SpudFiles

What if you used a glow plug to heat the water. Would it get hot enough? The only problem I could see is sealing the plug in a pipe ( steel of course).

well you could epoxy it into an end cap?

the easiest way is probably to heat the chamber with a blowtorch?

i don't think a glowplug would work well, even with small chambers.

dependent what glow plug you used

epoxy
i dont think so because in high temp (100c) will get soften like a gum
i cast the air pump chech valve ,just the heat the pump make he get soft, how the steam will ??!!
fiberglass
or get some joints

far_cry wrote:dependent what glow plug you used

epoxy
i dont think so because in high temp (100c) will get soften like a gum

http://www.jbweld.net/products/jbweld.php

Properties (psi)
Tensile Strength: 3960
Adhesion: 1800
Flex Strength: 7320
Tensile Lap Shear: 1040
Shrinkage: 0.0%
Resistant to: 500° F

glow plugs wont work very well, there not designed for heating up things, so they are low power and have low thermal mass.

I was just curious because I hooked one up to a battery and it heated up in just a few seconds and if I touched a piece of paper to it it instantly caught on fire.

You'd have to be thinking of a very small cannon and very well insulated cannon chamber to consider a glowplug to boil water. They use about 3 watts of power. Compare that to a standard kettle heating element which is around 2000 - 3000 watts.

Good point on the wattage used.

rp181 wrote:glow plugs wont work very well, there not designed for heating up things, so they are low power and have low thermal mass.

The thermal mass is irrelevant to a heater. Indeed, you usually want a low thermal mass (usually called heat capacity) if possible.

The killer here is the low power of the glow plug. Like Hotwired said, the glow plug from a small RC engine is only a couple watts. Even the glow plug from a large diesel engine is only about 1 KW at startup. The heat generated by the glow plug will decrease as the glow plug heats up, dropping to something like 500 watts after several seconds.

Jon_89, you are confusing temperature with heat. A glow plug will indeed get very hot, anything that gets hot enough to glow is damn hot. But what you really need is not "damn hot", you need lots of heat. The glow plug from a full sized diesel engine should work for a small gun charged with a small amount of water. For a larger gun you would probably need a couple glow plugs, or the heating element from a cook top or oven. You also need to make sure you don't short out the heater with the water.

Any steam charged gun would absolutely, positively need some type of safety pressure relief valve. You can get extremely high pressures with steam.

I'd like to see this project completed.... there had been so many threads discusing steam cannons and I haven't seen even one finished gun....

If I were you I would do as jimmy101 said and use a diesel engine glowplug... for a first gun of this kind I'd build it the most simple way and use a burst disk for safety reasons and convinience...

of course making the gun as small as possible would be a good idea....


what material are you going to use ?

Trust me when I say, steam guns are a b*tch. Trying to build even the simplest of valves that'll seal against several thousand psi steam is not an easy task, and that's not even getting into how the hell you're going to prevent the heating element from getting fried.

I've been meaning to build one for a while, just to see if I can do it, but the heating has always been the problem for me - I don't want to have to build a heating coil, and I REALLY don't look forward to the task of trying to figure out how to insulate it from the water it's heating, especially at higher temperatures and pressures. Perhaps use it to heat a fluid that doesn't conduct electricity in a tube down the middle, and use that to heat the water.

If you really want a simple single-shot steam gun, a big-ass fire is quite possibly the way to go. MIT managed to hit about 3000psi in 3 minutes with such a design.

Well this was just an idea but since it seems possible I think I will go for it since I cant figure out what to do with my time. I am thinking a really small steel nipple, union, and small bore barrel. What kind of pressures can you get with steam?

In answer to the question that you posted at the exact same time I did: If I remember correctly you can get over 1300 atm (or is it 1700 atm?) before all the liquid water in a container that was originally full has converted to gas. You can get as much pressure as you like with steam, but after it's all gas, you may as well be heating air.

Something tells me that you don't plan on going anywhere near 1 kbar, so you shouldn't need to worry about running out of water.

Yeah I dont plan on going very high but higher than my pnuematic cannons (120 psi). What would be a good size chamber for a steam cannon? I am thinking maybe like .5 inch by 6 inch.

Steel rod in the middle of chamber, and induction heater externally? The problem with that is finding a chamber material that wont get effected by the heater.