I have a 2001 Volvo S60 that I run for Lemons, the endurance race for 500$ cars. We've run it a few times with varying success, so it's time to focus on suspension. I have the engine out for other reasons(...) so I wanted to upgrade the engine mounts and subframe bushings. I'm cheap and always wanting to try new things so I decided to upgrade the existing subframe bushings instead of buying new ones or inserts. I bought 80A hardness castable polyurethane from mcmaster, a 25 in^3 (~400cc) 2 part mix. I then printed up some molds that match the matching plate that the bushings sit on.

Printed bushing molds
Mold next to matching backplate
Mold profile almost exactly matches plate

These molds were actually sized well enough for the offsize bushing as well! I cut out as much of the rubber as I could with a jigsaw, with the exception of the bottom tabs, those I left a little so the outside shell would sit at the right height.

Shell with rubber tabs kept
Keep some of the rubber tabs

These shells went into the printed molds, and I sealed the edge with hot glue, it only needs to keep back a liquid. I added wax to help seal up the edge. The center pipes then went into the mold, and a little wax was poured into the pipe. This should seal up the pipe for the polyurethane. Additionally, I managed to lose one of the center pipes. I replaced it with some pipe laying around, 33.6mm OD, 26.6mm ID, 47mm length. This was slightly thinner than the stock, but should be fine. I think this is 1 inch pipe.

Top view of the bushing with wax inside the pipe.
Seal the center pipe with wax

Once the molds were sealed, I filled the molds up with water, to measure the volume (1ml=1cc=1g), in addition to look for leaks. I sealed a couple with a lighter, both plastic and wax melt nicely. The molds were heated with a hair dryer to remove the water. I mixed enough poly for 1.2 molds, about 120ml worth. I measured them needing 90ml. I found it helpful to mark the cup with the needed amount, as well as measuring onto a scale. Helpfully, the density of the both parts was about 1g/ml. Unfortunately for the first mold, I did not mix the hardener. It came out a little clearer, rather than black. I'm hoping the hardener was the majority substance, and it was just the black particles that settled out. I shook it for subsequent pours. In addition, I did not mix all the needed mix at once. I did it in three parts, and poured the additional into the next mold. I did the whole process within 10 minutes, so I don't think it should be an issue. I had to add some tape, as I was leaking from the top. I poured the excess into my prototype mold. We'll see how it turns out in the morning.

Molds poured and curing
Molds sitting on a box on the stove