Tiny I.C. Engine

[gbritnell]

Hi Kel,
The valves don't need to be hardened. If you did I'm afraid they would warp. The only way to have hardened valves is to leave them oversized, harden them and then grind but like I said it's not necessary.
George

 

[GailInNM]

Arv,
My current spark plug is made with Corian at Georges suggestion. I will describe it in detail in a post a little later along with some photos. I made several changes, but to answer your immediate question the ground electrode is just like a standard automotive plug. It was machined on to the body blank as a straight protrusion and then bent over at assembly time. So it's just a matter of tweaking with a feeler gauge to set the gap.

Kel,
I have no visible wear on either the cam or cam follower. I used 12L14 steel for the cam and 2024 alum for the follower. The follower is polished a little bit, but the cam still shows machining marks because I did not polish it like I should have. The only wear on the engine that I know of is there is a little extra clearance on con rod big end. Con rod is 2024 alum and crankshaft is 12L14.

Gail in NM

 

[kcmillin]

Gail, Thanks for your answer.

I had the same problem with the connecting rod. I ran her hard a fast for a few tanks, cranked up the timing and held on! Well, needless to say the con rod journal was hashed. Instead of making a new connecting rod I drilled the hole a few thou oversize and then made a bronze bushing. I made it on the lathe then split it in one spot and stretched it over the con rod journal. The split's irregularities keep it in place by gripping on the aluminum connecting rod. Since then I have ran it without trouble and the con rod has no noticeable slop and runs freely.

I should note that I adjusted the torque on the con rod cap a little tighter each tank for a couple tanks until it seated properly enough to run free with the cap tightened all the way.

I should also note that I used a small side cutters to split the bushing, and did nothing further to it before installation. I am positive there is a better way.

Kel

 

[gbritnell]

Hi Kel,
The next time you make a split bushing try this.
Take the 2 pieces of the material you are going to use (brass-bronze) and make rectangular strips out of them. Lightly tin one side of each with 50/50 solder. Flux them up and clamp them lightly together. Now heat with a small propane torch until you see the solder squeeze out from the sides. Let cool and clean up any extra solder.
Now put the bar in your 4 jaw chuck and get it on center. Turn the material to your bushing size and part off. Now just heat with the torch until it pops apart. Clean up the solder and mount the bearings. I put a small hole in one half so that I can put a pin in the cap to prevent it from spinning.
George

 

[kcmillin]

George, WOW your brimming with good ideas. I like that method very much.

I should point out that the bushing I made was .005" thick. Would this be to delicate to solder and machine out? I could just make the bearing block hole bigger though.

THANKS!

Kel

 

[kcmillin]

Since there has been experimentation with fuel for the Tiny I though why not propane.

Well, I just got the Tiny running on propane. Crudely I might add. I simply held the un-lit propane torch up to the carb and gave her a spin and she took off! I adjusted the speed by turning the knob on the torch. This should only be done outside because there is a lot of propane not getting into the engine. If a properly made LPG delivery system is made then the Tiny will indeed run on propane.

Just though I would add this.

Kel

 

[gbritnell]

Hi Kel,
I don't think it would work at .005. The thinest wall I've made was about .025.
Well here's today's update. I finished the gears, cut the cam, made the cam follower, the rocker arm clevis and pushrod. It's getting close. I'm going to use a Hall sensor on it and I want to make it so I can adjust the timing a little so I'm going to pull up the Autocad and do a little design and layout. I think I'll make a little bracket that pivots on the crank and mount the Hall on this. The magnet will be mounted on a small disc outboard of the Hall sensor. I should be able to squeeze it in without much trouble.
George

 

[gbritnell]

Here's the last 2 pictures of today's set.
George

 

[kustomkb]

It's looking really nice George.

Can't wait to see it run. Thanks for your added design input as well.

 

[putputman]

Looks great George. You sure put out a lot of work in a short time.

I really like the way you radius all the edges. It gives it a finished look.

