# Geared horizontal twin engine



## Brian Rupnow (Nov 26, 2020)

I have always thought that the most elegant cross head guides I've ever seen were on the Popcorn engine, as designed a few years ago by Stu Hart of the U.K.  Stu done the original in metric, then I took his drawings and basically redrew them in imperial inch size. I changed very little, and it has always been one of my favourite engines. A week or so has gone by since I finished my version of the Trevithick locomotive engine. I'm setting here this morning on my computer dicking around with the idea of a twin horizontal engine that incorporates the Popcorn cross head guides and operates the cylinder slide valves thru a set of gears similar to what I did on the Trevithick engine.


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## Brian Rupnow (Nov 26, 2020)

For the sake of symmetry and balance, I'll put a skinny flywheel on each side. The power take offs and the flywheels are both running on the camshaft.


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## Ken I (Nov 26, 2020)

Brian, I thought you were going to take it easy after the Treveithick engine and humping your lathe hither and thither - your work rate is inspirational - slow down man - you make me feel such a slacker !

Regards, Ken


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## Brian Rupnow (Nov 26, 2020)




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## Rdean33422 (Nov 26, 2020)

Brian that is a very good idea and an interesting design.
I will be watching.

Ray


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## Mike1 (Nov 27, 2020)

Brian, That's a interesting design, but flywheels on the eccentric shaft and not the crankshaft that intrigues me, could it effect the smooth running of the engine ?
I'll be watching with great interest.
Mike1


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## Peter Twissell (Nov 27, 2020)

Brian, Excellent choice in the 'Popcorn' style crossheads - a very nice design.
I would echo Mike1's comments about the gears. Each pulse of torque wil reverse the load through the gears, possibly causing noise and rough running. If the gears were transmitting only the power required for the eccentrics, they could also be much thinner and lighter.
Looking forward to seeing your design develop.

One of the projects I am currently working on is a twin engined motorcycle, with the engines coupled through gears. Other similar arrangements have shown that it is very important to time the two engines so as to minimise load reversals in the gear train.
Clearly the issue is much reduced in a small steam engine, but it is still a factor.

Pete.


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## Brian Rupnow (Nov 27, 2020)

Other people have used this gear driven design on single acting hit and miss engines, and it doesn't work well on them. The main reason it doesn't work well on hit and miss engines is that there is such great reversal of torque between when the engines hit to drive the crankshaft and then the torque reversal when the engine coasts, depending on the inertia of the flywheels to carry the engine thru a number of miss cycles. This plays Hell with the gear teeth. On a double acting two cylinder engine, you really don't even need much of a flywheel for them to run.


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## Steamchick (Nov 28, 2020)

Mike1 said:


> Brian, That's a interesting design, but flywheels on the eccentric shaft and not the crankshaft that intrigues me, could it effect the smooth running of the engine ?
> I'll be watching with great interest.
> Mike1


Usual practice is to have flywheels on crankshafts - because they are the most substantial for hanging a massive flywheel upon. The largest (stiffest) shaft will have bearings most able to cope with the non-running condition, where all the mass of the flywheel is pressing (usually) on only 1 or 2 bearings. But if another shaft is used, then it often needs to be beefed-up to take a flywheel. Also, the fastest shaft is better for flywheels, as they can be made smaller if running faster. Valve layshafts in whatever form may be running at half crank speed and therefore balance of crank and con-rods is a different set of calculations... - and I think (can't remember - but someone will) you cannot resolve the primary balance with a half-speed shaft. But if the eccentric shaft is separate form the crank and is at crank speed (lie Brian's design), then you may be able to balance the main crank primary mass, providing the linkage between the 2 shafts can  cope with the torsional vibration forces.... (=BIG Gears!). So it isn't common practice for many reasons.
With the loads on a model - Like Brian's design - I reckon the gears - if nicely meshed - will do fine. They look big.
Personally, I would have arranged the cylinder above the valve chest - so pistons drive a crankshaft with the flywheels directly mounted, and the eccentrics on the layshaft (below) can then drive the valves directly. Or if the eccentrics remained on the crank (as many engines exist) a simple and light lever could transmit the motion to the valve rods. - But that would be a different design to Brian's. 
With Brian's arangement, I think the balancing can be arranged so the primary crank imbalance can be resolved by counterweights on the crankshaft, then some secondary (or are they tertiary?) imbalances from side oscillations of con-rods be compensated by balance weights on the eccentric shaft. How about it Brian?
Can you post your balance configuration and calcs? I'm sure I'm not the only one who wants to learn more about this interesting design. Keep up the good work. - Will plans be available (prints/pdf will do?) when completed, so we can make something unique to display at our local club shows?
Sorry if my posts are a bit long winded. "new" configurations of engines - like Brian has drawn - really interest me from a design perspective. I can't see any new Machining challenges here?
Thanks Brian.
K2


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## lathe nut (Nov 28, 2020)

*Brina,* thanks for the start of something new and different, if you got it in your head and you have seen it running in the minds eye it shall come to pass and we shall learn, that is a neat Idea that I guess you call it three D, really looks good, anxious to see the build and hear it come to life, thanks for sharing with us, Joe


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## Brian Rupnow (Nov 28, 2020)

This morning I'm making gear blanks from steel. Whenever I buy a length of steel, I always buy it 2" or 3" longer than I actually need. All of the left over pieces are saved for jobs exactly like this. A lot of left over short pieces of shafting end up becoming gears for different projects. I'm not down to "zero scrap", but I try to use up every possible bit of steel that  I buy. The o.d. of the gear, the o.d. of the hubs, and the bore are all put in in this set-up. Then I will flip the part around in the jaws and turn down the remaining bit to the outer diameter of the hub. This gives me a portion of steel to hold in my 3 jaw vice mounted on my rotary table when I cut the teeth into the blank. Then the extra long hub will be shortened to size.


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## Brian Rupnow (Nov 28, 2020)

That's enough work for today. Both gear blanks are turned to size, and the main crankshaft support is roughed out. I have had a clever idea about cutting teeth in the gear blanks, but I will share that with you tomorrow.


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## Brian Rupnow (Nov 29, 2020)

This morning I cut the 36 tooth gears. Yesterday, as you seen, the gear blanks were made from two different pieces of steel. I wanted to cut these gear one time only. The gear in the chuck has an extended hub on one side which is held in the chuck jaws. Both gears have been drilled and tapped for set screws and will eventually get keyways cut directly below the set screws.  I inserted a piece of 3/8" cold rolled steel into the gear in the chuck, and that same piece of cold rolled extends thru the second gear, and on out to the tailstock chuck. Set screws are firmly cinched up on both gears, and this lets me cut both gears in one pass. This only works if both gears have the same number of teeth. Now I will trim the hubs on both gears to the finished dimension and add the keyways.


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## Brian Rupnow (Nov 29, 2020)

In this picture the gears have been cleaned up, and two test holes have been drilled and reamed in a piece of scrap aluminum at the correct center distance. Two scraps of 3/8" cold rolled rod are inserted thru the gears and into these holes. This way I can check that the gears mesh properly. If they are a bit too tight or a bit too loose, then I  can adjust the hole centers in the finished piece to compensate for that.---It makes me absolutely crazy if I just put the holes into the finished piece first and then find out that the gears don't mesh properly. There isn't any good way to fix that!!!


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## Brian Rupnow (Nov 30, 2020)

The bearing stand and gears are finished, and now I think I'll go after the cross-head guides. I happen to have stock of the correct size left over from some other project, and I'm trying to build this engine "on the cheap" which means using as much stock that I can from stuff just setting around here collecting dust.


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## Brian Rupnow (Nov 30, 2020)

Now, if you squint your eyes real hard, you can see the two cross head guides, turned to correct o.d. and cut to length.--I still have a bit of work to do on them tomorrow---


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## Tim Wescott (Nov 30, 2020)

I feel like it's too late for this comment since you're already commencing work -- but if you put the valves on the bottom and the power cylinders on the top, you'll be driving the flywheels with the crankshaft without any major changes to the rest of the engine.

(Well, aside from making it impossible to access the valves -- but I'm an engineer!  I have a reputation to maintain with the guys on the factory floor, and service).


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## Brian Rupnow (Nov 30, 2020)

Tim--I know a little secret about slide valve engines. The slide valve is held tight against the side of the cylinder (where the ports are) by steam (or air) pressure in the steam-chest. However, there is something called gravity that you have to contend with. If the valve slider is on the underside of the cylinder and you try and start the engine from zero pressure, then gravity holds the valve slider away from the ports and the engine will just set there and pee any  pressure out the exhaust ports until you give the engine a shake to get that slider up against the port faces. Some early steam engines got around that by placing a spring on the side of the slider farthest away from the ports, which held the slider against the port faces so as not to leak all the air pressure away.


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## Tim Wescott (Nov 30, 2020)

If I were the same guy who came up with all the bitty parts in the Citroen DS suspension, or whoever it was at Bristol that decided that a 9-cylinder radial engine should all the complication of sleeve valves (all those gears!) instead of a couple of bump rings, roller lifters and tappets, I'd advocate more parts.

I mean -- what's one little spring per cylinder?  That's only two.  Plus cover plates, and sliders, and ...

(I'm going to _stop being a smartass_ now. At least for the moment.)


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## Steamchick (Dec 1, 2020)

Hi Tim, Seems you are learning the lesson ("_stop being a smartass_ ") I failed to learn - being an engineer myself.... - and Old Grumpy Engineers DON'T learn new tricks.... - So what's this "stop being a smartass" stuff? I enjoy learning about things like gravity affecting slide valve sealing, which would not happen if you didn't ask? (Thanks Brian!) - And having worked in Automotive for a Japanese manufacturer.... I learned that "in the West" we re-design to overcome problems, but "in the East" they design a countermeasure bit and add it on... and add it on... and add it on... - E.g. The philosophy of "Complexity makes "Hondas" reliable", compared to "simple Western engines" that are less so? (But much better in other ways?) - That's why they won the war of "usability" in the 1960s. But the world has turned a lot since then... perhaps nowadays the universal attitude is one of "never mind how rubbish the design actually is, just fiddle it to work and we'll make money anyway"? - Or do I have a jaundiced view of Manufacturing Management?
Maybe as Engineers we choose what to learn? - like making the piece that exactly fits the jigsaw, not just accepting the piece that didn't really fit well?
Keep up the good work ALL! - Sorry for my grouse!
K2


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## Steamchick (Dec 1, 2020)

An aside.... Because I mentioned those "great" engineers - well Engineers and machinists - Honda.
 
- Enjoy!

