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Contra-Contra

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  • Member since
    January 2016
  • From: Salt Lake City, Utah
Contra-Contra
Posted by Sailor Steve on Monday, February 1, 2016 1:38 PM

I'm still new (joined three days ago), so I'm still not sure what I'm doing. I asked this in the 'New Members' section, and it was suggested I come here to start. I'm currently scratch-building a 1/72 Siemens-Schuckert E.I from 1916. The Siemens-Halske Sh.I engine was unique in that they tried to overcome the torque problem inherent in a rotary by having the engine and prop turn in the opposite direction.

I'm trying to find out how I can build (or preferably buy) a gear mechanism to allow that to happen in a space 15mm wide and 15mm deep. I have an idea how it should go, but I'm not good with soldering and I'm not even sure where I would buy gears that small.

Any ideas would be greatly appreciated.

  • Member since
    November 2009
  • From: Twin Cities of Minnesota
Posted by Don Stauffer on Tuesday, February 2, 2016 8:58 AM

Are you going to put a motor in it?  If it is a static scale model I wouldn't bother.  The mechanism will be a more involved project than all the rest of the model. In contests I have not seen operating features on a model influence the final results much.

Do you have a lathe?  Even with a lathe and commercial source gears it would be a big project, especially in that small size. If you insist on doing it, you might consider friction "gears" instead of toothed ones.  No one can eyeball rpm by eye accurately enough to detect any possible slippage. 

Don Stauffer in Minnesota

  • Member since
    May 2009
  • From: Poland
Posted by Pawel on Tuesday, February 2, 2016 9:43 AM

Hello!

I thought about it for a moment, and maybe mating modified LEGO gears to custom axles could cut it for you? You can get angled gears smaller than 15mm in diameter from LEGO.

Hope it helps and have a nice day

PaweĊ‚

All comments and critique welcomed. Thanks for your honest opinions!

www.vietnam.net.pl

  • Member since
    January 2016
  • From: Salt Lake City, Utah
Posted by Sailor Steve on Tuesday, February 2, 2016 6:47 PM

No motor. Long ago I did Seafire 47 with a contraprop, with just a brass rod for one shaft and a brass tube for the other. No gears, but when you blow on it they do turn in the opposite directions. The idea here was to just spin the prop with a finger and see the engine rotate in the opposite direction.

There is a builder in Russia who made it work with an SSW D.IV. http://www.dishmodels.ru/gshow.htm?p=9420 Unfortunately the Siemens-Halske Sh.III engine does not have the prop rotate in the opposite direction from the engine. He has a couple of pictures and a diagram, but I didn't really understand it.

Anyway, I had pretty much given up on the idea and thought I'd give it one last shot. Thanks for the answers.

  • Member since
    September 2012
Posted by GMorrison on Friday, February 12, 2016 4:38 PM

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXDLD4

This kind of thing might be a good start. I can't easily design the thing in my head, but there's a lot of bevel gear differentials for R/C cars.

The major gear diameter of this one is 19mm.

 Modeling is an excuse to buy books.

 

  • Member since
    January 2016
  • From: Salt Lake City, Utah
Posted by Sailor Steve on Friday, February 12, 2016 10:27 PM

That is a good start! Thanks for that.

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