I have started on a 1/4 scale 1941 Willys to display the smallblock. Probably the blower motor if I ever get it finished. I think the mix of scales will show the engine without overwhelming the car too much. In any event I borrowed a 9" rear end to copy and was going to machine a steel buck to form the shell over. I didn't have any 3/4 inch material handy and wasn't looking forward to the machine time to cut and shape it for a one time use when I spotted some pink scrap foam. It was all that was left of the carousel tool holder project but two pieces were big enough for the buck. Less than an hour later from a cold start there it was. Since I had some finish work to do on it there was no need for a coating although not having it caused a runnout at the top with the head pressure of the Kush head. I kept pouring to insure the fill and caught all that metal in the steel pail. I have formed the two halves, but haven't welded them together yet. The buck was mounted between centers and I turned the axle tube ends round and blended them into the carrier. The bulge on the left is the runnout and didn't have any effect on the end result. I machined steps to hold in a vise and blanked the sheet steel with modeling clay. A slot for a clamp to hold it and a little heat and I'm done with the buck. Kelly, is that bolt pattern for the third member an SAE standard? It looks like an oval, but I can't find any description of it.
How about a jag IRS for that thing instead? Pieces of one can be seen on my garage floor. I have GOT to get that headache back together!
I made a conventional pattern for a punch to form the rear cover and then it occurred to me that I could use the casting to make the die in foam. I even used the latent heat in the casting and after about four attempts got a foam pattern. I sprued it up and buried it in my sand bucket. I buried it just a litlle deeper than the last piece and didn't have a runout this time. It only took some minor Dremel work to smooth it enough to stamp a sample. Even though the foam pulled away slightly from the heat of the punch the fit was too close and the first piece sheared under the press. I reduced the punch diameter slightly and this is the result. I did some initial hammer work and shrinking of the perimeter, but the rest was done under the press.
This isn't lost foam, but it does go with the differential in application. I made up a simple pattern to cast 1/4 scale American Dragmasters to fit go kart tires for the rear of the Willys. Some lathe work and a session on the CNC to cut the slots. The tires are 8" in diameter and so will scale as a 32" slick. I was running out of weelium and just threw in some old sprues and cutoffs from some lost foam and paid for it with poor quality casting. So these will just be rollers for the build.
I think ESC has been busy with the sheet metal work for the coupe. It's hard to maintain multiple build threads. It's not casting but if you're interested in the project have a look here. http://allmetalshaping.com/showthread.php?t=18551 Best, Kelly