Thanks Jack!

Most of the danger will come from the construction of the Spud Gun, not the use, PVC being what it is, will be the main cause of failures, usually explosive. PVC is not air pressure rated. Schedule 40 PVC is most certainly pressure rated. Your local hardware store likely has both pressure rated and...

A pretty basic spudgun can launch a baseball at speeds (~200 MPH) about twice as fast as a major league pitcher can throw the same ball. So yes, they are dangerous.

Like D_hall said, YOU CAN NOT PUT TOO MUCH FUEL IN A SPUDGUN AND MAKE IT EXPLODE. Too much fuel = NO FIRE. For propane, the combustibility limits in air are about 3% to 9%. (The correct amount is ~4%). If you put in more than 9% propane the fuel - air mixture is too rich and WILL NOT IGNITE. And for...

That is likely just residue from the spray and that kind of cap isn't meant for pressure so it is leaking a bit (not a big deal). I would suggest (1) switching to butane or propane and (2) metering your fuel. For a chamber that big, you probably need something around 100 ml of gaseous fuels. You can...

You can get the piezo BBQ igniters for pretty cheap. And they work just fine (and no battery to replace).

$2.25 at Walmart
https://www.walmart.com/ip/Piezo-Spark- ... /565163086

that will work if you have an ignition coil. If you have the entire flash unit then there is a trigger coil on the circuit board. You can remove the big-ass photo capacitor since it is only charged to 300 V, which is not enough to get a spark across a gap. There is a second, smaller cap that gets d...

Nice job!!!

It doesn't take much of a web presence to host online code. But if you don't already have a web server of some kind then it is definitely a barrier, plus cost $20/year forever.

Perhaps SpudFiles could be the long term host?

Go for it.

But how will you measure the diesel?

The MOST critical thing is the correct amount of fuel. If you are off by 10% the gun won't ignite, let alone fire. The correct amount of fuel is much more important than what the fuel is.

What is it that you would like to know?

It will most likely to decrease performance. Mostly because of how hard it would be to accurately measure. In general, hydrocarbon fuels have nearly identical energy contents per unit air. http://www.inpharmix.com/jps/Combustion_fuels.html The only outliers are Hydrogen (not a hydrocarbon) and acety...

A mesh screen would kick up turbulence but also suck up a lot of heat. We have discussed before if running the chamber fan during firing might increase the burn speed. Way back when I measured burn speed in a closed chamber at 1x with/without the fan running and with one or three sparks gaps. There ...

The point is to know how to solve problems (not just this problem) without resorting to magical numbers specific to only one problem, like 22/15. Dimensional analysis is based on the most fundamental mathematical fact: you can multiply anything by "1" without changing the underlying amount . If you ...

300 meters is a long way. Remember that a pneumatic is probably going to be operating at less than 150 PSI, which is the max pressure of a typical shop compressor. Compare that to a typical 0.22 rifle that has an effective range of about 150 yards. That low power rifle operates at twenty thousand PS...