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Old Nov 21, 2011, 10:47 PM
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carbondale il
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knlever, Your diagram is close to what I'm going to try. Except the wing isn't big enough to put the pulleys inside. Instead they will go inside the engine nacelles and the belts will be exposed just in front of the LE of the wing.
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Old Nov 26, 2011, 12:59 PM
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carbondale il
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Here's the plan I'm using as a guide.
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Old Nov 27, 2011, 07:37 PM
Just shut up and build!
Sri Lanka
Joined Mar 2010
652 Posts
Kevin

Have you seen this? It was in Vintage - scroll down

http://www.rcgroups.com/forums/showt...7#post19967610
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Old Nov 27, 2011, 07:40 PM
Just shut up and build!
Sri Lanka
Joined Mar 2010
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Kevin

Have you seen this? It was in Vintage - scroll down

http://www.rcgroups.com/forums/showt...7#post19967610

Called the Moore drive - it was on the front page of RC groups
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Last edited by knlever; Nov 27, 2011 at 07:48 PM.
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Old Nov 28, 2011, 01:41 PM
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carbondale il
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knlever, This drive train mechanism looks like it would be rather sloppy if it worked at all. The U-joints just don't look like they would turn without binding and stopping the unwinding process.
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Old Nov 28, 2011, 04:14 PM
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Ajax, Ontario, Canada
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The Moore drive supposedly worked well for the very few who tried them
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Old Nov 28, 2011, 07:48 PM
Just shut up and build!
Sri Lanka
Joined Mar 2010
652 Posts
Like a lot of things, you have to try it and see. I don't think that anyone would publish plans for a drive that was not working. Maybe You Tube...

Meanwhile, more finds:

http://www.hippocketaeronautics.com/...p?topic=6511.0

Search for : "Moore drive" rubber powered
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Old Nov 28, 2011, 08:16 PM
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carbondale il
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I stand corrected.

knlever, thanks for the links. There is some interesting and informative conversation going on there. It looks like the belt drive I've been planning would only give me 50% energy efficiency of the rubber motor. It looks like a chain drive would be better. Another problem is the rubber would mostly be behind the CG in the fuselage so possibly a lot of weight would be needed at the nose to balance. Using a chain drive instead of a belt drive would cause less drag and there wouldn't be the stress the belts would put on the wing.
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Last edited by kevin matthews; Nov 28, 2011 at 08:35 PM.
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Old Nov 29, 2011, 06:14 PM
Just shut up and build!
Sri Lanka
Joined Mar 2010
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Is there any way you can get a test rig set up? Your could build your system with the props, rubber and mechanism and mounting points and nothing else, then see how much thrust you get, and how much the thing weights. You can then work out the wing loading and thrust to weight ratio.
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Old Nov 29, 2011, 07:21 PM
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I just don't think this can be done.
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Old Nov 29, 2011, 08:02 PM
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carbondale il
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Just talked to a guy about engineering the drive train. Two rubber motors - one in front of the fuselage sprockets to the nose and one a tad shorter behind the fuselage sprockets...wound from the front, would work. The problem here is that the total length would only be 14", not much it seems for two or three loops of 1/4". At any rate, a chain drive is the way to go.
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Old Nov 29, 2011, 08:12 PM
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carbondale il
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THREE!!!! Three rubber motors - one in front and the two in back connected by a small hook. That would give me a 21" motor all wound from the nose.
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Old Nov 30, 2011, 04:28 PM
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Kev - a shorter motor doesn't have to be a problem if you are able to incorporate some kind of gearing to give you more actual prop revs. Then you can just have a short thick motor giving high torque. The problem might be building a system that can cope with transferring that through to the props that is also light enough.

I like the three motors idea though.

I think Knlever's suggestion is valid - this thing will succeed or fail on having appropriate wing loading and power values... that's gonna be the challenge.

Jon
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Old Nov 30, 2011, 04:57 PM
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Jon, For competition I must have a 1 to 1 gear ratio. I've contacted three micro roller chain and sprocket companies and am waiting to hear back from them about availability of what I want and cost. knlever provided a link to a video where a micro roller chain was used to drive a propeller with an electric motor. It worked and if I can afford it, I'll go with a roller chain/sprocket drive train. It looks like it would run smoothly and with very little resistance. It looks like they are available in plastic. Three motors in line is just a thought. If used they would all wind up at the nose with the sprocket unit, which would be in the fuselage, at the first 1/3 of the rubber motor. If the three motor system works then so would a two motor system where the aft motor is twice as long as the nose motor, I think. I'm considering the older idea of a single rubber motor and a transfer system in the nose which would in turn connect back to the sprocket unit in the fuselage which turns the propeller sprocket units.
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Old Nov 30, 2011, 05:16 PM
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Quote:
Originally Posted by kevin matthews View Post
...For competition I must have a 1 to 1 gear ratio....
Hmm so that does mean motor length is important then.

Although you still have a good advantage: if you think about it for each motor turn you get 4 revs! Albeit from 4 different props but it's still a kind of gearing (legal too!) Of course you probably have smaller props than a single engine model of the same size... but if you can make the net power absorbed from 4 small props big enough, it all helps the turns/duration problem.

I saw an Emanuel Fillon semi-scale twin flying boat in a magazine a while back - the article wasn't very detailed but it was powered by a single motor in the fuselage with mecano gears in the nose - the 'transmission' was done with bowden cables I think.
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