I haven't looked that closely to the Toni Clark design, I will take a closer look and see what I think. Since weight is a bonus in this application, keep the mag and take power from the back if you can. Definitely a toothed belt. Since the mag weight is no issue, I wouldn't go gas/glow.

Mark

I had a closer look at the TC design and it looks pretty practical to me. They don't have an outboard bearing support on the rear crank projection, it is cantilevered off the cases from the look of it. They use the big aluminum tube as a bearing carrier for an inner shaft that carries the prop hub at the front and the driven sheave on the back. The only thing I would change would be to swap a toothed belt for the double V setup. Copying their general layout and system will get you in the ballpark without too much trouble, I would think.

If you plan on paying someone to make all these pieces, be aware it will likely cost more than the TC one. If you have a machinist buddy or can do it yourself, then it is a much more reasonable plan.

Mark

(Note I was trying to be funny with the madniseum line.) Guess that’s why I still have a day job.) There cases are made from magnesium.


Have any of you ever used Stainless steel bearings in a project as replacement bearings?
How about ceramic bearings? If you have could you tell us how they worked and if they’re was any benefits over a standard bearing.
How would you balance the rotating mass?

Ah well, that's how it goes. I ride MX for fun and nobody has offered me a factor ride, either...

A number of pattern guys use S/S bearings in the OS160, they last a lot longer than the OEM bearings. Ceramic are supposed to offer slightly less friction, but I have never tried them. They use them all over in F1 cars because of that, but the cost is brutal.

If the prop shaft is fully machined and everything well made, balancing will be unneccesary for parts that small.


Mark

Well TC cost is 300EURO that’s 500$ CDN. Then there is the cost of logistics customs brokerage and the unit is for a G38. I could try to buy the one from my brother. When it’s all said and done. I think I will be over 1000$ CDN. I can get a new engine lathe for about 500$ CDN. And I can make a lot of other stuff for cheep. I all ready have an engine. Maybe 100 $ or so in materials. I think I will have this done for 800 bucks. And own a hobby lathe.
Yes I think the best way is the TC system and take the power from the back of the engine. Then I can use a cog belt like you suggested. I could take the power from the front. But then I need an electronic ignition. Or gas on glow. If the unit is 2 lbs then I will be at the 7 lbs in the nose to balance the plane. I think it will work. But now I take back that it will be easy to make it. A lot of machining! If I farm it out I think I will be at about 800 bucks. Or more.

I think regular bearings are fine the prop will pull 25 lbs tops if it’s balanced. There will be no up or down movement. If it’s a cog belt there will be very little tension puling down. They can’t be very tight or they will fail. Even bronze bushings will do. But you will have to grease on a regular basis. The shaft will only turn at 3000 rpm no faster then an electric motor. I think a lot less stress then the bearings in the engine that are under heat, and 3 times faster.

Sealed ball bearings should be fine, just check the axial load rating. The toothed belt will exert significant side force due to load and they do get tensioned a significant amount to keep them from jumping teeth. Just check the tension on a Harley belt drive and see how tight they keep those. It is still less tension than a V belt, though.

Mark

Mark it should be about the same as a timeing belt not tight but snug. is that right! I find if a timeing belt is too tight it wines.

If I had a dollar for every time I have said a similar thing...

If you don't value your time, then it is a cool project that you can say you did yourself. But there is a learning curve with the machining, especially getting good bearing fits, and sorting the other stuff accurately as well. The base plate, mounting pieces and split clamps that the prop shaft tube sits in all require machining, much of which will be milling and line boring operations that your lathe won't do. A good excuse to buy a small mill, as well. Also, watch what you are getting for tooling. Outfitting a lathe or mill can often cost far more than the machine itself.

Don't let me discourage you, just make sure you are not in a rush and budget about 3x as many hours as you think it should take. And enjoy the ride!


Mark

That is a fair comparison. I think you will want more tension than a timing belt, but that is the general range. If you spec a toothed belt, Gates (and other suppliers) have charts that will tell you how much horsepower the belt will take, tension settings and more. Going through that info will increase your success rate, for a few evenings spent reading and learning the details.

