Sprag clutch for RC models
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This is also called a one-way bearing, a freewheel clutch, a cam clutch or an overrunning clutch !
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- Source
- Printables
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- Vehicles
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- Creative Commons — Attribution — Noncommercial
You might have come across my slipping gear https://www.printables.com/model/490489-slipping-gear-clutch-gear-for-rc-cars and I have explained why I needed that.
Now here is another piece of design that can work with my slipping gear but can also be used on its own: a sprag clutch ! In the meantime I've changed the shaft profile but it is doable to drive the pentagonal shaft through the slipping gear clutch.
So what is the purpose of this new design?
A slipping gear will slip if it gets too much torque; but it will do so in any direction. Sometimes you would like it to happen only counterclockwise for instance ; so you need a device that locks in one direction and rotates freely in another direction.
That's exactly what a sprag clutch will do. This design is quite tiny because it is supposed to go inside a RC car gearbox so better use a pair of tweezers to put in the small parts.
Put the sprag center inside the sprag ring; then put the sprag poles (X3) as shown on the picture. Then snap the cover on top. Finally drive the shaft through the sprag center.
When holding the ring, you can only rotate the shaft in one direction; if you need to change the blocking direction simply flip over the sprag center and the sprag poles.
The nice thing is that you can put some grease (for when you are in freewheel mode) in and it won't prevent the sprag clutch to lock in the other direction.