Gear & Electric Motor Specs Needed

[Bill Montgomery]

I registered as a 'student' because that was the only category I could choose.
I'm actually a retired pipefitter who is attempting to build a spinner platform for ice skaters to train on.

I have a 20 inch spinning platform that will support over 300 lbs.
I need to know what siz rubber drive wheel and what size of 110 volt electric motor i need to turn the platform 20-30 r.p.m.

thanks for any assistance.

Bill M.

 

[mfgenggear]

Bill

If may suggest, you may need to hire an engineer, and explain what you are trying to make.
will there be a gear box involved, or pulleys, or direct drive, a sketch might be helpful.
to many unknowns. sketch is worth a thousand words. how much HP and what RPM of the electric motor.
may need a rheostat to control the RPM,

 

[geesamand]

Tricky question because an ice skater can apply sudden bursts of thrust as they skate or stop, and those could translate into shock loads on the drivetrain. These are notoriously tricky to estimate on paper and generally come down to durability in practice.

 

[Bill Montgomery]

Thank you both for your replies to my question.
Regarding "thrust on the drive train"....not sure what you mean.
The skaters are just standing still while the platformn is spinning.

 

[DAVIDSTECKER]

Bill,
Here are some basics.
If you want the final RPM to be 30 RPM you will need to know what RPM the motor turns at.
Most motors are about 1,800 RPM so if you divide 1,800 by 30 you get 60 which is how much gear reduction you need. ie 60:1.
If you are going to turn your 20" platform on the outside rim using a 5" rubber wheel then you would have a 4:1 reduction there.
To find out what the gear ratio of gear box you need to complete the drive train, divide 60 by 4 and you get 15.
So your gear box needs a 15:1 gear ratio.
If you get a Gearmotor from some place like Grainger that has a speed control built in I'd say shooting from the hip a 1/3 to 1/2 HP motor should do the trick since you can ease into the final speed.
You can look for calculations for acceleration based on the weight of the skater and how fast you want to accelerate the turn table.
google something like Engineers Tool Box for calculations.
Jumping from Zero to 30 RPM would knock them off their feet.
Once you skater is up to speed it shouldn't take too much power to keep them turning if you bearings are good.
A quick disclaimer; you are solely responsible for your creation.
Best regards, David

 

[Bill Montgomery]

Dear David,
thank you so much for your feedback and calculations you provided.
I really appreciate that.

Regards,
Bill M.

 

[mfgenggear]

https://www.engineeringtoolbox.com/electrical-motors-hp-torque-rpm-d_1503.html

 

[BrianPetersen]

Friction is the big unknown here. How much torque does it take to turn that "spinner platform"? Is it on ball bearings, or is it sliding friction and if so, what are the materials involved and how smooth are they and how are they arranged to support this platform (are they at the center supporting a shaft? are they support pads around the outside? affects how much torque it will take to turn the platform).

The other one is the inertia - not just the weight, the moment of inertia around the axis of rotation. 300 pounds tightly concentrated around whatever the rotation axis is, is a quite different matter from 300 pounds some distance out from the rotation axis. And, how fast do you expect this to speed up and slow down?

Not all gearbox designs are appropriate for something like this. A non-backdriving worm drive gearbox (selected on the grounds of "cheap") will come to an abrupt stop when the worm stops turning ... almost without consideration of what happens downstream of it, including breaking stuff or sending things flying.

 

[chicopee]

frictional force on the spinner from skating can be estimated conservatively while the skater is in a forward motion only, however, it will be tricky to figure out the frictional forces when the skater transitions from a straightforward or backward motion to a rotating motion as the skater will need to grip the ice with his skates; then what happens if the skater falls from either motion. You'll need a sensing device to stop the spinner for the skater to stand up or get out of the way from the spinner.

 

[DAVIDSTECKER]

Bill, you're welcome.
Let us know how things work out.
Best regards, David