Bearing replacement question

[XTREEC]

Do you guys always replace bearings in pairs? As in both ends of a common shaft. Drum shaft bearing failed and I’m trying to decide if I should do both sides.

 

[Reach]

Drum bearing? Yes, replace them both. If you don't, you'll have to replace the other one soon anyway. And as much work as it is to take the drum out, you'll save money in the long run.

 

[Reach]

What chipper is that, anyway? That does not look like a very heavy drum bearing to me.

 

[XTREEC]

What chipper is that, anyway? That does not look like a very heavy drum bearing to me.

Morbark Twister 12. Well used.

 

[XTREEC]

Drum bearing? Yes, replace them both. If you don't, you'll have to replace the other one soon anyway. And as much work as it is to take the drum out, you'll save money in the long run.

Thanks. I’m hoping removing the drum isn’t as bad as lifting the upper feed wheel for bushings.

 

[Evo]

@Reach do you need to remove the drum? Can’t you just support the weight and take slack out with a chain hoist to replace the bearings?

But 100% replace both sides while your in it.

 

[Reach]

@Reach do you need to remove the drum? Can’t you just support the weight and take slack out with a chain hoist to replace the bearings?

But 100% replace both sides while your in it.

It might be possible to change the bearings without removing the drum altogether, but it is certainly easier in my opinion to cut the old bearings off and clean the shafts to put the new bearings on if the drum is not in the chipper.

Looks like that chipper has to have the bearings removed altogether to get the drum out though, due to the way they are installed. I suspect that getting the bearings off of that shaft is going to be quite a fight. Bandit builds there so that you can unbolt the pillow blocks and lift the drum out with the bearings installed, I think it is a much better design than what I see in that picture.

 

[Bart_]

To what Reach said, I've seen many vids where mechanics try to force a bearing or component off an uncleaned, corroded, dented, keyway channel edge bashed etc shaft and had a big fight or failure. Where possible/needed a pristine deburring, de bumping, diameter high spot removal prep, cleaning polishing and light lube (WD40) makes removal more viable. If that route is contra-indicated, cut the bearing off first prep the shaft second would be the pragmatic method.

Don't forget to avoid applying installation load to the roller elements as it can ruin the roundness of the rollers or dent the raceway surfaces - premature failure. A pipe contacting only the inner race is good for installation. Also beware of installed preloads as you tighten it down, again premature failure. To that end bearings often have self alignment ie pillow block and big clearance bolt holes but flange mount can't take up alignment/preload axially along the shaft direction.

Looking at that pic of a flange bearing locked into chassis retainer ridges it would seem to me that there must be some give somewhere along that assembly to allow the bearing to clear those ridges. Maybe on the other end? Maybe the drum is not locked axially wise to the bearing and floats with end thrust "guiding"?