Flail Mower Mott 72" Flail Mower bearing replacement & drive pulley spacing

[Zumdahl]

Good Evening. I have an old Mott 72 flail which needed to have the cutter shaft bearings replaced. I ordered a pair of the M-702408 bearing + housing combos from Flailmaster. Housing itself looks the very similar to the old one, with three bolt holes that line up great and grease zerks on the housing face. However, the face that mates with the pulley sits proud compared to the old bearing.

This first picture shows the original bearing & housing:


And the new one mounted to the flail on the drive pulley side.


And the step of the process where I realized I had a problem. The shaft itself no longer goes all the way through the pulley:


I'm sure it's something I've done. Before I took it apart the shaft was pretty much dead flush with the outer edge of the pulley.

The cutter shaft doesn't seem to be shifted left to right. The first set of knives on each side are spaced evenly from the mower sides.

The bearings are supposed to come fully pressed in, but I suppose I don't know if its actually bottomed out against something in the housing.
Really wrenching down the bolt that holds the pulley might gain me smidge, but I don't imagine it'll be enough for the shaft to go fully through the pulley.

Any advice is much appreciated!

 

[whirly]

Is it possible the housing is not seating in the frame? It looks like the distance for the shaft to be flush with the pulley is the same or greater than the amount of bearing that is sticking out of the housing.

Pics of both bearing unmounted, side by side,would help.

I have a Mott 72" I can look at in the morning.

 

[leonz]

Good morning Zumdal,


If you look very closely at the second image its either distorted or there is something wrong with the inner bore. you have a huge amount of metal shavings, and metal dust in and around the bearing housing and that is not good.

both bearings are locked with set screws and locking rings if I remember the sequence correctly and they should both be a slide fit never a press fit bearing set for the flail mower rotor.

Do you have fine emery paper of 400 grit or greater? the flail mower rotor stub shafts should just slide through the bores with no trouble.

You need to clean the bores with some isopropyl alcohol or hydrogen peroxide and a double thickness of the blue paper shop towels.

You have a fit problem of some kind that needs to be fixed.


I have a copy of the Mott mower manual I can email to you directly if you would like to have it. Please send me a PM for the manual at your convenience.

 

[Rocky Hoffler]

It seems your dealing with flailmaster they have been helpful to me about superced parts it’s worth a call also Mott was bought by Alamo there are part breakdowns available good luck

 

[Zumdahl]

Is it possible the housing is not seating in the frame? It looks like the distance for the shaft to be flush with the pulley is the same or greater than the amount of bearing that is sticking out of the housing.

Pics of both bearing unmounted, side by side,would help.

I have a Mott 72" I can look at in the morning.

The housing itself sits tight against the frame. The bolts that hold the housing on force it as tight as possible. You're right, that the distance the that the shaft is recessed is more than how proud the bearing stands.

I pulled the new housing off again, and took photos of it side by side with old.
From the outside of the mower:


Inside of the mower:


And from the side. This shows how far out the replacements stand.

 

[Zumdahl]

I just attached a handful of better pictures of the bearing. Do you still see the shavings you mention? I think it might have just been oily finger prints and a bad picture.

The stubs slide easily through the bores, though I didn't do anything with locking rings. The bearings were pressed into the housing when I received them. I literally just slid the entire assembly over the shaft and tightened the three bolts. The set screws were going to be next but I hadn't tightened them yet because of how out of place the shaft seemed.

In hindsight I'm realizing I should have fully replaced one side of the mower and tightened it down, then done the other. Is it possible I've just shifted the entire shaft a quarter inch to the side? The outermost knife stations really do look centered compared to each side.

Good morning Zumdal,

If you look very closely at the second image its either distorted or there is something wrong with the inner bore. you have a huge amount of metal shavings, and metal dust in and around the bearing housing and that is not good.

both bearings are locked with set screws and locking rings if I remember the sequence correctly and they should both be a slide fit never a press fit bearing set for the flail mower rotor.

Do you have fine emery paper of 400 grit or greater? the flail mower rotor stub shafts should just slide through the bores with no trouble.

You need to clean the bores with some isopropyl alcohol or hydrogen peroxide and a double thickness of the blue paper shop towels.

You have a fit problem of some kind that needs to be fixed.


I have a copy of the Mott mower manual I can email to you directly if you would like to have it. Please send me a PM for the manual at your convenience.

 

[Zumdahl]

Since I already had it apart, i tossed the old housing & bearing back on to check fit. Shaft is still recessed a bit, but not nearly as much as with the new bearings. Spacing it hard to see here, but its 3.25mm in.

I assume I can shift the shaft a bit before tightening the set screws. The new assembly sits another 7mm proud of the surface. If I tried to shift shaft that far, I'm almost positive the the outer blades would hit.

 

[whirly]

As you can see the bearing sticking out on the outboard side is half the problem. You might mic the thickness of the housing to see if that is the other half of the problem.



The real issue is the sheave. If it sticks that far out it won't line up with the drive sheave.

If this was my problem and the only issue was the one in the attached pic, I'd assemble it and measure how far off the 2 sheaves are then take it to a machine shop and have them remove the excess.

[Edit] you may just need to remove the excess.

 

[Zumdahl]

The housing themselves are identical as far as I can tell. It does seem like the new sheaves are just 6-7mm longer. The sheave is inserted to be flush with the inner side of the housing. I do have space between the mating surface of the flail drum at the back of the sheave. Is it possible to press the sheave further in so that it sticks out the back of the assembly instead of the front?

 

[whirly]

... Is it possible to press the sheave further in so that it sticks out the back of the assembly instead of the front?

Do you mean the Bearing?