Building A Steam Engine From A Lawn Mower
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Boiler plate is a very soft high grade of steel. Good boiler plate up to 3/4-inch thick can be hammered over on its self without showing any signs of cracking or stress. An example of stress cracking is putting a rod or bearing vice and bending it back and forth until it breaks. The harder the steel the sooner it'll happen. That's why boilers should only be made of boiler plate. Also all A.S.M.E. boilers are stress relieved after being welded by placing them in an oven for several hours to relieve the stress of the welds.
A.S.M.E. boilers are hydrostatically tested at 150 percent of working pressure and no more. One inspector said that at the factory they'd have to scrap it if tested too high because of possible over-straining the boiler. I've heard several guys say they run their 100-pound boilers to 300 pounds to test them.
Stress cracks can be too small to see or hidden under grease or scale or some part of the engine.
Water used for a hydro should be between 70 degrees and 120 degrees. If too cold you might strain the boiler; if too hot you defeat the purpose.
I didn't write to talk about boilers, so I'll quit here. But boiler safety is a pet peave of mine. I saw a guy running an engine with 26 patches gobbed on and 13 were still leaking. When I saw that, I left. Apparently the guy didn't realize the responsibility he had to the public. Some people have no business running an engine and couldn't care less. Sooner or later one's going to pop and we're all going to pay.
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