Measuring and Straightening a Crankshaft

[Martin W]

A few week ago I picked up an old Ottawa hit and miss drag saw. Been tinkering with it. The crankshaft is all wallowed out where the overriding clutch is and the Woodruff key has been worn to unusable.

My plan was to preheat and weld up the wallowed out shaft and weld up the key way, and Center. Mount it in the lathe in the four jaw and support it with a steady rest . Re drill the Center and then turn between centres to the right dimension and cut a new key slot in the mill.

Before I started I put the crank between centers just to check. It is out 70 thousands on the bearing journals From the ends of the crank. The crank is about 24” long with about 8” of shaft at each end for the cast pulley and overriding clutch on the other end.

If I mount it in the 4 jaw I can get one journal with no run out, but the other one is .037”

What is the proper way to measure this? How do you check for out of round journals?What are my options for straightening this? Will I need to pour new Babbitt bearings? The Babbitt looks fine., so do the journals.

Its 102 years old and it looks as if it’s had a hard life. Someone has welded the one counter weight on the crank. The piston has a broken Wrist pin casting, which I haven’t even got to yet.

Any and all suggestions are appreciated. Thanks
Cheers Martin

 

[Lo-Fi]

Are you sure it's steel? Experience on (ironically younger) steam locomotives suggests that "steel" of that era wouldn't come near classing as such in accepted terms now.
Which is a long way of saying it may not take too well to welding. Your mileage may vary! Silicone bronze braze repair might be a good option.
To straighten it, I'd look up some of Keith Fenner's old videos. He had some great content on marine shafting; the methods will be the same. Got a hydraulic press available?

 

[Martin W]

Thanks
Yes it is steel. I have a hydraulic press. I was hoping to straighten it on the lathe? Maybe with a hydraulic jack? Trying to figure out how to properly measure it.
Martin

 

[matthewsx]

I wouldn't try that with my lathe, have you considered making a new one?

Also, we need pictures....

 

[f350ca]

Just to clarify, between centre's the journal beside the centre has .07 runout?
If thats the case it sounds like the journals are worn out of round. Should be able to check that by measuring the dia at different points across. Could easily be the case with the piston load always on one side of the journal.
If the journals are wore that bad when you chuck one end 24 inches out could easily show .037 runout.
If the centre's are in fact good could you turn the journals down and re-pour the bearings? You'd of course have to sleeve the flywheel and clutch then.

Greg

 

[C-Bag]

Sounds like a heck of a project Martin. Pics would really help as most of us are familiar with engines but

old Ottawa hit and miss drag saw

is outside my experience. Greg is on it with measuring the journals but you are also on the right track with getting how to find “zero” to measure everything from. Me, I’d have it on a set of v blocks on my surface plate to figure out what was up using my Starrett height gauge before I’d trust my lathe. YMMV.

 

[Martin W]

Just to clarify, between centre's the journal beside the centre has .07 runout?
If thats the case it sounds like the journals are worn out of round. Should be able to check that by measuring the dia at different points across. Could easily be the case with the piston load always on one side of the journal.
If the journals are wore that bad when you chuck one end 24 inches out could easily show .037 runout.
If the centre's are in fact good could you turn the journals down and re-pour the bearings? You'd of course have to sleeve the flywheel and clutch then.

Greg

Thanks Greg
There is .037" difference from one journal to the other if I mount it in the 4 jaw and get it zeroed in on one journal.
If I pour new babbit, I should be able to leave the ends the same size for the pulley, as the journals are already smaller?

 

[Martin W]

Sounds like a heck of a project Martin. Pics would really help as most of us are familiar with engines but

is outside my experience. Greg is on it with measuring the journals but you are also on the right track with getting how to find “zero” to measure everything from. Me, I’d have it on a set of v blocks on my surface plate to figure out what was up using my Starrett height gauge before I’d trust my lathe. YMMV.

Good thinking on the V blocks!

 

[Martin W]

I wouldn't try that with my lathe, have you considered making a new one?

Also, we need pictures....

Making a new one may be over my pay grade. Lol I will get some pictures tonight if I make it out to the shop

 

[f350ca]

Was thinking of turning all the end down, but your right, you could turn just the bearing area.

Greg