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.
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.
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.
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.