Traction engine clutch

[MattMaie]

I know from having operated a few in my day that steam traction engines, and many early gas tractors, have a friction clutch with expanding shoes that engage the flywheel. I work for a company that builds marine winches and while doing some assembly work today, I gained a partial insight into how the clutch works. The winch I war working on had a clutch consisting of two toothed dogs that meshed together when engaged. One of the dogs was linked to a bracket attached to a lever, and this bracket had two bronze pins in it that rested in a groove, so when the clutch was engaged, the dog could spin freely. So from that I got a general idea of how the clutch on a traction engine worked, but how are the expanding shoes linked up?

 

[gbritnell]

The clutch is made up of of 6 pieces not counting the flywheel. On the crankshaft is a fixed piece that has 2 wings on it. These wings as I call them go out to the inside diameter of the flywheel, with clearance. Mounted to the outer ends of the wings are the two clutch shoes which are circular in shape and have wooden inserts for friction against the inside of the flywheel. Attached at the center of each clutch shoe is a turnbuckle link. These links connect to a sliding collar which is free to slide on the crankshaft. This is known as an over-center clutch. When disengaged the sliding collar is to one side of the vertical centerline of the clutch shoes. When it is moved toward the centeline it moves the shoes out against the flywheel. It is adjusted to travel just past center whereby it is held in position by the pressure from the shoes against the flywheel. It can't disengage by itself because it needs applied pressure to move it past center.
gbritnell

 

[gus]

The Honda 50 Cub Motor Bike has a centrifugal clutch. Did not dawn on me that 51 years later,I would have to make one. Same clutch worked so well that I have no reason to open and repair.And so I have no idea how it works.