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by jimmy101
Fri Apr 03, 2020 1:10 pm
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Re: Pnuematic Cannon Making Very Loud Noise....!

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
by jimmy101
Thu Jun 04, 2020 10:29 pm
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Re: Calculations related to pneumatic cannon.

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...
by jimmy101
Thu Jun 04, 2020 11:04 pm
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Re: Potato Howitzer

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.
by jimmy101
Mon Jun 15, 2020 4:58 pm
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Re: I was hoping for some feedback on my oxy-propane combustion cannon.

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...
by jimmy101
Mon Jun 15, 2020 4:53 pm
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Re: I bring you some cannon performance data

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.
by jimmy101
Wed Jul 15, 2020 6:40 pm
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Re: Calculations related to pneumatic cannon.

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...
by jimmy101
Fri Feb 19, 2021 4:35 pm
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Re: Need help

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.
by jimmy101
Wed Feb 10, 2021 11:23 pm
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Re: Need help

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...
by jimmy101
Thu Feb 25, 2021 12:28 am
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Re: Adding Multiple Sparks In Combustion Chamber

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