Mark

I went to Gates web site. Check some of these drives and belts out. This is very do-able.
http://sdp-si.com/web/html/newprdbelts4.htm

Yes they look like they might work. I sent Gates an Email hopefully they will get back to me, and I will post whet they said. I don't think they will get back to me for a few days because of Christmas. so have a Merry Christmas to all.

Yes, it is very do-able. Much more difficult drive systems are done every day in industry and we can just tap into all that experience and technology right off the shelf.

Hewismayer, I hope you hear back from Gates. If you get nothing from the main company, look up some local suppliers and see if they have any catalog info or other brochures available. You should be able to find everything you need in already published literature and stock catalog items. Small toothed belt drives are used all over the place in industry, this is definitely not rocket science.

Keep us posted, this is a neat project and I would like to see it on the finished model. If you need any more help, let me know. Feel free to PM me if you want to take it off-list.


Mark

av8tor1977

Show them the 5 OS 70's that are set up as a rotary engine.

My hard drive crashed and I lost the pictures or else I would.

Also the link if you have it.

Man, you put me to work! I don't have the pics nor the link here on this computer, so I had to "search" for it. You know how the "search" works here..... Anyway, an hour later here it is:

http://www.rcuniverse.com/forum/m_66...%2Cgear/tm.htm

Some beautiful work. We never heard any more about it though....

AV8TOR

Hmmm, after looking closer, I see that is not the original link either. Oh well, I tried....

AV8TOR

Thanks for all the work.
I ASSumed you had the pictures on your computer.

And that it was a simple little thing.
Now I have my old pictures back.

The engineering that went into this is amazing.
I had the video of it running at one time.

Yeah, I'm pretty sure I have them on my other computer, that is packed away at the moment.

I never saw a video of it running though. Any chance of remembering/finding where you got it?

AV8TOR

That's pritty cool!

You could try something like this. This is about a 3:1 ratio and I origionally ran it on a Ryobi 31cc. I didn't have it balanced well so I made a starter out of the belt and pulleys. I think I ordered them from Fastenall about 5 years ago??? Costs weren't too bad either.

How does that starter work? Been thinking of making one like that myself.

AV8TOR

That’s exactly what I need. I am going to check out the local scrap yard and see what junk they have. I have a timing belt from an old sunbeam lawnmower it will handle 3 hp. It is a little long where the gears will be about 4" apart. I would like them 3" apart. I know I will need a lathe to set the bearings in the tube, and a collar on the bolt or axel that attaches the cog and the hub so they won’t be pressed against the tube. I thought everything will be balanced if it was either store bought or turned on a lathe?

One small correction. Toni Clarks G38 drive uses a 32x18 at around 3000rpm.
All the manufactures of reduction drives I know off uses vee-belts, and not toothed/timing belts. The reason, as far as I know is, that the pulsating power delivery of a single cylinder engine destroys the belt rather quickly. Even my Mick Reeves G62 drive wears the belt quite a lot due to slipping at idle.

Mick Reeves / G62. Uses a wide "multi-vee belt" http://www.mickreevesmodels.co.uk/~m...ccessories.htm
Scale Warbird Prop Drives / DA50. Uses two vee-belts. Tried timing belts at first, but they were destroyed too fast. http://www.warbirdpropdrives.com/30601.html
Wolfgang Schlundt / G62 and G45. Uses four 5mm Gates vee-belts. http://www.modellbau-schlundt.de/
Toni Clark / G38. Two Gates 5mm vee-belts. http://www.toni-clark.com

Thank you for the information. It is very helpful that will explain why Toni and the rest use a v belt. I am starting to re think the project. And use a 3/8 v belt and I can attach a hub from a starter. You know how they have a v belt grove. I was thinking of mounting in a block of aluminum two 30mm x10 sealed ball race bearings. With a 10mm bolt with a collar machined to 8mm attach a 3/8x4 ½” pulley, and a prop hub to the contraption. Attach the block to the motor mounts with a couple brackets supporting the block. Can adjust it by shimming the block! I guess it would be better to put it on paper! Either that or copy what Toni did. With two blocks mounted to the motor mount suspending a tube and two sealed ball race bearings. With an axel and a pulley on one end and a hub on the other! I will need to re design the motor mount. To take the power from the rear of the engine! what do you guys think?

Tony's method is very simple and robust. Don't forget that that huge prop will also mean huge gyro loads on your reduction system. The TC method is built to handle those loads.

Mark