Did you know that in the 1980s the Honda engineers used doppler-shift anemometry to develop a quieter starter motor? - Bosch and Lucas used "Human ears" - but as the engineers were old they couldn't hear the higher frequencies made by the smaller higher speed motors Honda's supplier was developing? - and didn't care about the noisy traditional designed European parts.The Honda starter was 20~25% lighter, more reliable (on comparison bench durability tests), 20% lower cost, more efficient (starter torque per amp), but made a quieter but different noise to the "old design" so we bought the Bosch part - German engineering - that was least reliable, but had the best returns and replacement policy for Europe as a whole! I missed the point of that decision.
K2


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## Steamchick (Dec 1, 2020)

Brian Rupnow said:


> Now, if you squint your eyes real hard, you can see the two cross head guides, turned to correct o.d. and cut to length.--I still have a bit of work to do on them tomorrow---


Didn't squint - put my glasses on and read the drawing!
I like someone who has a calculator on his bench. Just surprised there are no blue finger-prints on the keys....
I have a scratch and slate - actually, I use it with chalk. It works, but slower. But I can do drawings on mine!
Is there a clever balancing trick to get the flywheel over the edge of the bench without toppling-off? - Or are the gears sufficiently massive to counterbalance the flywheel?
I do appreciate your work. Keep up the good thread!
Thanks!
K2


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## Brian Rupnow (Dec 1, 2020)

These do end up making a beautiful cross-head guide, but Oh My Goodness there are a lot of machining sequences to get to the finished product from a piece of round cold rolled steel!!!


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## Brian Rupnow (Dec 1, 2020)

So, as I was saying, these are probably the prettiest cross-head guides I have seen. There is a world of work in machining one of these, and it all has to be done in the correct sequence or you paint yourself into a corner and find that you have nothing to hold onto for the next machining operation. One done, and one more to go, tomorrow.


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## Brian Rupnow (Dec 1, 2020)

Steamchick--That's not a flywheel. That is an 8" v-pulley. I power the v-pulley with a 1/2 horsepower electric motor for a half hour to "run in" the shafts, gears, and bearings, so as to have minimum drag when it is assembled with the engine.---Brian


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## Steamchick (Dec 2, 2020)

Clever... 
Thanks Brian. (I assumed it was a V-Pulley being used as a flywheel to check the smooth running of the gears - didn't appreciate the "running-in" process!). So I guess the gear shaft mount is bolted to the bench - or something (to take belt tension?)? - Which would explain why it doesn't fall off the bench?
Cheers.
K2


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## Brian Rupnow (Dec 2, 2020)

No, it was just posed on the end of my desk to get a shot of all the components finished so far. I will post a family shot of all completed pieces by the end of the day.


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## Brian Rupnow (Dec 2, 2020)

And that, my friends, makes two beautiful cross head guides. I'm very pleased with the way they both turned out. I started this morning at 8:30 and machined until 3:30 to finish the second cross head guide. (That included time to eat my lunch and walk sixteen minutes on the horrible treadmill. We have 9" of snow here now, so my fat mans walks in the bush trails are ended for this winter. Not sure what part I will make next, but I have to check my stock and see what material I have.


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## Brian Rupnow (Dec 2, 2020)

I think I'm going to dive into the Rupnow fortune and buy some brass tomorrow. This engine almost demands that the flywheels be made of brass. Almost all of what remains to be built can be steel or aluminum, but I really like the color contrast of brass. I wish that there was some other cheap, exotically colored metal, but I'm pretty well stuck with two predominant colors. Steel and aluminum are very similar in color, no contrast there, and the lovely yellow of brass really makes it "pop". I'm not a huge fan of paint, and anodizing or black oxide coating is too expensive for my tastes.


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## Rdean33422 (Dec 2, 2020)

I agree Brian brass just looks nice and machines well.  It is also stronger than aluminum but I just wish it wasn't so expensive.
Ray


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## Tim Wescott (Dec 2, 2020)

You could make steel flywheel tires for shrink fit on aluminum wheels.

Polish up the steel, heat it until it's a pretty color, drop the aluminum in and let it shrink.

It should give some corrosion resistance while you're at it.


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## Brian Rupnow (Dec 3, 2020)

This morning I loaded my wheelbarrow full of money and went shopping for material. The place I usually shop did not have any 5" x 3/8" brass (for flywheels) nor did the have any 1 1/2" x 1" brass (for cylinders). The 3 pieces you see in the picture cost $60. Then I went to my other metal supplier, and they had no 6" x 3/8" brass, but they did have a piece of 1 1/2" x 1" brass x 12" long, and it cost $71 and won't be here until tomorrow. That means that I now have to go and see the local robber-barons and see if they have any 5" x 3/8" brass to make flywheels.


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## Steamchick (Dec 3, 2020)

If I could get it cheaper for you I would, but trans-Atlantic postage and Customs would rob you blind anyway!
I try and buy from a scrap-yard when I can get something of a suitable size. You just don't know the grade of material - but sometimes that doesn't matter on a model. (Just "Does it polish nicely?"). But the last one sold stuff at £5 per kilo and has since gone the journey of time. I need to find a new "non-ecological" scrapyard that can sell stuff "because they can". - Just realised... most scrapyards are VERY ecological - because they recycle everything they can! (for money).
Ho hum.
K2


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## Brian Rupnow (Dec 3, 2020)

Somebody suggested that I buy cast flywheels. Remember--I'm in Canada, home of the brave and the penniless. For me to buy a cast iron flywheel , eat the currency exchange, the tax, and the shipping, I might as well use brass. An executive decision has been made. The flywheels are going to be made from hot rolled steel (which is dirt cheap) and painted the color of my choice. The amount of machining will be exactly the same, the weight will be almost the same, and the painted flywheels will look like they might be brass. In fact, maybe I'll lie!!!--I'll paint them and tell people that they are made of brass.--Who's going to know??


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## Brian Rupnow (Dec 3, 2020)

Along with running around town buying material and walking on the horrible treadmill for 20 minutes, I was able to finish a base for the geared engine. I would have rather made something on my lathe, but it's nice to have a baseplate to assemble all the pieces on.


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## Brian Rupnow (Dec 4, 2020)

So--Today we are taking our lead from Sesame Street. Today we are going to make round things. Four cylinder end caps to get the ball rolling, and then maybe a a couple of cross heads.


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## Brian Rupnow (Dec 4, 2020)

So today I picked up my piece of brass to make cylinders from, along with a piece of 6" x 1/2" hot rolled steel flatbar 12" long which will become flywheels. That cost $87.74 along with the $60 I paid for the other steel and aluminum and brass. So, it looks like the butchers bill for this engine is going to be around  $148 and that doesn't include the material that I already had when I started this build.


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## Brian Rupnow (Dec 4, 2020)

Making round parts went quite swimmingly--Until I broke off a #10-24 tap. Tried all of my usual tricks to remove it, and none of them worked. Will remake that part tomorrow morning.   BAH!!!----HUMBUG!!!


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## Tim Wescott (Dec 4, 2020)

No scrapyards in your area?  There's one just down the road from here that sells steel, copper, brass, and aluminum by the pound.  Of course, it's often mystery metal (although I do have some 6061 from them that came marked).

Granted, I haven't checked to see if they're still here given COVID.


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## werowance (Dec 4, 2020)

hate that on the tap breakage.  bah humbug is a very clean version of what i would have said. 

on the base plate.  the nice rolled edges,  how did you do it?  a round over end mill,  a router bit or ?

looks good.

and oh yeah on the brass,  i know your probly tired of hearing it but yep, scrap yard or i have a guy who takes down burned homes, old radio towers etc.  in other words home demo.  he often brings me brass.  i am surprised to find  out how much of that stuff is in old homes and business's.  actually large stuff.  radio towers in specific


now if you go to s scrap yard,  may i recomend looking for oxygen concentrator machines.  those tote around oxygen machines you see some having.  the larger ones for home use not the little portable ones.  they have some pretty large brass cylinders in them.  2 per machine that i have found.  and have fitting pistons with teflon rings to go with them.  and usually cheap as the dont know about that,  they just want the electric motor out of them


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## Brian Rupnow (Dec 5, 2020)

Hi Werowance --I used a radius die in my mill on the four sides of the baseplate but I wasn't real happy with the results.--Then took it out to my giant stationary belt sander and used it to round the corners even more.


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## Brian Rupnow (Dec 5, 2020)

I like myself a lot better today. No taps were broken and all of the holes ended up in the right place. Tomorrow I can forge ahead with either the cylinders or the flywheels.


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## Tim Wescott (Dec 5, 2020)

How do you make the insides of those cross-head guides smooth enough that a cross-head will be happy sliding therein?


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## Brian Rupnow (Dec 5, 2020)

The inside hole of the cross-head guide is reamed to 5/8". The cross head is turned to 0.626" diameter. Then I use a brass lap to open up the inside of the cross head guide using 600 grit lapping paste until the cross head is a smooth fit.


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## Brian Rupnow (Dec 6, 2020)

Every day, a few more parts. Hardest job of the day was standing out in my unheated main garage sawing out flywheels from that piece of 6" x 1/2" hot-rolled steel. I need a new blade on the saw, and it doesn't cut very fast right now---and if you lean on it a bit then the drive belt slips. ---Thought I might freeze to death before I got the flywheels cut out. Tomorrow I hope to completely finish the flywheels.


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## Peter Twissell (Dec 6, 2020)

I have two heaters in my workshop.
One is a propane blower type.
It's effective, but it creates a lot of water vapour. I have to open the doors at both ends after i'm done to ventilate the place and prevent condensation on the machinery.
The other is a hacksaw!


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## werowance (Dec 6, 2020)

Hi Brian,  in the upper 30's lower 40's here in F not C   whats it up North? kind of cold in my shop today,  the fingers still stiff and cold.   on the raidus die you said you started with,  if you get a chance while taking pics,  would you mind to throw one in of the bit please and thank you?

Progress is looking very good.


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## Brian Rupnow (Dec 6, 2020)

Daytime temps are around 30F, night time down to maybe 20F. We've got about 9" of snow here, but it's fairly new---grass was green at end of November.
ball nose endmill on left, corner rounding endmill in center, and 45 degree chamfer end-mill on right.


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## Ghosty (Dec 6, 2020)

Hi Brian,
It is 86F here at the moment, only went down to 68F last night, and my A/C is on the fritz, I feel for you with the cold weather.
Still looking in.
Cheers
Andrew


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## werowance (Dec 7, 2020)

Thanks Brian for taking the time to post those.  i have a pointed end mill like number 3 and have seen the ball nose mills like number 1 but have never seen the roundover bit like number 2.  ill have to shop around for some.   but wanted to say thank you for show them.  have seen some use router bits but was always afraid to try it. need to get one and try on a little scrap aluminum or something



Brian Rupnow said:


> Daytime temps are around 30F, night time down to maybe 20F. We've got about 9" of snow here, but it's fairly new---grass was green at end of November.
> ball nose endmill on left, corner rounding endmill in center, and 45 degree chamfer end-mill on right.


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## Richard Hed (Dec 8, 2020)

Brian Rupnow said:


> Every day, a few more parts. Hardest job of the day was standing out in my unheated main garage sawing out flywheels from that piece of 6" x 1/2" hot-rolled steel. I need a new blade on the saw, and it doesn't cut very fast right now---and if you lean on it a bit then the drive belt slips. ---Thought I might freeze to death before I got the flywheels cut out. Tomorrow I hope to completely finish the flywheels.


I insulated my garage as it was too cold to work in, then I added a heater.  It's much better but when the REALLY cold weather comes, am not sure how it will be.


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## Brian Rupnow (Dec 8, 2020)

And today we have two lovely steel flywheels, bored, reamed, and keyseated. There is a lot of work in two flywheels cut from hotrolled plate, but they turned out very nice. These guys will end up being painted and polished, along with a few other accent pieces on the engine.


