Flail Mower Grass getting sucked through the bearings on Mott F5

[goatchay]

Hi to all,

First of all, I wanted to say that I have probably gotten through about 40-50 pages of the flail mower Mega-Thread lol, such a wealth of info. Thanks to all who have contributed to it, I look forward to reading all of it!

I recently inherited two Mott flail mowers from my Dad. I used to cut with one of them when I was a kid in the 70-80's. One is a 4 foot unit and the other is a 5 footer. I got him a zero turn many years ago, so the Motts have been sitting idle. I am now on a piece of property that I think they will be ideal for, so I am in the process of giving them a little TLC, etc. I will hopefully be able to successfully attach some pics at the end of this post.

The green 5 foot unit came on the back of a Yanmar YM195 that my dad got from the school board. He did not use that one for long because he got the 4 foot Mott from the school board a short time later and felt that it was more suited to the Yanmar, plus it was reverse rotation/front discharge and he preferred the quality of the cut that it gave.

I am focused on getting the 5 foot mower in shape because I think the rotation will make it more suited for what I am trying to mow. My property is largely Bahia hay grass. It was planted by the previous owner and is VERY well established and THICK. Normally my neighbor mows if for hay and bales it. He has been having equipment issues so it has not been mowed or cut since the last time it baled, which was in December.

I gave the green 5 foot Mott a decent inspection and everything seemed ok, except for a weak spring that I replaced. Also gave it a good greasing everywhere. I am using it on a borrowed Deere 45 hp (35 pto) so the original pto shaft did not leave enough overlap (only about 3"). I put fitted and installed an new PTO shaft. I also sent some pics to Flailmaster in order to help identify it so that I could order new knives, spare idler and belt etc. They were extremely helpful. I think that the belt is original because it actually has MOTT 100058 stamped/burned into it. I suspect that the blades are original too.

Flailmaster ID'd it as a Mott 60, so I ordered a belt, knives, clevis and cotter pins, etc. I would later find out that the ID was incorrect. While I was waiting for delivery, I decided to give it a test run. My dad always used it on a well kept St. Augustine lawn and swore to me that they were designed for turf and could not handle tall grass/brush. Growing up in south Louisiana, I had never seen another flail mower and had no reason to question that statement. Now you seem them doing roadsides etc and I've shown my dad videos of what they are capable of, which I really was not aware of until recently. I love this thing!

Anyway, on to the test drive/mow. I am cutting very thick Bahia, which is close to 2 feet long. It's very ropey/stringing and wants to wrap up on a regular rotary mower, even when it's 4 or 5 inches. I was proceeding at a hair north of 540 rpm and ground speed of about .5-1 mph. Everything looked great, it looked like a sidewalk through the middle of a jungle lol! Everything was going fine for a few hundred feet, when suddenly with very little warning, I smoked the belt. It popped off almost instantly. I was watching the pulleys since my ground speed was so slow. Prior to that, it was running very smooth with no vibration.

When I stopped the tractor to inspect things, I could barely turn the the cutter shaft even with both hands on the pulley. I looked under the mower and a ton of grass had been sucked up into the edges/ends of both sides of the cutter shaft. I hate this Bahia and I'm in the process of trying to kill it all. I spent several hours making little headway with a razor knife, small utility shears, pocket knife, needle nose, etc. Barely made a dent and still couldn't even see the shaft. Finally put a propane torch to it and was able to burn the bulk of it off.

The strange thing so me is that it was also wrapped up on the outside of the mower, between the pulley and the mower shell. At first, I thought that it just wrapped up here too because it got caught up in the rotation mass of the pulley/shaft etc. But it really looked like it was coming OUT of that area, like it had been pulled through from the inside of the mower shell and through the bearing.

I finally got the pulley off and then the triangular grease cover, and sure enough, the grass was sucked/pulled past the edge of the cutter shaft, somehow through the washer that seals the back of the bearing, though the cage of the bearing itself, though the pulley spacer and out onto the keyed part of the shaft where the pulley/sheave sits. That blew my mind.

