine is being cranked over. (It wouldn't do that if plug wasn't firing.) Compression isn't real great, but then with these engines I build, the compression generally isn't great until the engine starts and runs for 10 or 15 minutes to seat the valves 100%--then they have crazy compression. Bottom line is, that in all of this head changing and sparkplug changing, the engine has only fired once and that was a result of indexing the sparkplug. It fired once and immediately blew the head gasket. Valve lash is set at "about" 0.010", valves are definitely closed when not up on the cam lobes. The internal shape of the combustion chamber is the same as countless other engines I have made, that ran successfully. I'm totally buffaloed for the moment.


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## johwen (Dec 28, 2021)

Time to try another coil or spark wire cable. It is obvious there is no spark at the plug under compression. This could be because the spark voltage is too weak to jump the gap under compression pressure. Try the ignition coil set up on and engine  you know runs and see if it starts. Close spark plug gap down to about .020" as if the coil is week it may jump a smaller gap.  If you have compression and fuel then the only other requirement is spark. If you have fuel and compression the only other area is spark not getting to the plug. John


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## minh-thanh (Dec 29, 2021)

Brian Rupnow said:


> Compression isn't real great, but then with these engines I build, the compression generally isn't great until the engine starts and runs for 10 or 15 minutes to seat the valves 100%--then they have crazy compression.


 
 The valve and seat will be more airtight when the engine is running I don't know but I think it depends on the valve surface and seat surface,
When I make the engine, I always try to make the valve and seat airtight from the beginning, If the piston, ring, cylinder is ok then the engine always has good compression from the beginning, then I only care about the ignition timing as well as the spark


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## Brian Rupnow (Dec 29, 2021)

So, here I am at the end of a 9 week build. To achieve this build in that time span required that I worked on some aspect of the engine every day of that 9 weeks. The engine looks good, I am satisfied with that. I am confused as to why the engine won't fire. There is nothing here that is different from all of my other running engines, other than the sparkplug. The sparkplugs are brand new, from a different supplier, and far be it for me to question  a brand new sparkplug. There is a possibility that the plug is shorting out internally, but if it was shorting out internally, then it would short out internally when laid out on the block. It doesn't. It gives a bright blue spark just like a good sparkplug should. My "need to machine something" has been satisfied (for now). Now I go into the detective phase of this build, and that is the part I don't really care for. I know I have fuel. I know I have compression. I'm not 100% sure I have spark. Even an engine with screwed up valve or ignition timing will fire when the engine is being turned by an electric drill. It may fire at the wrong time in the cycle, it may just give "pops and farts", but it will fire. You can hear it fire, and you can see smoke, and the cylinder will get warm. You can feel it kicking back against the drill when it fires. I'm undecided where this will take me now, but I will be sure to keep you informed.---Brian


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## Gordon (Dec 29, 2021)

I don't want to question your conclusions but I have had similar situations where the battery was too weak to produce a good spark under compression. Check to be sure that your battery is at full charge. Perhaps use your battery/ignition box on another engine. If the other engine runs it almost has to be the spark plug.


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## Brian Rupnow (Dec 29, 2021)

The sparkplug is not leaking around the threads. Someone on one of my forums didn't believe me when I said that the engine did have adequate compression, so they wanted a visual on it. Here it is. This doesn't get me anywhere closer to having the engine run, but it is kind of a fun video.


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## stevehuckss396 (Dec 29, 2021)

I sent 2 plugs. Have you tried the other one? If so the plug with the smaller gap would be my preferred plug. I test every plug before they leave here. I have also had that design in my peewee for 11 years and they still work very well. I stand behind my plugs so if you think that is the problem I can have replacement plugs in the mail in just a few days at no charge. I will even cover the postage.


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## Brian Rupnow (Dec 29, 2021)

Steve--I don't know what is going on. Your plugs fire fine when laying out on the cylinder, and I have no real reason to believe that they aren't firing under compression. I'm trying hard to figure out what is happening. I've tried both the plugs you sent me with no difference in what is going on. Something is happening that I don't understand. I will find my way thru it, I don't think that the problem is with your sparkplugs.---Brian


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## Brian Rupnow (Dec 29, 2021)

The engine just ran!!! God loves me after all. When all probable things have been tried, it is time to try the improbable. There was only one thing left to try that didn't involve machining something. I kept getting mixed signals about whether the sparkplug was really sealing against compression leakage or not.----So----Ten minutes ago I backed out the sparkplug, coated the threads with green 638 Loctite, then reinstalled the plug. Waited ten minutes and engine started up and ran like a trooper. I will get a video up tomorrow morning. I am so relieved.


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## Brian Rupnow (Dec 29, 2021)

638 is my "go-to" choice for Loctite. It is an excellent sealant, but releases very easily with a bit of torque. Like I said, all of my engines run---eventually. Some run right away and surprise me. Some require much thought and fiddling with. Out of about 20 engines, I haven't seen this happen before. I keep thinking that if I build enough of these small engines, I will get to the point where I can diagnose whatever is wrong and fix it immediately.  The most difficult thing is knowing that everything is adjusted and set properly, and still the engine won't run. Thank you all for your suggestions and your interest.


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## Richard Hed (Dec 30, 2021)

Brian Rupnow said:


> 638 is my "go-to" choice for Loctite. It is an excellent sealant, but releases very easily with a bit of torque. Like I said, all of my engines run---eventually. Some run right away and surprise me. Some require much thought and fiddling with. Out of about 20 engines, I haven't seen this happen before. I keep thinking that if I build enough of these small engines, I will get to the point where I can diagnose whatever is wrong and fix it immediately.  The most difficult thing is knowing that everything is adjusted and set properly, and still the engine won't run. Thank you all for your suggestions and your interest.


I am very surprized by that.


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## Jasonb (Dec 30, 2021)

The other 20 engines had commercial plugs with sealing washer, I raised the sealing issue as soon as I saw photos of the new plugs, Steve is not at fault as he just made them to the design he was sent.

Likewise 638 should not release easily but could be weakened by the heat of a hot cylinder head, it is really a retainer, for sealing and stopping threads coming lose use a studlock or thread sealant then less chance of stripping the head if you need to remove the plug


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## Steamchick (Dec 30, 2021)

Well done Brian, Obviously your accumulated experience got there in 10 minutes, where many of us would spend 10 days.... Is there a wway to fit a copper shim washer as a seal for the spark-plug? Many years ago, I had a motorcycle that had a "poor" seat fro the spark-plug to seal. I used copper washers - that were a thin-walled tube - which were very successful. But maybe a regular copper shim washer will suffice? (Or even a paper gasket washer?). I have used PTFE thread tape on many a gas connection that is otherwise "iffy". Takes cylinder head temperature as well.
Whatever works for you is fine.
K2


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## johwen (Dec 30, 2021)

The High tension Voltage goes up as the compression is raised and Likewise goes up when you increase the gap of the plug. You could try a couple of extra  battery volts as well. Just make one change in the ignition at a time so you can Isolate what is causing the problem, but it has to be lack Of spark Cheers John.


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## GailInNM (Dec 30, 2021)

Brian,
Is there any possibility that your fuel has become accidentally contaminated. I fiddled and fussed for a couple of hours trying to get a known runner started before discovering that I had been using some of last seasons fuel.
You might try running one of your known good runners with your fuel to make sure. Seems like you have tried most everything else at this  point.
Gail


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## Brian Rupnow (Dec 30, 2021)

The fuel I used was new fuel. The battery is fully charged. There is nothing wrong with Steve Huck's sparkplugs. they work fine. I had Steve make two "special" plugs for me, and I knew there was very little shoulder on these plugs to snug down against the top of the cylinder. I didn't think they would leak around the plug threads, but I was wrong. We live, we learn.


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## Brian Rupnow (Dec 30, 2021)

So, here we are. The culmination of a two month thrash!!! I had a few problems sorting out a reliable head gasket, but solved that by going to a Viton o-ring head gasket instead of the treated cardboard that I have used on previous i.c. engines. I had major issues getting the engine to fire, but traced that back to leaking threads around the sparkplug. There was nothing wrong with the sparkplug, it was my funky threads in the cylinder head that were causing me grief. Once I got that sorted, the engine ran like a race-horse. These Traxxas carburetors have the touchiest throttle lever in the world. That throttle is intended to be operated by a servo, so is very touchy indeed. That is why during the video my finger doesn't leave the throttle lever--if I take my finger off the throttle the engine tries to run wide open and scares me half to death. I miss-spoke in the video and said the motor has a 1" stroke---that's not correct, it is actually 1 1/4" stroke. I will sell these plans (about 50 sheets) for $25 paid to my Paypal account. Contact me if you want to purchase a set of plans. Thank you for following my build on the forum.---Brian Rupnow


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## GailInNM (Dec 30, 2021)

Congratulations, Brian.
Glad you got it all sorted out.