 

[lee9966]

Lots of nice ideas here, and fun to read especially since I am making a Tiny also when I get a few hours here and there.

Gail, thanks for the spring wire, much appreciated.

Kel, propane huh? I put aside the guts of one of those refillable butane barbecue lighters and was thinking of messing around with it on this engine once I get it running.

Thanks all,

Lee

 

[gbritnell]

Gents,
Here's a couple of updates for today. First is the muffler. I went with a somewhat traditional hit and miss type muffler. The bolts holding it together are 1.0x.25 mm. (.039 dia.) It is spaced .04 apart so it should breathe fine.
George

 

[gbritnell]

Here's the second update for today. I designed the parts for the ignition setup. They consist of the timer lever which will hold the Hall sensor. It will be clamped into the slot with a piece of .015 against one side. I didn't want to just use the 0-80 screw against it figuring it might put too much pressure on one spot. The timer lever has a bronze bush as the shaft will turn inside of it. It will be secured with a 0-80 socket head screw and allow about 15* timing adjustment. The other disc holds the magnet. I made it like you see figuring that the minute amount of weight on the magnet side would be offset by the stock on the other side of center, who knows.
I'll be off for the weekend as the wife and I are going to the model engineering show in Zanesville, Ohio.
More updates next week.
Oh by the way, the carb drawing has a note that says solder a short piece of .062 tubing into the mixer. I don't understand this. Maybe one of the Tiny veterans can explain it.
Thanks,
George

 

[putputman]

George, I soldered a piece of 1/16 O.D. tubing into the spraybar so I could use 1/16 I. D. plastic tubing from the fuel tank to the fuel mixer.

I like your timing mechanism. It looks like it will really compliment the rest of the engine. I have tried to dream up something similar to that but I just couldn't come up with anything.

I have one concern. Every time I have talked to Roy Sholl he told me not the mount the hall sensor on metal. I have always either use a plastic mounting or have use shrink tubing as an insulator between the hall sensor and the metal mount. Maybe I misunderstood what he was telling me so I am interested in seeing how your unit works out.

Looks like it is getting close to making noise.

 

[GailInNM]

My Hall devices have all been mounted on metal. On TINY it has aluminum on 3-1/2 sides.
Gail in NM

 

[lee9966]

I have one concern. Every time I have talked to Roy Sholl he told me not the mount the hall sensor on metal. I have always either use a plastic mounting or have use shrink tubing as an insulator between the hall sensor and the metal mount. Maybe I misunderstood what he was telling me so I am interested in seeing how your unit works out.

I just ruined my second hall sensor, I had it mounted on metal inside heat shrink tubing. My guess the first time was that I had a poor ground on the engine body and the spark decided to ground through the chip. The second time the ground was just fine, so I don't know what happened there. Good thing the sensors are so cheap, I ordered ten of them.

I think I will mount one in a plastic block. I sure wish I knew what made the first two fail.

Lee

 

[gbritnell]

I have all of my Hall sensors mounted in aluminum brackets. The only problem I ever had was because I used sensors of unknown origin. I have good ones now and have many, many hours on my engines with no trouble.
The biggest problem I've had is having a poor ground and allowing the high voltage to leak back through the Hall sensor. They don't like that at all. Here is a picture of the Hall sensor mount on my 4 cylinder OHV engine. The one on my 302 is similar but I don't have a recent picture of it.
George

 

[GailInNM]

It's been a week since Jim left. I spent the first two days recovering. When we play with toys, we play HARD with toys. And, with him being about 10 years younger than I am he has a little more energy.