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## Richard Hed (Dec 8, 2020)

Brian Rupnow said:


> Every day, a few more parts. Hardest job of the day was standing out in my unheated main garage sawing out flywheels from that piece of 6" x 1/2" hot-rolled steel. I need a new blade on the saw, and it doesn't cut very fast right now---and if you lean on it a bit then the drive belt slips. ---Thought I might freeze to death before I got the flywheels cut out. Tomorrow I hope to completely finish the flywheels.


WHY not take some time out to build a small rocket stove for your shop?  They are marvelously efficient.


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## Peter Twissell (Dec 8, 2020)

Nice job on the flywheels, Brian.
I assume you cut rough circles on the power saw before turning?
In the absence of a powered saw, I tend to do the minimum sawing and Di most of the metal removal on the lathe or mill.


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## Brian Rupnow (Dec 8, 2020)

My bandsaw has a metal cutting blade 3/4" wide. It doesn't cut curves very much at all. Those flywheels were cut from a piece of hot rolled 1/2" plate. First they were cut out as square plates, then the 45 degree corners were cut off, which left me with 8 sided octagon shaped pieces. Then one side was covered with double sided sticky tape and held against the face of my 3 jaw lathe chuck with pressure from a live center in the tailstock. They were turned to perfectly round in the lathe, then held in the reverse jaws to do the cavity in each side and the center hole.


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## Brian Rupnow (Dec 8, 2020)

One of the things that I often have to ask myself, is 'What part do I make next?' Sometimes there is a logical chain of parts that must be made in a certain sequence, other times it doesn't much matter. When I threw together the 3D model of this engine, I designed a crankshaft without thinking a lot about how I would fabricate it. Today I had some design time available after finishing the flywheels, so I took a much closer look at how I would actually make the crankshaft. This was the result, and it looks easy enough, so I will probably work on it tomorrow.


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## werowance (Dec 8, 2020)

Brian, in your opinion,  metal advertised as simply hot rolled or cold rolled which do you normally find easier to work with?  im thinking there are different alloys in both hot and cold rolled but i find many are just advertised as simply hot or cold rolled steel.  i know cheap cold roll seems to finish in a splintered or almost cracked look.  not smoothe like say 12l14 or 1215 does.  just wondered how hot rolled non specified alloy cuts for you?

edit - i guess i should rephrase cracked to just a grainy not smoothe cut


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## lathe nut (Dec 8, 2020)

Brian, they really look nice, that is several hours of work but guess like you say it to cold out there, I don't see how you all can survive that kind of cold weather for that long of a period, here in South Louisiana if it gets to 30 I think we gone to free to death, it took me a while to figure out what was meant by Cabin Fever, fellow better have a hobby and a place to keep warm, thank for the show and tell, Joe


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## Brian Rupnow (Dec 9, 2020)

If you make a part which is going to be machined on all sides, then hot rolled is cheap and machines very well---Hot rolled is the least expensive material but has a rather nasty exterior finish that you wouldn't want displayed on a model. If you machine a part on some faces only and depend on the "as purchased" finish of the part to show in some areas, then cold rolled steel has a much superior finish.  It is a bit more expensive than hot-rolled steel. Hot-rolled steel moves very little during the machining process. Cold rolled steel has a lot of built in stresses from the cold rolling process, so will "banana" on you if one side is machined and the other side is not. As far as machinability goes, they are about equal in my opinion. I have switched from HSS cutters to carbide tooling, because I simply can not keep HSS tooling sharp enough all the time.


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## Richard Hed (Dec 9, 2020)

Brian Rupnow said:


> If you make a part which is going to be machined on all sides, then hot rolled is cheap and machines very well---Hot rolled is the least expensive material but has a rather nasty exterior finish that you wouldn't want displayed on a model. If you machine a part on some faces only and depend on the "as purchased" finish of the part to show in some areas, then cold rolled steel has a much superior finish.  It is a bit more expensive than hot-rolled steel. Hot-rolled steel moves very little during the machining process. Cold rolled steel has a lot of built in stresses from the cold rolling process, so will "banana" on you if one side is machined and the other side is not. As far as machinability goes, they are about equal in my opinion. I have switched from HSS cutters to carbide tooling, because I simply can not keep HSS tooling sharp enough all the time.


Is it possible or a good idea to machine cold rolled to within a few thou, then heat it to destress the stuff and finish later?  What about if it is necessary to re-harden it later?


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## Brian Rupnow (Dec 9, 2020)

You can not harden cold rolled steel unless you use Casenite and surface harden it. Heating it to destress it is just wasted heat.


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## Brian Rupnow (Dec 9, 2020)

Todays work consisted of putting oil holes and galleries into the main crankshaft support block, and making all of the crankshaft parts and silver soldering them together. Highlight of the day was a visit from my friend Terry, a gentleman who shares a common interest with myself about building and machining small engines. We both sat around my office wearing masks and telling each other how tired we are of this damned virus thing. Terry has built a few of my engines, and does marvelous work.


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## Brian Rupnow (Dec 9, 2020)

Tomorrow, after I completely finish the crankshaft, I will work on the eccentrics and eccentric straps.  In the past I have made one piece eccentric straps and a two piece eccentric to hold the straps in place. That works, but it requires rework to a standard socket head cap-screw to make everything fit into a small area. I'm going to do something a little different here. I will make the eccentric from one piece with a flange on each side to keep the eccentric strap in place. The eccentric strap will be two piece with #4 capscrews holding the two halves together. With this design I can use a standard #4 shcs with no modification, and the eccentric strap ends up being much simpler  to machine.


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## L98fiero (Dec 10, 2020)

Richard Hed said:


> Is it possible or a good idea to machine cold rolled to within a few thou, then heat it to destress the stuff and finish later?  What about if it is necessary to re-harden it later?


Yes you can stress relieve CRS but doing it before you do the machining would be the way, the reason it warps when being machined is because of the built in stresses from the cold working processes. Because it's stress relieved instead of annealed, if you can do that, it will still machine like CRS instead of HRS, at least that's my experience.


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## ajoeiam (Dec 10, 2020)

Richard Hed said:


> Is it possible or a good idea to machine cold rolled to within a few thou, then heat it to destress the stuff and finish later?  What about if it is necessary to re-harden it later?


If you choose to do such - - - please don't machine to within a 'few thou' - - - - that won't leave you with enough to remove to give you 'good' parts. 
I would suggest somewhere between 30 and 50 thou and even then I would be using 2 cuts - - - -you know - - - just in case. (Murphy tends to be a regular visitor when I'm around - - - - grin!)


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## Brian Rupnow (Dec 10, 2020)

Crankshaft is finished and installed. No real drama. I have to file off that little bit of key sticking out past the end of the crankshaft, and then I can move on to eccentrics.


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## awake (Dec 10, 2020)

Brian Rupnow said:


> Making round parts went quite swimmingly--Until I broke off a #10-24 tap. Tried all of my usual tricks to remove it, and none of them worked. Will remake that part tomorrow morning.   BAH!!!----HUMBUG!!!



As an aside, I find that I break more 10-24 taps than any other size. I asked about it on PM one time, and the consensus was that this size requires more torque per cross section than any other, due to the relatively coarse threads. 10-32 is so much easier to tap, so I've tried to switch over to that ... but I have a ton of 10-24 fasteners on hand, so it is hard to leave it behind entirely. Of course, one can always drill a bit larger to get only 50% thread engagement, and that will help considerably ... but too often I forget that little trick until just after I hear the "tink" of the tap breaking. Grrr ...


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## Richard Hed (Dec 10, 2020)

awake said:


> As an aside, I find that I break more 10-24 taps than any other size. I asked about it on PM one time, and the consensus was that this size requires more torque per cross section than any other, due to the relatively coarse threads. 10-32 is so much easier to tap, so I've tried to switch over to that ... but I have a ton of 10-24 fasteners on hand, so it is hard to leave it behind entirely. Of course, one can always drill a bit larger to get only 50% thread engagement, and that will help considerably ... but too often I forget that little trick until just after I hear the "tink" of the tap breaking. Grrr ...


Yes, oversized holes help a lot but I also found that 3-flute taps are stronger than 4 flutes.  I never buy 4 flutes.  I thimk that odd flutes are better than even, howeveer, I am not too sure about that.  I just notice that three flutes are better ones (in mhy not very humble opinion) than four.  Anybody else notice this?


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## awake (Dec 10, 2020)

I've switched to using spiral point or spiral flute taps - the former is two-flute in the 10-24 size, and pushes chips ahead of itself (perfect for through holes); I'm not sure how many flutes the latter is - may only be two flutes - this type pulls the chips out. Both of these have improved my success rate ... but still the 10-24 size is the easiest to break, at least of the taps I regularly use.


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## Richard Hed (Dec 10, 2020)

awake said:


> I've switched to using spiral point or spiral flute taps - the former is two-flute in the 10-24 size, and pushes chips ahead of itself (perfect for through holes); I'm not sure how many flutes the latter is - may only be two flutes - this type pulls the chips out. Both of these have improved my success rate ... but still the 10-24 size is the easiest to break, at least of the taps I regularly use.


come to thimk of it, I believe 2 flutes are far better than four.  For some reason, four flutes are weak in the middle where they are connected to the center.


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## Brian Rupnow (Dec 10, 2020)

Every time I make eccentrics, I seem to find a slightly different way of machining them. These turned out quite well, and all I have to do now is drill and tap them for set screws. They do not get a keyway, as they have to be able to rotate on the shaft to set the timing.


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## Tim Wescott (Dec 10, 2020)

So, your method of machining eccentrics is always -- eccentric?


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## Brian Rupnow (Dec 11, 2020)

Tim--My wife said the same thing. She said she was going to bring her camera down to my shop and take a picture of "An eccentric machining an eccentric" and paste it on Facebook!!!


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## Richard Hed (Dec 11, 2020)

Brian Rupnow said:


> Tim--My wife said the same thing. She said she was going to bring her camera down to my shop and take a picture of "An eccentric machining an eccentric" and paste it on Facebook!!!


That's a real insult alright!  Who, in their right mind, would use facecrook?


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## Brian Rupnow (Dec 11, 2020)

My wife is a political hack. She worked most of her life for the federal government in Canada, and loved every minute of it. Now she gets on facebook and fights with all the Americans about their own political shenanigans.  I keep telling her to leave the Americans alone, or we'll be having the black helicopters landing in out back yard.


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## Richard Hed (Dec 11, 2020)

Brian Rupnow said:


> My wife is a political hack. She worked most of her life for the federal government in Canada, and loved every minute of it. Now she gets on facebook and fights with all the Americans about their own political shenanigans.  I keep telling her to leave the Americans alone, or we'll be having the black helicopters landing in out back yard.


I understand--it's a real comedy.  If the black helis showed up at my place, I'd just tell them, "Here I am, where's the handcuffs?"  The onlyway to stop those criminals is to jam the prisons with innocent victims--they can't afford to put us all in prisons or FEMA concentration camps.  Too costly.


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## Brian Rupnow (Dec 11, 2020)

The eccentric straps are finished and installed. The flanges on the eccentrics keep the straps from moving side to side, and yes, they do miss the crankshaft throws when everything is rotated.