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## CFLBob (Dec 30, 2021)

Conrats, Brian.  

Going through the engine as you did - while we watched - reminds me of that Sherlock Holmes quote, "once you have eliminated all the rational causes, whatever remains must be considered, regardless of how improbable it may be."  Eliminating the valves, the timing, the position of the spark gap and everything else left the compression leaks around the spark plugs.  

(I've probably butchered the Sherlock Holmes quote - but it's like that).


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## Brian Rupnow (Dec 30, 2021)

Bob-I was thinking of Sherlock when I wrote that.


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## Brian Rupnow (Dec 30, 2021)

Tomorrow I'll make up a "Casey Jones" throttle lever and linkage from it to the carburetor. A couple of Belleville washers between the throttle lever and the baseplate will add enough friction to keep the throttle from vibrating out of place.


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## Brian Rupnow (Dec 31, 2021)

Today, after some minor tweaking and tuning and the addition of a Casey Jones style throttle lever, the engine is running much more sedately. The folks who I generally buy Belleville washers from are temporarily out of stock, so even with the addition of my throttle lever the engine wants to "creep" to a higher rpm.--That gets scary as heck when the engine pulls the throttle wide open. My next trick will be to add the piston with cast iron rings and see how well it runs.---Brian


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## stevehuckss396 (Dec 31, 2021)

Hey Brian. Maybe try a throttle with a spring. Then you can rev when you want and it will return to idle when unattended. Also easy to adjust idle just by screwing the shaft in and out of the ball socket piece.


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## Brian Rupnow (Dec 31, 2021)

Thanks Steve---I didn't use a spring because I am going to use this engine to power something else. I like to have my throttle set up so I can advance it against a load and leave it advanced to keep the engine from slowing under load and stalling out.


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## ShopShoe (Jan 1, 2022)

Brian,

That's running beautifully now. From reading all your adventures with this engine, I take your "I'm Happy" as quite an understatement. We're all happy that you have arrived at a good place with this engine.

I like, the look, the sound, the finish, and the whole package you have made here.

--

Is there a chance you could make a "sandwich" of washers made of different materials to provide enough friction to prevent the throttle from creeping? I've been able to do that in the past, but not in anything so fiddly as your throttle.

--ShopShoe


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## Brian Rupnow (Jan 1, 2022)

Hi Shopshoe---Happy New Year--I have some Belleville washers on order, they will be here this week or next. The trouble with stacking washers is that the pivot bolt at the bottom of the throttle arm will unscrew if you leave it free enough to move by hand. If you tighten the screw so it doesn't vibrate out of position, then it is too stiff to operate with your fingers.---Brian


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## L98fiero (Jan 2, 2022)

Brian Rupnow said:


> Hi Shopshoe---Happy New Year--I have some Belleville washers on order, they will be here this week or next. The trouble with stacking washers is that the pivot bolt at the bottom of the throttle arm will unscrew if you leave it free enough to move by hand. If you tighten the screw so it doesn't vibrate out of position, then it is too stiff to operate with your fingers.---Brian


It appears that the carburetor throttle has a square to locate the arm, why not rotate the arm 90° and place your Casey Jones style throttle lever 90° to the engine cylinder, I suspect the vibration of the running engine is parallel to the cylinder which is why the level moves in the first place.


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## Brian Rupnow (Jan 3, 2022)

When you can take a heat treated ring and bend it like this, it's a pretty good indicator that you have used the wrong cast iron to make the ring. It will also bend like that before heat treat. It will work as rings---I have two engines operating quite fine using rings made from this material.  Today I am going to use the two remaining cast iron rings that were made in that batch to see if they will run my engine. I am also going to take steps to buy the correct cast iron for ring making. My local supplier doesn't know squat about the cast iron he is selling.


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## Gordon (Jan 3, 2022)

I am interested in what you find on the correct cast iron. Trimble says centrifugally cast moly iron but nobody seems to knows what that is. Others seem to use whatever junk they can find and everything works just fine. I am not against spending a little more money if it gets good results but I don't know what to ask for or where to get it.


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## werowance (Jan 3, 2022)

i wonder if the the guy at otto engine works that supplies the rings for the webster would be willing to share what CI he uses on his rings?


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## Brian Rupnow (Jan 3, 2022)

I have spent the morning googling, and the top choice for iron to make rings from is Grade 17 Meehanite. I have been searching for a source for it in Ontario, but haven't found one yet.---Will keep you posted on what I find.---Brian


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## aka9950202 (Jan 4, 2022)

My Webster rings we made from the  rear brake  cylinder of a mini. I know that they would be good quality metal. 

Should I  do it again  I would make  a mandrel to match the inside bore, super glue the brake cylinder them turn the outside round. Last time I used the 4 jaw chuck and it was a pita!

Cheers, 

Andrew in Melbourne


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## Brian Rupnow (Jan 4, 2022)

A little help here please--from North America--I have determined that the material I am using for piston rings is the wrong kind. I buy it from a local steel supply shop and they don't really seem to know much about the cast iron which they are selling me. I am sure they are selling me ductile iron, because when piston rings are made from it, they bend easily. Not break!!! Even after heat treat they bend. I have just about worn out the internet this morning searching for correct ring material. My research tells me that cast iron material for rings should be A--Pearlitic grey cast iron with a low modulus of elasticity.  B--centrifugally cast, not ductile  C--Durabar cast grey iron  D ---fine grained grey cast iron  E--pulltruded .
If you live in the U.K. you should use class 17 Mehanite  (I don't live in the U.K.)
 I need a foot of this material in 1" diameter (well actually it's a bit more than 1" because it is cast) but I am having a terrible time figuring where to buy this stuff in Canada. It's heavy, so shipping charges will be high. If I buy from USA and can get a foot of the proper material I can probably eat the shipping cost. What I really need to know is where the heck I can buy this material (preferably in Canada but USA will do).---and what exactly is it that it's called when I go to order it?---Brian Rupnow


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## L98fiero (Jan 4, 2022)

Brian Rupnow said:


> A little help here please--from North America--I have determined that the material I am using for piston rings is the wrong kind. I buy it from a local steel supply shop and they don't really seem to know much about the cast iron which they are selling me. I am sure they are selling me ductile iron, because when piston rings are made from it, they bend easily. Not break!!! Even after heat treat they bend. I have just about worn out the internet this morning searching for correct ring material. My research tells me that cast iron material for rings should be A--Pearlitic grey cast iron with a low modulus of elasticity.  B--centrifugally cast, not ductile  C--Durabar cast grey iron  D ---fine grained grey cast iron  E--pulltruded .
> If you live in the U.K. you should use class 17 Mehanite  (I don't live in the U.K.)
> I need a foot of this material in 1" diameter (well actually it's a bit more than 1" because it is cast) but I am having a terrible time figuring where to buy this stuff in Canada. It's heavy, so shipping charges will be high. If I buy from USA and can get a foot of the proper material I can probably eat the shipping cost. What I really need to know is where the heck I can buy this material (preferably in Canada but USA will do).---and what exactly is it that it's called when I go to order it?---Brian Rupnow


Call Terra Nova Steel & Iron, 3595 Hawkestone Rd, Mississauga, ON L5C 2V1, (905) 273-3872, they are distributors for Durabar


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## Brian Rupnow (Jan 4, 2022)

I talked to Bernie at https://hobbymetalkits.com/ and this man seems to know what he's talking about. I ordered a foot  of the 1" diameter cast iron which meets all of the specs for making rings.  The material itself is only about $14, USA but the shipping from Wisconsin is going to be horrendous. This will last me for the rest of my life making rings. I'm sure that there are companies in Ontario that sell exactly the same material, but I haven't been able to find them or contact them.


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## CFLBob (Jan 4, 2022)

FWIW, I've had good luck with Hobby Metal Kits in overall quality, fast shipping and all that.  

