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Counter-rotating props on a single engine? - 5/29/2004 10:00 AM   
scubyfan


 

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Status: offline 		Hey guys,

I'm thinking about doing a scale model of a certain plane, and it is set up like this: http://www.scaleworkshop.com/gallery/images/xp56ms_4.jpg

Is there a way to get one engine to rotate two propellors in opposite directions? Has anyone done this on a model, and if so, how?

Thanks in advance!

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RE: Counter-rotating props on a single engine? - 5/29/2004 12:24 PM   
bigchap


 

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Status: offline 		i have seen an article in a magazine here in the u.k.,it was about 2 years ago but i can't remember what magazine it was,they were using a gearbox which was commercially available,i know o.s. made gearboxes for i.c. motors so perhaps it was one of theirs,sorry i can't tell you more but i'll try and find out.

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RE: Counter-rotating props on a single engine? - 5/30/2004 1:18 AM   
scubyfan


 

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Status: offline 		That seems to be the ticket. Please let me know if you find out.

Can anyone else comment?

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RE: Counter-rotating props on a single engine? - 5/30/2004 4:29 AM   
CP140



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Status: offline 		You would need to end up with a hollow drive shaft with an internal shaft turning the opposite direction to get contra rotating props. You're going to need gears etc capable of running at the max rpm you expect your engine to develop and you would need to keep it fairly light. Sounds like you've got your work cut out for you!

The Tupolev TU-20/TU-95 "Bear" uses contra-rotating props... not quite sure how it was set up. Unfortunately none of my books are very specific about the "plumbing".I remember seeing something about a gear box for an OS engine, but I think it was a gear reduction drive... not sure how you would adapt it for use with contra props...

I'd suggest making friends with a really good machinist! Good look with your project!

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RE: Counter-rotating props on a single engine? - 5/30/2004 5:23 AM   
scubyfan


 

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Status: offline 		Hi,

If there is no one making these, I will be forced to do one from scratch. Obviously it will take experimentation (and some money...), but it is doable. I'm just surprised that such a thing is not available on the market. How difficult would it be do hardened metal gears to reach this end? So many airplanes and craft have used counter-rotating props, and it does have advantages, other than the scale appearance.

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RE: Counter-rotating props on a single engine? - 5/30/2004 6:00 AM   
JohnVH



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Status: offline 		heck, if someone can make a working turbofan, sure this can be done too

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RE: Counter-rotating props on a single engine? - 5/30/2004 6:11 AM   
MinnFlyer



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Status: offline 		Wish I still had access to a machine shop. Sounds like a fun project.

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RE: Counter-rotating props on a single engine? - 5/30/2004 7:11 AM   
scubyfan


 

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Status: offline 		I found a fellow who can do one for me within the next few months. I will let you guys know how it turns out.

Is $150 for a one-off, fully machined, enclosed, bearing-laden gearbox a good price? I'm not too sure on what the going rates are for such things.

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RE: Counter-rotating props on a single engine? - 5/30/2004 7:28 AM   
rmh



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Status: offline 		A Russian modelerdid abeautiful scale model years back and I think, did his own engines and propboxes .
scale buffs probably know who did this -

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RE: Counter-rotating props on a single engine? - 5/30/2004 9:16 AM   
JohnVH



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Status: offline 		I would think $150 would be cheap. Sounds like alot of work, which by the hour gets spendy.

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RE: Counter-rotating props on a single engine? - 5/30/2004 9:42 AM   
CP140



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Status: offline 		$150! I'd say you got a bargain. Will you be able to post pics/weights etc? It should be quite the showpiece when it's done...

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RE: Counter-rotating props on a single engine? - 5/30/2004 9:53 AM   
scubyfan


 

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Status: offline 		Hi guys,

I will definitely give you guys all the info once it arrives and is tested. That will be in a few months, though.

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RE: Counter-rotating props on a single engine? - 5/30/2004 12:01 PM   
bigchap


 

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Status: offline 		sorry,scuby,i have drawn a blank,but i am going to try a uk forum and see if anyone remembers the article.

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RE: Counter-rotating props on a single engine? - 5/30/2004 2:23 PM   
Chevelle


 

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Status: offline 		With all the power available in today's R/C engines, the counter-rotating props aren't needed to fly the plane. It seems to me that it would be easier to extend the prop shaft, put on a dummy prop with a bearing in it that will slip on the shaft and then add the fixed drive prop. The dummy prop would rotate in the first props wash. If would spin in the opposit direction if the pitch was reversed. I've never done it but it does seem easier.

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RE: Counter-rotating props on a single engine? - 5/30/2004 3:04 PM   
MinnFlyer



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Status: offline 		Chevelle's right, but it wouldn't be as Cool.

And 150 bucks is dirt cheap!

