DC motor transmission puzzler - RC Groups
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Feb 04, 2013, 04:12 PM
Registered User

DC motor transmission puzzler

Hi all,

I have a small model design problem which I 'm hoping you may be able to assist with resolving.
I 'm a software developer by trade and so am quite inexperienced in the engineering/build area of a project, though pretty good at complex Arduino coding!

In its simplest form, my issue is this;
I have a fairly high-torque 12v DC motor driving a basic pulley and belt transmission in both clockwise and counter-clockwise directions.
What the design requires is that the motor shaft be automatically disconnected from rest of the system when there is no current being supplied to the motor, in order that the pulley may be freely rotated by hand.

Some kind of clutch would seem to be the answer but I am unaware of any which would suit this purpose. Most are built for large industrial purposes and are far too large for hobby modelling designs.
I have investigated spring, electo-magnetic and centrifugal types on the internet but am no closer to a solution... so I thought I 'd ask some experts!

Any help or advice you could give would be VERY much appreciated.
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Feb 07, 2013, 02:27 AM
Co-heir with Christ
Dcope17's Avatar
RC heli centrifugal clutch possibly...
Weed eater clutch or if needed a scooter or motorcycle centrifugal clutch.

All depending on RPMs and torque.
Feb 07, 2013, 04:14 AM
Registered User
Thanks for your reply - much appreciated!

Torque is 0.14 Nm (1482 g.cm)
RPM is around 200-250 rpm

As you can see, these figures are quite typical of a 12v DC motor, but not in the same ball-park as that required by scooter/motorcycle clutches.

Never heard of a 'weed eater clutch'! Will investigate
Feb 11, 2013, 08:20 PM
Registered User
I low cogging (detent) motor might be an alternative.
Feb 18, 2013, 01:29 AM
Co-heir with Christ
Dcope17's Avatar
The clutch on my weed eater works on a 1.1HP engine. It has a spring that holds the friction things in and when the RPMs are high enough, the friction parts start touching the bell and gets everything spinning. The advantage to this is you can test different springs to get it to act how you want it to...
Feb 22, 2013, 05:06 PM
Registered User
He wanted to drive the motor in both directions. Most clutches don't work well in reverse. So if going that route would probably need two clutches.

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