Looking to build an engine reduction system! Similar to the one Toni Clark makes for the G38. Has anyone done this yet? If you had! What did you do to achieve the build? If not any one interested I will let you know how mine goes.

We are always interested in people's projects. Keep us posted.

AV8TOR

ya...me 2...Capt,n

Yes I will let you guys know how it goes. I don't think it should be too difficult. Toni Clarks G38. It turns a 32X13 propeller at 3000 rpm with a tuned pipe, and its flying 40lb planes, at half throttle. He clams that you can climb vertical and it lifts in the sky like a balloon. Very scale like.

Yes I'd be interested in your project also. always looking to learn something new! Can one of you post a link to the Toni Clarks G38 project? I'd like to get more info. thanks guys

This is the link to Toni Clarks catalog it’s the only way to see his product! http://www.toni-clark.com/index_en.htm I think if I scrounge around. I think I can come up with a contraption. The gear reduction is on page 60.

I would like to come up with something for use on my (still to be built) 1/3 scale Sopwith Pup. At one point I was looking in the industrial catalogs/internet sites at pulleys, belts, etc. But I got sidetracked and never continued. It will be interesting to see what you come up with.

Just remember that due to the reduced prop speed, you will correspondingly need to use a prop with more pitch.

AV8TOR

Well, Pe Reiver's prop/power calculator says that a 32x13 @ 3000rpm will make around 24lb of static thrust (depending on the prop load constant you use) and needs 2.44hp to do that. Not nearly enough to pull vertical with a 40lb plane for any length of time.

Mark

We developed the reduction gear for our Sop with
Pup so as to be able to fly a model with scale size
propeller. But to test the gearing we first put this
into our Tiger Moth which weighed 14 kilos. If I try
to tell you the possibilities that our Tiger possess
with such a power unit it will be impossible to believe
unless you have seen it yourself. Many who have
seen our Tiger for the first time with the reduction
gear installed have all said the same, they would
have never believed it unless they had seen it for
themselves. For take off, full up and full throttle, take
off run is about 5 meters, I wait until I can see the
full platform of the Tiger and the I let off the elevator,
the Tiger will continue to climb vertically, with
the speed of about that of a hot air balloon. When
the Tiger has reached about 30 meters and hanging
on the propeller, due to the torque she starts
to turn slowly and like the hot air balloon is blown
along by the wind
this is a quote from the catalog of Toni Clark. 14kg is 30 lbs I stand corrected. And 24lbs of thrust is not bad for a 38cc engine most 50 cc are getting 25 to 26 lbs. But the problem with 1/3 scale pup is the cowl is so large. You need a 24� prop or larger. That’s why everyone uses the Zenoah G62. But with a 1/3 scale pup a 39� propeller is scale. And they say with Toni’s muffler and reduction system, the plane sounds and looks scale. Thanks for the calculations they sound right on the money. I am still in the thinking stage, and it will probliy be a couple of years. When I am finished! I will need to buy a lathe. I thought of using a chain drive but 2.5 to 1 is about 4� and 2.8 is 5� using #35 chain. It might work. To turn a 32� prop you need a big hub that’s where I need the lathe. I think a lot has to be done the way Toni did it.

AV8TOR I was just wondering if you the same guy, in the discussions on gas on glow conversion.

Yep, that would be me. "Mr. Gas/Glow"

AV8TOR

Yes I was reading a couple of dozen pages on gas on glow it was very interesting.
I have a 28cc Mac I would like to try it on. So its 10 nitro 10 caster glow fuel 1/3 and 2/3 regular gas. And if that’s right all I need to know can you flip start the engines or do you need a starter? And will it wreck the diaphragm in the carburetor after time.

I would use a toothed rubber belt instead of a chain. The belt is tougher, doesn't stretch and offers a bit of cushioning in the drive system.

That system would work very well for flying a 30lb bipe that flies slow and has lots of lift. Big props at lower RPM are more efficient as well.

Mark

Hi,

I put all the info on Gas/Glow operation consolidated into two posts on this page here in the forum: http://www.rcuniverse.com/forum/m_8009384/tm.htm

Yes, the engines easily hand start. For some reason even easier than a CDI spark ignition engine!

BTW, I would also use a belt drive system over a chain in a reduction drive.

AV8TOR

Toni Clark uses a twin v belt from Gates! I was thinking cog belt about the size of the old sunbeam electric lawnmowers. ½ in belt is too heavy maybe 3/8 in belt might work. Or use the same belts Toni uses and turn the parts out of aluminum. Maybe time to invest in a small lathe! The chain drive is too big a small standard sprocket is 16 tooth and is about 2� and a 45 tooth is 5�. The prop shaft will have to be at least 4� away from the crank, and the chain is heavy. I think this contraption will be heavy enough mad of aluminum.

Well, here's the thing about that. When people think about a reduction drive, they right away think about a long shaft and two bearings widely separated on the shaft, like the Toni Clark system shown below. That's going to be heavy no matter how you do it.