The only issue I've had is they tend to have a smaller selection than either Online or Speedy Metals.  If Bernie told me he had an alloy that was good, I'd trust him.


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## dnalot (Jan 4, 2022)

Hi

I use cast iron from McMaster Carr and it makes very nice rings. their smallest rod is 1.25 inches and cost is about $17 for 12". 

Mark T


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## L98fiero (Jan 4, 2022)

dnalot said:


> Hi
> 
> I use cast iron from McMaster Carr and it makes very nice rings. their smallest rod is 1.25 inches and cost is about $17 for 12".
> 
> Mark T


McMaster-Carr doesn't sell to individuals in Canada, with few exceptions, you have to be an educational institute of some sort or a business.


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## dnalot (Jan 4, 2022)

L98fiero said:


> McMaster-Carr doesn't sell to individuals in Canada, with few exceptions, you have to be an educational institute of some sort or a business.



That sucks. I refuse to buy from a business that refuses to sell to me.

Mark T


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## dsage (Jan 5, 2022)

Brian:
Read back a bit (post 247)
L98fiero gave you a place in Mississauga. That's where I get it and all the model makers in the Toronto and Hamilton  clubs go there too. You could drive there.
They usually deal with BIG quantities but I have walked in the door and picked a piece from their cutoffs. If you walk in I suggest you should take what you can get (size/length) within reason. Rather than bother them with cutting. They don't usually deal with small quantities but they have been accommodating. If you order it ahead you should have no problems with any order. Order it as a cash sale. They usually deal with their account customers. But I've had no problems.

From above:
Call Terra Nova Steel & Iron, 3595 Hawkestone Rd, Mississauga, ON L5C 2V1, (905) 273-3872, they are distributors for Durabar


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## Brian Rupnow (Jan 5, 2022)

dsage--Sometimes living in Barrie is like living on the dark side of the moon.  Mississauga is an hour away from me and I have never heard of Terra Nova Steel and Iron and I'm buying something that I'm not 100% sure of what to ask for. The man I bought my cast iron from specializes in metal for model engines, and when I spoke to him he knew exactly what I wanted. I may die of a heart attack when I see what the shipping charges are from Wisconsin, but at least I will know that I ambuying the correct material.---Brian


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## Gordon (Jan 5, 2022)

Is the problem with shipping costs to Canada due to actual shipping costs or duty coming into Canada. If it is duty could someone in the US receive it and reship it? I am not familiar with the relationship between USPS and Canada Post.


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## Brian Rupnow (Jan 5, 2022)

Today is a "machining free" day.  Hooray!!! My little machine shop doesn't have a spare inch of room anywhere in it. I wanted to have some dedicated cabinets for small bits and bobs that were important, and didn't have room for anymore cabinets inside my shop. I didn't want them too far away either. A quick survey of the wall space I had available outside of the machine shop showed that I had a 12" wide area of free wall space between my shop door and the wall adjacent to it. A quick search thru the Princess Auto website showed  almost exactly what I wanted 11" wide for $14. I bought two of them and mounted them in the wall space, and spent a good part of this morning moving  things and making labels so I would know what was in the cabinets. As much as I like machining things, it's quite nice to have a rather laid back day where I do something else that needed doing.


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## Brian Rupnow (Jan 5, 2022)

Gordon--I have to spend $1.27 to buy one USA dollar. Shipping from USA to Canada costs anywhere from $15 to $45 depending on the weight and size of the thing being shipped. If the border authorities get involved and decide that my package may be full of illicit drugs, they open it and charge me $50 for border inspection. Then I have to pay %13 sales tax for being a good Canadian boy. Canada is a great place to live, but it isn't cheap.----Brian


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## Iampappabear (Jan 6, 2022)

Resource Metals in Oakville supply Class 40 cast iron, they will happily sell to the general public and are and easy group of guys to deal with.

Home

I have been very please with the cast iron purchased there but no idea how it would perform as piston rings.


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## Brian Rupnow (Jan 6, 2022)

And now---I have a strange story to tell (but it has a happy ending). Couple of days ago I had the engine setting on my side desk, chugging away happily, and I was congratulating myself on what a clever fellow I was to build an engine like that. And then----it quit!!!
Well Poop!!--Must be out of gas. Opened my fancy blue gas tank, and it had lots of fuel. Okay, if it isn't fuel. it has to be spark. I pulled the sparkplug out and laid it on the cylinder head and cranked the engine. Lots of spark!! Well sir--What do I do now? The automotive gasoline in the tank had been changed out for Coleman fuel, because Coleman fuel doesn't stink when it's being burned. Maybe the engine was seizing up, but I've never really had that happen. I grabbed the flywheel and gave it a couple of spins, and it turned freely, so determined that the engine hadn't seized. Maybe the set screws in my ignition cam had slipped and the engine had "jumped time". Checked those screws out and they were tight. Maybe the set screws in one of my timing gears had slipped and the valve timing had gone screwball. Checked those set screws and they were still tight. Maybe the Viton piston ring had failed and I had lost compression--but no, engine still has terrific compression when turned over by hand. Maybe something wrong with the carburetor--but no, those carbs don't have any small moving parts that can fail or vibrate out of place. How strange!! My engine won't run, and I can't diagnose what is wrong. Had some serious thoughts about making another head with a vertical sparkplug in it (A 1/4-32 sparkplug would fit beside the valve cages)--I laid it out on my 3D program and it would work, but Damn, there's a lot of work in making a cylinder head. I looked at my files from ten or eleven years ago when I built my own sparkplug for the Kerzel engine, but I really didn't want to do that. Went to bed, disgusted with small engines in general. Today I thought, "If the engine ran okay (which it did) and the engine then stopped without any clanks or bangs or obvious signs of distress (which it did), then what can possibly have changed? I pulled the sparkplug out and looked at it under my lighted magnifier, and seen that the spark gap was only about .005". Enough to give a bright spark when laying out on the cylinder head but not enough to light the charge of fuel under compression. Fetched out my trusty jacknife and opened the gap to about .025" and reinstalled the plug. Engine started right up and ran like a race horse. Relief, relief!!! I have no idea what closed the spark gap up while in the engine. Maybe a piece of dirt from when I was trying the piston with the cast iron rings. Maybe it was the bad engine fairy.--I don't know, but man, I'm glad I got it sorted out without having to remake anything.


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## Brian Rupnow (Jan 6, 2022)

Lampapabear--thank you. I will give them a call.---Brian


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## Brian Rupnow (Jan 7, 2022)

Today I'm just piddling around putting in time. I had to look thru all my various bins of junk to find something, and what I actually found was a plethora of pistons. I see two with Viton rings, one with cast iron rings, one with no rings, and one that had been lapped into a cylinder without even any ring grooves. I have no idea why I saved these, nor what was wrong with them. I guess it's part of the "Never throw anything out" syndrome that I have. I'll keep them. Most of them have a thick enough wall that I could perhaps use them in an engine with a 31/32" bore some day.


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## werowance (Jan 7, 2022)

Brian,  if you are looking for a project may i humbly suggest the brass stirling 60 done in Rupnows imperialized version.   not that i am looking for redrawn plans in imperial sizes for it or anything wink wink.  

but seriously the piston with 2 rings on it already install sort of looks like the webster piston?


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## Brian Rupnow (Jan 7, 2022)

werowance--Do you have a link to build plans in metric or a running model/--Brian


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## werowance (Jan 11, 2022)

Hi Brian,  sure do - page 8 (plans-for-everything.com) 
and if you do decide to imperialize it ill definately purchase a set from you.
and i should also say nice build on this engine.  i like the thought of using an oring as a head gasket.  nice build


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## Brian Rupnow (Jan 11, 2022)

werowance--No, I won't be building that engine. It looks very nice, but it's not my kind of thing. I have built one Sterling engine a few years ago, and it works great. I will try to find a link to it.--Brian


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## werowance (Jan 12, 2022)

Thanks Brian


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## Brian Rupnow (Jan 13, 2022)

I'm not finished with this engine yet. I'm waiting for a length of the right kind of iron for making rings to arrive here from Wisconsin. In the meanwhile I've been tidying up my shop, putting away tools, and changing a stripped nylon gear on my milling machine and adding a lever/lock I designed to my mill to keep it from jumping out of low gear. ---And, having my first experience with annular cutters. After a bit of confusion on my side (ordered three of the wrong R8 holders, returned them and bought one of the correct holders for the annular cutters) I am most impressed with the way these annular cutters work.


