Author Topic: wheel rpms  (Read 1812 times)

Offline ed in cny

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wheel rpms
« on: November 16, 2012, 09:17:28 AM »
I am building a small pipe organ and am now working on the drive system. It is hand crank so I need to make the wheels to drive the music. Here's the thing I have modified the organ somewhat so it isn't to the plans. If I were to give the sizes of the wheels is there some place I can get it figured out? I need to be able to crank the drive handle six times for one turn of the take up spool. Between these two there is a clutch wheel and a smaller wheel. I have attached a video of a guy named Tom Bogus that has also been building one. He is playing his with the face off the organ so you can see how things work. I need to figure this out before I loose more of my hair.

The wheel sizes are:

Crank handle 7 1/2" dia
Small wheel on same shaft opposite end 3/4" dia
Clutch wheel 2 3/4"
Take up spool 3 3/4"

I can modify the wheels to get the right speed but I have no idea what ones need to be adjusted if any do. Any help on this would great. I'd like to get this part of my build finished. it's one of the last things I need to do.
« Last Edit: November 16, 2012, 10:24:23 AM by Stilldrillin »

Offline David Jupp

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Re: wheel rpms
« Reply #1 on: November 18, 2012, 03:41:20 AM »
It isn't clear from your description or the video exactly how the drive train is arranged.  There was a fiarly similar thread not that long ago.

I am assuming that 'small wheel' drives 'clutch wheel' which drives 'take up spool' - crank handle diameter does not matter,  cluthc wheel diameters does not matter (just fills space between other wheels).  Diameter ratio of 'small wheel' to 'take up spool' gives overall gear ratio (looks like a 5:1 reduction from the figures given).

Remember that this is based on an assumption of the drive arrangement which may not be correct - perhaps post a simple sketch of the wheels.

Offline sebwiers

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Re: wheel rpms
« Reply #2 on: November 18, 2012, 10:05:00 AM »
My assumptions & conclusion were same as Davids.

You want 6-1 instead of 5-1, so making either the shaft wheel 20% bigger OR the take up 20% smaller should do.  That will require re-spacing the shafts.  I'd suggest a bigger shaft wheel (.9 inch) because it moves the shaft less, and also gives a stronger mechanism (smaller wheels = more force on wheel surface to transmit same torque).