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Author Topic: RPM reduction and other quandries  (Read 696 times)

Offline Andy F

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RPM reduction and other quandries
« on: October 08, 2021, 10:23:47 AM »
This might seem like a daft question but is there some sort of magic formula that can be applied for fitting one motor to one paddle wheel for a particular speed range?

Forget the 6 shaft monstrosity I was alluding to the other day, this one will have one wheel centrally mounted and I'm wondering about the best way of delivering power to the wheel using most likely a 385 motor and a 7.2v nimh.
I don't really want to go down the rubber band route if I can help it. If that was the only option then I'd prefer chain drive but I'm really more leaning towards gears or similar. Altogether a more 'solid' feeling.

For anyone who feels the need to know, the model will be roughly 32" long and the paddle will probably be around the 3" diameter 2"wide mark and I'm looking for a  roughly walking pace cruising speed.

I think what I'm really asking here is what would be the ideal RPM for a wheel that big for a believable model speed.

Any ideas?

Offline william stafford

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Re: RPM reduction and other quandries
« Reply #1 on: June 05, 2022, 09:50:30 PM »
my recomend is tooth belts,MXL should be ok w 385 and 3:1 reduction, aim for 300/350 rpm at paddle wheel, if you use a 545 motor go w
HTD belts, i have stripped MXL, you can use the speed control too slow paddle wheels, but if its at maximum speed, bad luck

Offline Bierjunge

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Re: RPM reduction and other quandries
« Reply #2 on: June 14, 2022, 09:50:17 PM »
A 32" long model will be able to obtain a hull speed of not more than 2.5 mph or 3,7 feet per second. At this speed, a 3" dia wheel would rotate at 280 rpm if we neglect slip between wheel an water.
A no-load idle speed of 300 to 350 rpm, as suggested by william, therefore seems perfectly plausible. Pretty high revs for a paddler, though.


Offline william stafford

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Re: RPM reduction and other quandries
« Reply #3 on: June 28, 2022, 08:20:12 PM »
you can always throttle back w speed control, as i do to about 50\60%, but if the wind comes up when you are out on the lake, full steam ahead !!
you cant do that if you only have 150/200 rpm at the wheeli use gear head motors w 1000 rpm out put shaft, to HTD/MXL 3:1 tooth belts, much better than gears as no noise, plenty of these motors on the net, but if i couldnt get them i would just add1/2 belt reductions and make mt own


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