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## Brian Rupnow (Jan 15, 2022)

Today I went digging thru my stock of brass, and found a length of 1.25" diameter brass. This will be big enough to make a 7/8" external lap from. I may make a new piston from cast iron, and lap it to be a very precision fit into the cylinder bore. This will definitely help with the compression issues. I will still make new cast iron rings for the piston, when my length of cast iron specifically for making rings from arrives here from Wisconsin. Right now my aluminum piston has about 0.002" diametral clearance in the cylinder. I should be able to bring that down to 0.0002" diametral clearance  with the lap and a cast iron piston.


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## CFLBob (Jan 15, 2022)

Thanks for that.  You reminded me of a place where I could use something similar.

Totally unrelated, but ideas tend to work that way.


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## Brian Rupnow (Jan 15, 2022)

So---this is the external lap for a 7/8" piston. It is drilled and reamed to 0.875" thru. I've stuck a 7/8" piston into one end of it for "show and tell". In actual use, there are no rings installed on the piston. The sawcut lets it open to greater than 0.875", and lets it close to less than 0.0875". The single shcs in the center provides the clamping force to close it. In use, the piston is mounted on an arbor of lesser diameter that fits into the counterbore in the piston and cross-pinned thru the piston pin bore, and is held in the lathe chuck. The brass lap is coated with 600 grit lapping paste on the inside and held in your hand, and is worked back and forth on the rotating piston at about 70 rpm. You start with a slightly oversize piston and work it with the lap until it will just fit (somewhat tightly) into the cylinder. then everything is disassembled and brushed with dishsoap and an old toothbrush to clean away any remaining lapping paste. You have to be ready to quickly let go of the lap if it "grabs". Don't want your arm wound up in the lathe!!! If it does "grab", you let it go, shut off the lathe, and then walk everything out to your bench press, press the piston out, then back into your lathe to finish it up.


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## Brian Rupnow (Jan 16, 2022)

When I made this external lap, I reamed it with a 0.875" reamer. After I put in the saw cut, it closed up a bit  due to internal stresses in the brass and reads about 0.870". Next step will be to coat a piece of 7/8" round cold rolled in my lathe, add some lapping compound to it, and lap to an even 0.875" inside diameter. At that point I will tighten the cross bolt and close the sawcut up a bit more, and again lap it on the 7/8" diameter rod until I reach a point where the i.d. is 0.880" inside diameter when the clamp screw is backed off. This way I can make my piston .002" to 0.003" oversize, then using my external lap and lapping paste bring the piston down to an exact 0.875" diameter for a snug fit inside the cylinder.


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## Gordon (Jan 16, 2022)

Why do you want to lap the piston? Compression is dependent on the rings, not the piston. Unless you are trying to run without rings the size of the piston, within reason is not important. Unless you have a perfectly lapped piston and a perfectly lapped cylinder compression is determined by the rings.


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## Brian Rupnow (Jan 16, 2022)

Gordon--I have an aluminum piston with cast iron rings, and the piston is 0.002" less in diameter than the cylinder bore. The rings are "almost good enough" but not quite. They do hold compression but not enough for the engine to fire. By reducing that .002" piston clearance down to almost nothing, there will be less room for compression to leak down past the rings. Also, by making the new piston from cast iron , same as the cylinder, I won't have the differential expansion that will make an aluminum piston "grow" inside a cast iron cylinder when heated up. Cast iron has enough free graphite in it's metallurgical make up that it will generate less wall friction than an aluminum piston.


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## Gordon (Jan 16, 2022)

Brian: You may be right but there must be some reason why in almost all cases they are using alum pistons in a CI cylinder. I would be inclined to think that the problem is with the rings, not the piston. I will be interested in seeing your results.


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## Brian Rupnow (Jan 16, 2022)

Gordon--I am pretty sure they use aluminum pistons because of the tremendous weight difference, an aluminum piston only weighs 1/3 of a cast iron piston. This great reduction in mass lets the engines rev hire and be much more responsive to the throttle .


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## Gordon (Jan 16, 2022)

I am also kind of running an experiment here. I am back to working on my Atkinson Differential engine. I can get it to run for 15 seconds and then die. I am sure that the problem is compression. Compression on this engine is marginal even if everything is done exactly right. I have made probably six attempts at making rings for this engine. I finally decided to purchase a set of rings from Otto (Dave Reed) to see if that works better. These rings are 3/32 wide instead of .040 but the thickness is about the same at .055. The gap in the rings is quite a bit wider than on the ones I made. They are quite a bit stiffer. They are going to have more drag but hopefully better sealing. I am also thinking about a heavier flywheel. The present flywheel is aluminum, and I am not sure if additional inertia wins or more power to turn it wins.

OK Enough of stealing your thread. Sorry. Back to my cave.


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## Jasonb (Jan 16, 2022)

Brian Rupnow said:


> Cast iron has enough free graphite in it's metallurgical make up that it will generate less wall friction than an aluminum piston.



That lump of ductile iron you are using won't have anywhere near as much free graphite in it as the grey iron you are waiting for.


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## Brian Rupnow (Jan 16, 2022)

Thank you for that Jason. I didn't know that.---Brian


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## Nikhil Bhale (Jan 17, 2022)

Hi Brian,
What if you machine some oil grooves below the piston ring groove. Small size V grooves to hold the oil on piston. Maybe it will help in reducing leakage past the piston, improving compression.

Regards
Nikhil


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## mayhugh1 (Jan 17, 2022)

Nikhil Bhale said:


> Hi Brian,
> What if you machine some oil grooves below the piston ring groove. Small size V grooves to hold the oil on piston. Maybe it will help in reducing leakage past the piston, improving compression.
> 
> Regards
> Nikhil


Or, make the rings the correct size?


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## Brian Rupnow (Jan 17, 2022)

Mayhugh--you may have different information than I do. What size do you think the rings should be.--Brian


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## stewart drummond (Jan 17, 2022)

rings correct size (tension in cylinder), correct (proportional to cylinder) ring gap , honed & crosshatched cylinder , lubricated cylinder (splash,drip fed ,anything but dry cylinder wall) , but 'piston material to increase compression'? thats not really how these things
 work


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## mayhugh1 (Jan 17, 2022)

If you're putting cast iron rings on an aluminum piston, the piston diameter should be 1-1/2 to 2 thousands less than the bore diameter. The installed cast iron rings should be exactly the same size as the bore within a few tenths. The rings must be round and contact the cylinder wall all around for maximum compression. How to accomplish this is covered in the Trimble articles you already have as well as in numerous ring-making posts in various builds on this and other forums using the same method. 

If you can hold tenths with a toolpost grinder, use it to grind the blanks for your rings rather than a cast iron piston. Most of us, though, turn the ring blanks to within one or two thousandths of their final diameter and then polish using 400g - 600g paper to get the final OD with a great surface finish to boot. You also should be making all your measurements with a micrometer if you aren't already. Calipers just aren't accurate enough for piston ring work. - Terry


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## Brian Rupnow (Jan 18, 2022)

Okay--Back to the external lap. When I made this lap, I drilled and reamed it with a 7/8" reamer, and it was a perfect 0.875" i.d.  Then after I put the sawcut in it, it closed up to something less than 7/8". I thought about this for a while and decided to set it back up in my mill and run the reamer thru it again. That worked, but the lap still wanted to close up a bit. I mounted a piece of 7/8" cold rolled steel in the lathe and turned a 1 degree taper on it. Then I coated the cold rolled with 600 grit aluminum oxide paste and with the lathe turning about 70 rpm I worked the lap back and forth  slowly over the tapered end by hand until it slid freely over the 7/8" cold rolled steel shaft. This was done without the clamp screw in place. After it slid freely over the shaft, I took it out to my bandsaw and ran the blade thru the existing cut again. Then back into the shop to run it over the shaft a few more times to knock down any internal burrs from the sawcut. Cold rolled steel comes in about half a thou undersize, so I know that at this point my lap is 0.8745" inside diameter. Next step will be to gradually tighten the clamp bolt and continue running the lap over the cold rolled with the 600 grit paste. When the clamp bolt has been tightened up enough to close the sawcut, then I know that when I release the clamp bolt the lap will spring open to something greater than 0.875". Not sure how much greater, but then it will be at a point where I can begin lapping my cast iron piston from "oversize" to a "perfect fit" in the cylinder.