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## Larry G. (Dec 11, 2020)

Brian Rupnow said:


> Every day, a few more parts. Hardest job of the day was standing out in my unheated main garage sawing out flywheels from that piece of 6" x 1/2" hot-rolled steel. I need a new blade on the saw, and it doesn't cut very fast right now---and if you lean on it a bit then the drive belt slips. ---Thought I might freeze to death before I got the flywheels cut out. Tomorrow I hope to completely finish the flywheels.


What are the engineering and mathematical considerations in thinning the inner portion of a flywheel, leaving a thick rim?
I understand the mass at the greater radius absorbs, or delivers,  more torque than mass closer to the center of rotation.

In commercial installations of colossal size and weight, such as the Tod Engine in the Youngstown, Ohio steel rolling plant , reducing the less "productive" mass near the axle eases the bearing load, but at what loss to the energy storage of the system? 

In model engines appearance counts as much as function, and barbell weights win no prizes.  

Sorry to send you back to your freshman Mechanics texts, but if you have any questions on Photographic Engineering, perhaps I can be of help.

Thanks,
Larry


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## Brian Rupnow (Dec 11, 2020)

It is really only the outer rim of the flywheel on an engine that does the work. If you could build a flywheel with a hub area for mounting it on the shaft, and the last 1/2" of the outer rim, you wouldn't even really need the thinned out web section. Of course that's not really possible, so you thin down the web area as much as you can, because the mass in the web area isn't really doing anything to help the engine run. A double acting steam engine is always under power, going either direction---except---at top dead center and at bottom dead center where there is a "dead spot". The inertia of the flywheel rotates the engine thru these momentary "dead spots". On a single acting steam engine or on a 2  cycle engine, the flywheel inertia keeps the crankshaft turning thru 180 degrees of the complete circle where the engine is not "under power".  On a 4 cycle i.c. engine, it gets even worse, the flywheel has to actually rotate the crankshaft thru a full 360 degrees before another "power stroke". Hope that answers your question, without going into the physics of flywheel design.---Brian


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## Brian Rupnow (Dec 11, 2020)

Tomorrow I start making cylinders. These cylinders are a bit different, because there is no profiling on the outside. They are rectangular, but there is a lot going on inside. I have made the tapped mounting holes in the underside in exactly the same position as the tapped mounting holes in the topside where the steam-chest bolts on. Two ends are tapped for cylinder end-caps, and two remaining sides are blank. (Except for the exhaust exit hole).


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## Tim Wescott (Dec 11, 2020)

Putting in the physics that Brian leaves out, and hopefully not confusing things too much: the moment of inertial is proportional to mass times radius squared, where radius is the distance of that mass from the center of the circle.   After a whole lot of math (or cheating by looking at tables, and a _little _bit of math), you find that a flywheel with all of its mass concentrated on the rim is twice as effective for the weight as one that's just a flat disk.  If I'm guessing right, Brian's flywheel probably has a moment of inertia about 60% higher for its mass than if he'd used a bit thinner stock and made it perfectly flat.


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## Steamchick (Dec 12, 2020)

Brian Rupnow said:


> Tomorrow, after I completely finish the crankshaft, I will work on the eccentrics and eccentric straps.  In the past I have made one piece eccentric straps and a two piece eccentric to hold the straps in place. That works, but it requires rework to a standard socket head cap-screw to make everything fit into a small area. I'm going to do something a little different here. I will make the eccentric from one piece with a flange on each side to keep the eccentric strap in place. The eccentric strap will be two piece with #4 capscrews holding the two halves together. With this design I can use a standard #4 shcs with no modification, and the eccentric strap ends up being much simpler  to machine.


Hi Brian, I have just seen your eccentric strap design. Very neat and conventional. But maybe you can teach me the merits of 
1) the cap screws going from the cap into threads in the body  - instead of the other way around?
2) using tapped threads in the eccentric strap instead of through holes and nuts? (I used holes with through bolts and nuts on a table engine eccentric - just seemed simple that way?).
3) Are the 2 halves of the eccentric strap dowelled - I guess too small for that so does the eccentric naturally align the 2 halves when tightening cap screws? Or is there a close fit of the shank of the cap screw in the through hole to determine mutual alignment of the halves?
4) My friend made his eccentric strap - for a steam Mill engine - but split along the axis of the eccentric rod. I.E. perpendicular to the split-line you (conventionally) have. Would there be any disadvantage doing it his way? - He was using material from his scrap bin and he thought it would be a talking point!
Is the eccentric mass significant when balancing the crankshaft? - I must admit I haven't thought of this till just now, but as it will be near 90 degrees from the crank it may off-set side oscillations of the con-rod - I think? - Or does it make it worse? - I need to have another look at your gear arrangement and twin shafts to work it out - unless you already have a CAD section that shows the shafts, rods  and gears?
I'm just curious - and willing to learn.
Thanks, I'm enjoying your build and the work you are presenting. A good tutorial!
K2


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## Steamchick (Dec 12, 2020)

werowance said:


> Thanks Brian for taking the time to post those.  i have a pointed end mill like number 3 and have seen the ball nose mills like number 1 but have never seen the roundover bit like number 2.  ill have to shop around for some.   but wanted to say thank you for show them.  have seen some use router bits but was always afraid to try it. need to get one and try on a little scrap aluminum or something


Hi Wereowance. Not sure if it will help... but: When I did a job as Workshop Manager for a short-term welding and machine shop making busbars and connections for and Aluminium Smelter contract... we needed to machine aluminium bars (8" x 2" and a couple of feet long) 45 degrees before welding on the "flexible" connector (made from a pack of 1mm aluminium sheets). The aluminium was soft "99% pure electrical grade". We used a woodworking machine that would go up to 20,000rpm and used woodworking bits in the flycutter. (4in diameter?), The swarf (wire wool) flew! Also we used the same flycutter arrangement to machine 8" wide flat surfaces in 2 passes on bars that were drilled as the pads for the electrical bolted joints. - The only problem we had was clearing the volume of swarf.... The woodworking shop that sold us the machine had a suction dust collector - The aluminium swarf ("candy-floss") we produced had to be manually cleared and compressed and still filled huge volumes for little weight of scrap.
So maybe woodworking tools at high speed will work for you?
Do tell...
K2


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## Brian Rupnow (Dec 12, 2020)

Ssteamchick--eccentric straps are not pinned. They fit between two flanges on eccentrics and can't move. The advantage of having the bolts set up the way I do is that the heads end up resting against a flat surface. The bolt heads are almost as wide as the eccentric straps, so they can't be counterbored. If the split was 90 degrees to the way I have it, every time the rod came under pressure or tension the forces would bear directly on the split, and I don't think that would be good. and yes, there is a very close fit between the cap screws and the eccentric straps.


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## Steamchick (Dec 12, 2020)

Thanks Brian, a logical explanation.
 I worked on HV circuit breaker design in the 1980s.  An Engineering Professor from the local university advised on finit element analysis they had been doing (rare in those days) and advised that typical rod ends should have the following "simple rules" applied. (1) Adequate side material to take the dynamic forces in tension applied to the bottom-half of the bearing. In the case of your eccentric that is the tensile force and stresses in the bolts. (2) adequate stiffness of the "beam" section of the bottom half of the bearing, considered as a simple beam - in the case of your eccentric end "bottom cap" that would be a beam of section of the cap, between the 2 bolt centres and loaded at the centre. 
I guess the loads of the valve on the eccentric are really tiny, and the eccentric relatively large by comparison, so the design is more than adequate, however configured. 
On my friend's longitudinally split eccentric cap, the tensile forces at the sides are contained in the brass of the eccentric strap but the stiffness of the end of the eccentric strap is ensured by the clamping force of the steel bolt at that point, and the  2 clamped faces of the eccentric strap. In terms of the split point being at point of maximum bending moment, I guess the design is not the best - or stiffest - but is adequate for his model - a scratch built version of a Stuart no. 1. Vertical DA single.
A new observation - for discussion: The flywheel is like the solid disc flywheel common on many traction engines, road rollers etc. How will you balance this against the crank-shaft and eccentrics?  I know how to do the calculations, (a bit of fun in your case of 2 cranks at 90 degrees, plus eccentrics rotating in the opposite direction?) but I was wondering if you were going to bolt-on counter-balance weights, or drill holes or something to remove metal from the opposite side? I think curved brass counterweights against the bright steel could look quite attractive? - with tiny steel bolts securing them? I have seen cast spoked flywheels on models that have been drilled on the outside of the rim and it just doesn't look so good to me.
Excellent work you do.
Thanks
K2


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## Richard Hed (Dec 12, 2020)

ajoeiam said:


> If you choose to do such - - - please don't machine to within a 'few thou' - - - - that won't leave you with enough to remove to give you 'good' parts.
> I would suggest somewhere between 30 and 50 thou and even then I would be using 2 cuts - - - -you know - - - just in case. (Murphy tends to be a regular visitor when I'm around - - - - grin!)


Yes, thank you, I would not remove the part from the chuck at all for 'only a few thou', that's what I meant, what you said.


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## Richard Hed (Dec 12, 2020)

Steamchick said:


> Hi Brian, I have just seen your eccentric strap design. Very neat and conventional. But maybe you can teach me the merits of
> 1) the cap screws going from the cap into threads in the body  - instead of the other way around?
> 2) using tapped threads in the eccentric strap instead of through holes and nuts? (I used holes with through bolts and nuts on a table engine eccentric - just seemed simple that way?).
> 3) Are the 2 halves of the eccentric strap dowelled - I guess too small for that so does the eccentric naturally align the 2 halves when tightening cap screws? Or is there a close fit of the shank of the cap screw in the through hole to determine mutual alignment of the halves?
> ...


Steam,
Could you clarify your first point?  The others I get but the first is, unclear?


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## Brian Rupnow (Dec 12, 2020)

Was I busy today??---Yes, you can bet your bippy that I was. 32 holes drilled and tapped, bore and air passages machined in. I've been at these cylinders all day, and I'm going upstairs to set with my good wife and drink rum now!!!


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## Brian Rupnow (Dec 12, 2020)

Steamchick---Simple answer--I don't balance them. This is a low rpm model engine. There is a way to calculate the required balancing weights, but it is complex and requires a very sensitive weigh scale that I don't have.


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## Richard Hed (Dec 12, 2020)

Brian Rupnow said:


> Was I busy today??---Yes, you can bet your bippy that I was. 32 holes drilled and tapped, bore and air passages machined in. I've been at these cylinders all day, and I'm going upstairs to set with my good wife and drink rum now!!!


Whoa!  Such beautiful progress.  At this rate, you will be done shortly and have it puffing away.


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## Tim Wescott (Dec 12, 2020)

Brian Rupnow said:


> Steamchick---Simple answer--I don't balance them. This is a low rpm model engine. There is a way to calculate the required balancing weights, but it is complex and requires a very sensitive weigh scale that I don't have.



Ahh -- for infernal combustion 2-strokes, the rule of thumb is to put half the reciprocating weight on the crank pin, and then balance the assembly.  If you don't hit it exactly, you just remember that your motor can't be perfectly balanced anyway.

