Posted by Sherman in Idaho [72.47.153.61] on Tuesday, April 14, 2015 at 13:14:48 :
In Reply to: Re: anyone re-tin bearing insert? posted by Don in Missouri [12.206.185.66] on Sunday, April 12, 2015 at 23:26:31 :
It's one thing to re-pour a bearing in some old slow-speed machinery where the shaft is 2" in diameter, the bearing is 3-4" long, and the shaft turns at a few hundred RPM, and quite another to make a babbit bearing for an internal-combustion engine. I've done the former, but wouldn't attempt the latter. It was tough to get it clean enough, and the right temperature, to avoid bubbles and inclusions, which are harmless in a big, slow bearing. To do it properly, the babbit should be scraped for oil clearance after pouring, but in the old days, a lot of guys just let it "wear in". They would also start with a stack of shims under the bearing cap, and then remove them as the bearing wore down.
There's no need for molds, though. The usual procedure is to block the shaft in position, use "babbitrite" putty to block and gap at the ends of the shells, heat the shell good and hot with a torch, and pour the lower half around the shaft. Some would use thin shim stock around the shaft for oil clearance. Others would scrape it or figure it would wear in. Then you put paper or shim stock up to the shaft on top of the lower half, put the top shell in place, block the ends with babbitrite, and pour the upper bearing through the oil hole. When it's cool, you take it apart, drill out the oil hole, and use a cape chisel to cut oil grooves in both halves.
I understand the early engine builders translating that practice into car engines, but it really wasn't adequate. I think at best you need to have the shells lined by an experienced shop. It's not like something you would do out in the field to an old steam engine. I'm pretty sure the automotive engines used a harder babbit allow than the high-lead alloy used in old slow-speed machinery.