Anyway, I am in the process of disassembling it. While doing so, I realized that my parts did not match up with the Mott 60 manual that Flailmaster sent me. After reading through many threads on here (including the one by LD1 when he was dealing with different sized bearings on each side, my mower is very similar to his) and looking at some old advertisements on ebay, I came to the conclusion that I have an F5 instead of a Mott 60. I kindly received a parts diagram from Michelle at Montage and Peter at Maritime Farm Supply. My mower looks identical to this, including the 3 point brackets, gearbox, slotted mower shell, both pulleys the same size, etc.

I have the press in bearings. I have the housing removed. The bearings are stamped "BRG 206 KL" "MADE IN USA" "FAFNIR"?? and possibly "C2"??

-----------Would it be wise to go ahead and replace the bearings at this time while I have everything apart?

I like that fact that the outside face of the bearing isn't sealed so that it can be visually inspected. Not sure if new ones would be sealed? The bearing seem fine, although I am almost sure that they too are original. And as I said, it's basically apart now. I had to tear it down to this point to remove the grass.

The cutter shaft is basically just sitting inside of the shell. I really don't even see how it can be removed unless it is narrow enough to slip though the holes in the mower shell if the knives are removed? Nevermind, just looked at the pics and that's not possible either??


I realize that this is a long post and I do apologize. I just wanted to give some background on the problem. I have two main areas/questions that any input or help would be greatly appreciated on.

-------------- 1) Has anyone every fabricated some kind of guard to prevent the grass from getting drawn into the end of the cutter shaft? I would hate to go through all of this only to have the same thing happen during the first few hundred feet that I mow again. There is very little room between the inner wall of the mower shell and the first set of knives and the factory weights. I didn't know if anyone was successful in adding some kind of guard or deflector to that space?


My second question involves the knives. Since we were under the assumption that it was a Mott 60, I ordered the MH 386 knives from Flailmaster, which are 5" long and 1 1/4" wide. I should have measure mine but failed to. Mine are actually only 3/4" wide, according to the F5 parts diagram, they are a C5 knife, and the only one listed to go on that mower.

---------------2) So my question is, can I substitute the wider knife (MH 386) in place of the skinnier one (C5)? Other than that, their profiles are identical, bend at the same place, etc. These would be heavier obviously. They may work better on the Bahia as well. I just don't know if they are compatible to replace the C5??


Thanks to all who took the time to read through this lengthy post and to all who may contribute to helping me find a solution to the grass-wrapping issue.

Chris

 

[goatchay]

I am not working on or using the yellow 4 foot mower with the D rings at the moment, I just included pics of it to show the differences between it and the older F5.

Here are some more pics of the grass, bearings, etc.. as well as the old and new knives that I don't know if they are compatible since they are wider.

 

[goatchay]

Additional pics, hopeful this helps.

 

[goatchay]

Last pics of parts diagram for Mott F5 flail mower.

 

[jthibodeau89]

On my Deere 390 the end of the rotor is recessed into a collar on the bearing housing. The rotor also has a spur that overlaps the OD of housing collar. This is very effective at stopping grass wrap. My JD 26A does not have this design and is currently down awaiting a bearing replacement due to grass wrap.

If grass came through the bearing, I would consider it dead. I trotted to run my 25A after cleanin up and greasing, but the ball retainer cage failed shortly after.

I plan to modify the 25A with some sort of collar arrangement like the 390 this winter.

 

[goatchay]

On my Deere 390 the end of the rotor is recessed into a collar on the bearing housing. The rotor also has a spur that overlaps the OD of housing collar. This is very effective at stopping grass wrap. My JD 26A does not have this design and is currently down awaiting a bearing replacement due to grass wrap.

If grass came through the bearing, I would consider it dead. I trotted to run my 25A after cleanin up and greasing, but the ball retainer cage failed shortly after.

