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Author Topic: Reduction drive  (Read 1647 times)

Offline ash

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Reduction drive
« on: February 23, 2006, 06:53:50 PM »
When I finaly get around to doing a Hawker Typhoon for F4B scale, it will almost certainly have a geared reduction drive system to turn a near scale sized prop in the scale direction at the correct speed for flight.

With some of these huge engines now emerging under the new rules, we're seeing 16" props at under 7000rpm. I suspect a small engine with a reduction drive might be able to acheive the same thing with a possible weight or cost advantage.


Assuming weight and cost are not a detriment, does anyone have any thoughts on the viability of the idea in stunt?
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Adrian Hamilton - Auckland, NZ.

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Re: Reduction drive
« Reply #1 on: February 23, 2006, 07:03:23 PM »
I usually won't reply in this section but I will this time. Engines are designed to develop peak HP at a given RPM. While true you could run gear reduction system on a engine but it will more that likely cause some problems with the application that we use our engines in. The prop pitch acts as a gear box. De pitching the prop to get the model speed where needed while still attaining peak HP for the given RPM range, Clear as mud!

Maybe Randy will post and clear the watter.
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Offline Louis Rankin

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Re: Reduction drive
« Reply #2 on: February 23, 2006, 11:16:39 PM »
Rather than use reduction gearing I would go 4 stroke or diesel.  Diesels will swing amazingly large props at lower RPMs.  Diesels also have a realistic sound like 4 strokes.
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Louis Rankin
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Offline phil c

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Re: Reduction drive
« Reply #3 on: February 24, 2006, 11:48:23 AM »
building a sturdy, reliable reduction setup to a weight is hard.  You'll notice many have come and gone over the years in the RC world.   Almost always a small motor with a reduction gear is heavier than just simply using a larger motor.

Detune an ST91 or OS 91 or get one of the super zoot ones with the crank cut for left hand rotation.  They all should swing a 16 in. prop for a scale ship.
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phil Cartier

Offline RandySmith

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Re: Reduction drive
« Reply #4 on: February 24, 2006, 12:14:05 PM »
Gear reduction drives are not a good idea  and  do not work very well on our single cylinder  motors, (There is a lot of banging going on in there)
The motors  we  use  are  very  hard  on  metal gears  and I can tell you from first hand experience  they do not last long.
If you did something like this, it would be  better  to use a  belt drive, maybe use one of the tiny aramid fiber drive belts.
Or best solution  just use a mild timed BIG engine to turn the prop.

Randy
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Offline ash

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Re: Reduction drive
« Reply #5 on: February 24, 2006, 07:19:59 PM »
Toothed belts are definetly the best transmission for this kind of thing. In order to get the rotation right for the Typhoon project, I was thinking of a nylon or fibre drive gear on a damper. There are huge 46 powered RC cars using this kind of thing now: www.minirccar.com/images/genasis/motor_pipe_setup.jpg

Yeah, I could get a big .91 or something and in the end I may just do that, but I do like to look into and try out these hairbrained things just because I can. A small engine on a reduction drive system would also make it easier to incorporate remote starting in a big scale model. This is sometimes done in WC level F4B craft, but obviously is a few steps too far for stunt! ;D

I think this one can go into the "ideas to try when I REALLY have nothing better to do" bank ;D
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Adrian Hamilton - Auckland, NZ.

Offline Dennis Pedersen

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Re: Reduction drive
« Reply #6 on: February 24, 2006, 08:05:58 PM »
If you want the lowerer RPM and reduction go with the RCV 60 or 90 as these are factory gear reduced motors already and work great in war birds due to there inline firing .A freind has the 60 and it runs great.I cannot remember exactly but I beleive he runs a 16-12 prop at 5800 prop RPM.
http://www.rcvengines.com/
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Dennis Pedersen
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Offline Phil Smith

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Re: Reduction drive
« Reply #7 on: February 26, 2006, 05:10:44 PM »
Adrian,
           There are successful reduction units from Doug Galbreath (USA) so it is possible to gear our little motors, just takes time and money.
We've got the RCVs in stock at the shop and I been looking for an excuse to run the demo .60..........

Phil.
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Phil Smith
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Offline RandySmith

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Re: Reduction drive
« Reply #8 on: February 26, 2006, 08:31:40 PM »
HI Phil

I tried the RCV 60 , it is not a very strong engine ,at least the one they sent me was not ,and  I would seriously doubt  it  has the power to turn the prop  he is  looking  to run on this  plane

Regards
Randy
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