MAKING A CONROD BEARING .

[tjc1989]

As a youngster I helped (watched) my father replace the babbit bearings in a then ancient sawmill. The pillow block bearings were a cast iron shell that split horizontally and held the babbit insert that was formed by pouring it into the shell with the shaft in place. The old babbit was dug out of the shell and then the shell was reassembled around the shaft and bolted to the bearing support just as if the machine was working. Then the old babbit and a bit of new babbit was melted in a cast iron pot over a charcoal fire and poured into a hole in the top half of the cast iron bearing shell until the shell was filled to the parting line (the center line of the shaft). When the bottom half cooled, a thin wood strip was inserted on top of the bottom babbit to keep the top half from sticking. Then the top half was poured. When it cooled to solid form, the shell was taken apart and the babbit bearing surfaces "scraped" with a spoon shaped knife just a little to provide an oil clearance. Then it was all put back together and tried. If the bearing got too hot, it was taken apart and scraped a bit more to increase the oil clearance.

It was a lot of work, but then the only tools were a wrench to take the bearing apart, the babbit, babbit pot, and the scraper. Not nearly as quick as running down to NAPA, but you could do it all yourself.

Great story. Love to hear how things had to be and could be fixed, rather than replaced. Imagine the stories your grandfathers could tell of the maintenance and repair of their World War II experiences in the field on remote islands in the Pacific on planes, tanks, jeeps, etc. They couldn't just run down to the local parts store for a replacement part.

 

[Chilly807]

We used to do this kind of thing at work, on older steam turbines generally. I've never cast the bearings myself, but I've scraped a few to fit. What we did was use a mandrel shaft to fit the bearings. The mandrel shaft was exactly the size of the turbine shaft plus the desired clearance. You put prussian bluing on the shaft, and fitted the caps in place. Anywhere the bearing showed blue it was scraped (high spots). Gradually the new bearing were scraped to the right profile and fit. It took quite a while to do one bearing, but when you were done it made a fine job.

Chilly

 

[Wis Bang]

One of the few tools I have from my grandfather is his babbit scraper. I keep it in the same tool box drawyer as my dad's tappet wrenches and 40's - 50's era valve spring compressors...

It looks like a thick oversize pairing knife that was forged around 1/2 of a mandrel to make a curved surface.

Dad's cousin was a privateer motorcycle hillclimber in the 50's - 60's and he used Prussian Blue to shape his oversize pistons removing metal from the smeared areas until the piston would 'just' go past TDC to get the most compression possible...Lot's of old tricks and ideas are becoming lost.

 

[fixit]

Default Re: MAKING A CONROD BEARING .
One of the few tools I have from my grandfather is his babbit scraper. I keep it in the same tool box drawyer as my dad's tappet wrenches and 40's - 50's era valve spring compressors...

It looks like a thick oversize pairing knife that was forged around 1/2 of a mandrel to make a curved surface.

Dad's cousin was a privateer motorcycle hillclimber in the 50's - 60's and he used Prussian Blue to shape his oversize pistons removing metal from the smeared areas until the piston would 'just' go past TDC to get the most compression possible...Lot's of old tricks and ideas are becoming lost.



That statment just about sums things up. These days most so called engineers are just fitters with no idea how repair things.They just replace with new and all the skill that was on tap not so long ago is becoming lost
there was a whole lot more achived in the past with less tools and a bit of inginuity

 

[Mighty Dodge]

I restored a JD H some years ago. It needed new main bearings.....none are made. Some guys use a brass bushing. The machine shop re-babbited the shells as well as the rods turned out great.


M.D.