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## Brian Rupnow (Jan 19, 2022)

The external lap is finished. When the clamp bolt is loose, the lap measures about 0.880" inside. When the clamp bolt is tightened, it measures 0.870" inside. I will machine my cast iron piston to 0.880" diameter, and then with the lap I will lap it down to a point where it is a snug fit into the cast iron cylinder.


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## Brian Rupnow (Jan 20, 2022)

A bit of explanation now, on what I've been doing. I was very surprised when the engine didn't want to run with the new cast iron rings I made for it. And then, I figured out that I had used the wrong kind of iron to make the rings from. This was surprising, because the rings were made from the same stick of iron that made two or three sets of rings that did work in the engines they were made for. The shop I buy my iron from didn't seem to know if this was ductile iron or the other type of iron. I found out after the fact by seeing how easily the rings bend.  My current piston is aluminum and is 0.873" diameter, riding in a cast iron cylinder. When the engine wouldn't run, I made a second aluminum piston the same diameter with a viton ring for a reality check, and the engine ran fine with a viton ring. I then ordered a stick of the correct type of iron for making cast iron rings from Wisconsin, and it showed up here yesterday. I have a choice now--I can make new rings and put them on the existing aluminum piston----or---I can make a new cast iron piston which is a closer fit in the cylinder and put new cast iron rings on it. This is why I made the brass external lap, to lap the new cast iron piston so it would be a closer fit in the cylinder.-not an air tight seal, but much closer to it than the aluminum piston was. I'm not worried about thermal expansion, because the piston and cylinder will be the same material so if the piston grows a bit from heat, the cylinder will grow as well so it shouldn't seize on the piston. At the same time I was waiting for my new iron, I started a new thread about the possibility of using my Toolpost Grinder from Little Machine shop to grind the piston to the exact outside diameter instead of lapping it. I got so many varied answers to that question that I decided not to do it. So, armed with the knowledge I have collected, I will now make a new lapped cast iron piston from the old stick of cast iron from my local supplier and new cast iron rings from the new correct material from Wisconsin.


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## minh-thanh (Jan 20, 2022)

Hi !
I know you have measured the inner diameter of the cylinder
, but ...maybe...try making a ringless piston, and test it with the cylinder , if they have good compression, it means your cylinder is fine and just focus on the rings or grooves on the piston.


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## Brian Rupnow (Jan 20, 2022)

Meet the new piston--Looks an awful lot like the old piston. However, it's made of cast iron, not aluminum, and it's 0.003" larger in diameter than the old piston (the one with rings on it).  I had hoped for 0.005" larger in diameter, but you work with what you get. If it works better than the old piston, we're golden. If it doesn't, I had the material anyways and it's 2 1/2 hours out of my life that I can spare. Sometimes I'd swear that my lathe is bewitched.--It never takes off less than I wanted it to, but frequently takes off more!! Tomorrow I'll make some new rings and heat treat them.


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## Brian Rupnow (Jan 20, 2022)

Things didn't go the way I had it planned. My plan was to turn the new piston to about 0.880" diameter, and then use my external lap to bring it down to around 0.877" for a snug fit into the cylinder. On the last pass, which was intended to bring the piston down to 0.880"', the machine Gods laughed and when I measured the piston with my micrometer it was 0.876". Didn't leave enough on the diameter to even bother using the lap. I think it's probably time to pull the topslide off my lathe and tighten up the nut which the cross-feed screw engages with, and then tighten up all the gibs. The new piston is good enough to use, but I would have been happier if things had worked out the way I planned.


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## Jasonb (Jan 21, 2022)

What are you measuring the bore with ? a few posts up it was "a perfect 0.875" ?

Brian, did you read my post earlier about TCGT inserts or sharp HSS, you will be able to sneak up on the size far easier with them as a standard TCMT insert being blunter tends to ride over the surface when a small cut is applied until you sudden lt find it cuts but will be several times more than the feed.

Two small grub screws in the back of the cross slide nut to adjust backlash but that is not likely to be the cause of your overcutting.


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## Steamchick (Jan 21, 2022)

Jason, re: your post earlier _"about TCGT inserts or sharp HSS, you will be able to sneak up on the size far easier with them as a standard TCMT insert being blunter tends to ride over the surface when a small cut is applied until you sudden it find it cuts but will be several times more than the feed."_ = an interesting theory.
I think I have experienced that.
But I have also taken to honing a razor sharp edge on the tungsten carbide inserts - especially blunt worn inserts - to get a bit more work from them. I use a diamond hand dresser or diamond wheel. That sharp edge seems to make them much more controllable. I have brazed various broken segments from inserts onto square steel bars to make my own tools - very successfully. Especially useful on some incredibly hard cast steel bar I have been making swarf with! But I do find the key to machining cast iron (grey, hard, or whatever) is to get the cutting speed slow enough that it cuts cleanly into dust. Needs bags of torque from the motor. But too fast - there always seems to be a specific speed for the material hardness - and the tool doesn't cut, but "burnishes" the surface - when the cast iron wins and erodes the tool faster than the tool can cut metal. I was taught to listen to the cut as a teenager, I still use that and I'm sure I can hear when the tool hits a harder spot and fails to cut properly if running too fast... To that end, I don't run as fast as I possibly could on "unknown" cast iron, in case of harder inclusions that could spoil the cutting action. The tool always need redressing afterwards... as the proper edge will have gone.

BRIAN - for finer finishing cuts on cast iron/steel, I always use a hard, re-sharpened tool, and drop the speed 10~20% so it cuts cleanly at the low pressure for the tiny cut. Try it on some scrap (Then tell me if it doesn't work?),
Thanks,
K2


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## Steamchick (Jan 21, 2022)

Brian - and anyone interested - a bit of my history. When I started work in the engine refurbishing machine shop (about 1967?) one of my first jobs was to clear the shelves of all the pistons, and put them back (after cleaning shelves etc.) in numerical part number order. I found that most of the older pistons were iron. Even in the late 1960s some old engines were still being re-furbished that had cast iron pistons. I remember that aluminium pistons were supposed to have really appeared during WW2 - for high performance engines, but many old (pre-1940s?) cars had side valve engines with cast iron pistons. However, I do know of the Austin A7 side-valve engine from 1930s with aluminium pistons, and Triumph, Sunbeam, etc. motorcycle engines of 1930s with aluminium pistons.
Does anyone else know when Aluminium superceded Cast Iron for pistons on car engines?
K2


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## werowance (Jan 21, 2022)

on the subject of CI pistons,   when i did the rebuild on my old farmall tractor,  it origionally had CI pistons.  the new sleeve/piston kit had aluminum pistons.  one thing i noticed right away after the rebuild is that i had to always choke the engine on a cold start whereas with the CI pistons i never had to use the choke at all. once it ran for 30 seconds or so it was fine.  i always wondered what the difference was.  was it the added weight of the pistons? CI maybe heating up quicker than Aluminum?  idk but is something i always wondered about.  the old CI pistons and sleves were very worn with a huge lip at the top.  the engine was very worn before the rebuild.


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## Brian Rupnow (Jan 21, 2022)

Okay--I'm going to run with what I got. The new cast iron piston is marginally smaller than I had intended, but it is still within the recommended 0.002" smaller in diameter than the cylinder bore. The piston rings will be cut from my new piece of iron from Wisconsin, and the o.d. will be turned to match the cylinder bore of 0.878". The o.d. of my piston is 0.876" dia. and I cut the ring grooves to be .046" wide x 0.045" deep. So---the rings will be cut to 0.045" thick, and 0.876-(.042+.042)=.792" i.d.  That will give 0.001" total side clearance when the ring is setting in the .046" wide groove, and 0.792" i.d. will give 0.003" radial clearance between the inside of the ring and the bottom of the groove on the piston.


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## johwen (Jan 21, 2022)

Hi Brian I take it you are using the Trimble method to make your rings but don't over cook them. Please make a sleeve that just slides over the  heat treatment fixture no air gaps around the fixture and sleeve. and wrap clean paper around the ring pack this will burn and consume any oxygen and prevent oxidation of the ring surface. Cook for 15 minutes at the red heat of the assembly let cool naturally. Push the finished ring over a gentle taper to split you will find the ring sealing surface should be clean without any scale. A couple of slides up a honed or lapped bore should give you great compression. Doing this never had a sealing failure. Good luck John.