(But aside from having a nifty counterweight incorporated into the flywheel, I like your method of just observing it's low speed).


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## Brian Rupnow (Dec 13, 2020)

This morning I whittled out a pair of steam-chests. The steam-chest covers will be machined from mild steel and painted to match the flywheels.


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## Richard Hed (Dec 13, 2020)

Brian Rupnow said:


> This morning I whittled out a pair of steam-chests. The steam-chest covers will be machined from mild steel and painted to match the flywheels.


I'm just curious about where y;oou get all that brass?   I have about 200 lbs of the stuff in containers waiting to be made into ingots or cast that I have had for a couple decades becauise the stuff is so expensive but easily (relatively) melted.  Do you have a cheap source?


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## Brian Rupnow (Dec 13, 2020)

There is no cheap source for brass. I buy my brass from a metal supplier right here in Barrie, but I cry a little bit every time that I do.


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## Richard Hed (Dec 13, 2020)

Brian Rupnow said:


> There is no cheap source for brass. I buy my brass from a metal supplier right here in Barrie, but I cry a little bit every time that I do.


Well, eventually, I am going to get my foundry set up and melt down this alu and brass into ingots, and I hope, a couple casts.  Im wondering if you know anything about melting alu and brass.  I know alu one can use soda or buy commercial gas removers (apparently hydrogen) and slag materials but I don't know about brass.  I would thimk it too would have some kind of gas remover, can one use the same stuff as with alu?  Have you done foundry work?


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## Brian Rupnow (Dec 13, 2020)

I have no background in foundry work. I know the principals and theory, but have no hands on experience.


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## Richard Hed (Dec 13, 2020)

Brian Rupnow said:


> I have no background in foundry work. I know the principals and theory, but have no hands on experience.


Looks like yu have lots of room for it.  I am stuk in a small city lot


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## Steamchick (Dec 14, 2020)

Brian Rupnow said:


> This morning I whittled out a pair of steam-chests. The steam-chest covers will be machined from mild steel and painted to match the flywheels.


Hi Brian, you are progressing well with this engine. Looking good! Will the inside of the MS valve covers have any anti- corrosion on them? Do you run steam? Or just compressed air? As most of my models are cast iron, and I run steam, I always have to wash-out the wet with lots of WD40, then oil with steam oil after running. Just time consuming maintenance... I have seen a valve chest cover (removed) which was painted inside, but not on the joint faces, as the slide valve didn't contact the cover. Seemed to work OK? I was wondering about copper plating? Phosphating? Or tinning? (I have lots of spare plumbers lead solder?). I'll be glad of "easy" suggestions?


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## Brian Rupnow (Dec 14, 2020)

Steamchick--I run my engines on compressed air. Occasionally I give a squirt of light oil into the airline, knowing it will lubricate the slide-valve and the piston. I never wash my engines out after I've run them. I don't put any coatings on my slide valve nor my cylinders. In this particular case I am making the cylinders from brass and the slide valve from mild steel, simply to avoid the galling of running two identical metals together.----Brian


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## Brian Rupnow (Dec 14, 2020)

Today was the day to make slide valves and control rods. I dug around in my "scrap brass drawer" and actually found a little bit of bronze to make the rod ends out of. The slide valves and control rods are cold rolled steel. The cross nuts in the slide valves are cold rolled steel. That's enough work for today.


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## Brian Rupnow (Dec 15, 2020)

Oh!!--I do love it so, when a plan starts to come together. No major pieces made today that show, but about 8 or 10 that don't, and they are all required to make this thing run.










.


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## Brian Rupnow (Dec 16, 2020)

Today has been designated "Connecting Rod Day". Since I'm dealing with a bit of Cabin fever due to Covid and winter, I'll do a complete run-thru on this subject. Con rods for internal combustion engines all look basically the same, except for size. Con rods for steam engines come in a few different shapes, and there is a bit of "mechanical art" involved in a steam engine connecting rod.


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## Brian Rupnow (Dec 16, 2020)

I had a length of 1/2" square brass that I will make the con rods from. These rods will be turned between centers, not held in a chuck. As a consequence of this, the exact centers are marked out by using the handy little 45 degree angle tool in the picture. The material (as per my hand sketch) is made 0.2" longer on each ends to allow for center punch marks. The material has been coated with layout dye, and the point at which major diameter differences occur they have a line scribed around them. After establishing the exact center of each end, the pieces get a good center punch mark, so they can be turned between centers using a lathe dog.


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## Tim Wescott (Dec 16, 2020)

I'm drooling over your handy 45 degree angle tool.  BTW.


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## Brian Rupnow (Dec 16, 2020)

I have a couple of old lathe dogs that hardly ever get used. If this was something super critical, I would remove the chuck and put a dead center into the tapered socket in the end of the spindle, however for what I'm doing, I simply chuck up a piece of cold rolled with the one end turned to the specified angle. The other end is supported by a dead center in the tailstock chuck. I do have a live center, but on short pieces like I am doing here, it takes up too much space. I will put a dab of grease on the end of that tailstock dead center, and the turn the round portion of the conrod down to 0.25" diameter over it's full length. I know that the drawing specs out 0.236" diameter, but I'm going to make it a bit heavier.


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## Brian Rupnow (Dec 16, 2020)

Eventually, the round area of the shaft will get worked down to .250" diameter. This will require left hand cutters, right hand cutters, and possibly even parting off tools to work the 1/2" square brass down to 0.250' diameter.  This is trickier than it sounds, because as the diameter reduces, the part wants to spring away from the cutting tool, then dig in when it rebounds. All you can do to prevent that is to take progressively smaller depth cuts and use really sharp tooling. Since I have machined away the black center mark, I will restore that mark with my black marker, then set my compound rest over two degrees and work from the center out towards the ends. When one side is completed, I set the compound rest over two degrees in the other direction and working from the center machine out towards the other end. Note that the last two cuts must be made with the topslide, not the normal lead screw.


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## Brian Rupnow (Dec 16, 2020)

And here is the con rod with a 4 degree included angle running from the center out towards the rectangular ends.


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## ajoeiam (Dec 16, 2020)

Brian Rupnow said:


> Today has been designated "Connecting Rod Day". Since I'm dealing with a bit of Cabin fever due to Covid and winter, I'll do a complete run-thru on this subject. Con rods for internal combustion engines all look basically the same, except for size. Con rods for steam engines come in a few different shapes, and there is a bit of "mechanical art" involved in a steam engine connecting rod.
> snip



You left a bit of a tease when you indicated that IC engine con rods are quite similar but no information on con rods in a steam engine other than mentioned that a 'few different shapes' are used. Would you have any docs or urls that you would care to point the curious to?

TIA


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## Brian Rupnow (Dec 16, 2020)

And con-rod day comes to a close!! It was a long but successful day, with many interruptions. In the end, at the close of the day, I have one finished con rod, installed. Tomorrow, I hope to have the other one.


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## werowance (Dec 16, 2020)

that looks really nice. the rod just barely clears on the bottom (a hair is good as a mile) which makes it look nice

on another note.  if you ever get bored and want to describe in more detail the procedure to cut an ecentric circle or offset circle on another circle,  ill try to listen and hopefully understand it.  doing it on a 4 jaw and measuring the offset is what eludes me.  even more so when there are multiple ecentrics on a single base circle and not just one


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## Steamchick (Dec 17, 2020)

Tim Wescott said:


> I'm drooling over your handy 45 degree angle tool.  BTW.


The "Engineer's centre square"
Apprentices used to make them, now the Chinese may them for just a couple of £...
I have one my Father made - as an apprentice.
Bigger ones cost more...








						LARGE CENTRE CENTER SQUARE 3" 75MM MEASURING ENGINEERING TOOLS RDGTOOLS  7435353647566 | eBay
					

LARGE CENTRE SQUARE.



					www.ebay.co.uk
				



Also: Search for "45degree centre finder"... and find many forms of the same principle.
Very useful on round, hex, square material, also on cast material, where a series of scribed lines can give a pattern that will "surround" the centre of the casting...
Apprenticeships were a very good way to learn.... very thorough, and guided by experts - as this website holds.
K2


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## Steamchick (Dec 17, 2020)

Brian Rupnow said:


> I have a couple of old lathe dogs that hardly ever get used. If this was something super critical, I would remove the chuck and put a dead center into the tapered socket in the end of the spindle, however for what I'm doing, I simply chuck up a piece of cold rolled with the one end turned to the specified angle. The other end is supported by a dead center in the tailstock chuck. I do have a live center, but on short pieces like I am doing here, it takes up too much space. I will put a dab of grease on the end of that tailstock dead center, and the turn the round portion of the conrod down to 0.25" diameter over it's full length. I know that the drawing specs out 0.236" diameter, but I'm going to make it a bit heavier.


Thanks Brian for explaining such a simple alternative to stripping off the chuck to fit a centre. And also the use of a dead centre in the drill chuck in the tail-stock to give more clearance....  A problem I had yesterday and did the same thing!
K2


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## Steamchick (Dec 17, 2020)

werowance said:


> that looks really nice. the rod just barely clears on the bottom (a hair is good as a mile) which makes it look nice
> 
> on another note.  if you ever get bored and want to describe in more detail the procedure to cut an ecentric circle or offset circle on another circle,  ill try to listen and hopefully understand it.  doing it on a 4 jaw and measuring the offset is what eludes me.  even more so when there are multiple ecentrics on a single base circle and not just one


I once used a small 3 jaw self-centring chuck offset in a large 4-jaw chuck to machine big-end journals on a 180 degree twin big-end crank-shaft: It worked - same off-set: interesting set-up, but the imbalance was horrendous and I could only run the lathe at a very slow speed. 
The better alternative is to make a simple block with clamp screw to take the round stock and mount eccentrically in the 4 jaw chuck - or on a face plate - when normal turning of the eccentrics can easily be achieved. Using a face plate gives scope to add a balance weight for the eccentric material, for better (smoother) running of the lathe. Returning the "eccentrically turned" stock to the self-centring 3-jaw chuck or collets - or between centres - will then be appropriate for machining main journals.
But "better men than I" can teach us all better methods...
K2


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## Brian Rupnow (Dec 17, 2020)

Both connecting rods are finished and installed. They fit and everything still goes round and round----but---what a pig to get into place!!! The original design was for one piece connecting rods, and they went into place with no difficulty on the single cylinder popcorn engine. However, with twin cylinders, there is simply no good/easy way of installing them. I have changed the detail drawing of the con rods, so that they now have bolt on end caps. this will make it a lot easier for the next person to build this engine.


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## Brian Rupnow (Dec 17, 2020)

Slide valve actuator rods and ends are finished (mostly) and in place. That's all for today folks. good wife is calling me for supper!!