I once had an Ultralight Airplane that had a reduction drive that had just a short shaft to hold the prop pulley, and the pulley itself had two ball bearings in it. (The pulley shaft was anchored and did not turn.) It was quite light, and if that system could support 50 horsepower and a 5 + FOOT long prop and fly my heavy butt around for many, many hours, I think a similar system could be made to work on our little engines. That's how I would go about it.

AV8TOR

Did any of you notice in that catalog he was using madniseum as the metel for his engines cases?
If you were to take that motor shown, remove the coil and flywheel spark plug and install the gas/glow system. I bet the weight would be a pretty close to even trade off. [X(]Would there be any ways to further reduse weight? (In case I'm wrong)
How big of a shaft would be needed say for a 45CC engine?
What RPM would the engine turn and what would the RPM of the shaft turn? (What reduction gearing)
What prop sieze and pitch would be your goal?
What type of bearings would be needed to support the shaft?
From what I'm reading on model air plane design you design your plane around a motor. What plane would best be used as a test subject for this motor? P-39?

Just a thought, you should try spellcheck next time. It is hard to read your post as it is... Just sayin'.

Now to the questions:

1) Shaft size is dictated mostly by prop size and what you plan to do with the engine. You need a smaller shaft for a slow, gentle flying WWI bipe than a balls-out aerobatics plane. I am a mechanical engineer, so I would size it based on the design loads and then add a fair bit to account for prop gyro loads.
2) RPM can be anything you like. You take the prop you want to use and figure out how much horsepower it takes to turn it at your desired RPM, then work back a reduction that lets the engine make that much power. You need an engine that will make the power at an RPM that will be reasonable for the prop, too. A bit of iteration is required here.
3) Prop size and pitch need to be determined first and then everything else comes after. In Hewismayer's case, he wants a 39" prop for his 1/3 Sopwith Pup because that is the scale size. So, that sets the diameter. To get the pitch, you need to decide how fast the model must fly at full throttle, then figure out what RPM that will be at and if your engine can turn that prop load at that RPM. You need to work back and forth to get a pitch that will fly the plane and that your engine can turn properly.
4) I would use sealed ball bearings for the shaft. You would need to check the axial load rating on the bearings to make sure they can carry the thrust load as well as the radial load.
5) Best test subject is an old, ugly, easy flying test mule. Save the nice scale plane for after you know your power system is reliable and has been proven.

Mark

Well that is what I was thinking at first. Until I saw Toni’s! I was going to take the power from the front of the engine but the pulley is in front of the flywheel! Too much tension on the parts I don’t think the belt will get tight enough. Unless I went to gas glow then the flywheel could be eliminated! So one cap off the front of the crank case bolts 2 bearings in the cap! A bolt or axel threw the bearings into a machined prop hub on one end and a 3 ½ pulley on the other, out of aluminum. On the crank a 1 ¼ pulley! The right size belt maybe 3/8 v belt and the right tension! It should work. What do you think? It won’t be any different then an ultra light setup. The whole thing might end up lighter. But on an 1/3 scale pup I don’t think a little wt matters.

Mark everything I post is in word. Spelling and grammar should be correct. Unless I have the propeller custom made. The largest zinger makes is a 32x13. That is what Toni Clark in Germany makes for the Zenoah G38. I am using the 42cc Poulan chainsaw engine. I am trying to recreate what they have done. For the Poulan! Good point on the thrust load on the bearings witch is only 24lbs. I can test that by pulling on the shaft when done. The final test will be on a test stand with a couple of tanks of gas. And when the plane is completed! I will conduct a thrust test with a fish scale tied to the aircraft. But any help is welcome especially form a professional. As it is all new to me!

sorry i missed a few posts.

Oh yes the ratio on Toni’s is 2.8 to 1 at 3000 rpm his engine is 8400 rpm a little high for a 2 stroke gas. But still ok I think.

Not yours, Chicks5 was the one I was referring to. Yours are fine to my eye.

Mark

You can't test the bearings by pulling on them, you need to check the bearing rating to see if they will live while turning RPM. I expect the loads we are talking about are fine, but the bearings are small, too. I am used to much bigger pieces in my work, so my seat of the pants feel is off for these small items. I would use a toothed belt instead of a V, they need less tension and work much better overall.

8400rpm on a Zenoah is fine, they like to spin pretty high rpm and are tuned for that. The 42cc Poulan engine should make more power and torque than a G38. You may be able to use less reduction and not have the engine screaming as much if you want to avoid that.

You may want to look into ultralight props, they are similar sizes and may have more variety available.

Mark

The bearings I was thinking of using, are the ones they use in the crankcase of weed eater engines. But you are right I should check the thrust load. I have seen bearings fall apart with a slight tap! My brother has the G38 and the numbers of power is close. But the Poulan is a little more powerful, and the power is reached at a lower rpm. You’re right! What do you think should I copy Toni’s design or have 2 bearings side by side in a cap mounted behind the flywheel on 2- 6 mm crankcase bolts. Remove the flywheel and use an electronic ignition. So the pulley will closer to the bearings. And use a cog belt or gas with glow conversion. Also weight of the plane is not important. Because the plane needs 6 to 7 lbs to balance! Right now the engine is 5lbs on the nose with hub and flywheel.