Then back to TINY. Since we had cooked two o-rings, the first order of business was to replace the cylinder with one that I had made up with increased cooling. Cylinder temperature did not really change very much so I did not do a sustained high speed test run. Since I had lapped the cylinder so it had a smooth finish and a parallel bore it was only about an hours work to make a new piston out of cast iron and lap it to fit the cylinder. I lapped it a little tight as is my practice. It took about 10 minutes of running for it to find it's own fit. Cylinder temperature dropped considerably, down into the 125 degree F range when running hard, and when running rich at about 2000 rpm the cylinder temperature was down to where I could press my finger on the fins for about 10 seconds before it got uncomfortable. When running hard, the head temperature would still sizzle spit, but that is sort of expected as there is a PTFE head gasket that insulates the head and no cooling fins on the head. I only made one sustained high speed run of about 10 minutes to measure the cylinder temperature. Also there is noticeably less friction turning the engine over with the exhaust valve held open.

While I am quite happy with the results of the lapped piston, I do not recommend it for first time builders of IC engines. The o-ring gives very satisfactory results except for high speed sustained runs. It is easy and very forgiving. If someone wants to do a lapped piston, I would suggest that they do a 0-ring version first and get all the bugs worked out. I have lapped many piston/cylinders so it was easy for me, but lapping is an acquired skill and should be left until you have the engine running with an o-ring first.

One problem with the lapped iron piston. I have more vibration due to the heavier piston. The aluminum piston with o-ring built to Arv's drawing weighs in at 1.39 grams. My first Iron piston weighed 3.66 grams and Tiny would "Walk" around the bench a little bit at any thing over about a guestimated 3000 rpm. Piston was reworked by thinning the crown and skirt down and got to 2.44 grams. Still more vibration than I would like at high speed. I have made up a grooving tool to thin the piston wall above the wrist pin and think that I can get another 0.3 grams out of it. If not, I can live with the vibration level it is at.

I have lost track of total time on the engine, but I have put about 90 ml of fuel through it with the iron piston. That is about 8 to 9 hours. The needle sensitivity has improved with the iron piston and I now have a little over one turn between full rich and full lean. It will start reliably on one flip anywhere within the 3/4 turn range in the middle of this. Fuel mix now in use is regular gasoline with 3 percent WD40. I still have lots of lube on the iron piston so will drop to 2 percent WD40 the next time I mix a 100 ml batch of fuel.

Other tidbits for those thinking of making a hit or miss out of tiny. Some time back I removed one of the flywheels. I could not tell any difference in operation except that it accelerated up to speed a little bit faster. In it's current configuration, running about 1/2 throttle, I can hold the exhaust valve open for about 3 to 4 seconds and the engine will catch on the first stroke after I release the valve. I then takes about a dozen power strokes to get back up to speed.

I have a hit-n-miss governor drawn up, but I really don't like it much. Want to mull it over for a few more days before I actually build it.

As soon as I take a couple more photos of assembly, I will post my version of the spark plug along with a drawing. Nothing really unusual with it. Just my way.

Lee: Glad you got the wire. If all the people I sent wire out to build a TINY we will have to have a TINY convention. Lots of interest everywhere. I will be watching for your build to start showing up on these pages.

George: Nice looking muffler. I made one that plugs in to the vertical exhaust pipe on mine. Works well, but does not look a s nice as yours. Since TINY is so small it does not make much noise so I run it without the muffler most of the time. Besides the exhaust flap is disabled when running with the muffler and I like to see it bob.

Gail in NM

 

[gmac]

Gail;
Thanks for the "field test data"!! Do you think that changing the cylinder head gasket to copper or some other conductive material would help reduce head temp and put the cylinder barrel finning to work sufficiently to be worthwhile doing?
PS - I assume it was Viton o-rings that were failing.
Cheers
Garry

 

[GailInNM]

Garry,
A copper or soft aluminum would probably move some of the head heat into the cylinder. Before I was trying to keep the heat out of the cylinder because of the 0-ring. Yes, they were Viton o-rings, but remember that I was abusing them to see what would happen. In any normal operation they would not fail. I got 30 hours on the first one keeping high speed operation down to maybe 5 minutes at a time. I was interested in seeing what they would take in the way of abuse if I decided to try them in a higher performance engine. Using TINY as a test bed. Unless some one just wants to play, the o-ring is the way to go.

Are you building any engines these days?

Gail in NM