How can I straighten a large cast pulley?

I'm guessing it was knocked over or dropped while being moved, and was bent. Close inspection by mounting on a straight shaft (or just back on the pump if your sure the crank is true) with a pointer on the outside diameter would show where it's out. If it bent one way, I bet it would bend back with the proper setup. The approach Mr Whoopee pointed out would also be an option. Mike
 
The pulley was likely straight from the factory. FOMOGO's inspection idea is excellent! The blue paint is suspicious
for one thing as the compressor surely started life with multiple belts. If one of the fan blades were
cracked and repaired and painted it would likely have the aberration you are experiencing. Another thing, the first
photo looks like the pulley possibly has a sleeve in it. Could some previous owner have attempted to repair it ?

Putting hydraulic pressure on the pulley could break it so would proceed with caution. One final thought...If there
is any play when you just slide on the shaft, could you possibly install a thin shim in the right place to lessen the wobble
at least some? I would experiment with that first as it would be harmless to try.
 
If you put pressure on that pully to correct the wobble it will BREAK! I would mount it on a known true shaft to verify the crank is not bent, I have seen mang bent crankshafts. If it wobbles & the crankshaft is true then it's a machining problem & was that way from the get-go. How many belts do you run on it? There is paint in the belt grooves. Have you used a POLY BELT? Checked belt alignment?

Just saw you only run one belt, I would almost bet if you used 4 MATCHED belts or POLY-BELT problem would be solved. Just my 2 cents.

Breakage is a concern, but if it bent one way will it bend back? probably not worth the risk.
I tried 2 belts, the motor has a 2 groove pulley but they were not a matched pair and the length difference was to much so I ran the shorter one until it gave up then ran the longer one and now it's given up. I bought a double belt to fix it but I must have measured wrong and it was to long so I tossed it aside and ran it the way it was. I'm in the process of changing the motor pulley to a larger size, should increase the compressor speed about 20%, it's only turning about 325 RPM now, the new pulley will get it up to about 400 RPM. I modified the mounting hardware so with the bigger pulley and more adjustment room the double belt should fit.

With 5HP compressors running single belts I figured that this would be ok with a single belt, it's a 5 HP motor, I don't know what the compressor head is rated for.
 
That job needs to be done in a mill. Bore and braze a bushing in, then finish bore.

I thought about that but without a boring head... but this morning I remembered buying one for a project a while back and then not doing the project, guess I forgot I had a new one on the shelf, :bang head:

Now I would need advise on indicating in a 22.5 inch circle on the mill table, I don't think I have enough travel to use an edge finder, I'll need to make something to mount an indicator in the spindle that can reach out a foot.
 
They built it that way for a reason, try more belts.

It's unlikely the spec requires it to run very true, as long as it's driving the pump it's doing the job it was designed for.

John

True, but it does cause some vibration/shake I'd like to get rid of if possible.
 
When you say "wobble" do you mean axial or radial? Simple English is is moving side to side in line with the motor or is it moving in the direction of the belt travel?

The first could be a casting flaw that can't be corrected or it could be a misaligned bore which could be fixed. The second would be an off center bore which could be fixed.

My guess for why you are running it with one belt is that the pulley on the motor you have only has one track. It would actually be easier to make a replacement for that with 4 tracks and run it with 4 belts.

It's axial wobble, I guess it could have came like that but I assumed it got hit at some point in it's life and bent.

Pulley on the motor has 2 tracks, see previous answer fir full story of laziness...
 
Does the wheel appear to be damaged? How old is this machine? Perhaps it has been like that since day #1. Granted it would be nice if your drive belt didn't jump off from time to time - but I'd have a go at playing with the alignment, play with the tension, try a couple different types of belts. I agree it would be nice if the flywheel ran mostly true - but don't wreck it trying to fix what isn't really broken.

I have a 5HP compressor with a flywheel about that big - it has two grooves but it only had one belt on it when I bought it 18 years ago - it was far from new then (I'm still running the same belt it came with).

I can't see any damage but it may become apparent when I clean the pulley, the only date I can find on the machine is on the tank cert plate and that is 1936. The compressor ID plate is attached to the mounting plate on the tank and the welds look factory so I think it's original.

That was my thought process that a 5HP compressor is good with 1 modern belt, maybe in 1936 the belts couldn't handle it.
 
I'm guessing it was knocked over or dropped while being moved, and was bent. Close inspection by mounting on a straight shaft (or just back on the pump if your sure the crank is true) with a pointer on the outside diameter would show where it's out. If it bent one way, I bet it would bend back with the proper setup. The approach Mr Whoopee pointed out would also be an option. Mike

That's what I thought, it got bent. but now I'm concerned about breaking if I try to bend it back, Cast does like to break.

I need to put an indicator on it and see how it's bent, the crank measures good. I had a thought, clamp the wheel to the side of the press and then put a shaft in it and push on the shaft with the ram to tweek it back.
 
The pulley was likely straight from the factory. FOMOGO's inspection idea is excellent! The blue paint is suspicious
for one thing as the compressor surely started life with multiple belts. If one of the fan blades were
cracked and repaired and painted it would likely have the aberration you are experiencing. Another thing, the first
photo looks like the pulley possibly has a sleeve in it. Could some previous owner have attempted to repair it ?

Putting hydraulic pressure on the pulley could break it so would proceed with caution. One final thought...If there
is any play when you just slide on the shaft, could you possibly install a thin shim in the right place to lessen the wobble
at least some? I would experiment with that first as it would be harmless to try.

The whole thing was painted blue when I got it, pretty good paint as it held up in the groove with a belt running in it.
I don't think that is a sleeve but I'll know more when I get it cleaned up.

It's tight on the shaft, I had to use a puller to get it off even with the clamp bolt out.
 
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