Mott 72 Flail Mower sparking and throwing belt

[PanarchyMills]

I just inherited an old Mott flail mower, I think it's model 72, and it has the fine cut rotor. I replaced all the flails and took it for a spin today and it was vibrating like crazy, and as I revved it up, it started vibrating harder and the flails were hitting the surround and sparking. The flails are moving in the direction of the tires (forward and down), and I replaced them with what I'm 99% sure were the correct flails. It is smooth at low rpms, but I can't rev it up without it freaking out. I didn't notice any crazy slop in the bearings when I was servicing it...
I'm pulling it with a case 990 and can't even get it halfway to 540rpm.
I then tried advancing with it through the cover crop thinking that under load it might even out, but it kept throwing the belt.
Please advise!

Some of you may enjoy the photo below: my wife took the truck for a long weekend and I needed to get it to the field where the tractor was

 

[dieselscout80]

Can you post a picture of the rotor where the knives attach?

What little bit of it shown makes the spacing of the knives look like the non fine cut version.

I have not seen very many pull type that size to cool.

 

[John0829]

I would get it so I could slowly spin the rotor and check it for being bent. Since you said you replaced the knives I think you would have spotted any missing/broke stations where they should have been but it might pay to count them to be sure you have the same number in each row. My money is on the rotor being bent.

First pull type I have seen as well!

 

[PanarchyMills]

Here it is while I was switching it over to new flails. Based on the Flail-Master catalog, I spec'd it as fine cut: 92 stations, 184 blades. Mott PN 101993 for the flails, which I bought from R&R products (PN# R400515) because they were a better price than flailmaster. Every flail was replaced, as well as some missing D-rings, so everything should be well balanced. I'm going to run out there today and check again for play in the bearings, but everything was well lubed and smooth while I was servicing it (flipped upside down).

If I can get it running, it will be perfect for managing cover crops and chopping the chaff from my small wheat operation, but I can't have sparks like that in August when I'm running it over the windrows of dry chaff. Thanks for any help folks can share

 

[leonz]

Whoever owned this Mott flail mower abused it and made a mess of it as
the knife mounting stations are all screwed up!!!!!!!!!!!!!!

If your throwing belts three things come to mind;
1. a worn stretched V belt
2. the wrong V belt
3. one of the pulleys is out of alignment.


The rotor is unbalanced and the tire and wheel assembly on the left in the
picture is damaged/bent.

Is the worm gear height adjuster able to crank????

 

[PanarchyMills]

Whoever owned this Mott flail mower abused it and made a mess of it as
the knife mounting stations are all screwed up!!!!!!!!!!!!!!

The rotor is unbalanced and the tire and wheel assembly on the left in the
picture is damaged.

Is the worm gear height adjuster able to crank?

Thanks for the reply, will you please elaborate? How are the knife stations screwed up? That photo was in the middle of me replacing the flails. Now they are all new, so they should be balanced, right? And by tire and wheel assembly, do you mean the belt drive? everything is well lubricated, moves smoothly, and the height adjuster cranks well. The drive shaft from the pto spins freely and well when the belt is disconnected. But yeah it was an old machine that lived down in a canyon for the last 50+ years

 

[leonz]

1. The left wheel in the photo is what I am referring to, the wheel connected to the shaft connecting the 2 wheels appears to be bent.

2. The D ring hangers are incorrectly mounted on the flail mower rotor

 

[PanarchyMills]

1. The left wheel in the photo is what I am referring to, the wheel connected to the shaft connecting the 2 wheels appears to be bent.

2. The D ring hangers are incorrectly mounted on the flail mower rotor

Thanks for the quick response - The drive pulley from the pto as well as the rotor pulley all appear to be in good condition, and in-line with the idler, if that's what you mean. But I will double check that today and take some photos. That would be something if the D-rings are incorrect. I was going off of the original (which I doubt had been replaced), as well as this photo from flailmaster for the fine-cut setup. Can you describe what it should be like?

