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Test results and postmortem for the HYBRID Taternator II

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: Dumbascii » Thu Dec 14, 2006 9:13 am

markfh11q wrote:My guess is the white powder is an oxide of aluminum . . .

Yes - that might be it. It only started when I started using oxygen which coincides with switching from a copper fuel distribution tube to an aluminum tube. The powder is on everything, but is definitely thicker around the tiny orifices in the tube. The aluminum tube was used because copper has a problem with acetylene, and I'm unlikely to keep using acetylene because of the detonation issue. All the more reason to stop using freaky oxygen . . .
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Unread postAuthor: King_TaTer » Thu Dec 14, 2006 5:14 pm

thats awsome I hope you pursue the MAPP/oxygen thing in the future. that would be awsome to see happen in its perfected form.
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Unread postAuthor: Spudinator » Sun Feb 11, 2007 7:27 pm

My hybrids did the same thing with spuds, just spit out mist, not a single chunk of potato to speak of heh. The vaporization is not caused by the burst disc, its the pressure wave that does it (trust me, this issue has been beat to death on spudtech some time back). It does it when using aluminum foil, PET, rubber, anything (aluminum foil proves it isnt the disc, that stuff has so little mass it hardly counts for anything).

The white coating could be oxidation, but I would think its burned starch like you said dumbascii.



The sabot issue... Do milk jug lids fit in your barrel like they do in SCh40 PVC? if they do, perhaps cutting the back the potato flush with the breach, then placing the milk cap behind it could help solve the issue (though I think there will still be a bit of spud-mashing occuring heh). Sticking with air/fuel I think would be better than direct oxygen heh, its cheaper while staying close to the same power level as pure oxy (albeit with a higher-pressure mix) and also adds the benefit of a buffer gas to keep the detonation problem down a bit.
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Unread postAuthor: Dumbascii » Fri May 04, 2007 10:48 am

Spudinator wrote:The sabot issue... Do milk jug lids fit in your barrel like they do in SCh40 PVC? . . .

Yes, but they are so thick I would not be able to force the breech closed all the way, so the blast would try to open the handles. I've molded 3" long automotive body filler projectiles. I have very high hopes that they will stay intact. I used a bunch of cut off barrel pieces as molds, slicked with motor oil. The body filler shrinks a tiny bit, so the fit is perfect - loose but close.

Spudinator wrote:Sticking with air/fuel I think would be better than direct oxygen heh, its cheaper while staying close to the same power level as pure oxy (albeit with a higher-pressure mix) and also adds the benefit of a buffer gas to keep the detonation problem down a bit.

Yes. The oxygen was just too weird. Everything is rebuilt now, I'm just waiting for a warm weekend! I'll post results soon.
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Unread postAuthor: dongfang » Wed May 09, 2007 1:50 pm

Hi,

> 10 psi and still not sonic? That sure is bad news for my VTS (Vegetable Transportation System) plans.

How long is the barrel? Considered a longer one? My sonic combustion, which is sonic only with things much lighter than vegetables, has 5m (5 ft).

*** OOPS! I did mean 15 ft here, not five .. ***

Nice gun though. You could also consider ice slugs.

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Soren
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Last edited by dongfang on Thu May 10, 2007 4:14 pm, edited 1 time in total.
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Unread postAuthor: Dumbascii » Thu May 10, 2007 2:36 pm

dongfang wrote:Hi,

> 10 psi and still not sonic? That sure is bad news for my VTS (Vegetable Transportation System) plans.

How long is the barrel? Considered a longer one? My sonic combustion, which is sonic only with things much lighter than vegetables, has 5m (5 ft).

Nice gun though. You could also consider ice slugs.

Regards
Soren

The barrel is currently 8 feet. The trouble is that the spud slugs vaporize.

I made the aluminum molds for ice slugs, but it is such a pain to keep them frozen during transport, that I gave up on ice. Transportation is required because this thing can't be used anywhere near people - insane mixes are as loud as a gun.

Should be able to test out the body filler slugs this weekend! Heee . . .
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Unread postAuthor: dongfang » Thu May 10, 2007 4:09 pm

Hi,

I did mean, a pressure low enough to keep the spuds intact, but a longer acceleration distance.

OK, understand about the ice. How about wax candles then? I could find some that fit my gun almost perfectly. The excess will shave off in the same way as with spuds. It could be fun having a candle vaporize hitting the target, _and_ having the vapor ignite.

Anyway, very nice gun. I would still say, get a longer barrel. The longest one I have tried was 117 calipers, and it still did not have any "congestion" problems. I said 5ft in the previous post; it was 5m ~ 15ft.

Regards, and happy testing
Soren
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Unread postAuthor: Dumbascii » Fri May 11, 2007 3:04 pm

dongfang wrote:Hi,
OK, understand about the ice. How about wax candles then? . . .

Excellent idea. The same aluminum molds could be used to pour melted wax. Ultra light, I'll bet they go faaast! Going to make some tonight.

dongfang wrote:...I would still say, get a longer barrel. The longest one I have tried was 117 calipers, and it still did not have any "congestion" problems. I said 5ft in the previous post; it was 5m ~ 15ft.

I saw a 20 foot barrel on a PVC pnematic that could do unbelievable damage. I opted for higher power and shorter barrel to keep it a bit more portable. The current 8 foot barrel is unwieldy enough . . .

Pray for nice weather Saturday.
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Unread postAuthor: dongfang » Fri May 11, 2007 4:19 pm

Hi,

OK, but once you melt those brightly white candles, they become denser! Apparently they are made of little wax pearls that are pressed together. I prefer to cut them for that reason.

Yes I understand your option. My 15 footer is made of 2 sections that plug together. The longer one will barely squeeze into a station wagon (plastic).

Happy shooting
Soren
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