Mystery gear removal on snowblower

550Doug · Apr 15, 2020

I've picked up an old snowblower made by McKee Bros, model 500. It had a top gear with a chain that drove the bottom gear on the input shaft of the gearbox. I have removed the chain and the top gear and would like to remove the bottom gear so that the pto shaft attaches directly to the gear box. However, I'm having trouble determining how that bottom gear is attached to the 1.25 inch input shaft.

The pictures show that there is a collar on the shaft and the gear is keyed onto the collar. Also there is a shim between the gear and the collar. I've got the large key almost out but the gear will not move even with a 3 pronged gear puller. The mystery to me is how does that collar attach to the shaft? I don't think it would be a woodruff key. Any ideas?

Roger Tomfohrde · Apr 15, 2020

At jus under the 9 o'clock position is that a set screw? Did someone drill and tap a screw in there , if so it has to come out before the outer sprocket will come off. Check to see if it is a hex head. That may be your problem. I have not seen that done before but I know I have not seen it all.

550Doug · Apr 15, 2020

Here is a video showing the amount of play on the shaft.
Yes the one hole is threaded and may have had a set screw at one time, but I've checked with allen wrenches and no results.
Gearbox

Jim.ME · Apr 15, 2020

Is the gear a tapered fit on the hub (collar)? Measure front and rear of the gear to check.

There is something showing on the collar 180 degrees for the gear key. Is it a key way in the hub?

Remove the setscrew in the 9 o'clock position that Roger mentioned. The try tapping the gear towards the gear box. The gear might be finding a set screw in the hub.

If you are definite in your plan to put the PTO shaft direct to the gear box, you can always take a torch and cut the gear and hub off, rather than continuing to spend time messing with it. Do you have a plan for a shear coupling or slip clutch? It really should have one.

Janicholson · Apr 15, 2020

Use a hacksaw or reciprocating saw with a metal blade, and cut the key sticking out behind off flush with the back of the
sprocket. next, punch the remaining piece of key out the back. next take the same saw and cut down through the sprocket
into the keyway, slicing it through so it is split. ise a sacrificial old screwdriver as a wedge to split the gear where the
chain rides (radially, down at the shaft, not along the shaft. If it doesn't wedge open, cut through the other side to give
it little "expansion" room. A plasma torch, or Oxy/acetylene cutting torch is faster. Jim

550Doug · Apr 15, 2020

I measured the front of the collar to be 2.125 inches and the rear measured 2.1875 but that includes the shim. So it appears that the collar is not tapered.
I am also confused at why there is that small slot between the shaft and the collar, 180 degrees from the large key slot.

retired farmer · Apr 15, 2020

Unless your tractor pto sits on the ground you are going to have a pretty radical shaft angle from the looks of it.

550Doug · Apr 15, 2020

It's hard to see from those pictures but the whole 3pth frame will move forward about 6 inches by removing and adjusting 6 bolts.

Janicholson · Apr 15, 2020

It could be a roll pin, the offset in the key ways shows some stress. Jim.

Mike(NEOhio) · Apr 15, 2020

Looks to me like that collar is threaded on the input shaft and that the key had sheared once and the sprockey (gear?) spun on it. Shims are taking up the wear. Was there a set screw in that hole on the face? I've seen repairs like that with the hole on the joint with a set screw to keep it on. Was there a set screw in that hole? If you took one out there could be another under it. Double them to lock.

wore out · Apr 16, 2020

I would say you have some type of Taper-Lock bushing/sprocket, perhaps even home-made or blacksmith shop-made.

Taper-Lock sprockets are commonly used on industrial machinery and not farm machinery 'cause they cost more than a cheap farm machinery sprocket, but have the advantage of being able to adapt to/grip a worn shaft to keep a machine operating.

Looks that's just what a P.O. tried to do, as I doubt that sprocket and hub are OEM.

Typically, there would be three screws used, and two more threaded holes to force the sprocket and hub apart when disassembly is needed.

Here's a photo of one such setup, GOOGLE Taper-Lock sprocket for more examples.

If your sprocket is made like in a typical fashion and all the screws have been removed the sprocket should come off of the hub by whacking it towards the gearbox.

550Doug · Apr 16, 2020

(quoted from post at 02:11:40 04/16/20)
I would say you have some type of Taper-Lock bushing/sprocket, perhaps even home-made or blacksmith shop-made.

Taper-Lock sprockets are commonly used on industrial machinery and not farm machinery 'cause they cost more than a cheap farm machinery sprocket, but have the advantage of being able to adapt to/grip a worn shaft to keep a machine operating.

Looks that's just what a P.O. tried to do, as I doubt that sprocket and hub are OEM.

Typically, there would be three screws used, and two more threaded holes to force the sprocket and hub apart when disassembly is needed.

Here's a photo of one such setup, GOOGLE Taper-Lock sprocket for more examples.

If your sprocket is made like in a typical fashion and all the screws have been removed the sprocket should come off of the hub by whacking it towards the gearbox.

Thank you. I've never heard of such an animal, but I think you've nailed it. I will try this approach.

Mystery gear removal on snowblower

550Doug

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Roger Tomfohrde

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550Doug

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Jim.ME

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Janicholson

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550Doug

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retired farmer

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550Doug

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Janicholson

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Mike(NEOhio)

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wore out

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550Doug

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