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Old 09-13-2006, 04:49 AM   #1
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Question Counter Rotating Props?

I have a DH88 comet under construction. I would LOVE to have counter rotating props going (electrics are great for this)

Will a pusher prop work as a counter rotating prop? Or will it be lossing to much effienency thus not developing the same thrust as the normal prop?

Any ideas/thoughts/suggestions/experiences??
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Old 09-13-2006, 04:56 AM   #2
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Originally Posted by rckrazy View Post
I have a DH88 comet under construction. I would LOVE to have counter rotating props going (electrics are great for this)

Will a pusher prop work as a counter rotating prop? Or will it be lossing to much effienency thus not developing the same thrust as the normal prop?

Any ideas/thoughts/suggestions/experiences??
hi rckrazy and welcome to the group. the correct term is contra rotating props and i must ask. why would you want to have them on your plane?
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Old 09-13-2006, 05:34 AM   #3
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Someone has them under development and I saw the prototype on a site but I can't remember where it was.
Honestly it looked like one Himax running through another Himax with a hollow shaft.
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Old 09-13-2006, 06:38 AM   #4
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The DH88 is a twin-engine plane; see below. I think rckrazy is simply looking for a matched set of props -- one normal and one reverse -- so they can rotate in opposite directions.

- Jeff

DH88 Comet:
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Old 09-13-2006, 06:40 AM   #5
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hi ah clear skies and good flying.
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Old 09-13-2006, 09:31 AM   #6
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Counter rotating is what rckrazy meant (as in the P-38 and many other full-size twins). Contra-rotating is a completely different thing.

rckrazy, a pusher prop on one side will work (if you can find one the right size). Since by reversing the motor you'll be turning it exactly as intended its efficiency will not be affected.

I doubt if you'll notice any difference in the way it flies but there's nothing to stop you from trying it for yourself.

Steve
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Old 09-13-2006, 11:42 AM   #7
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Originally Posted by slipstick View Post
Counter rotating is what rckrazy meant (as in the P-38 and many other full-size twins). Contra-rotating is a completely different thing.

rckrazy, a pusher prop on one side will work (if you can find one the right size). Since by reversing the motor you'll be turning it exactly as intended its efficiency will not be affected.

I doubt if you'll notice any difference in the way it flies but there's nothing to stop you from trying it for yourself.

Steve
At SEFF there were two manufactures showing two inline motor running in opposite directions with a prop on each motor, counter rotating props. One prop was directly behind the other. Don't know if they were custom props or a product that is readily available.

Himax was one of the people, can't remember who the other was. Sorry.

Try calling Himax.



.......................................
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Old 09-13-2006, 12:10 PM   #8
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here is a video of a setup on rcu

http://www.rcuvideos.com/view_video....e=&category=mr

and

http://www.rcuvideos.com/view_video....e=&category=mr

in a Cub

2012 SEFF Night Bowling Champion!
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Old 09-13-2006, 12:43 PM   #9
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hi thanks for clearing that up for me but im still confused. from his description i assumed he meant this. see first pic in article http://en.wikipedia.org/wiki/Contra-rotating_propellers two props spinning opposite directions on the same shaft. not to props spining different directions on seperate shafts. clear skies and good flying.
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Old 09-13-2006, 02:51 PM   #10
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Ken, not very realistic on a DH-88 I think.
www.ramoser.de have left-hand props, available at www.aircraft-world.com

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Old 09-13-2006, 02:54 PM   #11
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Originally Posted by ron_van_sommeren View Post
Ken, not very realistic on a DH-88 I think.
www.ramoser.de have left-hand props, available at www.aircraft-world.com
hi thats why i asked why he would that setup on that particular plane. i knew it wasnt scale. there was a misunderstanding of the question clear skies and good flying.
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Old 09-13-2006, 11:46 PM   #12
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http://www.rcuvideos.com/view_video....a7acb6a06a751e
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Old 09-14-2006, 05:57 AM   #13
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ragbag,

We were the other company at SEFF displaying a motor with contra-rotating props...the PJS 3D 550R Double. PJS won the best product for 2005 at a show in Europe for the PJS 3D 550R Double motor. They now have a larger version of it, the 3D 1500 Double.

The props at the show on the 3D 550R double were PJS 8 x 6 Carbon Fiber with the PJS aluminum spinner that is made for this motor. A PJS Supermarine Spiteful was at the show with this setup installed, but did not fly. You can see video of this motor running and the Supermarine Spiteful flying at our website.

Jerry

www.visionhobbies.com
sales@visionhobbies.com

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Old 09-22-2006, 04:58 AM   #14
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Default CR Props

Originally Posted by rckrazy View Post
I have a DH88 comet under construction. I would LOVE to have counter rotating props going (electrics are great for this)

Will a pusher prop work as a counter rotating prop? Or will it be lossing to much effienency thus not developing the same thrust as the normal prop?

Any ideas/thoughts/suggestions/experiences??
Hello rckrazy,
What size CR props are you needing?

John
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