Conic Clutch design

[tornitore45]

I am building a model tractor.
The plan call for a clutch Brass to Steel 1" diameter 5/32" thickness (width)
The plan specify a single side angle of 20 degrees (40 Included)

I think the angle is too steep, thinking it should be a releasing type coupling but just barely, I am inclined to make it 10 degrees

Anyone has a though or experience to share?

[Russ Hanscom]

According to my 1916 Halsey's handbook, the cone angle should be greater than 8 - 10 degrees to prevent sticking. Angles slightly above 10 degrees are used with spring loaded clutches. 15 - 20 degrees are used with mechanical linkage engage/disengagement. The angles given are measured between the rotating axis and the cone face.

Your numbers appear to be in the recommended range.

[pete]

That steeper angle also may have been a work around to gain extra surface contact area. For some items on models and the non scalable laws of physics they work against us. So you need to sometimes cheat a bit to get it to work. And my limited information matches up with Russ's, under 8-10 degrees is a self holding taper, above that there classed as self releasing. 30,40,50 taper mill tooling used with tool changers verses a Morse Taper as one example.

[liveaboard]

There is also the issues of galling and sticking, spinning and slipping...
I looked into it once for a project I never built.
Design will depend on the materials of the parts, the force holding them together when engaged, the force releasing them, the torque acting on them, and so on.
If someone has done the engineering already, designed and tested it, I say be happy and build it that way.

[tornitore45]

Thanks all, you gave some points I did not consider. Galling and the fact that a steeper angle gradually converts the clutch from a conical type to a disk type changing the the distribution of radial and axial forces.

[Russ Hanscom]

Then there is the issue of materials. Historic ones mainly used cast iron or oak or leather on cast iron. For a model probably does not make much difference.

[Bentworker]

Cone clutches made me think of BCS walk behind tractors (made it Italy). They use a cone clutch to couple the engine to the transmission. The tractors are still made today, there are exploded diagrams and videos of the clutch out on the internet if you think they may be of use to you. The tractors are in the 5-16 horsepower range so the cone clutches may be similar to what you are building.