Compressor crank problem ?

[tigler]

Picked up a lovely little Ingersoll Rand compressor yesterday, type T30, but a 3HP single phase which are quite rare. Just 2 problems, one, it was the journey from hell ! Honestly the worst journey I've had in years, 4.5 hours to get to Coningsby from Worcester, but it didn't end there, the M42 and M6 on the way back were also like hell !
Problem number 2, I think the crank is bent ! I noticed runout on the flywheel during the test run when I arrived, about 3mm at the edge. The guy definitely wasn't aware of this and it was otherwise fine. I decided to take a punt on it with a reduction in price.
I tried to gauge the flywheel hub, bush style, whilst I was there but it isn't conclusive that it had runout, unlike the edge of the flywheel.
Flywheel is a clamped parallel fit, so that rules out a dodgy taper. No evidence of tampering. The flywheel is such a heavy casting I cannot believe it's bent.
So, assuming the crank is bent, do we think it's viable to true it up, as in, unbending it ? If so, what would be a suitable method, obviously with the crank removed ?
The only reason I'm going to this sort of effort is that I've wanted one of these for ages and they are difficult to come by in good nick.

 

[wyn]

I had the same problem with a T30 i was given.
The pulley had some run out...probably droped on it at some time.
When i stripped it down the crank was bent.
I trued up the crank in a lathe but it was a bit of a mare to hold it and had to weld it to some bar.
Once it was true i had to make up a bush to take up the gap.

I have a few pics of it here.

 

[tigler]

Yes, I've seen some of those pix previously. Mine is a smaller capacity T30 than yours but I guess it has the same crank configuration. Would I be correct in saying the crank is supported on just one mainshaft with an overhung crank pin ?

 

[wyn]

Would I be correct in saying the crank is supported on just one mainshaft with an overhung crank pin ?

Yes that's right, the main shaft with two bearings and the pulley, then the crank weight and on the other side of it the shaft the con rods run on.

 

[gordon stephenson]

Had a similar problem with an industrial petrol Flymo, think the blade had hit something hard at a fair old speed, the motor was still running fine, I managed to take off the blade and used a decent length tube to straighten it, I figure it was running OK after it was bent so thought a bit of opposite and equal force might just work, And it did, as mentioned if stripped it could take a bit of holding so left it built up supported by it's main Brgs

 

[tigler]

I was thinking it might be do'able by supporting the shaft in V blocks either side of the bend, then using a hydraulic press with a soft metal buffer ? As the shaft runs in ball races I reckon it shouldn't be hardened so not in danger of cracking

 

[roofman]

I was thinking it might be do'able by supporting the shaft in V blocks either side of the bend, then using a hydraulic press with a soft metal buffer ? As the shaft runs in ball races I reckon it shouldn't be hardened so not in danger of cracking

yep thats the road ide be walking down too...set up in a lathe with a dial gauge you will be able to get it better than new