Kubota B2782 snowblower destroys its chain after every use! Help!

[87mark7lsc]

Hey everyone, my work tractor is having an issue with its snowblower attachment it's a Kubota B2782 63" snowblower. We put new #50 chain on and within an hour of use every time, the chain loses all of its oil, rusts severely and the pins and bushings wear out and cause the chain to stretch. We tried stainless chain this week and it didn't rust but it still wore the pins and bushings out and stretched the chain. We've never seen anything like it and we also have the identical New Holland snowblower made by the same company and have no issues with it. What is causing the chain to do this? I oil it with chain oil and have also tried a spray

 

[Winmac]

That is very unusual, I assume auger bearing are in good condition with Sprockets in correct alignment ?

If you could post some pictures a fresh set of eyes could spot a issue.

 

[87mark7lsc]

All bearings are tight on it and we aligned the sprockets with a straight edge. I usually run the snowblower 4-5 hours a use and will be using it tomorrow. When we have a chance to disassemble it I will take some pictures. Is there something specific you'd like to see?

 

[Kanook]

I have the same blower and it makes a bloody racket in the chain reduction drive but I don't see the issue you describe (yet). How many hours total on the blower? The manual calls for only 1/16in deflection and calls for chainsaw bar oil for lub every 4 hrs...presumably bar oil resists throw=off.

 

[CalG]

Hey everyone, my work tractor is having an issue with its snowblower attachment it's a Kubota B2782 63" snowblower. We put new #50 chain on and within an hour of use every time, the chain loses all of its oil, rusts severely and the pins and bushings wear out and cause the chain to stretch. We tried stainless chain this week and it didn't rust but it still wore the pins and bushings out and stretched the chain. We've never seen anything like it and we also have the identical New Holland snowblower made by the same company and have no issues with it. What is causing the chain to do this? I oil it with chain oil and have also tried a spray

To tight!

Run some slack!

What you are seeing as rust, is fretting corrosion. Destroyed pins? TOO TIGHT!

 

[87mark7lsc]

The attachment has about 700 hours use on it and was bought in 2008. We completely disassembled it after using it Friday and ordered a bunch of new parts for it. We've noticed that the big impeller sprocket keeps loosening its set screws and walking on the shaft. It seems like even with a new chain on when you turn the assembly there is a point with less chain slack and it is binding. We noticed that the housing that the small sprocket is held into has a slight twist to it and I know we've welded it in the past because it cracked. The shaft showed slight wear where the sprocket was sitting. That small sprocket and shaft have to be just a little off when turning and jerking the rest of the assembly

 

[Sodo]

Hey 87mark7slc, there could be a misalignment and you are wise to check for that. But if you're running new chains on old sprockets make a note of this.

#50 chain is 5/8" pitch (measured pin to pin). 5/8" = .625" As a chain and sprocket set wears out, the metal does not stretch, the chain stretches by the fact that the pins and holes ovalize. Consequently a #50 chain of 5/8" pitch (.625") becomes something like .650" pitch with the extra pin slop. What this does is wear the sprocket out to be a .650" pitch sprocket. The chain climbs higher on the teeth, and creates its own cradle for the chain roller, at a slightly larger diameter.

I made this image from a pic showing what happens when an old stretched chain is run on a new sprocket. This is the opposite of the discussion (new chain on worn sprocket) but it's the best I could come up with but it illustrates the problem of running mis-matched parts (old and new) together. Hope this makes sense. Wish I knew photoshop better. Also .650" is a gross exaggeration, probably more like .630".

Then when you put a new .625" chain on the old .650" sprocket, the chain tension cannot spread across several teeth on the sprocket, consequently ALL of the chain load goes into the ONE link, on the first tooth if driving sprocket (or last tooth of the driven sprocket). Because it's not spreading across several links, and ALL load going into one link at a time, the chain wear is very very high.

If you run new chains on "OK" sprockets, the chain will wear out (stretch) quickly to match the "OK" worn sprockets. If the sprocket is a little worn, it will settle out "OK". If the sprockets are a lot worn, you will ruin your new chain. There is a balance where replacing one or two components works OK, but if either is worn beyond a certain point you have to replace all sprockets and chain too.

Sorry I can't tell you where that sweet spot is, it depends a lot on the cost of the chains and sprockets. OI can try to find an image to help if anybody's interested. Many folks find that simply replacing all (chain & sprocket as a matched set) is better for them. Certainly it's better for "the shop" and can be better for the customer too.

 

[87mark7lsc]

New sprockets are going to be put on this time. We bought a new shaft, bearings, retainers and will put a new chain on. We'll see what it does..

 

[Kanook]

Sodo.....excellent write up and explanation...I learned something today...Thanks

 

[Sodo]

Glad to help also glad it was appreciated.