|
Torque is transferred from the coupling to the shaft by a key. Thrust loads fore/aft are transferred by the set screws. It's important that the set screws seat into drilled recesses in the shaft, otherwise it's easy for things to get loose. And if they get loose the prop and shaft can slide aft out of the coupling.
Navy practice is to add some pieces to the coupling. The shaft gets a groove machined in it a bit back from the front end. The coupling goes on past the groove, then a pair of half-circle plates fit into the shaft groove. It all gets bolted up to the next piece forward.
If the shaft pulls out of the coupling, it isn't good. If it just pulls aft a little, you lose propulsion. If it pulls aft a lot (like through the stuffing box) you could lose the boat.
|