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## Steamchick (Dec 18, 2020)

Hi Brian. I am enjoying your build - and tutorial (including cat and Wife notes!). In trying to understand your remark about the assembly of con-rods... is the problem simply that you need to address the big-end of con-rod to crank-pin laterally to rod axis, while the cross-head only permits axial motion? I guess you hand to assemble the cylinder with con-rod and cross-head and then fit this assembly to the crank? A lesson in "design for assembly" that I didn't spot earlier. I must try harder!
But when I worked for a major automotive factory we actually did this sort of thing - because in the total cost game it was the best solution. In the 1980s, I was fascinated by the assembly of a carburettor to manifold where 1 nut with difficult access was wrapped with a spiral of string, held on the end of the stud, then the string pulled to wind the nut onto the stud. Poor design overcome by assembly skill? There were many examples like this.
Keep up the good work,
K2


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## Brian Rupnow (Dec 18, 2020)

This morning I'm setting here dreaming up an intake manifold for this engine to get air into it. Rather than just hooking an air-line onto a hose barb, I want this engine to have a control valve to govern the air flow.  I had to reach back about 10 or 12 years to my steam donkey engine and have a look at the air control valve I designed and built for it, because it worked very well. This new air intake control valve looks totally different rom the steam donkey engine valve, but it has all the same guts in it.


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## Steamchick (Dec 18, 2020)

Hi Brian,
I'm curious to know "the guts"! - I'll not be surprised if you have them in your CAD - even exploded!
K2


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## Steamchick (Dec 18, 2020)

Will the Throttle be controlled by a "maritime" type of wheel and linkage? - or just a simple knob for the finger and thumb? - I suggest "Maritime", as this engine reminds me of the configurations for Side paddle-wheel boats where the engine was sited low, but the crank was situated higher - in line for the paddles.
While I think of it, I'll bet you have some clever scheme for linking cylinder drain valves? - Or are they "not required" on this if only an "Air" engine?
Another odd question: What do you plan for timing when designing and Air engine instead of steam? - I.E. how much (crank angle) advance on the eccentric - and how much cut-off do you set on the valve? I'm asking because I understand steam can have an earlier cut-off than if the engine is just used for air, but the Lead of the eccentric is just to do with engine speed, and may be different depending on the number of cylinders? I've not read anything that I can remember on this so unsure of the subject! So please excuse if a "stupid" question.
Ta,   K2


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## Brian Rupnow (Dec 18, 2020)

The vertical lever swings 90 degrees to provide full pressure to the both engines. Since I only run these engines on air, they don't require cylinder drain valves, but those are easily added if someone wishes to run on live steam. To time an air engine you put the piston at top dead center, then with the set-screws on the eccentric hubs unlocked, you turn the eccentric hubs until the slide control valve is at mid travel, then lock up the set screws. If you want opposite rotation you set the piston at bottom dead center before doing this.


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## Brian Rupnow (Dec 18, 2020)

This morning I lapped the brass cylinders. I have brass expanding laps, but didn't want to risk brass on brass. The cylinders were originally reamed to 0.500" with a machine reamer. A piece of cold rolled steel 1/2" shafting is always about .0005 to .001" undersize, which makes it unsuitable for a lap. 01 Steel however, comes in exactly on size, at a full 0.500" diameter, and will not pass freely thru the hole in the cylinder---but very close. So--I chuck up a piece of 1/2" diameter 01 steel, coat the end of it with 600 grit lapping paste, and with the lathe running on it's lowest speed, I SLOWLY AND CAREFULLY work the brass cylinder onto the lap. Not all in one go.--Maybe an eighth of an inch, then back off, then maybe a 1/4" and then back off and keep at it in 1/8" increments until the lap passes all the way thru the cylinder. Generally it sticks solid at some point and requires a trip out to my arbor press to press the stuck 01 steel out of the cylinder. You have to be damned sure that when it begins to seize that you can let go cleanly and not wrap yourself up in the lathe. After the lap passes completely thru the cylinder, work it back and forth slowly about 20 times, and you are finished.


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## Steamchick (Dec 18, 2020)

_Thanks Brian!_


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## Brian Rupnow (Dec 18, 2020)

These are the pistons (aluminum) and the piston shafts (cold rolled steel). The pistons and the shafts are threaded #10-24 and joined with #262 Loctite thread locker. The pistons, as they currently are, are 0.504" diameter, and will not fit into the cylinders. After the Loctite has 24 hours to "set up" I will lap the pistons into the cylinders. There will be no piston rings, only a couple of small oil retention grooves in each piston. These were the last parts of the engine, except for the intake manifold system, which I will start work on tomorrow.


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## Brian Rupnow (Dec 18, 2020)

Made a mistake--Kissed a snake--That previous picture is wrong. I have just remade the aluminum pistons. They should be only turned to 0.562" diameter with no oil grooves. They still get Loctited to the threaded piston rod and left 24 hours to dry. Then, to ensure concentricity, the steel rod is gripped in the chuck, and the piston is turned down to about .002 to .003" oversize and the oil grooves cut into it, THEN it gets lapped into the cylinder.


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## Steamchick (Dec 19, 2020)

Thanks for the correction Brian - I'm not speaking for anyone else - but I didn't notice your mistake! - Actually, if the grooves are machined to the correct ID before you finish machining the OD of pistons concentrically to the rods, then they will still function as labyrinth seals (and retain oil) - even if a thou or so eccentric. - I think? And doing it that way, would you not also ensure that cutting the grooves does not deform the piston OD? - I know the lapping will eliminate any burring or distortion from machining grooves, but maybe you can work to just a 0.001" oversize and have less lapping? - From my experience with full sized mass-produced car engines, the finish machining of pistons should be "coarser" than the amount to be lapped, so the surface is finished to "flat topped" machining, with half-Vee grooves in it which are "lower friction" (from shear of oil films) and ensure oil retention all along the surface of the piston... This was a point specifically discussed between a Japanese "expert" and Hepworth and Grandage "expert" when we were selecting the company with suitable expertise to make pistons for my Company. H & G tables a paper that explained how their pistons had lower "skirt friction" in real engines than certain competitors, because of their particular (patented?) machining of the skirt surface. Probably inconsequential to you, for the performance of you engine..? - But may be of interest to someone out there?


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## Brian Rupnow (Dec 19, 2020)

So---If you wondered what a lapped piston looks like, then this is it. After setting overnight while the Loctite set up, the pistons were turned down to 0.502" with a very sharp carbide while the piston rod was gripped in the three jaw chuck. Then a very slight touch with a diamond lap brought them down just far enough that one end of the piston would start to fit into the cylinder. Then they were covered in 600 grit lapping paste . I held the cylinder in my hand and worked it (again, very slowly) onto the piston (The piston is still being turned by the lathe). Once I had it lapped enough to fit thru the cylinder, I came in with the corner of a very sharp tools and cut the two oil grooves.  Of course, like almost any metal, this operation raised a ridge of material on each side of the oil groove---So---More lapping paste and then one more light lapping into the cylinder to get rid of the raised up ridges on the piston.


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## Steamchick (Dec 19, 2020)

I figured you would have burrs to lap-away... so your first method (machine the grooves before finish turning on the con-rod) would not have the "raised ridges" to lap. Plenty of ways to "kill this pig!".
But "well done" for an excellent job anyway!
K2


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## Richard Hed (Dec 19, 2020)

Brian Rupnow said:


> So---If you wondered what a lapped piston looks like, then this is it. After setting overnight while the Loctite set up, the pistons were turned down to 0.502" with a very sharp carbide while the piston rod was gripped in the three jaw chuck. Then a very slight touch with a diamond lap brought them down just far enough that one end of the piston would start to fit into the cylinder. Then they were covered in 600 grit lapping paste . I held the cylinder in my hand and worked it (again, very slowly) onto the piston (The piston is still being turned by the lathe). Once I had it lapped enough to fit thru the cylinder, I came in with the corner of a very sharp tools and cut the two oil grooves.  Of course, like almost any metal, this operation raised a ridge of material on each side of the oil groove---So---More lapping paste and then one more light lapping into the cylinder to get rid of the raised up ridges on the piston.


What effect did the lapping have on the cylinder?  Did it come out oversized by say, half a thou?  What happend?  I am considering doing this, following your method, but I would like to know all the effects.


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## Brian Rupnow (Dec 19, 2020)

Happy Gasket to me--Happy Gasket to me---This is how I make all of my gaskets. 0.030" general purpose gasket from an automobile supply store. I use it for head gaskets on i.c. engines too. It's cheap, and I've never had a failure from the gasket degrading. I print them out on a sheet of printer paper, glue them to the gasket material with a glue stick, then use a leather-workers punch, a pair of scissors, and a surgeons scalpel to cut them out.


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## Brian Rupnow (Dec 19, 2020)

Richard--even when cut with a reamer, the inside of the cylinder is microscopically rough. The first reaming with the 01 steel shaft and 600 grit paste removes all the ripples and ridges and leaves a smooth surface.  If the cylinder was iron and you could find a 3 stone brake cylinder hone small enough, it would accomplish the same overall effect. If you could look at the surface of a lathe turned piston, you would again see a rough finish. By making the piston .001" to .002" oversize and lapping it into the cylinder, it polishes the piston to the same finish and diameter as the inside of the cylinder. That is almost the only way to come up with a mostly air tight seal between the piston and cylinder when no piston rings are being used. Can it be measured?--Not with the equipment I have. My micrometers smallest divisions are thousandths, not ten thousandths.


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## Brian Rupnow (Dec 19, 2020)

Oh Happy Happy--Joy Joy---Even though I know the computer said it will work---Even though I have a lot of experience with these small engines---It still just makes me light up when all the major parts are assembled and they really do go round and round and up and down with no big interferences or glitches. This was only the first side, and I still have to test/fit the second side, but I'm stoked!!!


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## Steamchick (Dec 20, 2020)

Nice one Brian! Looking forward to seeing both sides connected - and valves connected. Maybe a short video at that point?
K2


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## Brian Rupnow (Dec 20, 2020)

Here we are at the "running in" stage. The motor is a 1/4 hp. 1750 rpm appliance motor, and with the pulleys I have on there, the geared engine is turning about 400 rpm. The engine was "tight", but I was able to turn it through a complete 360 degrees by hand with no interference. The eccentric straps are very tight on the eccentrics, so I have loosened off the connecting bolts to free the strap up a bit. After 10 minutes of running, I will shut things off, inspect, and tighten those bolts a bit more. Over the course of a 1 hour run in I will have all the bolts tightened up to spec, and all of the tight spots worn away so the engine is free to rotate with no binding.


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## Brian Rupnow (Dec 21, 2020)

It doesn't look like much---but---there's a whole days work there. I did take time out to eat and to go to my nut and bolt store to buy a couple of new 1/16" hex wrenches, but other than that I've worked on this air control valve all day. I still have to build the handle and drill and tap the steamchests where this valve bolts on.


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## Brian Rupnow (Dec 22, 2020)

I have had a rather scattered day today, but did manage to finish and mount the air control valve. I am very close to having a running engine here. I have some rework to do on the piston rods and then when I put the flywheels back on, this thing should run.


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## werowance (Dec 22, 2020)

lookin nice.


