Just before my birthday this year, a long-time friend stopped by with a gift. It was a 1930’s Wards Gasoline Hot Plate, Model D-67. This is a type of stove not typically used for camping and is sometimes referred to as a Cabin Stove. It’s not portable like a typical suitcase stove, but it’s not large like a range stove either. Immediately, I thought I might take it on a hunting trip, but upon further inspection I realized that it was going to need some work.
The stove came out of a ranch home in Alamosa, Colorado and had decades of grease on it and had a fair amount of rust. I tried to open the valve but it was stuck and the check valve was also stuck so I couldn’t pump it up either. I added some CLP to the valve and the check valve and let it sit overnight. To my surprise, both freed up the next day. So, I rinsed the tank with some denatured alcohol, fueled it and gave it a go.
The stove lit up easily but the flame went out after 5 seconds or so. I tried again and again, and each time it would light but then die out in a few seconds. I searched the web and couldn’t find any info about it. A member of the Coleman Collector’s Forum commented that it was made for Wards by the Prentiss Wabers (Preway) company in Wisconsin and in his catalog was known as the Model #367. But, still I could find no information concerning the inner workings, so I had little choice but begin disassembly. Given that air came out easily from the generator, I guessed that it must have a fuel flow problem.
I removed the generator and the valve assembly from the large side-mounted fuel tank and sure enough I found that there is a pick-up tube screen, very similar to the one on my Aida lantern torch pickup tube, which was clogged and also, the pickup tube was mostly blocked. So, I set to cleaning it, eventually removing the old screen and replacing it with a piece of another.
The valve is an interesting design, if you like mechanical stuff, showing how Prentiss Wabers solved the instant lighting challenge in their own way. It’s similar to the American Gas Machine (AGM) in that the fuel tube is completely separate from the air tube, and unlike Coleman who integrated the two into a dual inner/outer tube design.
The short fitting on the bottom of the valve body sits above the fuel and is for adding air when the stove is cold. The long tube sits in the fuel.
After pumping air into the tank, the valve is opened a ¼ turn, the generator is opened and the stove it lit. After a 20 seconds or so, the valve is opened fully, which cuts off the air supply and allows raw fuel into the generator where it is vaporized. But, how does this work?
The valve stem has two machined surfaces on the end of the valve stem. The pointed end goes into a machined surface inside the valve body which is basically the Off/On function. The ¼ turn allows air and fuel to pass to the generator.
When the valve is fully open the reverse face of the valve stem backs up against the threaded insert fitting which as an air hole drilled in it. This is how the valve blocks the air flow so the tank can provide full fuel flow to the generator.
This is a pretty neat design. AGM, as shown in my 3927 lantern blog post , uses an opposing air shut off valve/spring, whereas Coleman used a stainless steel rod in the Fuel/Air (F/A) tube. Interesting, right?
As mentioned earlier, the tank has a pressure gauge which I’ve been pumping up to 20 or 30 . . . psi? I don’t know what the typical pressure should be, but it takes a lot of cycling of the pump to get it to 30, but then, I don’t have very much fuel in there either.
I reassembled everything and ensured all of the fittings were tight and gave it some pressure to check for leaks. Then, I opened it up and it lit and burned nicely. I added some more pressure and opened the valve of the second burn and it lit as well.
It still pulses a bit, but I’m not sure right now if that is due to low pressure or if I need to clean the generator. For now, I’ll test it out a little more and see how it goes.
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