|Custom Cast Parts
H&R Challenger with custom cast parts from first series.
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Recently, prompted by several posts on the CinC and GHQ web boards, I started to look into ways to add baggage and equipment to the exterior of my vehicles. While on-vehicle baggage such as backpacks, ammo crates, fuel drums etc, had been the hallmark of In Service Miniatures, that company appears to be long gone and its miniatures no longer available.
A quick search on custom casting led me to Alumilite (www.alumilite.com) and their family of molding and casting products. Their site is extremely well designed and contains all the instructions you need to get started. Their 3-minute, non-toxic two part casting resing and 8-hour high-strength molding silicone semed to be just what I was looking for, so I ordered their mini-casting kit from InternetTrains.com, which offers their products at a discount.
Meanwhile, I need some actual masters to work with. I ended up making them out of bakeable clay (Sculpey) which has two advantages -- it doesn't shrink at all during baking and it costs about $1.79 a slab. It is a little tough to work with, its very soft and can be a bit sticky, but overall, works quite well. After making a variety of vehicle accessories (cargo, bags, jerry cans, barrels, camo tarps, etc) I glued them to a sheet of stock plastic to make a mold of them:
Pouring the mold was extremely simple. I put a ring of plastic cup around the master and sealed the sides of it with clay. I mixed the two part silicone and painted the first layer over the master, then poured in a bunch more to make it stronger. Retrospectively, I used too much and could have made the mold much thinner. In 24 hours, I pulled off the clay and pulled out the mold:
After messing around with the resin a bit, I began to get the hang of it. It is two part, and once mixed, it begins to cure in about three minutes. Consequently, you have to move fast once you mix it. I now mix only very small batches (1/2 tbsp of each part). Helpful hint: If you put both parts of the resin in the refrigerator for about 40 minutes, the cure time is slowed to about 5 minutes. This can make a real difference when making many small pieces at once.
I encountered two problems during the casting process. The smaller problem was that the flash was too thick; there is bound to be some with a single-piece mold, but it was too thick to trim easily. The solution was to scrape the mold with a straight-edged piece of plastic after the resin had been poured. This will leave a thin layer of flash, enough to pull all the parts out in a sheet. Here is an example of a completed sheet of accessories removed from the mold and sitting on top of it about 10 minutes after pouring:
The second, and more serious problem, was the large number of air bubbles that were in the parts. Ultimately, I did four things that got rid of the problem in 90%+ of the casts:
1) Microwaved the mold for two-three minutes on high prior to casting.
2) Coated the mold with an extremely light dusting of regular baby powder, and then shook it off.
3) Put both the A and B parts of the alumilite resin in the refrigerator, which slowed the curing time and let me poke out many of the bubbles with a toothpick.
4) Trimmed away all the excess silicon on the top of the mold to eliminate as many of the potential air pockets as possible. This took a while, and a steady hand with the exacto knife, but really helped.
are shots of test pieces on H&R UK Challengers and Warriors.
I added accessories to six Challengers and five Warriors.
This Challenger has a camo net on top, and a four pack of jerry cans on the side of the turret.
This Challenger has a rolled camo net on the back of the turret bustle and a series of duffels on the side of the hull. While most militaries refrain from putting gear on the sides of the hulls in peace time, it seems to be a common practice in war zones. Ultimately, this turned out quite well:
This rolled tarp is a little indistinct -- I am going to need to alter or eliminate it for the next master set.
After painting, I am rather pleased with the first set. Several things became apparent, however:
I like the effect of the camo net, but it needs to be both wider and flatter.
The Jerry Cans came out well, and this camo netting looks a bit better.
This model came out the best of the lot. The varied bags and duffels on the side look good, while the small parts on top look more realistic.
The Jerry cans on the left-hand Warrior are insufficiently distinct and need work. The tarp on the right-hand Warrior looks good, but might look better on a large GHQ/CinC vehicle.
Here are some beat up Canadian M113s with baggage added. These are actually my test pieces. Machine guns are from the bulk CinC pack.
Mold 2: Baggage
Based on what I learned with the first generalized baggage mold, I moved ahead with the second. I decided to do only a single subject in a mold, but to make far more individual items. For my second mold, I focused on baggage only and skipped cargo loads and tracks. As of April 20, I have just completed the master, with 85 unique items.
I am also working to make sets of track links for attachment to hulls and turrets. So far I am having mixed success. I decided early on that I would not worry about the track guides -- at this scale, the are probably far to minute anyway.
My first shot at this was to make a master mold out of poly clay and use it to cast resin masters. I could then cut and trim the resin parts to the proper shapes. This turned out to be far more difficult than I had planned.
I really need to assure that the top of the mold (which will form the back of the tracks) is flatter. I had planned to carve the flat, but this proved far too difficult. Overall, this mold produced about six lengths of useable track.
One interesting thing I learned in the process was that Sculpey makes a decent resin mold. Even without the use of mold release, it was fairly easy to remove the cured tracks.
I am currently working on a second set of track molds, made with a bit more precision. I will update this page as I make progress.