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## Brian Rupnow (Jan 21, 2022)

When I part these rings off from the parent stock, there are a few things to consider. First, I know the ring thickness I want. My target figure is 0.045". Second thing is that I must know the thickness of my parting off tool, which in this case is 0.039". Third thing to know is that I want to make the rings about about .004 to .005" thicker than my target figure, because each side has to be lapped against a cast iron surface plate. Fourth thing to keep in mind is that every time I part off a ring, I must sand and deburr the end of the parent metal before I cut the next ring. That means that I only have one face on each ring that must be lapped. So, in my case, it meant that every time I parted off a ring, I had to move the carriage 0.088" before I parted off the next ring. Then I go thru all the parted off rings and check to see which side is the "bad side" and needs to be lapped. When all of the rings are brought down to "finished thickness" they have to be split. Then the ends are filed so that when the ring is in the cylinder there is a 0.004" gap between the ends. Then they go into my oven, mounted on a special fixture that spreads the ends apart to a "target dimension" for a four hour heat treatment to "set" the gap .


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## a41capt (Jan 22, 2022)

Hi Brian, I know I don’t have anywhere your experience, or that of the other modelers on this site, but I’d like to pass along a method I’ve found to be very effective for parting off cast iron rings.  I have set up a die grinder with a dremel abrasive cutoff blade in my tool post, and it does a remarkable job of “parting” off my rings. This leaves a very precise cut with no remaining lip to clean up, and preps them perfectly for polishing the sides on my plate covered by 400 and then 600 grit paper.

Thanks for letting me shoot my mouth off, and I hope you have as much good success with your rings as I’ve had with mine!
John W


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## Brian Rupnow (Jan 22, 2022)

A41capt--yes, I see that recommended in my files on how to make rings. Unfortunately I don't have any thin cut off wheels for my grinder. Thank you for stopping by and saying Hi.---Brian


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## Brian Rupnow (Jan 22, 2022)

So, as of this morning I have parted off 13 cast iron rings from my new stick of iron from Wisconsin. The o.d. is equal to the bore of my cylinder. The i.d. is calculated so that when installed there will be 0.003" radial gap between the inside of the ring and the bottom of the groove in the piston. The rings have been deburred and had the edges broke on one side---they were deburred and sanded on the exposed side before they were individually parted off. They are all "over thickness " by .004 to .005 and that will be addressed when I dress the side which is not deburred on a cast iron surface plate with a sheet of 600 grit aluminum oxide paper on it. They have all been examined under a magnifying light and the "bad side" marked with a black marker.


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## Brian Rupnow (Jan 22, 2022)

The rings have been fully deburred and taken down to the correct thickness. They have been split using a very sharp cold chisel, then the ends have been filed so that when inserted into  my cast iron cylinder they have a 0.004" gap. Here they are mounted on my heat treat fixture and spread over a 0.131" drill and ready to go into my heat treat oven for 4 hours at 1100 degrees. The extra rings which didn't fit on the fixture will be appropriately identified and kept for a future build.


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## Gordon (Jan 22, 2022)

I find it interesting that for something which is supposedly as precision as ring manufacturing that folks do it so many different ways. Heat for 1 hour, 3 hours, 4 hours. Use an enclosed tube and burn a piece of paper inside or use Brownell paste or just let them turn black and polish them. Seems like one person uses crude methods and the rings work just fine and the next person holds everything to +/- .0001 and they do not work. I have been going through the exercise again with my super frustrating Atkinson Differential and I have tried making rings several times and even bought rings from Dave Reed (Otto) and still cannot get enough compression.


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## johwen (Jan 22, 2022)

Now Brian do you put a sleeve over the jig and wrap paper around the rings to remove the oxygen and prevent oxidation of the sealing surface of the rings? John


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## Brian Rupnow (Jan 22, 2022)

No Johwen I do not. Anything that boils out of the fixture or the rings is easily removed with a brass bristled brush and dish soap.


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## Brian Rupnow (Jan 23, 2022)

This is a picture of the rings on the heat treat fixture after 4 hours at 1100 degrees. The fixture and the rings look like crispy critters, but some scrubbing with a brass bristle brush and  liquid dish soap cleans them up to a much better look.


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## Brian Rupnow (Jan 23, 2022)

This is the rings after removal from the heat treat fixture. They will still require a bit of clean up, but they are essentially finished. Note that each ring has now taken a "set" to the 0.131" diameter of the drill between the ends of the rings. When compressed into the cylinder, that gap narrows down t 0.004", and that spring force is what keeps the ring tight against the cylinder sides.


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## dsage (Jan 23, 2022)

SO now go the extra (simple)  step and try Terry's light mask technique to see how well they fit in the cylinder. The extra few minutes is worth it.


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## awake (Jan 23, 2022)

Gordon said:


> I find it interesting that for something which is supposedly as precision as ring manufacturing that folks do it so many different ways. Heat for 1 hour, 3 hours, 4 hours. Use an enclosed tube and burn a piece of paper inside or use Brownell paste or just let them turn black and polish them. Seems like one person uses crude methods and the rings work just fine and the next person holds everything to +/- .0001 and they do not work. I have been going through the exercise again with my super frustrating Atkinson Differential and I have tried making rings several times and even bought rings from Dave Reed (Otto) and still cannot get enough compression.



Yes, when it comes to rings, it often seems that one goes round and round in circles ...

But some people seem to be able to run rings around others ...

I was trying to come up with one more pun to round out the set, but I was afraid that someone might be as upset as if I'd pist on their cornflakes ...

Okay, I'm done now.


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## CFLBob (Jan 23, 2022)

Gordon said:


> I find it interesting that for something which is supposedly as precision as ring manufacturing that folks do it so many different ways. Heat for 1 hour, 3 hours, 4 hours. Use an enclosed tube and burn a piece of paper inside or use Brownell paste or just let them turn black and polish them. *Seems like one person uses crude methods and the rings work just fine and the next person holds everything to +/- .0001 and they do not work.* I have been going through the exercise again with my super frustrating Atkinson Differential and I have tried making rings several times and even bought rings from Dave Reed (Otto) and still cannot get enough compression.


(bold added by me)

I've been noticing this, too.  I haven't tried to make rings yet and this is one of those things that sticks my head.  I bought Dave Reed's rings for my Webster and it ran for a few minutes a few times, then never again.  Is it rings?  Valve leakages?  I just don't know. 

The profession I retired from had a reputation for the same sort of things.  Circuits wouldn't work or tune properly for one guy but another guy could make them work just fine.  Can't tell you how many times I heard that it was "black magic."  I thought it was pure physics, pure Maxwell's equations. 

My interpretation was that there are little things that some people did and weren't aware of to put in their instructions or tutorials, or perhaps told themselves "everybody knows that" or "everybody does that."  Maybe they were just better observers of what was going on.  I suspect that the differences in rings is something like that.  Little things that make a difference that people don't think of or don't realize they're doing.


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## minh-thanh (Jan 24, 2022)

Hi CFLBob !



Gordon said:


> . *Seems like one person uses crude methods and the rings work just fine and the next person holds everything to +/- .0001 and they do not work. *


 
I've done a few ringless piston engines including 2 stroke and 4 stroke, and it runs pretty well,..so I think: The cylinder is the crucial and important part.
   Just my thoughts - With me, finishing a cylinder well enough,  rings only works to increase the tightness between the piston and the cylinder. If the cylinder isn't good enough, the rings can't "fill in" the cylinder's defect and that's not the ring's function !


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## Gordon (Jan 24, 2022)

minh-thanh said:


> Hi CFLBob !
> 
> ..so I think: The cylinder is the crucial and important part.
> Just my thoughts -



So if that is the case, what is the best way to machine the cylinder? Boring bar, reamer, hone, lap.


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## minh-thanh (Jan 24, 2022)

Gordon !
It is probably the best way !
  I don't know how are you!? But making the cylinder can take hours, sometimes I have to redo it just because the cylinder is not really good
  My first cylinder was aluminum, I chose aluminum because it's soft and easy machined and cheap  but it took me a few months or more to make it good enough.
 If the machines are good enough, the time for hone and lap will be less and back


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## Brian Rupnow (Jan 24, 2022)

I think ring making is one of the dark arts. Sometimes everything works perfectly and my engines run with home made rings. Sometimes, using the very same material and same method they don't work. I have tried to take all guess work out of the machining and heat treating process and be methodical about making rings. I think that somewhere in the ring making process I have to go to a graveyard at midnight and kiss a black cats a$$ to make things work consistently.


