Speaking of excavator counterweights, .....,
When the Cat 315 first came out, it was a little in the ass. Especially with a larger bucket. Halton would cut a hole at the top of the counterweight, dig out a hole in the mortar mix and pour in lead. Weld the top back on and fix the paint.
I would use a needle scaler to dig a hole. There was a lot of metal fillings and other small pieces of steel mixed in with it. The trick was to leave a couple inches of mortar along the rear to insulate the paint and CAT decal from the molten lead.
Molten lead. Just imagine the OSHA nightmare of having an employee do that, nowadays.