I decided to make some trailer hitch fire department emblems for my local fire department (I'm a member also). I was hoping to sell some and make some extra cash. I wanted a part that required no machining, so I made the part that goes into the hitch receiver from lost foam and the rest of the pattern from MDF.
Here are all of the pieces. The pattern has a pocket on the back of it that will hold the ring in place. The ring holds the foam part in position while I'm ramming up the mold.
This is what the mold looks like when it is all rammed up. The 2nd image is the mold after it has been opened up. The + on the pattern is to let me know which side of the pattern is the top so that I can assemble the foam correctly. The 3rd image is the other half. The MDF ring get removed and the foam stays in place.
Here I've installed the sprue cup and packed sand around it to prevent the cup from moving/leaking.
The first image is right after I made the pour. After a few minutes, the sprue cup gets been removed. After about 20 minutes, I broke the mold open. Looks like it should work!
Some images of the casting. Even the hole in the hitch part turned out :)
Here is the painted part. I first primed it, then painted the whole thing red. I then took a vibrating sander and removed the paint from the front face. Finally, a coat or two of clear was applied to the whole part.