I plan to modify the 25A with some sort of collar arrangement like the 390 this winter.

Thanks so much for the response. I hadn't thought of attaching something to the rotor, I was thinking of trying to attach something to the collar of the bearing housing. I have been brainstorming and looking at this thing, but not coming up with much in terms of ideas. Thanks again! I'll see if I can find a pic of a JD390 cutter and see what you are referring too.

 

[goatchay]

On my Deere 390 the end of the rotor is recessed into a collar on the bearing housing. The rotor also has a spur that overlaps the OD of housing collar. This is very effective at stopping grass wrap. My JD 26A does not have this design and is currently down awaiting a bearing replacement due to grass wrap.

If grass came through the bearing, I would consider it dead. I trotted to run my 25A after cleanin up and greasing, but the ball retainer cage failed shortly after.

I plan to modify the 25A with some sort of collar arrangement like the 390 this winter.

I can't find a decent pic of the cutter shaft of a 390. Is the mechanism that you are talking about sort of like a shroud that covers the collar of the bearing housing, or is it something sharp that spins and cuts the grass before it can wrap? Thanks again.

 

[leonz]

Hello Chris/goatchay,


I want to welcome you as the newest member of the "Flail Mower Nations".

Please fill out the rest of the information on the member ID form so we can help you further.

If I remember correctly the flail mower rotor on the 25A and 290 and 390 have a metal bar welded to the flail mower rotor to shear of any grass buildup on the bearing housings. you will not be able to do that with the Mott mowers you have. you should plan on raising the cutting height up a little to reduce the plugging until you have a better handle on your Bahia Grass.

A couple of things jump up from the ground and slap me about this. Where is the internal seal for the old bearing??? the seal is supposed to be on the inside of the flail mowers side weldment's.

The new knives will be fine as all the knife stations have the new knives as it will be unbalanced other wise and an unbalanced rotor is what keeps me up at night and is not good. You will just need to start up slowly and they should be much better at slicing the Bahia grass quickly.

You should invest in a wet well grinder from Micromark (79.99+tax and shipping) and the angle setting gauge from Woodcraft to set the tool rest angle from woodcraft (29.99+tax and shipping) so you can maintain the knife edge on the side slicers and prevent the temper from being ruined-assuming they are heat treated side slicers.

Leon

 

[goatchay]

Hello Chris/goatchay,


I want to welcome you as the newest member of the "Flail Mower Nations".

Please fill out the rest of the information on the member ID form so we can help you further.

If I remember correctly the flail mower rotor on the 25A and 290 and 390 have a metal bar welded to the flail mower rotor to shear of any grass buildup on the bearing housings. you will not be able to do that with the Mott mowers you have. you should plan on raising the cutting height up a little to reduce the plugging until you have a better handle on your Bahia Grass.

A couple of things jump up from the ground and slap me about this. Where is the internal seal for the old bearing??? the seal is supposed to be on the inside of the flail mowers side weldment's.

The new knives will be fine as all the knife stations have the new knives as it will be unbalanced other wise and an unbalanced rotor is what keeps me up at night and is not good. You will just need to start up slowly and they should be much better at slicing the Bahia grass quickly.

You should invest in a wet well grinder from Micromark (79.99+tax and shipping) and the angle setting gauge from Woodcraft to set the tool rest angle from woodcraft (29.99+tax and shipping) so you can maintain the knife edge on the side slicers and prevent the temper from being ruined-assuming they are heat treated side slicers.

Leon

Hello Leon,

Thanks for taking the time to respond, I appreciate it. I've read many of your posts here and I realize that you have a vast amount of knowledge and expertise regarding flail mowers.
Thank you for the welcome and I will update my info/ID ASAP.

Just for reference, I think that the grass height is set at the second to highest position (of 4). I will double check that. When on concrete, the distance between the blades and the ground is about 2".