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RE: Counter-rotating props on a single engine? - 5/30/2004 3:42 PM   
scubyfan


 

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Status: offline 		Yes, it does seem easier and a lot of people have done it (like the guy who built that Bear), but being an obsessive ****, it wouldn't feel the same to me, knowing it's a dummy. I'm really not doing it for gain of any kind, perhaps other than personal satisfaction.

quote:

ORIGINAL: Chevelle

With all the power available in today's R/C engines, the counter-rotating props aren't needed to fly the plane. It seems to me that it would be easier to extend the prop shaft, put on a dummy prop with a bearing in it that will slip on the shaft and then add the fixed drive prop. The dummy prop would rotate in the first props wash. If would spin in the opposit direction if the pitch was reversed. I've never done it but it does seem easier.


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RE: Counter-rotating props on a single engine? - 6/1/2004 11:21 PM   
ampbomber


 

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Status: offline 		Here are a couple of articles on contra-rotating prop gear boxes.

R/C Scale Modeler Oct '88 had a gear drive for an IC engine and R/C Scale Modeler April '89 had one for an electric with gear and belt drive.

I'm currently working on an electric Tu-95 (107 inche WS) that will have contra-rotating gear boxes using the miter gear concept. Scale prop size is about 12".

Here is the gear article. I'll post the other in following post.

Attachments
Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize


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RE: Counter-rotating props on a single engine? - 6/1/2004 11:23 PM   
ampbomber


 

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Status: offline 		Here is the second article

Attachments
Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize


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RE: Counter-rotating props on a single engine? - 6/2/2004 1:32 AM   
scubyfan


 

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Status: offline 		Wow, thank you so much!

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RE: Counter-rotating props on a single engine? - 6/2/2004 3:26 AM   
F1992


 

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Status: offline 		TO: scubyfan
Sir!
I have analogical problems at the same time but only for FP(Fly platform).
Contr-rotation for me - NO PROBLEM, because props ave his shaft.
There is as far i understand more dip ruts...

Therefor i would like to know before how you decided problem w/ prop.?
did you using symmetrical profile prop? What is brand? What is pitch direction?(tractor/pusher)?

please response asap. OK.
Please E-mail me. <fstaras@cs.com>

PS. May be it will be useless but
Two monthes ego i sow or magazine RC or on forume differential-device for contr-rotation (very small for electric models)

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RE: Counter-rotating props on a single engine? - 6/2/2004 3:35 AM   
scubyfan


 

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Status: offline 		Howdy,

I'm sorry, but I do not understand your question. I will not be making the gearbox, if that's what you're asking, so any technical questions regarding that I will not be able to answer.

What was it that you wanted to know?

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RE: Counter-rotating props on a single engine? - 6/2/2004 5:02 AM   
ampbomber


 

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quote:

ORIGINAL: scubyfan

Howdy,

I'm sorry, but I do not understand your question. I will not be making the gearbox, if that's what you're asking, so any technical questions regarding that I will not be able to answer.

What was it that you wanted to know?


Scubyfan,

I think what F1992 is asking is, what are you going to use for props after you get the gear box? I have to agree with him, making the gear box is not a problem. Propellers will be your biggest problem especially if you want scale props as shown in your picture. From the beginning you have to pick a scale for your project that you can power efficiently with your gearbox-prop combo.

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RE: Counter-rotating props on a single engine? - 6/2/2004 7:42 AM   
scubyfan


 

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Status: offline 		I will be getting the propellors custom made, also. Everything has been shrunk down to scale, and so will be the propellors.

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RE: Counter-rotating props... and PROBLEM W/PROP - 6/2/2004 7:42 PM   
F1992


 

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Status: offline 		Friends!
I have problem almost clouse to scubyfan...(project w/FLY PLATFORM).
I don`t have of experience in field RC Planes, but i have big experience as aviation engineer and inventor...
So, my problems are:
1.The second prop on my FP have to have:
a/ counter-rotation
b/ for 'tractor" prop pitch - conditional coll "negative" (tractor prop pittch -conditional coll 'positive")
c/ "tractor' pitch "negative" as far i know, don`t making.
d/ as rule blades of props making with unsymetrical profile, therefore it isn`t possible to use as pusher prop.
e/prop w/changing pitch, as minimum $105
2. Therefore my project under sword of Damocles....and lost money
3. Who have idea or recommends PLEASE
Thanks

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RE: Counter-rotating props... and PROBLEM W/PROP - 6/2/2004 8:20 PM   
ampbomber


 

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Status: offline 		F1992,

Check out this thread. We did a lot of talking about C-R props here. Go to post #24 of this thread for more info on props.

http://www.rcuniverse.com/forum/m_1448339/anchors_1448339/mpage_1/key_contra%252Drotating/anchor/tm.htm#1448339

BTW, what plane are you thinking of modeling?

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