Why you need proper babbit techniques.

Pouring babbitt is often intimidating to people when they first encounter it, I know I thought of it as such when I first had to do it. But with the instructions or help from someone who has done it before, it really is not such a daunting task. Things can go bad however, if it is done by someone who does not know what they are doing. These connecting rod bearings out of a very rare Twin City tractor were done by someone who was supposedly a professional. I was not impressed This first picture displays that the babbitt is not bonded to the bronze shell, look at the upper left hand corner.

Here it is pooled up on top of the bronze shell where the shims would sit.

Here you can see a void which by itself isn't that big of a deal, but again you can see it is not adhered to the bronze shell. This picture also gives a good view of the machinists poor job on the thrust surface. Instead of machining the proper radius, he just machined a void. Basically this left only the corner of the bronze shell touching the crankshaft for a thrust surface.

Here I peeled the babbitt away from the bronze shell, starting at the point in the first picture. If it were properly bonded to the bronze shell this would not happen. The bronze shell needs to be properly tinned and the tinning needs to get hot enough to melt and adhere to the babbitt when it is poured into the mold

Here is the bronze after pulling the babbitt off. You can see it was tinned, at least partially. The large brown spot felt like oil, and I'm not exactly sure what was going on there.

In the end, I'm probably fortunate that first person to do the job did it poorly, because the end result left me much more confident in my own work. Pictures of the work I did to fix these to follow.

12-25 Case

K extension rims

16-30 Twin City Main Bearings