Does anyone have any advice on making a solid-cast resin HO car into a hollow body? I know, I know: just hog it out with a motor tool. There may be more to it than that. How thin can I make the walls? I want to use the result as a master for casting more of them so it may need to be stiffer than just a one-off. Have you done it?
The purpose is to make a body shell of car only available in solid-cast for a car assembly factory diorama. I'll remove the front fenders/hood and fabricate a firewall. There won't be any glass windows in it, just openings. I'll also have to fabricate a floor pan for it as a separate part.
I've hollowed out all sorts of N scale vehicles. I mount the brush attachment for my shop vac near by to minimize the mess. I like to use amber colored resin versions if I can, as they are the easiest to judge how thin you are making the part. I use about eight different bits during the process. Start with the largest bit you can for material removal. Remember also that the smaller diameter bits require a lot less pressure on them since the force will be spread over a small area. Keep a firm grip on the master - I will only work on a few at a time and then let my hand rest for a few hours. In HO, I would try to work on perhaps two at a time. Plus, the combination of a shop vac and a Dremel tool are quite loud. I try to imagine what the shape of the vehicle is as I grind on the inside, and hold it up to a light once in a while to judge how uniform the thickness is. If you aren't sure how thin you have made it by the amount of light that is coming through, drill a small hole through one of the window openings that you have ground close to, and compare the the thickness of the material that is left with the brightness of the light near the hole you made. For openings like wheel wells and windows, I try to never let the cutter go right through. Instead, I always try to leave about .005 inches or less remaining and carve out the openings by hand with an X-acto knife. If you let the cutter make the openings, it can catch on the edge and will ruin your work. Don't ask me how I know this. Regarding the thickness of the finished part, you can easily cast parts with a .010 inch thickness, but areas that won't be visible can be left thicker. I always try to make the roof, the window pillars, and the wheel well edges as thin as possible for a realistic appearance.
Thanks, rasputen. I, too, like the transparent resin bodied kits but I'll save them for cars that I won't be hollowing out. My first attempt was on a solid color resin 1937 Studebaker pickup truck made by Cutter. It came out pretty well so far. Your suggestions are spot on, especially not grinding through the window areas but instead using a hobby knife.
I ground through the body a little bit below the passenger side window so I cemented a piece of .010" styrene behind it and applied some Squadron putty. When it is set I'll clean up the patched area as well as the rest of the excess material on the casting.
Last Edit: Aug 22, 2014 4:03:11 GMT 1 by zed: Aug. 21, 2014: The link to a photo-hosting site was replaced with the actual photo.
This is a Greg's Garage 1948 Tucker that I'm in the process of hollowing out. It will be just the main body and floor (made from sheet styrene) to represent a body being shipped* to an assembly plant via railroad. I discovered too late that the body is warped (see yellow lines on the rear view). I don't think it will be noticeable so I'm not going to try to correct it. Ideally, this body would be used as a master, after attaching thin styrene to the door and window openings, to resin cast a couple dozen for railroad car loads.
*Unfortunately, I found out later that when bodies were like this were shipped by rail that the doors were hung on them by the manufacturer. It's too late to try to add them back onto this body.
Here is another Greg's Garage 1948 Tucker. I've only hollowed out the lower part of the inside of the body. I'll be leaving the windows solid. From another Tucker I've removed the front and rear bumpers so they could be attached separately to a new chassis. Unfortunately, I discovered too late that this body is warped -- the passenger-side rear drooped considerably. I cut off the corner and glued it back where it should be located. This model, too, is intended to be a master. That will make it possible to build models of all 51 of the real cars. Making the "chrome" parts separate from the body will make painting much easier. I'll probably use one of the spray-on finishes like Alclad2 or Spaz Stix.