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## Brian Rupnow (Dec 23, 2020)

After building and running 40 engines, I have reached a milestone. I no longer find it difficult to make the parts. (As long as they are designed in a reasonable manner). Since I am the guy that machines the parts, I have a fairly good eye for what is doable, given the machines that are in my shop. So---I don't have any problem designing the parts. I (mostly) don't have a problem machining the parts. The next thing to get a handle on is putting all of the parts together and  getting them to work together in harmony.--Kinda sounds like a workers paradise, doesn't it)!! All of the components for this engine are machined. They are all assembled. I have found that if I leave lots of clearance on all of the parts that are assembled, then the engines run easy, but after an hours running all of those fits get sloppy as Hell. And you can't machine material back on!!! The alternative is to leave just enough clearance to assemble the engines. When everything is assembled and all the nuts and bolts are tightened up, the machines are generally "seized" and won't turn over at all.  So---I don't cinch all of the nuts and bolts down dead tight. I snug them up, but not too snug. then I "run in" the engine with an electric motor and v-belt drive for half an hour---Then I shut the motor off, inspect everything, then tighten up all the nuts and bolts a bit more, but still not "dead tight". I may repeat this three or four times, until I reach a point where all the fasteners are tightened down fully and the engine still turns freely. That's where I'm at on this engine right now.


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## Tim Wescott (Dec 23, 2020)

That's an interesting comment on running in.

Car engines manage to run from scratch (well, except for formula 1 engines -- apparently you need to pre-heat them for 30 minutes before you dare start them).

But back in the 1990's our ace engine rebuilder would build 'em to last forever -- and warn us that the cost of that was that the break-in period was about 5000 miles!  Everything would be just a bit tight, and you'd have to run the engine carefully, but in the end it'd have 200,000 or 300,000 miles of hard living pulling a truck around before you had to worry about it.


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## lathe nut (Dec 23, 2020)

Brian, that is going to be a cute running motor you have there and know that it will work out, you designed it with the end in mind, I worked for years at a company that the younger fellows started coming in they had there degrees to prove how stupid they were, send out a set of plans to the in house fabricators and those fellow knew it was not going to work but the kid engineer told them how smart he was and they going to prove him wrong by not saying that they see mistakes so several million dollars later when the equipment would not work on the job site they proved there point to the kid but that only got worse and more money lost, I told one of kids one day you should have to be able to make the part and make sure it works before it going on job sites, you are not an asset you are liability, course they got rid of several of them only to get another batch that was more stupid, I finally made it to retirement 46 year, long enough to see us go down the slippery slope, your advice on break in was great, thanks for sharing, Joe


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## Steamchick (Dec 24, 2020)

I was one of those graduate engineers... but started my "apprenticeship" at 13 - part-time cleaning, then using, machine in a machine shop, re-furbishinge engines and compressors of all sizes. By 19 I was told I'd had at least as much train as the full-time apprentice. But 50 years on I am still learning. The best combine academic and expertise, like Brian, and that's my goal...
Nice work Brian.
K2
K2


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## ajoeiam (Dec 24, 2020)

Steamchick said:


> I was one of those graduate engineers... but started my "apprenticeship" at 13 - part-time cleaning, then using, machine in a machine shop, re-furbishing engines and compressors of all sizes. By 19 I was told I'd had at least as much train as the full-time apprentice. But 50 years on I am still learning. The best combine academic and expertise, like Brian, and that's my goal...
> Nice work Brian.



IMO that kind of training is how you get a capable mechanical engineer. For the last who knows how many years people go to university for 4 years and then they're experts. A few use a co-op program and they get to learn a little bit of on the job stuff. Its easy to see paper engineering expertise - - - - you know when you just can't get at stuff to fix it or to remove it - - - or you need to take off the radiator and loosen engine mounts to change a water pump. The last 15 to 20 years - - - - to compensate for inadequacies all the engine intricacies for setup are hidden in software - - - - supposedly stuff that makes the engine work better - - - - yet these engines and the machines they're in - - - - well they are irreparable - - - - but that's the idea - - - - it makes more money for the company. I wish I could create a total boycott of all the useless stuff that is being foisted on us - - - - starting with automobiles that have no idea what economical travel is (second being appliances that don't even last 10 years).
> rant off


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## Steamchick (Dec 24, 2020)

40-odd years in industry - the private sector that makes profit, pays tax and doesn't rely on government support - I learned a long time ago that happy customers buy your products again. So most of the design of modern products is designed to the desires of the committee of the public that buy the products... combined with what the government permit through regulations.
Not necessarily what everyone wants.
K2


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## Brian Rupnow (Dec 24, 2020)

I learned early on that you don't antagonize or lord it over the guys in the shop. You are young and green. Some of the guys in the shop have been there 50 years, and seen it all. If a shop guy gets you aside and privately tells you something you designed isn't going to work and explains why, you damned well better listen. If you play the "I'm an engineer so do exactly as I specified" the shop guy will build exactly what you asked for. And it won't work. And then there will be a meeting between management, engineering and the shop steward. WHY did our shop do something so patently stupid and waste the companies money? And then the shop steward will say "My machinist told Brian that wasn't going to work, but he Brian blew him off and said he was an engineer and to do it his way. Then for the next week you walk around feeling about 2" tall, and wondering if maybe you should have taken up farming or sky diving instead of engineering.


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## Steamchick (Dec 24, 2020)

I was taught that as a kid -from stern words, or a clip around the ear. "DON'T tell your betters what to do". Served me well. But also "Don't stop asking, just listen and consider the advice".
K2


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## Brian Rupnow (Dec 24, 2020)

I believe this is the last part to be machined for this engine. Since the main air valve is a single feed and is then split to run out to each cylinder, there is no way to test and set up the engines individually. This single air feed adapter lets me take the main valve and air manifold off the engine, and then it attaches to one steam chest to set up only that engine. Then it is removed and attached to the other engine for setting it up individually. After both engines have been set up to run individually, then this part is removed and the normal valve and air manifold are reattached to the engine.


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## Tim Wescott (Dec 24, 2020)

I liked working at FLIR Systems, because when you got a part back from the model shop, you got your drawing, too -- with all sorts of annotations and corrections.  In red.  It was great.  After the second time I gave them a nicely detailed, incorrect drawing, I just started giving them rough sketches like the real ME's did.  Things went smoother after that.

(And sometimes there is a point to getting a part assembled exactly according to your directions -- "I want to know where my design is wrong, so I can fix it".  We had a guy on the shop floor who'd do that all day, or build it up and mark up the instructions where they were cockeyed.  He could barely speak English, but his writing was fluent.  We had another guy, from the same region of the world, fluent English, would use it to complain all day long about engineers -- but if you tried to hand him a red pencil he'd treat it like you were throwing a venomous snake at him.)


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## Brian Rupnow (Dec 25, 2020)

All of the teachers in my engineering apprenticeship were Dutchmen who had immigrated to Canada. They were very patient and kind and all belonged to the Dutch Reform church, so if you gave them any kind of a chance they would do their best to look after your immortal soul as well. They could be quite severe and strict, but that was quite uncommon. They were great teachers and great people. I live forever in their debt. They are probably gone now and I hope they all went directly to their version of Dutch heaven.----Brian


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## Brian Rupnow (Dec 25, 2020)

Santa came to our house last night, same as he always does. I must have been a good boy this year because I ended up with new socks, t-shirts, sweaters, and a new pair of shoes. I generally buy "odorless" varsol to wash down oily, greasy parts with. After considerable time "running in" my newest engine, and constantly supplying it with squirt can oil, it was filthy with a mixture of oil and powdered aluminum and brass. I was out of odorless varsol this morning, so tried to sneak some lawnmower gas into my workshop and wash down the engine. I immediately got yelled at by good wife for "Stinking up the house", so had to abandon that idea. Much later in the day, I finished cleaning up the engine and machined a new cam-shaft with keyways for the flywheels and a flat for the set-screws in the central gear. Tomorrow, if things don't come amiss, I am going to ty and run this engine.  After I get it running to my satisfaction, I will remove the flywheels and the steam-chest covers and paint them.


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## lathe nut (Dec 25, 2020)

don't want to get her mad you might be sleeping in the yard and stuck to the ground by daylight.


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## ajoeiam (Dec 26, 2020)

Brian Rupnow said:


> Santa came to our house last night, same as he always does. I must have been a good boy this year because I ended up with new socks, t-shirts, sweaters, and a new pair of shoes. I generally buy "odorless" varsol to wash down oily, greasy parts with. After considerable time "running in" my newest engine, and constantly supplying it with squirt can oil, it was filthy with a mixture of oil and powdered aluminum and brass. I was out of odorless varsol this morning, so tried to sneak some lawnmower gas into my workshop and wash down the engine. I immediately got yelled at by good wife for "Stinking up the house", so had to abandon that idea. snip


Its not always easy to find but I bought a 5 us gal pail of a citrus based cleaner. 
Not sure if this is the product but it could be something like this:   Eco Orange Citrus Cleaner| World's Best Citrus Cleaner| The only cleaner you will ever need   - - - - I am not endorsing this particular product - - - - just providing a possible example. This kind of product is MUCH easier on the hands - - - - it doesn't stink and yet it cleans parts well and leaves a thin coating so rust isn't an issue pdq. Would recommend looking for this kind of cleaner!     (another option: Orange Peel-Citrus Cleaner - SpecChem  )


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## Brian Rupnow (Dec 26, 2020)

Thought I would have a runner today, but it didn't happen. The current valve control rod set-up is not strong enough, and due to the stresses involved the 1/8" diameter steel rod bent and then broke just beside the blue nut in the top picture. Tomorrow I will canibalize all of the existing parts and fabricate a new brass piece as seen at the bottom of the picture, which will have much more resistance to bending or breaking.  Also, I am going to have to add a piston ring to the pistons. I can re-use the existing pistons and simply turn a ring groove in them.


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## Brian Rupnow (Dec 27, 2020)

Today I revisited the valve control rods. These rods have a high bending moment applied to them if there is any binding between the eccentric strap area and the eccentric itself. As the eccentric revolves, this sets up a reversing moment in the rod, and if the rod is smaller than 1/8" in the threaded area, it soon fails in a stress type failure. I'm not concerned about weight, so have spent part of today making newer heavier links.


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## Brian Rupnow (Dec 27, 2020)

This time around, I fitted the eccentric straps to the eccentrics off the engine. The broken 1/8" connection rod was totally my bad. Sometimes I try to cut corners, and end up in the $hit. The holes in the current and the earlier version of the eccentric straps was reamed to 0.750". The eccentrics were a couple of thou oversize. I thought I could work that down while running the engine in and gradually tightening the connecting bolts as things loosened up. This resulted in failure of the 1/8" rod. I have a vertical spindle sander here that takes different diameters of rolls. I used it to open the 0.750" bores on these new "eccentric straps" to 0.752+/- and then worked the final bit down with 600 grit lapping paste. Like the saying goes, "The hurrier I go, the behinder I get".----Brian


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## lathe nut (Dec 28, 2020)

Hey Brain don't be so hard on your self, think we all get in that situation, make it with what we have and hope it will be stout enough to work, considering that you are building it from what is is in your mind's eye not something that someone one else has built and worked out the bugs, you did great, love the connecting rods that really looks with the flywheels, I know that you won't give up and won't give in.


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## Anatol (Dec 28, 2020)

Hello Brian
I enjoy your thorough and thoughtful posts. In this case, i'm slightly shocked by the unusual and massive valve 'webs' you've made, fine as they are. I think every valve connecting rod and eccentric I've ever seen has been of the form you originally made. Was the breakage a result of simply too tight a fit? If so, why didn't  you simply ream or lap the straps? I see that the relevant stress riser is at the joint, which is in this case a thread. Isn't there another mechanical solution for rod-meets-strap? clamp, transverse key, set screw, clevis, ... or simply a larger dia rod?


