Damaged and Sticking Motor Sheaves

[billmayo]

The lower sheaves are not. The key has moved forward out of the keyway and was sticking out of past the outside sheave a little bit. I had to pull it out with pliers before I was able to get the outer sheave off, which took lots of pulling. The keyway on this sheave was already damaged, the aluminum being split a little so that the keyway on the sheave is now an open channel. (I made it worse during removal, but I had decided to replace it immediately when I saw it.) I've ordered a new key and outer sheave. The sheave that is mounted on the moter shaft is firmly on there and is misaligned slightly with the keyway. I have loosened (removed) the set screw, and the sheave is still bound on there. - Mark

I find the above problem can result from walking the drive belt off the motor sheaves and letting the Floating Sheave snap back againest the Fan Sheave. This loosen the Fan Sheave set screw and allows the key to move as the headstock speed is varied. This action also causes the spacer behind the Fan Sheave to indent into the Fan Sheave hub and cause the Fan Sheave to rub againest the motor housing.

When there is no belt on the motor sheaves, always have control of the Floating Sheave like when the spring is being compressed. Also watch that your finger tips are not between the motor sheaves when returning the Floating Sheave back againest the Fan Sheave. It does smart if you are not careful.

[Lablover]

I just found the same problem on my Mark V. The set screw on the non-floating motor side sheave had come loose and allowed the key to slide out past the floating sheave which in turn jammed the floating sheave into the fixed sheave. The floating sheave has a slight crack where the key was forced up but I think it will be ok.

My question is how long should the sleeve between the motor and the fixed sheave be? Thank you

[DLB]

I just found the same problem on my Mark V. The set screw on the non-floating motor side sheave had come loose and allowed the key to slide out past the floating sheave which in turn jammed the floating sheave into the fixed sheave. The floating sheave has a slight crack where the key was forced up but I think it will be ok.

My question is how long should the sleeve between the motor and the fixed sheave be? Thank you

I don't know if those spacers are all identical in length for all variations of the motor over the years, I would guess that they are not. I have one in my hand that measures 0.411". The important thing is where the fan sheave is positioned in relation to the fan or motor housing. Close but not in contact is what I go by.

- David

[JPG]

Steel spacer and aluminum sheave creates a propensity for the sleeve to become embedded into the softer sheave and thus reduce clearance. I agree as close as possible without any contact. That set screw is one of the few places where a gorilla is recommended. Only the set screw keeps the key from sliding.

[Lablover]

DLB, my sleeve measures about the same as yours and the sheave is close but does not rub on the motor housing so I think it is ok for now. Thank you for the replies.