How can I straighten a large cast pulley?

If you have a full size mill like a Bridgeport and a lathe make a short arbor to help indicate the pulley on the table. Then bore it and sleeve. Lock it in with some super duper loctite or epoxy.
I wouldn't try to straighten cast iron even with heat.
Mark
 
Before attempting to bore and bush the pulley do some more measuring on the compressor shaft and the bore of the pulley. It's likely the shaft isn't full diameter at the end, and the bore is oversize. I also have a Kellogg compressor that at one time had a similar wobble at the pulley. I researched boring and bushing, as well as using a taper lock. In the end all of those options were discarded because boring the pulley would have left the remaining sleeve without enough strength to remain true even when silver soldering in a bushing. I was afraid the cast part would crack when applying sufficient pressure to the cinch bolt to secure it to the shaft.

In the end I found the keyway on both the shaft and the pulley had worn to the point the pulley would not stay tight to the shaft. The resolution in my case was to true the keyway in both the pulley and on the shaft, then make a custom key, both longer and wider than the standard that came with it. I also used Loctite shaft retainer to hold the pulley tight to the shaft.

The pulley on my compressor has been tight and true for 5 years since the repair

If your shaft is worn to the point shaft retainer won't work Loctite also has a product called FixMaster for repairing wallowed out keyways and undersize shafts.
 
I did a similar thing as one of the suggestions above with a zamak pulley. Even with slow gentle bending, I ended up breaking it. I put it back into service by sandwiching it between two steel plates and torquing bolts in until it was straight and stable. It won't come apart, but you don't want to get caught in any protruding parts. Eventually, I guess I will replace it.
 
I think it is just a standard 5/8" v belt, just 4 of them. I've only been running 1.

Kvt the only date I can find is on the tank and it's 1936


It's not relevant to your pulley question, but if your tank was manufactured in 1936, you may want to give some thought
to it's safety due to rust:

 
I'd check the shaft very carefully and the bore alignment. This could be done by laying a plate across the rim and fitting a shaft to the bore, a good square and a flashlight are all that is needed, If misaligned an easy way to fix is hire a Magdrll and get two cutters, one at nominal bore and another say 1/8" or whatever deemed suitable,(and don't discount Metrickery for getting odd sizes), larger. Use the nominal bore size to center and clean up bore then switch to the larger size. Drill and fit a sleeve with epoxy and cut the slit a couple of days later when the epoxy has set. Ream and fit. I'd work from the outer face.
The grooves and the faces of the rim are machined at the same time so the face will be square to the grooves .
 
I like the suggestions about checking it out first. Check the shaft's diameter at various places and check it with an indicator to see if it's true. Mic it to check for the diameter and compare that with the pulley.

For the pulley, I would first just check against a flat surface, simply such as your granite table (not even precision table).

If the shaft is bad, then that would need to be trued up.

If the pulley is the problem, my suggestion would be to find yourself some fire bricks and heat this up to certain temperature and prepare to true it up some how (clamp, etc.).

But ..., what if the pulley is not bent, but its center axis is not the same as that of the outside? Maybe make a tight fit rod, insert it in and check it with a dial indicator as you rotate it? If it's bent, maybe heat it up, weld it then drill it out with a mill or bore it with a mill and put an adapter into it (better idea)

But the experts here probably have better hand on experience and advice
 
it seems yours seems even older than mine which means prob hard to find a good pully for it.
I agree that to much pressure could break it, would not try using the press on it.
To test it you could put it on a known good shaft supported by a bearing on each end and held some how. Then put an indicator on it You should be able to check both the hub area and the outer area. This will also allow you to get a true measure of how far out it is. and possibly what the problem is
Just my 2 cents
 
it seems yours seems even older than mine which means prob hard to find a good pully for it.
I agree that to much pressure could break it, would not try using the press on it.
To test it you could put it on a known good shaft supported by a bearing on each end and held some how. Then put an indicator on it You should be able to check both the hub area and the outer area. This will also allow you to get a true measure of how far out it is. and possibly what the problem is
Just my 2 cents

Finding a new pulley is out of the question, I found 1 that might work and it was $1300.00.

I got some time this morning to work on it again and I cleaned the crank shaft and remeasured it, it runs true and the diameter is 1.375 +0 - .002

I laid the pulley on a flat surface and the rim is as true as my flat surface, Cast table saw top.

There was a lot of crud in the pulley hole so I cleaned it out good and remounted it on the compressor and the wobble went from .490" down to .150".

It fits nice and tight when it's clamped down but has a little play when the clamp bolt is loose, I'm thinking I will see if I can shim it to get it a little better unless that's a bad idea. I may just live with the .150".
 

Attachments

  • VID_20190913_081820550.mp4
    1.5 MB
  • IMG_20190913_081808915.jpg
    IMG_20190913_081808915.jpg
    270.8 KB · Views: 23
  • IMG_20190913_081755539.jpg
    IMG_20190913_081755539.jpg
    242.7 KB · Views: 23
When I put the pulley back on the compressor it seemed to require to much torque on the clamp bolt to get it to quit having play so I took it off and set it up on the mill table and ran an indicator down the hole and the side was +- .010" so I put a snap gauge in it and the hole has .009" of taper, open on the side to the compressor.

My thought is it needs to be trued up, it takes more than 100 Ft Lbs to tighten the clamp bolt enough to stabilize the pulley, using my highly calibrated hand wrenches on a movable object, lol. I can't get a torque wrench on it but it's everything I can get by hand.

How thin of a sleeve can I get away with if I bore it true then epoxy the sleeve in then rebore the sleeve to size?

Also if I do this would I bore to final size with the clamp bolt out, clamped down or somewhere in the middle?

Thanks.
 
Seems like you're on the right path. Have you considered some thin lead sheet, or maybe the ubiquitous beer can shim. My inclination is still to leave the pulley as-is if you can, anything you do to fix it that's permanent might introduce other problems that are worse. Remember, as much as it might bother you to see it wobbling around if it makes compressed air it IS doing the job it's intended for.

John
 
Back
Top