Snapping roll bearings

[chris.olson]

When replacing the inner snapping roll bearing in my 8-row rota-disc head I notice the bearings are rubber-shielded (sealed), yet there's a grease fitting for each snapping roll, and the cutting roll.  Why use sealed bearings?  What good does greasing a set of sealed bearings do in the snapping rolls?  The outer cutting roll bearing is shielded to the rear and open-cage to the front, allowing the grease to re-lubricate the bearing.  This makes sense, so why isn't it this way in the snapping rolls for longer bearing life?
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Chris

[jordan]

The snapping rollers do have 2 sealed bearing in them. The grease zerk on the end of the rollers are just to keep moisture and dirt out of the sealed bearing. We have been using this system since 1997 and have very good success with it.

[chris.olson]

The snapping rollers do have 2 sealed bearing in them. The grease zerk on the end of the rollers are just to keep moisture and dirt out of the sealed bearing. We have been using this system since 1997 and have very good success with it.

I'd say "success" is a relative term.  I have 5,200 acres on my Rota Disk 8-row head and several of the inner snapping roll bearings are failed already.  On my last corn head, a CaseIH 8-row that used greaseable needle bearings in the snapping rolls, I had 11,600 acres on it before I had to replace the first bearing.  Admittedly, I run the Geringhoff head much closer to the ground to cut a low stubble height as opposed to the standard knife-roll header.  So the snapping rolls on the Geringhoff are handling more material length, feeding it to the cutting roll.  But it seems to me that there's room for improvement in the design on the Geringhoff as those inner snapping roll bearings evidently carry quite a bit of load when the row units try to flex from lots of material flowing thru them.

The failure I'm seeing can't be detected unless the roll and roll nose support is removed from the machine.  With the roll laying on the workbench, if there's any radial movement at all visible in the shaft it requires disassembly and inspection.  I find several (but not all) of the balls missing from the inner bearing, with the rear seal blown out of the bearing and broken pieces of bearing cage and metal filings in the chamber behind the bearing.  The front (between the inner bearing and locking collar on the shaft) is full of grease, evidently packed in there by the factory.

I'm not an expert on Geringhoff heads, but I am a mechanical engineer by education, and my conclusion is that the bearings are failing due to being overloaded.  The bearing gets hot, pops the seal out, the grease leaves the bearing and it starts grinding up balls because they're dry.  Five rows with failed bearings on an 8-row head, with none of the rolls being disassembled since new, is not a coincidence.
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Chris

[jordan]

That is very interensting  , Mr Olsen. We just do not have problem with those bearings, I have gone back in the history of parts sales and the sales were low. You most have a somewhat of unigue situation. I would like our field service people or an engineer come out to inspect your head. Prehaps we can determine what is going with your head. Please e-mail your address if you like and some one would be out to help. jordan

[chris.olson]

That is very interensting  , Mr Olsen. We just do not have problem with those bearings, I have gone back in the history of parts sales and the sales were low. You most have a somewhat of unigue situation. I would like our field service people or an engineer come out to inspect your head. Prehaps we can determine what is going with your head. Please e-mail your address if you like and some one would be out to help. jordan

That would be great.  We have the head serviced and ready for the 2009 season, so it is reassembled.  But I dug the failed bearings that we replaced out of the scrap bin.  We've also had two failures of the ball bearings on the cutting roll drive shaft in the #1 row unit gearbox.  I believe I have your email address from your profile, so I'll try that.
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Chris

[The Kid]

I Found that over greasing the nose cones will shorten the bearing life. I only give them one or two pumps every 12-15hrs. The grease is not for the bearings,its just a seal for dirt,dust and moiture

[chris.olson]

Harvest has been somewhat delayed this year due to slow development of the crop, delayed maturity and high harvest moisture.  So we've only covered 770 acres so far this season.  At this point we haven't had any more failures.  Before the season started we disassembled all eight rows, replaced bearings that had either failed or failure was imminent, and made sure everything was aligned properly upon reassembly.

A Geringhoff field engineer came to our farm and looked at the head prior to the start of the season and arriving a conclusion for the bearing failures is hard to do.  It could've been an alignment problem or it could've been bad bearings.

I wanted to send the failed bearings with the engineer when he was at our farm but couldn't find them.  One of my shop guys had put them in a John Deere bag and put them back in the parts shelves.  I found them after the engineer left and I'm going to send them to him in Germany when I can finally get caught up on some sleep after harvest.  After a close examination with a magnifying glass it looks to me like the cage failed in the bearings (it split in half at what appears to be spot welds), which allowed the balls to contact one another and pushed the seals out.  Once the seals are pushed out you lose the grease in the bearing and wear of the balls and inner and outer races is accellerated.  We never lost all the balls in any failed bearings - we found them with one or two balls missing with the rest of the balls free-floating in between the races, and the cage split in half.  I've seen ball bearings fail in this fashion from excessively high axial loads, but after thinking about it, the snapping rolls apply primarily radial loads to those bearings.

I'm sure Wolfgang (the engineer that came out) will be interested to see them when I send them to him.  The way harvest is going this year he'll probably get them for a Christmas present   :-)

[The Kid]

What roll bearing is going out more the big or small roll??I had to replace all the bearings on the big rolls because of the knife(weed) bracket was putting more load on that bearings. The bearings where not out just has a little movement to them. To fix it i put the same gard as other side on big roll.

[jordan]

The Kid,
I am interested. What guard did you use on the large roller?
jordan

[The Kid]

Its the same as the left snapping roll,but opposite.I think its an option in the parts manual.I'm sure its in the 00-03 manual.

[chris.olson]

What roll bearing is going out more the big or small roll??I had to replace all the bearings on the big rolls because of the knife(weed) bracket was putting more load on that bearings. The bearings where not out just has a little movement to them. To fix it i put the same gard as other side on big roll.

The small rolls are the only ones we've had bearings fail in.  We're also had a failure in a knife roll, and the knife roll output shaft in the gearbox, but that was definitely due to a misalignment problem.

I'm unclear as to what guard you're talking about.  But the stubble knives shouldn't put any extra load on the large roll as long as you keep them adjusted properly.  I check adjustment of the stubble knives every 200 acres or so and keep them about like a scissors so a piece of paper (about .002-.005") will just fit between the rotary knives on the large roll, and the stationary knfe.  We push our 2388 to capacity all the time and I've found that not only does it take more power to run the head with the stubble knives out of adjustment, they experience rapid wear if the gap gets too wide so it pinches the stalk off instead of cutting it.
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Chris

[VernonSanborn]

he snapping rollers do have 2 sealed bearing in them. The grease zerk on the end of the rollers are just to keep moisture and dirt out of the sealed bearing. We have been using this system since 1997 and have very good success with it.