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## minh-thanh (Jan 24, 2022)

Hi Brian !


Brian Rupnow said:


> I think ring making is one of the dark arts. Sometimes everything works perfectly and my engines run with home made rings. Sometimes, using the very same material and same method they don't work. I have tried to take all guess work out of the machining and heat treating process and be methodical about making rings.


 Why not look for other causes ? maybe another reason but it is not rings, the way you make rings or the materials .



Brian Rupnow said:


> I think ring making is one of the dark arts.
> I think that somewhere in the ring making process I have to go to a graveyard at midnight and kiss a black cats a$$ to make things work consistently.


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## Gordon (Jan 24, 2022)

minh-thanh said:


> Hi Brian !
> 
> Why not look for other causes ? maybe another reason but it is not rings, the way you make rings or the materials .



If it wasn't the rings or cylinder why will an engine run with O rings and not CI rings? If it was valves or gaskets etc it would not make a difference when using O rings.


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## minh-thanh (Jan 24, 2022)

Gordon said:


> If it wasn't the rings or cylinder why will an engine run with O rings and not CI rings? If it was valves or gaskets etc it would not make a difference when using O rings.



Just my opinion, because I only made 2 pistons with O-rings, so I don't have much experience with it.
  The O-ring is more flexible than a cast iron ring, so it easily increases the tightness between the cylinder and the piston - the high pressure in the cylinder will force the O-ring against the cylinder wall - and of course the same happens with the cast iron ring - but the O-ring will be easy to stretch to fit the cylinder's defect -
Example: an engine with a compression ratio of 7-1
If the ring is cast iron: Compression ratio is only 4 - 1
If O-ring : Compression ratio will be 6-1 or 7-1
   Again : Just my thoughts  !


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## Brian Rupnow (Jan 24, 2022)

The viton o-rings give instant gratification. They seal 100 % immediately and take any notion of compression leaking past the rings out of the equation. I think they are just wonderful.--That being said, I want to learn to make and use cast iron rings consistently and accurately. I have tried to come up with an accurate and foolproof and repeatable method for making cast iron rings that work. I am very close. I have invested over $1000 for a heat treat furnace and controller, and read about a thousand pages of "how to" articles related to cast iron rings. There is a lot of conflicting information available, and some of it is absolutely wrong.


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## minh-thanh (Jan 24, 2022)

There are a few different ways
Sometimes : Trial and Error - Try and be Patient !


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## Brian Rupnow (Jan 24, 2022)

The only issue I have with grinding the outside diameter of the piston, is that once the piston stock has been removed from my lathes 3 jaw chuck, it will never go back in the same way. My chuck has about 0.003"total indicated runout. What that means is that getting the piston back into the chuck exactly as it was before depends solely on good luck. I'm not sure that would really affect the way the piston works or not. If I use an external lap to bring the piston down to size, it doesn't really matter if the piston is exactly centered in the chuck or not, because the external lap is free floating and is held in my hand.


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## minh-thanh (Jan 24, 2022)

Brian Rupnow said:


> The only issue I have with grinding the outside diameter of the piston, is that once the piston stock has been removed from my lathes 3 jaw chuck, it will never go back in the same way. My chuck has about 0.003"total indicated runout. What that means is that getting the piston back into the chuck exactly as it was before depends solely on good luck. I'm not sure that would really affect the way the piston works or not. If I use an external lap to bring the piston down to size, it doesn't really matter if the piston is exactly centered in the chuck or not, because the external lap is free floating and is held in my hand.



Why don't you perfect the piston just once?!
  I have read your thread about making an OD grinder, You can do an OD grinder when your lathe is correct, but if the lathe is correct there is no need to do an OD grinder
When I make the piston, I make the outside diameter of the piston bigger than the inside diameter of the cylinder And then I lapping until it can slide into the cylinder.
  Then make a groove for the ring....
Lapping piston or cylinder: only slight pressure is required -
     The abrasive compound will do its job
    Don't apply too much pressure because compression and abrasive compound will   deform your piston or cylinder


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## Richard Hed (Jan 25, 2022)

Brian Rupnow said:


> I think ring making is one of the dark arts. Sometimes everything works perfectly and my engines run with home made rings. Sometimes, using the very same material and same method they don't work. I have tried to take all guess work out of the machining and heat treating process and be methodical about making rings. I think that somewhere in the ring making process I have to go to a graveyard at midnight and kiss a black cats a$$ to make things work consistently.


I've got a bunch of black cats.  You can have allyou want.


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## johwen (Jan 25, 2022)

Well Brian, The area I  differ with you is in the heat treatment  and I put two ring in each groove that are half the thickness of the ring groove less the appropriate clearances gaps are 180 degrees apart. They are encased in an outer sleeve and brought up to red hot temperature for around 15 minutes then let to cool naturally and when opened the treatment jig is opened up I only have the dress the width on an flat service plate to suit the groove. The rings have full tension I've never had a failure for sealing. They only need washing in kerosene after adjusting the thickness as the sealing surface comes out basically dark blue with no oxidation
Being an Auto engineer back in the 50-70's re ringing 4 cylinder car engine was a weekly occurrence many with tapered worn bores .005" out of round they still sealed. Today modern car engines the piston relies the ring to do all the sealing via the ring grooves as their is very little skirt on the gudgeon pin axis. When reboring cylinders the piston back in those days had full skirts and were ground oval to give more clearance on the gudgeon axis to prevent seizure.
John


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## Brian Rupnow (Jan 29, 2022)

After more trials and tribulations than you want to hear about, this is my 7/8" horizontal engine running with cast iron rings. This was much more of a struggle than I anticipated, but the fault was mostly that the grub screws holding the bottom timing gear had slipped enough that the engine was out of "correct valve timing".  To me, this is wonderful. This is the first 7/8" bore engine that I have installed cast iron rings in. In this video my engine is running on Coleman fuel.---Brian


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## a41capt (Jan 29, 2022)

Congrats Brian, another great runner.  Now that you’ve got iron rings perfected, you’ll probably never go back!!! 
John W


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## awake (Jan 29, 2022)

Congrats, Brian!

I'm pretty sure I remember a previous engine that you struggled with, only to find that a timing gear or cam had slipped. With that in mind, it might be worth designing your next engine with the timing secured by a key. You could still make the valve timing variable, by having the timing gear on a boss; the gear could adjust on the boss, and the boss is keyed to the shaft.

Just thinking aloud ... and shouldn't be, since you have made, what, 187 running engines now? I'll go see if my grandmother would like to suck eggs ...


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## Brian Rupnow (Jan 29, 2022)

Awake--it's a nice thought---but---if the boss was keyed to the shaft, then the gear would slip on the boss. Setting and maintaining valve timing is a very delicate thing---and it's not really visible to the naked eye.


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## awake (Jan 29, 2022)

I was thinking of the sort of variable timing gear arrangement that is found in some high-end cars. "Boss" is not the right term ... gear carrier, maybe? Where the gear has slotted holes through which it bolts into the carrier.


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## Brian Rupnow (Jan 29, 2022)

Andy--I'm curious---Have you built any engines?---Brian


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## awake (Jan 29, 2022)

Yes, a couple. This is something I have thought about doing on the next one. But see my disclaimer above - I realize I am coming from a place of great relative ignorance!

In my defense, this is not my idea; I have seen it somewhere in this forum. If I could point to the post, I would, since I am no doubt doing a poor job of describing it.

Also, FWIW, the engines I have built have the timing gear and cams keyed to the camshaft. That of course means that the keying has to be correct ... or else one has to have a way to adjust the rotation of the gear with respect to the key.


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## minh-thanh (Jan 29, 2022)

Brian Rupnow said:


> Andy--I'm curious---Have you built any engines?---Brian


Unnecessary .!!!
Andy is just giving an opinion, you can choose another way and do it the way you want and it's right for you


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## Brian Rupnow (Jan 30, 2022)

Engines are simple to build, but a tricky thing to set up and run. Most of the things that have to be "set up" are right there in your face, and it's hard to overlook them. Some of the things (like valve timing) are not really visible, and require a timing disc to really see whether it's right or not. My question wasn't a "put down".  I do get a lot of "why didn't you do it this way?" from people who have never built an engine in their life. A lot of what I do is something that you have to have successfully done yourself, to even understand what is going on. No harm--No foul.---Brian


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## awake (Jan 30, 2022)

<duplicate post>


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## awake (Jan 30, 2022)

Brian Rupnow said:


> No harm--No foul.---Brian



Agreed - I took it as an honest question. No problem.



