You can search these forums for "honking" for a number of posts about the problem.
There is also a brief page on the wiki at spud_wiki/index.php?title=Honking and spud_wiki/index.php?title=Sprinkler_valve_modification

The teacher isn't a "professor", it is a high school teacher so expertise in this area is probably limited. :) Mark.f gave a reasonable answer. Don't need much of a "computer", you can do it an Excel spread sheet. Wont be super accurate but were talking a high school project, not a DARPA project. Ju...

Looks outstanding. But the coax design is killing the performance. I would expect a gun that size to be firing something like a spud at about 150-200 MPH. From the video I would guesstimate about 50 MPH or less. Any idea what the chamber and barrel volumes are?

But it does looks sweet.

The biggest I usually see is 150 ml. That's big enough for 1x in a 3.75 liter (229 in^3) chamber, which is a pretty big chamber. https://www.amazon.com/Syringes-Scientific-Measuring-Watering-Refilling/dp/B07C71C1LH/ref=sxin_7_ac_d_rm?ac_md=2-2-bGFyZ2Ugc3lyaW5nZQ%3D%3D-ac_d_rm&cv_ct_cx=syringe&dchild...

Moonbogg wrote: ↑

Sat Jun 06, 2020 2:07 pm

jackssmirkingrevenge wrote: ↑

Sat Jun 06, 2020 6:05 am

jimmy101 wrote: ↑

Thu Jun 04, 2020 10:31 pm

Caliper in the fruit isle? Just take a little length of barrel!

"Security? Yeah it's that weirdo putting limes through a pipe again..."

Yeah, that wouldn't look good.

Meh. Put a cut in the 1/2" long piece of pipe and wear it into the store as an ear ring.

The ideal gas law is not usable in the situation of a pneumatic spud gun. Three state variables (pressure, volume and temperature)n al change. You need to do more complex stuff, like take in to account the heat capacity of the air. There are very nice tools for both pneumatics and combustion guns de...

hectmarr wrote: ↑

Fri Feb 12, 2021 6:45 pm

Look at this, it can illustrate for you how to work with rupture disc.

LOL, looks like the fittings salesman's wet dream.

Will the fueling method of syringe work for up to 6x or maybe 8x? The biggest syringe that is easy to get is 70ml. If you fuel into a vented chamber you are probably limited to putting in no more than about 20% of the chamber volume. After that you'll be losing an unknown amount of fuel as it leaks...

What Jack said.

Plus, more than one spark increases the spark gap, that means the gaps need to be smaller if you are going to use the BBQ piezo.

BTW, multiple sparks must be wired in series, not in parallel.
http://www.advancedspuds.com/multiple.htm

Gaseous fuels are usually pretty picky on the ratio being correct. For propane the combustion limits is about 3% to about 8% propane to air by volume. Outside that range the fuel-air wont ignite regardless of your ignition source. A meter pipe is perhaps the most elegant approach but overly complica...

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...

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 ...

What is it that you would like to know?

Nice job!!!