SpudFiles

Seen as you obviously haven't given it any thought, why have a fast metering system?

A 'fast' output for an electrolysis cell is 2.5 liters per minute- most reasonable sized combustion cannons are much larger. So why use a 2 second metering system?

the hydrogen is going to be produced ahead of time, then stored pressurized like propane in the gun, as I said in one of my previous posts.

kjjohn wrote:the hydrogen is going to be produced ahead of time, then stored pressurized like propane in the gun, as I said in one of my previous posts.

Oh good- seen as it's derived from electrolysis will you be using oxygen as well?

Make sure you take care with what your chamber is made of, considering hydrogen's rapid flame front speed. Around 80% faster than acetylene, and acetylene is like twice as fast as propane..just off the top of my head.

The oxygen will be supplied from the electrolysis as well. Of course it will be stored in a separate tank until entering the chamber with the hydrogen. I am assuming the chamber will be made out of copper or perhaps steel.

Alright.

Consider hydrogen embrittlement. This basically means hydrogen sneaks into any pores in your metal and results in damage.

Also, hydrogen will make any leak five times worse.

never thought of that. Does it make PVC brittle? I don't think so but I'm not sure. I could have a normal SCH 40 PVC pipe encase inside a stronger metal pipe.

Hydrogen is able to dissolve into many metals. Storing hydrogen in Nickel is common. Many metals don't pass hydrogen. It's time to do the research.

There is a reason Nickel is one of the components in a Nickel Metal Hydride battery.

I do not know of the compatibility in Copper, Aluminum, Brass, or PVC.

Many leak detectors use Helium or Hydrogen for leak detection of high vacuum systems.

A typical hydrogen leak detector is like this one;
http://www.schoonoverinc.com/products/L ... sistor.htm

A good place to start study is here;
http://en.wikipedia.org/wiki/Hydrogen_safety

thanks for all your help
my hydrogen project has been currently postponed, I may experiment with hydrogen later. the main reason I wanted to use it was because I wanted something more powerful than propane for a new launcher that I will be creating this summer. However, I was just researching alternate fuels, and came across MAPP gas. I have heard of it before, but did not know it could be used in spudguns, and it is more powerful than propane. perhaps in the future I will experiment more with hydrogen. again, thanks for all your help.

MAPP is going to offer 5 - 10% more power than propane...not an earth shattering improvement. There will more than likely not be a human noticable improvement in performance without using measuring instrumentation....especially with basic potato ammo...don't bother with anything but propane. MAPP is also 3x more costly.

Also, there is no reason (other than sheer experimentation) to pursue fuels in a spud type cannon beyond propane or MAPP. There's plenty of energy to be harvested there, especially as you move to hybrid designs. Hydrogen has far too many logistical problems to be worth the effort at this scale.

Actually for this gun I am going to be shooting 50cal slugs instead of potatoes, but I suppose there is not much of a difference.

Also, I can find MAPP for fairly cheap prices ($7 for 16oz). Still more than propane, but it wont break the bank. But you are right about hydrogen, I have found on this forum and from research that hydrogen's disadvantages outweigh its advantages.