Flail Mower Let's talk flail mowers

[Ozarks Landowner]

Didn't get a chance to work on mine today as I am having mower deck problems on my 154 cub lo boy. Gotta get that thing fixed before my yard gets too out of hand.

 

[leonz]

Ozarks Landowner my mower (Mott 72) vibrates the mower, tractor, and me until it reaches close to PTO speed and gets all the knives slinging outward then it smoothes out nicely. When I'm mowing I have my ear protection on and tunes going but if I hit a thick patch of grass and the mower slows it will vibrate slightly and I know to raise the 3ph before I even look back to see what happened. Then it's slow down until I get out of the thicker stuff.

I'm not sure (Maybe a pro can verify) but I think most flail mowers are designed to run very close to PTO speed. Actually its about the only time I run my tractor at that speed. So when you're trying it make sure you're at the correct speed. If you have all the knives removed you shouldn't feel much if any vibration no matter what speed you run it.

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Hello Steave,

If your mower is vibrating at low speeds that is not good. All you should have is the chatter of the side slicers bouncing around until the centrifugal force created by the high speed rotation of the flail mower rotor forces them to fully extend them selves into the proper orbit around the flail mower rotor.

The low RPM shuddering/shaking indicates there is something wrong with the rotor balance or possibly a bad bearing at this point.


You also need to keep your tractor engine running your Mott at the 540 RPM engine speed as it will not work well otherwise and you will smoke belts.

 

[Steave]

leonz

Hello Steave,

If your mower is vibrating at low speeds that is not good. All you should have is the chatter of the side slicers bouncing around until the centrifugal force created by the high speed rotation of the flail mower rotor forces them to fully extend them selves into the proper orbit around the flail mower rotor.

The low RPM shuddering/shaking indicates there is something wrong with the rotor balance or possibly a bad bearing at this point.


You also need to keep your tractor engine running your Mott at the 540 RPM engine speed as it will not work well otherwise and you will smoke belts.

Thanks for the help. I let the mower come up to speed and somewhere in between slow and PTO speed is when it vibrates. Actually don't let it sit there running at idle so it might just chatter at idle speed. I'll try that next time and just see. It has new bearings but that don't mean I don't have a bad one. My mule as you call it has a 2 stage clutch and I can let it come up to speed gradually.

I appreciate the info. I'm happy with the mower and it's used mostly on field roads that receive regular cuttings and a portion of my yard not cut with a lawnmower. It does a good job.

 

[CCWKen]

If you have a hollow drum rotor like most do, you can drill a hole in it and install about two pounds of Dyna Beads. Then plug the hole afterwards. A cheap alternative is glass beads (blasting media) and talcum powder. Start the rotor up slowly to distribute the beads and it will self-balance.

DynaBeads Tire Balancing Beads

Dyna Beads is used in many antique car tires all the time. Especially the wood spoke wheels where modern wheel weights aren't large enough or too obtrusive.

 

[shaeff]

I've read (and kept up with this thread) from the beginning. It may have been answered already but I don't recall- what weight/kind of gear oil should I run in my JF 25A flail mower? I'm at the point where I'm starting to service it and I'd like to drain the likely (very) old oil out and put in some fresh. This weekend I'll be replacing the belt (shredded when I got it) and starting on knife replacement, as many are broken or bent out of shape.

 

[Fallon]

I've read (and kept up with this thread) from the beginning. It may have been answered already but I don't recall- what weight/kind of gear oil should I run in my JF 25A flail mower? I'm at the point where I'm starting to service it and I'd like to drain the likely (very) old oil out and put in some fresh. This weekend I'll be replacing the belt (shredded when I got it) and starting on knife replacement, as many are broken or bent out of shape.

Any reasonable gearbox lube. These aren't precision gears. Most run 90wt gear oil. Unless the seals are shot, then many of us add grease of some sort rather than fix the seals. I used a mix of pourable grease & 90wt rather than $75 of new seals in a flail I paid $100 for.

 

[Ozarks Landowner]

If you have a hollow drum rotor like most do, you can drill a hole in it and install about two pounds of Dyna Beads. Then plug the hole afterwards. A cheap alternative is glass beads (blasting media) and talcum powder. Start the rotor up slowly to distribute the beads and it will self-balance.

DynaBeads Tire Balancing Beads

Dyna Beads is used in many antique car tires all the time. Especially the wood spoke wheels where modern wheel weights aren't large enough or too obtrusive.

This is very interesting. Being made for tires I wonder if the beads would spread out over the length of the drum.

 

[shaeff]

Any reasonable gearbox lube. These aren't precision gears. Most run 90wt gear oil. Unless the seals are shot, then many of us add grease of some sort rather than fix the seals. I used a mix of pourable grease & 90wt rather than $75 of new seals in a flail I paid $100 for.

Very good, thank you! Right on, I'm into my 25A for $300, came with a bucket of new knives and hangers, as well as a new belt. It's got rust holes in it and is generally in rough shape, but spins pretty smoothly even with broken and missing knives it doesn't vibrate much. I only ran it for a few seconds to make sure it was worth fixing.

Thanks!

 

[Fallon]

Very good, thank you! Right on, I'm into my 25A for $300, came with a bucket of new knives and hangers, as well as a new belt. It's got rust holes in it and is generally in rough shape, but spins pretty smoothly even with broken and missing knives it doesn't vibrate much. I only ran it for a few seconds to make sure it was worth fixing.

Thanks!

I'm into mine a total of $400-500. New belts, new knives & hardware as well as a PTO shaft. Fired mine up to promptly find out why some knives were missing. Busted out the plasma cutter to cut out the trailing sections of the hood that were getting hit. Welded a crappie patch job over that hole. It was working great & way better than my new rotary cutter.

Finally changed the gearbox lube in it recently when a seal started going. The pourable grease & 90 wt is working well.

On my latest job it blew a bearing & probably mounting flange on the driven pulls. Such is life. Need to finish pulling it apart & determine what all is busted back there to order replacement parts. In the mean time I'm using the better looking but inferior new rotary cutter.

 

[Steave]

If you have a hollow drum rotor like most do, you can drill a hole in it and install about two pounds of Dyna Beads. Then plug the hole afterwards. A cheap alternative is glass beads (blasting media) and talcum powder. Start the rotor up slowly to distribute the beads and it will self-balance.

DynaBeads Tire Balancing Beads

Dyna Beads is used in many antique car tires all the time. Especially the wood spoke wheels where modern wheel weights aren't large enough or too obtrusive.

Thanks for posting this. Ozarks Landowner might could benefit from trying this. Over the road truckers used to use something like this, I guess the glass beads with powder maybe, but I had forgotten all about that. Heck it might smooth mine down a bit also. Mine smoothes somewhere close to PTO speed and runs fairly quiet for an old Mott so I just thought it was one of those things it does when picking up speed.