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winterizing spud guns

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: Technician1002 » Fri May 25, 2012 10:53 am

Lower performance maybe with lightweight projectiles. However with dense projectiles, it may improve performance by having more thermal mass thus staying hotter longer through the shot and with denser gas, have less loss to blow by past the projectile.

Light Gas works well with light projectiles, but tends to be a failure with dense projectiles and projectiles with less than 100% barrel seal due to small leaks allowing high pressure losses.
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Unread postAuthor: jimmy101 » Fri May 25, 2012 1:16 pm

Labtecpower wrote:Cold air may be denser, but this will also lower the SOS, causing your guns to have a lower performance.
1) Assuming your 1x combustion is operating anywhere near the SOS, which is isn't.
2) The SOS inside the chamber is dependent on the temp of the gases. ~1100 FPS at normal temp, ~3000 FPS at normal operating temp. for the combustion gases.
3) Combine (1) and (2) and the SOS is completely irrelevant to a typical 1X combustion spud gun.

Even the SOS in the air in front of the ammo will rise as the ammo moves down the barrel since the air will be compressed and heated.

Air density also has relatively little affect on the performance. Normal atmospheric pressure only ranges from about 980 millibars to 1050 mb. That's a deviation from the mean of only 3.5%. Shot-to-shot variability in a typical spud gun is a lot more than that.
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Unread postAuthor: ramses » Fri May 25, 2012 2:43 pm

zeigs spud wrote: cars get better gas millage in the winter and lower altitudes.


I disagree. They get a slight performance boost (like a cold air intake or intercooler), but their fuel economy goes down dramatically.

The engine runs rich and shifts later to try to warm itself up. On my commute, I get 22-24 mpg during the summer, and sometimes less than 16 winter. This is why you see ecomoders installing hot air intakes on their engines. They get 150* F + air off the exhaust manifold and see a modest increase in fuel economy.

Also, in winter around here, you generally have to drive slower and drive through at least 1" of slush. And perhaps spin your rear wheels excessively :lol:
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Unread postAuthor: Labtecpower » Fri May 25, 2012 4:22 pm

Teeeh shootrinhg guns wirth nice hot weather is better, so higher performance :D

Sorry for puiing :D
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Unread postAuthor: Gippeto » Fri May 25, 2012 4:38 pm

Labtecpower wrote:Teeeh shootrinhg guns wirth nice hot weather is better, so higher performance :D

Sorry for puiing :D


Vodka swilling sod. :drunken: :lol:

"Time" here in about an hour. :occasion5:

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Unread postAuthor: Labtecpower » Fri May 25, 2012 5:04 pm

Heh give me a combi of that girl and the vat the's hgammerinh into :D
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