:

 

[leonz]

In your original photo please look at the right side of the photo.
The 7 or 8 knife mounting stations on the right side are different
and would cause it to be unbalanced.
Please upload more closeup pictures of the flail mower rotor.
I am also worried that the left rear wheel is bent on the cross shaft.

 

[jonsstihl]

I would suspect cutter shaft bearings or a bent rotor. I have the same setup but mine is 3pt mount. I had to replace both my cutter shaft bearings and I had to make a spacer to bring the pulleys into alignment because the belt was jumping around when I got into thicker grass.

d ring holders look right to me.

I would start with the rotor if you say the bearings feel ok. try and rig a fixed pointer close to the center of the rotor and turn the shaft slowly and watch the distance between the rotor and the fixed point. if you can see the distance change the rotor is probably bent too much. they did have a high speed option available that turned the rotor faster by changing the size of the pulleys.

 

[rgr33]

I agree with above posters. First thing I would look at is whether bearings are installed correctly.
Second thing is possibly a bent shaft.
I wonder if a driveline shop could check that out got you.

I have a really old Mott 60 inch that has been used hard every year, it does not have those kind of vibrations.

 

[PanarchyMills]

Thanks for the replies,
When the bearings go on these things, am I looking for play if I grab the ends of the rotor and yank it back and forth? Or is it more subtle and requires pulling the bearings and doing a visual/feel inspection? I'll hook up a magnetic indicator today and see if the rotor is bent. I think y'all are right about the rotor or bearings being the most likely culprit so I'll give those a good once over when I head to the field

 

[Locoweed]

If you raise the mower so it is about a foot off the ground does the problem disappear?

 

[TractorNoob85]

It might be worth taking the knives off and running the mower up in RPM to see if the drum rotates smoothly.

 

[PanarchyMills]

The problem occurred at all heights but seemed to disappear once I advanced into grass, but then the belt would jump off before I could get to full throttle. Not sure if the belt jumped off because of all the vibration, or if because the idle spring seems a little tired. I think I'll shorten the spring to try and re-tension it. The belt is old but seems ok. If I place another order I'll get a new belt...

 

[leonz]

Thanks for the replies,
When the bearings go on these things, am I looking for play if I grab the ends of the rotor and yank it back and forth? Or is it more subtle and requires pulling the bearings and doing a visual/feel inspection? I'll hook up a magnetic indicator today and see if the rotor is bent. I think y'all are right about the rotor or bearings being the most likely culprit so I'll give those a good once over when I head to the field.

If flail mower rotor bearings fail the knives will hit the
flail mower rotor shroud and wake up the dead.

If the one bearing is bad they both need to be replaced.

The Mott flail mower you have has no rear roller and that
is why the rear wheels are adjusted with the hand crank
worm gear to create the desired cutting height.

If the flail mower rotor is bent as I suspect it is because of the
vibration you have to decide if you want to replace it along with
new bearings as it will last for many decades when the repair is
done and the hand crank and worm will make adjusting the height
of cut very easy to do.

As I said earlier the rear wheel shaft cross shaft is damaged and the
cross shaft mating with wheel hub is bent.

 

[PanarchyMills]

Just got back from the field and it appears to be a bent cutter shaft. I checked with a magnet indicator and it was out at least 1/4" in the center. so I pulled the cutter shaft and I'm going to try and straighten it in the shop. Any tips are appreciated.

The bearings had no slop before I pulled the shaft and inspection after pulling the bearings shows no damage or play. I might get some replacements because it seems an easy swap but I need to get up and running quick as possible to get this field mowed...

If by rear wheel shaft cross shaft you mean the shaft between the pto gearbox and the first drive pulley, that does not appear to be bent. The pulleys appear aligned (idler pulled up out of the way in the photo)

 

[John0829]

If your rotor is out of round by a 1/4" or more you have found your problem.

 

[camshawn]

I would replace the bearing if they are a reasonable price since you have it all apart. They have taken some beating at this point.

 

[leonz]

It would be much simpler to take the flail mower rotor to a drive line shop as they will have a high speed balancer and the press to correct the out of round condition which is what you need.