Rear Finish Mower Gearbox castle nut and pulley problem

[n2zn1]

Hi guys,

I'm having a problem with my finish mower, where the main pulley attached to the gearbox won't stay attached to the shaft coming out of the gearbox. This problem developed recently when I changed out the belts on the mower, but had never happened before when I changed them.

Basically what happens is the 1" castle nut holding the pulley onto the gearbox shaft has come loose, and no amount of retightening will get it to hold correctly. When I start the deck up and the PTO starts, the gearbox shaft starts rotating as it should, and the force immediately loosens the castle nut, the pulley falls out of place, and the shaft just spins inside the pulley.

There is a 3/8" hole through the shaft that looks like it would hold something that would then screw down into the castle nut, but whatever was there before when it was working is apparently now long gone. Would just a regular nut/bolt/washer work, or is there some kind of special part I need? Cotter pins don't work (tried it already); I am not sure what has to go through the shaft to lock down the castle nut so it won't come loose.

The deck is a 72" LHG Clipper, which I guess is just a standard finish mower deck (have never seen another one and no info about it on the web). No manual for it either.

I've been using the deck (and others) for years and have never seen this before, but everything I've tried up to this point hasn't worked.

Any ideas?

Thanks, guys!

-Ken

 

[KubotaSam]

It sounds like the key between the pulley and the shaft has sheared or dropped out. Did you need to remove the pulley to change the belt?

 

[yankeerider]

There should probably be a cotter pin through the hole in the shaft- that's why the nut is castellated. Also make sure, like the previous poster said, that you aren't missing a key between the shaft and pulley.

Sent from my iPad using TractorByNet

 

[n2zn1]

I didn't have to take the pulley off to change the belts-I never have had to do that.

I didn't notice a key anywhere, or a place to put a key in the pulley or anywhere else. Not familiar with what a key looks like or where it would go.

There is the smaller hole for the cotter pin that goes through the shaft at the very bottom, through the castle nut.

 

[Baby Grand]

You said cotter pins didn't work - can you explain what happened - was it a good, close fit in the hole? A 3/8" hole would require an enormous cotter pin. Something doesn't sound right.
Any chance you can post a picture or three?
From what you have described, it sure sounds to me like you need a cotter pin or lock both thru that hole to engage the castellated nut & prevent it from rotating.

 

[n2zn1]

I pulled everything apart again tonight and put the gearbox up on the bench, and it does look like it needs a key, and the key is gone. There is a groove on the pulley and a hole on the shaft for the key. Thanks for the lead on that. Now to find a replacement key.

And to correct my previous post, it was a 3/16" cotter pin, not 3/8. Sorry about that!

 

[yankeerider]

The key should be easy-it's likely square stock you can cut to length with a hacksaw, available at a decent hardware store.

Sent from my iPad using TractorByNet

 

[alflen52]

does anyone know who makes the lhg mower,s?

 

[Tractor Seabee]

I pulled everything apart again tonight and put the gearbox up on the bench, and it does look like it needs a key, and the key is gone. There is a groove on the pulley and a hole on the shaft for the key. Thanks for the lead on that. Now to find a replacement key.

And to correct my previous post, it was a 3/16" cotter pin, not 3/8. Sorry about that!

Is it a straight thru key or a Woodruff key? A Woodruff is a half moon that sets in a slot made for it. Woodruffs do not have a set screw, they are common on tapered shafts. Castellated nuts are made to use a cotter pin through the shaft and the nut.

Ron