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## Anatol (Dec 28, 2020)

Brian Rupnow said:


> Also, I am going to have to add a piston ring to the pistons..



why?
Iron or O ring?
looking forward to hearing about this.


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## Brian Rupnow (Dec 28, 2020)

After much finessing today, I think I'm about half way home. I didn't o-ring the pistons because all my stores are closed due to Covid and I didn't have the size o-ring I need in stock. I do have one engine working. Don't have it all hooked up yet, but when I manually operate the slide valve, the piston  and cross-head take off like a wild thing in either direction. The other engine isn't doing it's thing quite yet, but is very close. It needs some more attention to the slide valve and steam chest I think. I've had enough fun for one day .


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## Tim Wescott (Dec 28, 2020)

I only re-read the story of the broken valve rods today - while 1/8" may be a bit light, it certainly seems that the main problem is the eccentric fit.  Did you consider just fixing the problem in the assembly as designed, then arranging for a better rod-eccentric fit before attaching that delicate little bit of ferrous lacework to a 1/2 horsepower motor to run it in?


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## Brian Rupnow (Dec 28, 2020)

Let me put it like this Tim---I THOUGHT it was fitted "close enough" to run it in and get rid of any tight spots. I was wrong. Today, I reworked the new eccentric straps so they were a definite clearance fit before reassembling to the engine. The new eccentric straps look rather monstrous, but I may like that.---If I don't, I still have the lightweight eccentric straps---all they need is new 1/8" rods.  I think I will include drawings of both the lightweight and the heavy duty eccentric straps in the drawing package and let anyone who buys the plans to make their own choice.


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## Brian Rupnow (Dec 28, 2020)

Anatol--If I do add rings to the pistons, they will only be buna-n rubber material. I will know better after tomorrow if I'm going to use rings or not.


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## Brian Rupnow (Dec 29, 2020)

So here we have it kiddies. After a sometimes frantic 5 weeks from concept to completion, we have a running twin cylinder engine with the flywheels running off the camshaft. I still have timing events to adjust, and some painting to do, but this "maiden run" has been successful. I will sell a complete plan set for this engine for $25 Canadian funds, and I will find a commercial source for the gears if you don't have your own gear cutters.---Brian


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## werowance (Dec 29, 2020)

That is nice Brian,  question on a cross head valve is the brass head inside the steam chest so close that it presses on the top and the bottom or what keeps the seal going on?  i mean i do understand covering one hole and un covering the other but what about leakage?  - never made anything other than a wobbler on the steam side so curious about the cross head valve.   love all the ecentrics and actuation.


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## Brian Rupnow (Dec 29, 2020)

Steam (or air) pressure inside the steam-chest forces the sliding valve down against the slots in the top of the cylinder. The higher the pressure is, the harder it pushes. Some people lap the two faces that slide against each other for a more perfect seal. The nut which sets inside the towers on top of the slide valve actually "floats"---It doesn't supply pressure anywhere except back and forth as the rod moves it. Nothing forces the sliding valve down against the cylinder ports other than steam (or air).


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## werowance (Dec 29, 2020)

ah so lets say the steam comes in from the top, and both intake and exhaust are on the bottom then.  thus constant preasure is applied to the top.  and some lubrication as well - which is im gussing why alot say to add steam lube to the boiler?


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## Brian Rupnow (Dec 29, 2020)

The slightly larger center port is exhaust. The smaller port to either side go to either the rod end or the cap end of the cylinder. The slide valve has a cavity machined in the bottom of it, so depending on where the eccentric is at, it either connects one end or the other to the exhaust port. The slide valve is only long enough to cover two ports at once, so the third slot which is uncovered lets pressurized steam/air into the other end of the cylinder.


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## werowance (Dec 29, 2020)

makes much better sense now. thanks.


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## minh-thanh (Dec 29, 2020)

An interesting engine , Congratulations !
Thanks for sharing.


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## cheepo45 (Dec 30, 2020)

Nice work!
Thanks for posting this build.
 Scott


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## ShopShoe (Dec 30, 2020)

That's great, Brian.

I've been following along and I really appreciate all of your progress reports. I'm looking forward to the video that shows it tuned and painted.

--ShopShoe


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## Brian Rupnow (Dec 30, 2020)

This is the final "wrap up" of my geared horizontal engine. Painting and polishing has been completed, and there really is nothing further to do on this project. It has kept me entertained for a month, and shows that yes, the flywheels can be mounted on a geared shaft which is driven by a gear mounted on the crankshaft. I have seen this discussed many times, but the answers were always a bit ambiguous. This answers the question. Thank you for following my build thread.---Brian


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## Tim Wescott (Dec 30, 2020)

Brian Rupnow said:


> ... and shows that yes, the flywheels can be mounted on a geared shaft which is driven by a gear mounted on the crankshaft. I have seen this discussed many times, but the answers were always a bit ambiguous. This answers the question. ...



Well, the jury won't _really_ be in until you run it for a year straight, then tear it down and inspect for wear.


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## Steamchick (Dec 31, 2020)

Well done Brian. Personally, I would have removed most of the material from within the eccentric straps as they simply look far too heavy to my eye. (Maybe you are a bit unsure yourself, from the tone of your posts? A web should be mostly space holding outer the outer (thick) rails apart, like any well designed "minimalist" beam. Possibly I would have made them using brass extrusions as 2 outer rails forming the triangle with the eccentric bearing, with just a couple of stiffening struts (for appearance) filling the triangular gap. Otherwise a nice looking job!
How is the balance? I wonder if you put the primary counterbalance (in opposition to the big-end, pistons, cross-heads and rods) on the crank, then applied some secondary counterbalance (for the side-to-side oscillations of the con-rods plus counterbalance for the eccentrics?) on the crankshaft? That way there would be little torsional oscillation in the gears. Could the counterbalancing even be achieved by the calculated drilling of gears, so un-drilled zones become the counterweights? Lots of scope with your design and I am curious as to what you have done.
I'm sure as a Design Engineer you can do the calcs, (I would love to see them to learn from you!) but  I just follow the calcs in locomotive design text books. Freezing outside today (and cold in the garage) so I may just have a play with the text books and slide rule myself on some guesstimated masses of your design!
Brian's fun becomes Brain fun!
Goodonya! - and Happy New Year. I look forward to more of your genius in 2021.
K2


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## Steamchick (Dec 31, 2020)

Sorry Brian, I trawled through my memory - and referred back to your posy #89 - you told me you don't balance the small models. So please ignore my forgetful stupidity (I.E. I forget how stupid I am!).
Werowance, your post re: valcves and sealing: refer to post #100 where Brian shows the linkage normally hidden inside the valve chest - that allows the valve to be pressed against the cylinder by application of the cross-bar and floating valve arrangement. - Another "Well done Brian!" - It is all there when you take the time to look - and look again!
Thanks Brian.
K2


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## ShopShoe (Dec 31, 2020)

Brian,

I seem to always like the level of bling you do: "Finished" looking, but not over the top. 

I think the blue color was a good choice for this engine.

I hope to see your next project when you are up for it.

--ShopShoe


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## timo_gross (Dec 31, 2020)

Hello Brian, 

I was trying to figure out the reason for the gear arrangement? ( I gave up reading all the posts for the answer ) Why does it make sense? Or is it only for the fun of using gears? Just wondering.

Happy new year.


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## Brian Rupnow (Dec 31, 2020)

Timo--That was purely a design experiment. I have built so many conventional engines that I wanted to do something different. I have never seen a real steam engine built this way, and I think the major factor was that it was more expensive to put gears on an engine. On a conventional steam engine the crankshaft  has the cams riding on it, and there is only the crankshaft to deal with. I would class this as a "novelty" engine.---Brian


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## Brian Rupnow (Dec 31, 2020)




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## Brian Rupnow (Dec 31, 2020)




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## IanN (Jan 1, 2021)

Hi Brian,

Glad to see you are including your original design for the valve rods / eccentric straps.  As you correctly pointed out the failure of the original items would have been due to incorrect fit.  I think the original design is much more elegant, while the heavier version looks seriously over specified.  As the well known engineering maxim goes - "If it look right, it usually is.  If it looks wrong, it usually is" - this rule does not apply after you have been to the pub....

All the best,
Ian


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## Brian Rupnow (Jan 4, 2021)

And, to finish out this thread, what could be better than a video of the engine doing some real work!!!---Brian rupnow


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## Steamchick (Jan 5, 2021)

Final "Congratulations" on a splendid model, showing an alternative arrangement for the power and valve gear train. A really splendid tutorial.
Thankyou Brian.


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## Steamchick (Jan 8, 2021)

Richard Hed said:


> Steam,
> Could you clarify your first point?  The others I get but the first is, unclear?


Hi Richard,
Just spotted this comment and I missed it previously so here is my reply. - sorry for the delay. (But I don't know how to explain it clearly!).
Brian's design has the cap of the cap-screw at the outer-end of the eccentric rod bearing cap, with the thread tapped in the half that also has the rod connected. I have seen alternatives on Motor-cycle engine cramkchafts, where the head of the big-end bolts are on the "piston-side" of the con-rod, with nuts on the "outer-shell" side of the big-end. So would it make any difference to the engine if Brian had taken his cap-screws from the Rod-side through to the "eccentric strap outer half" - with threads tapped in the eccentic outer strap side? Of course "the workshop" would profess it is easier to assemble his way, but in theoretical design it may be better the other way. Because "I don't know" I was asking if Brian had any reason for one way or the other? As it is a bench model, I am sure it doesn't matter, so the easy assembly arrangement is preferred. But on a "real" engine, there can be mass/balance issues, stress issues, material savings issues, and a whole host of things that Design Engineers learn to consider - and I find I have learned certain things that are contrary to how others do it - and often just because I just don't know "Why" best practice is "best"?
So if you have any advice I'll be glad to hear it. I didn't spend all my career in Design, just a small fraction of it, as after 7 years in Design in a few jobs I went chasing more money in a car factory, and after 6 years in engine design the department I was working in went 200 miles away, so I stayed and moved to QA - for 26 years! So I realise I am not the most experienced or knowledgable design or manufacturing engineer on this website. Now in retirement I am enjoying the design and manufacturing stuff of this site. - I learn something new most days.
One word of wisdom that I remember from Mr Honda, founder and owner of the Motorcycle manaufacturer: When asked "why is this bike 2 cylinders instead of 4 - like the previous version in this size? - Is there a design advantage - or something?" - He replied that "Honda can design any size of configuration to their high standards, but this 2 cylinder design was what the marketing people thought would sell more bikes. Both designs have merits - but changing the design would promote more sales, even if a small number of customers were lost because of the change - and profitability would increase"... And he was right. The press and market loved the "new" twin cylinder... So the "best engineered" design was irrelevant - the "highest profitability design" was considered the "best".
So Brian's reason for designing the eccentric strap may be for any one of many reasons. In his reply he said "The advantage of having the bolts set up the way I do is that the heads end up resting against a flat surface.  " = post #84. - That's good enough for me. It makes my question irrelevant.
Thanks,
K2


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