When I was a kid my father would embed stuff in plastic . . . coins, photos, sea shells, whatever. I never thought much about it until recently. If you’ve read some of my previous posts you’ve seen that I have become interested in fixing up old stoves. The fixing up old stuff comes from my father getting my brother and I involved in old Hudsons (for those who don’t know, Hudson, Nash and Rambler merged in the late 1950s to form American Motors a.k.a. AMC, makers of Jeeps and Eagle cars, Gremlins, Pacers, etc. which was then bought by Chrysler in the 1980s), while the stove part comes from my interest in backpacking.
Well, I bought some old M1950 stove tanks . . . and windscreens . . . and valve parts . . . and pumps from a guy not too far from here. However, he didn’t have any valve knobs. I looked around in stores to find something, heck anything, which would work, but nothing fit. I asked around online at places where people would have such things, that is, collector’s forums, people selling on ebay, etc. but nobody had them. In fact, one guy mentioned that if I did get some to let him know as he’d like to have some. “Wonderful”, I thought, “nobody has any”. What to do? Well, why not make my own?
Remembering back to my youth, I recalled my father using that two-part plastic which also seems to be called epoxy. I did some research and found a company called Smooth-On who makes pretty much everything I needed to make it happen. So, I asked a few questions about their high-temp epoxy, mold making silicones, and release agents and what follows are the results.
First, I needed to make a mold box. This isn’t for making the actual part, but instead for making the mold which makes the part. You embed the model, in this case the original valve knob, in clay and also some acorn nuts to help align the two halves of the mold. Then put it in the box, mix up some silicone and pour it on top.
After it cures for 30-45 minutes, remove the box and then carefully remove the clay from the silicone. Then put the silicone, with the model still in place, back in the mold box, spray on some mold release, add a filler hole made from clay, mix some more silicone and pour it in. After an additional 30-45 minutes remove it from the box and separate the two halves of your mold.
The front side of the knob mold came out just fine. However, the first mold of the backside of the knob had an air pocket in the screw-hole so, I remade it. It came out great . . . except . . . . . . the mold was difficult to fill and remove all the air bubbles which resulted in a less-than-full new valve knob (you’ll see this in a later photo). Bummer. So, I made a third mold, which wasn’t perfect, but I added some air vents to help remove the air bubbles. This worked better. (Third time’s a charm, I guess)
After trimming the excess epoxy I placed the knob in a small toaster oven for 2 hours at 175F and then 3 more at 300F. This is partially what gives this particular epoxy it’s high-temp capability, which by-the-way should be roughly 100 degrees higher than the original Bakelite knob. We’ll see.
I still need to work out the correct coloring, but it has been interesting to learn about plastics and what it takes to make your own things. I’ve got some more ideas . . . This is pretty fun!
Updated March 15th, 2015: The final version of this M1950 knob is now available at OldColemanParts.com. You can go there directly with this link: M1950 Valve Knob
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