Thanks for the explanation regarding how the Deere cutter shafts are set up. I'll keep brainstorming. One thing that did occur to me... an empty dog food/soup can is a very tight friction fit over the collar of the bearing housing that protrudes into the inside of the mower shell towards the cutter shaft. I was thinking about cutting a can down to about a 1" ring (or as long as I clearances allow) and maybe snipping some slits in it to allow it to be folded inwards towards the center of the shaft to make a cover/shroud of sorts. Stupid idea???

In regards to the seal on the bearing, it came out just as pictured. I have looked at pics of new 206KL bearings for sale on ebay etc and they look the same as mine....the outside is open and you can see the cage/bearings, and the inside face of the bearing that is resting up against the seat/lip of the housing and facing the inside of the mower has what I guess it a type of metal seal (the dark area between the races, that has the printing/lettering on it...or is that just the back side of the cage?) It doesn't seem like a total seal, more like a semi seal or guard because there is daylight on the outer edge of it, near the outer race, and fluid can pass through.

Further inboard of the bearing, a thick and very tightly fitted seal washer sits up against the interior side of the bearing. The washer is the exact OD of the bearing and rests inside of the collar. The cutter shaft butts up against it. i will try to get a good pic of it. It is in the schematic also. It seems like it would do a good job of keeping grass out for sure, if not tiny particles, dust etc. But the grass got through it somehow, through the dark metal shield/seal of the back of the bearing and out through to the pulley.

I am not sure if I am answering your question Leon. I can try to take some better pics of the bearings if you'd like. I have them both removed now and pressed out of the housings. I had a very hard time getting the drive side housing out of the mower shell. Once it finally came free, I was able to inspect that bearing more closely and it was a goner. The non drive side was almost like new in terms of feel etc. That side wrapped a ton of grass also, but it did not seem to make it's way completely through the bearing.

While I am at it, I might as well replace the outboard bearing for the drive pulley/extension shaft. But according to the schematic, it looks like a casting/assembly rather than a pressed in bearing (item number 21, part number 3-61)

I was also curious about how to preload the bearings or the torque spec on the two bolts at each end of the cutter shaft. One goes through the pulley. The other, non drive side just butts up against the bearing with a locknut and washer. As far as I can tell, the only thing that really ties the shaft and bearing together is the force of the preload/cinching up on those two bolts on the outside of the shaft. There are no set screws etc.

I definitely planned on replacing all of the knives Leon, I have read in your previous posts about the dangers of an imbalanced shaft. I just placed one on the shaft for reference to show the difference in width of the two. I also purchased new clevises and cotter pins.

So it is OK to replace the 3/4" inch knives with the 1 1/4" ones? I asked Flailmaster and I'm waiting on a response from them.

I also thought about removing the cutter shaft from the mower to make it easier to replace the knives on a table top etc.. I was going to leave a few stations blank so that there would be room for my hands to grab it to carry it etc. Does anyone see a problem with this idea? Or Should I just mount everything back up with the new bearings and then change the knives at that point as a last step?

Thank you again for the heads up on the wet grinder Leon. I have seen you mention wet grinding in several other posts and was looking around for one. Thanks a ton for the specific recommendation, as well as for the tool rests! That should make sharpening much more consistent.

How can I tell if the knives are hardened/heat treated, other than by asking Flailmaster, which is where I bought them? They have 803N stamped on them. My receipt just says MH 386 knives and they were .71 cents each. I did not specify heat treated.

I am going to try and keep brainstorming about my soup can idea lol!

Leon, in a previous post, I saw you mention the Franklin La area and Cote Blanche. I am in that area, are you familiar with it?

Thanks again everyone and have a great weekend.

 

[goatchay]

Leon, in that last pic before the schematic pics, you can see the washer I was referring to that seals up the back of the bearing. It's kind of hard to make out, it is mixed up with the grass. close to the shaft, not the bearing at that point.