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May 05, 2005, 11:01 PM
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Thread OP

Rubber powered Wyvern

Greetings all!

Here's some pics of my 20" span Westland Wyvern for rubber power. Almost ready to cover, but for a few more things to do. I want to try the front prop powered and the back prop free wheel in the opposite direction at opposite pitch. I'll will try a test to see if this will work. Any ideas?

Thanks again,

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May 05, 2005, 11:43 PM
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gossie's Avatar
You are a very nice clean builder, congrats.
Should think a contrarotating prop. freewheeling should work okay.
ls it from a kit???? or scratch built????
Very nice job, anyway.
May 06, 2005, 12:59 AM
Registered User
Ian Easton's Avatar
Looking good Tom.
I didn't realise it was only 20" span, for some reason I thought it was much bigger.
It should be interesting seeing this one go.
May 06, 2005, 01:04 AM
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Thread OP

It's scratchbuilt from a plan I bought from John Pond years ago. The plan says by Dave Pishnery. I did it my own way though. I like bigger models but the small ones are more pracical for my space. 20-26" is a good size for rubber.

May 06, 2005, 06:29 AM
Suspended Account
if i remember right. in don ross' book (Flying Models), there's something about counter rotating props and how to set them up.

BTW, sweet looking plane!
May 06, 2005, 11:09 AM
Registered User
Hi Tom,

Just a quick thought on your prop dilema, instead of making the front powered and the back freewheel, wouldn't it be easier to power the back, and freewheel the front?

The rubber is going to put a bit of pull on the prop(s) and I can see a rather complex bearing arrangment, or rather complex structure of tubes for shafting, to keep the back prop freewheeling. Maybe it's not as bad as I think? The sarge is right, Don does cover that (briefly) in his book, but believe it or not, Lego actually makes a contra-rotating gear setup. Flying Models magazine showed a picture of it a number of years ago, but you should check lego's web site for the gear set.

May 06, 2005, 11:58 AM
Free Flight rubber flyer
jwfinn's Avatar
Uh, go here. Pres Bruning did it.

Somebody in the FAC sells a contra-rotating prop setup. It's suposed to be for models your size range, so might work. I believe it was swinging two 7" props. It's supposed to work pretty well as I remember.

By the way, great looking bones. I wish I could build that well.

Good flying,
Joshua Finn
May 07, 2005, 01:33 AM
Registered User
Thread OP
Thanks everybody for the help!

Making the front prop free wheel is a great idea! Thank you TCARPENTER. I will make some rubber powered experiments to test this out before trying it on the Wyvern. I've heard of the gears from Flying Aces, and the lego gears. Lots of things to consider but the free wheeling thing sounds the easiest. At least for now. Maybe on a bigger one? Or another projest?

Thanks again, and best wishes,

May 07, 2005, 06:43 PM
Needs brain lubrication
biber's Avatar
To power both props would offer a fully compensation of propeller momentum, wouldn't this be a usefull gadget? Or is saving weight the more important point? I'm no freeflighter, just curious. Would it be possible to do it the way like i sketched it below, or to complicated, to heavy?

Of course on a Do 335 "Ameisenbaer" two counterrotating powered props would be easy since it is push-pull.

May 08, 2005, 04:57 AM
Needs brain lubrication
biber's Avatar
Well, errr, I tried to improve my poor drawing and the new version 1.1 can be seen below. Most heavy part of it would be the ballbearing (due to that fact only one is still left there). The tube could be made of balsa or one thin carbonfibre sleeve maybe. This idea is not thought up to details yet, but sure everybody has its own aproach to it anyway.

Tom, certainly my comments don't help you a bit since your model is near to getting covered already, but as I said I'm just curious. Anyway, that's great stuff you are doing with balsa and its a pleasure to read in the finally established FF forum!

May 08, 2005, 05:26 AM
Registered User
Kiwi's Avatar
I've always had a hankering to do an electric powered contra-rotating set up. My thought was to gear drive one prop and, from the other end of the motor shaft, belt drive the other prop so they spin in the opposite directions.
May 08, 2005, 07:57 AM
No Guts No Glory
kestrel2003's Avatar

Beautiful Model

Realy very nice Model. Hope it flys well.
May 08, 2005, 05:03 PM
Registered User
Tony Oliver's Avatar
Tom - another name for a free-wheeling prop is an 'airbrake'.

I have seen contra-rotating props done with two rubber motors - on a Gannet.

The front propshaft was attached to one motor and ran through a tube to which the second prop was fixed. That shaft had a nylon gear fixed to it and that in turn was driven by a same size gear powered by the second motor under the first.

Sometime around 1960 I think. I had a quick look but can't find the article or pic.

I love that model of yours - nice bit of 1/4 grain balsa for the cowl!
May 08, 2005, 05:29 PM
Suspended Account
what's the name of that model and scale you drew? got any prints or is that the only one? (i'd like to try and build it)
i love the little detail on the tail wheel!!
i'll bet it's a sweet flyer.
May 08, 2005, 06:04 PM
Needs brain lubrication
biber's Avatar
sgtdirt, the drawing is strictly not to scale and should give an idea of what might work. It did cost me at least half an hour of my expensive lifetime fummbling around with the pencil and a second half an hour to get the thing scanned and uploaded. And yes, the tail wheel is maybe the best idea I actually had that day . You want a name for it? Well, let's call it gazelle for its overwhelming grace .


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