Brian Rupnow said:


> require a timing disc to really see whether it's right or not



This is the point of potential disagreement. I have seen in many of your write ups that you use a timing disc to set the valve timing - which depends, of course, on being able to adjust the cams. I would suggest that it is possible to "hard code" the valve timing by locking together the relationship of the camshaft, cams, and timing gear via keys. If adjustment is still needed, the idea that I tried to describe above would provide the ability to make small adjustments; move a gear tooth to make large adjustments.

BUT - this is the point at which Brian's question is most pertinent. I can suggest that this is possible all day long. But I have not yet built one that works exactly that way. I have locked timing gear and exhaust cam together via keys (in an atmospheric intake valve engine), so the suggestion is partially demonstrated, but not yet the full scope of setting up both cams and getting everything right. That is a work in progress ... we shall see!


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## Gordon (Jan 30, 2022)

I think that a problem many new model engine builders have is comparing it to their experience with large engines. An adjustment on a full size engine may translate into a .001 adjustment on a model engine. Sheer mass and power may overcome some misalignment or friction in a V8 but will prevent a small engine from running.


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## minh-thanh (Jan 30, 2022)

Gordon said:


> I think that a problem many new model engine builders have is comparing it to their experience with large engines. An adjustment on a full size engine may translate into a .001 adjustment on a model engine. Sheer mass and power may overcome some misalignment or friction in a V8 but will prevent a small engine from running.


I usually adjust  all my engines the way my dad taught me when he works with a big engine and it always runs.


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## Gordon (Jan 30, 2022)

minh-thanh said:


> I usually adjust  all my engines the way my dad taught me when he works with a big engine and it always runs.


You have better luck than I do then. I used to be able to tune a car by turning the distributor until it sounded right and adjust the carburetor until it sounded right. On model engines I have had engines which would not run with timing +/- 2° or needle valve 1/32 turn off.


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## Brian Rupnow (Jan 30, 2022)

Minh-thanh---I am happy for you that your engines always run. Mine do too---eventually. The key word there is eventually. I spent a lifetime building and racing hot-rods with big V8 engines in them, and it was much easier to get them to run than these small single cylinder engines.


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## minh-thanh (Jan 30, 2022)

Gordon !
I think, With big engine: + / - 2 degrees will affect the performance....which we need.
  With small engine - homemade : + / - 2 degrees does not have much effect on whether it runs or not .


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## Brian Rupnow (Jan 30, 2022)

Today I'm going to call this engine "finished". It is doing everything I set out to accomplish, and is running with cast iron rings. There is a bit of a write up with the video. Thank you all for watching the build and for the helpful hints and suggestions. ---Brian


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## Brian Rupnow (Jan 30, 2022)

Andy--Your idea of having the relationship between the two cams "fixed" and the cams "fixed" in some rotational relationship to the cam gear is not a bad suggestion. If a person always uses the same cam (which I do) then it does make sense. I have almost always pinned my exhaust cam to the camshaft, but left the cam shaft to cam gear adjustable. The intake cam is not "fixed" to the camshaft. It is positioned rotationally by grub screws. What this gives me  is infinite adjustability for both the intake and exhaust cams. However, it does introduce more chance of something get out of adjustment. Minh tranh--a V8 auto engine has 4 cylinders firing each revolution. A single cylinder engine has one power pulse every second revolution. On a v8 engine these other power pulses during one revolution provides enough impetus to keep the engine running even if the timing is off a bit. On a single cylinder engine, which only fires once every second stroke, if the timing is not perfectly correct, then the engine runs down and stalls before it gets to the next power pulse.


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## minh-thanh (Jan 30, 2022)

Brian Rupnow !


Brian Rupnow said:


> Minh tranh--a V8 auto engine has 4 cylinders firing each revolution. A single cylinder engine has one power pulse every second revolution. On a v8 engine these other power pulses during one revolution provides enough impetus to keep the engine running even if the timing is off a bit. On a single cylinder engine, which only fires once every second stroke, if the timing is not perfectly correct, then the engine runs down and stalls before it gets to the next power pulse.


 
Yes, you are right!
  So when I do my small engines I usually try to make everything smooth : crankshaft - bearing, camshaft - bearing, gears - gears....
  And when I assemble, I check each part to make sure everything is smooth and they are smooth with the others.
The engine is assembled (no spark plugs installed): I have to be able to turn the flywheel by hand with light force - For V4 or I4, for 1 cylinder the force is lighter (with engines more than 4 cylinders I don't know. because I haven't done it yet)
    When the engine is assembled with spark plugs : The engine must have good compression
   And lastly : Adjust the timing and the amount of fuel (adjusting the amount of fuel seems to be the hardest part for me )
 With me: not smooth and friction is a factor that will destroy all efforts to have the engine run and it will contribute to incorrect ignition timing, cam timing...


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## ShopShoe (Jan 31, 2022)

Brian,

I certainly like this engine. I like the way it looks, like the way it runs, and like the way it sounds. I tend to  wait for one of your projects to be done when you say it is done, and I especially like the "Casey Jones" lever finishing this one off: Just icing on the cake......

Thank You for posting.

--ShopShoe


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## Brian Rupnow (Feb 17, 2022)

This video, made 17-Feb 2022 shows my most recently designed and built single cylinder horizontal engine running with a home made sparkplug. I had issues with the cylinder head, mainly because I messed up the  1/4"-32 threads for a standard sparkplug, so had to redrill and tap to a 5/16" fine thread. I had Steve Huck make me a "special" sparkplug with a 5/16" fine thread, but could never get it to work consistently. Then I made a sparkplug, but my design was a bit fishy, with a 0.060" spark gap. It would spark to get the engine running, but as soon as it warmed up, the spark would jump across the outside of the sparkplug to ground and the engine would stall. Finally, a redesign of the sparkplug with an 0.025" spark gap worked successfully, and the fact that the sparkplug is 3/8" longer than the first home made sparkplug keeps it from arcing to ground on the outside of the sparkplug. I am happy, the engine runs fine, and now I can put this project to bed. If you want to buy a complete set of plans to build this engine, contact me at [email protected]---Brian


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## rlo1 (Feb 24, 2022)

Brian Rupnow said:


> A bit of explanation now, on what I've been doing. I was very surprised when the engine didn't want to run with the new cast iron rings I made for it. And then, I figured out that I had used the wrong kind of iron to make the rings from. This was surprising, because the rings were made from the same stick of iron that made two or three sets of rings that did work in the engines they were made for. The shop I buy my iron from didn't seem to know if this was ductile iron or the other type of iron. I found out after the fact by seeing how easily the rings bend.  My current piston is aluminum and is 0.873" diameter, riding in a cast iron cylinder. When the engine wouldn't run, I made a second aluminum piston the same diameter with a viton ring for a reality check, and the engine ran fine with a viton ring. I then ordered a stick of the correct type of iron for making cast iron rings from Wisconsin, and it showed up here yesterday. I have a choice now--I can make new rings and put them on the existing aluminum piston----or---I can make a new cast iron piston which is a closer fit in the cylinder and put new cast iron rings on it. This is why I made the brass external lap, to lap the new cast iron piston so it would be a closer fit in the cylinder.-not an air tight seal, but much closer to it than the aluminum piston was. I'm not worried about thermal expansion, because the piston and cylinder will be the same material so if the piston grows a bit from heat, the cylinder will grow as well so it shouldn't seize on the piston. At the same time I was waiting for my new iron, I started a new thread about the possibility of using my Toolpost Grinder from Little Machine shop to grind the piston to the exact outside diameter instead of lapping it. I got so many varied answers to that question that I decided not to do it. So, armed with the knowledge I have collected, I will now make a new lapped cast iron piston from the old stick of cast iron from my local supplier and new cast iron rings from the new correct material from Wisconsin.


Hi, For the rings, what type of Cast Iron did you get and where did you get it from?  Thank you


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## Brian Rupnow (Feb 24, 2022)

See post #248---Brian


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