high torque motors and using freewheels

[zawk]

hi all

i would like to ask the probability of my concept working. basically what i plan to have is a high torque geared motor (~2 N.m /1.5 lb.ft)  attached to shaft coupler to fit onto a pinion bevel gear. obviously the pinion gear is then connected to the main bevel gear at 90 degrees onto a shaft at 1 : 1.5 ratio. however the shaft will run at around 60 rpm from another input where as the output speed of the motor is 10 rpm or so.

to solve the speed mismatch i thought of using a freewheel taken out of a rc heli gearbox. i havnt really looked into finding freewheel parts but was wondering if i can still transfer the torque from the motor to the shaft without matching the speeds??

thanks for the advice

[corrado33]

So let me get this right...

You have a shaft that is spinning from some source.  You want to connect it to another motor through various gears etc.  But the "other motor" won't be spinning as fast as the shaft?

[msprague]

I'm afraid the 10 rpm motor won't transfer any torque to the 60 rpm shaft through the freewheel.  If the shaft is already spinning at 60 rpm from some other source then what are you trying to accomplish with the 10 rpm motor?  You already have a 1:1.5 ratio, so you need another 1:4 (or higher) ratio between the 10 rpm motor output and the pinion gear if you need to maintain the 60 rpm.

If it is okay for the shaft to slow down to 15 rpm before the motor starts applying torque, then your concept will work.  The shaft starts at 60 rpm, slows down to 15 rpm, then will maintain 15 rpm by the motor.  Without the freewheel, the motor would act like a brake, but with the freewheel the shaft will slow down as if the motor was not there (or nearly so) until the point it would go slower than the motor which the freewheel will prevent. The freewheel is a one-way-clutch just like on a bicycle with handbrakes.  Going down a hill, you can't slow the bicycle wheel down with the pedals, but once the wheel is going slow enough for you to keep up with the pedals, you can apply torque and keep it going at the slower speed.

[zawk]

Aaahhhh

Okay many thanks for that.
We had a group project to demonstrate the concept of torque and angular speed. We thought we had a cool that idea that would show how you can add torque will maintaining speed but that didn't work out.

Hopefully there's some 1:4 gearboxes that out there to put onto the high torque motor. It's so annoying matching shaft and bore sizes.

Thanks again for the advice.