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?s with biohazard.

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: pat123 » Tue May 06, 2008 3:54 pm

I went outside to shoot it today and every time i shoot a hybrid or combustion I like pnuematics more and more. here are my questions.

1. If the propane combusted in the chamber without breaking the burst disk would it be possible for me not to notice it combusting? (I pumped it up to see what it would pop at, it popped around 90 psi.)

2. has anyone else had air leak through their wires? air is coming out between the metal wire and the insulation.

3. does anyone haave a really accurate way to measure the volume? Drex was talking about pouring water in with a measured container but I don't want to fill a 600ci chamber with water cup by cup.

thanks
pat
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Unread postAuthor: drex » Tue May 06, 2008 4:02 pm

you shot it with out me??? :(
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Unread postAuthor: SpudFarm » Tue May 06, 2008 4:04 pm

if the disk not bursts it will be a "plunk" and some smoke out of the union.
nova had leaks that way on the brass bruiser.. he put epoxy in the wire.
a water hose?

Edit: Nova used superglue.. some drops on the exposed copper on the chamber side
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Last edited by SpudFarm on Wed May 07, 2008 8:24 am, edited 1 time in total.
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Unread postAuthor: pat123 » Tue May 06, 2008 4:06 pm

Not a water hose inside the wires themselves.
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Last edited by pat123 on Tue May 06, 2008 4:07 pm, edited 1 time in total.
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Unread postAuthor: drex » Tue May 06, 2008 4:06 pm

pat, i have a crap load of epoxy.
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Unread postAuthor: pat123 » Tue May 06, 2008 4:09 pm

How can we epoxy inside the wires?
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Unread postAuthor: drex » Tue May 06, 2008 4:10 pm

use better wires :idea:
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Unread postAuthor: BigGrib » Tue May 06, 2008 4:12 pm

Yeah I've had a combustionleak out the wires before while using a burst disk. You would notice atleast some sound and you'd hear a hiss as pressure leaked off from around the wires.
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Unread postAuthor: DYI » Tue May 06, 2008 4:32 pm

Okay, here are some answers:

1. You would notice it. You can hear the burst disk suddenly bulge out. I liken it to the sound the SCTBDC would make when the pressure in the main chamber exceeded the pilot chamber pressure, and the disk switched from convex to concave almost instantly. It isn't tremendously loud, but you can hear it from a decent distance away.

2. A good rule with any pressure vessel is that anything that can leak, will leak. There is space between wire and insulation, and between individual strands of the wire. The solution: Use a single conductor wire, strip off the insulation at the end, and epoxy it where the insulation stops.

3. I used a 3 ounce syringe (the kind of thing you use to give injections to large livestock) to measure the chamber volume of my first hybrid. It took well over an hour, but I lost less than 1mL of water in the entire process. Also, as I said before, don't use water, use oil. Water will remain in the chamber and cause corrosion to the steel.

A faster approach than mine would be to fill the chamber, and then measure the water you're dumping out. An even faster approach would be to use my metering system, which doesn't require you to know the volume of anything.

Also, if your hybrid has anywhere near a decent seal, there won't be smoke coming out the union when it fires with an overly thick disk. If smoke leaves anything but the muzzle of your hybrid, you may have a bit of a problem :lol:
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Unread postAuthor: pat123 » Tue May 06, 2008 5:03 pm

Since I know the pressure of my meter, could I pump it up to say 150psi then let it into the chamber and see what the pressure is then. then divide that pressure by 150? that would give me how many times bigger the chamber is right?
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Unread postAuthor: DYI » Tue May 06, 2008 5:05 pm

You would need a gauge so accurate that you could buy 3 of my non-volumetric systems for the same price, but sure, if that's what floats your boat, go right ahead.
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Unread postAuthor: pat123 » Tue May 06, 2008 5:08 pm

If you don't mind telling how exactly does your metering system work?
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Unread postAuthor: drex » Tue May 06, 2008 5:51 pm

pat123 wrote:If you don't mind telling how exactly does your metering system work?


magic?

pat, do you think we will be able to launch this thing on Friday assuming we get the metering thing figured out?
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Unread postAuthor: pat123 » Tue May 06, 2008 6:13 pm

yeah it is sparking every time and has a perfect seal other than the wires.
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Unread postAuthor: Lentamentalisk » Tue May 06, 2008 6:14 pm

DYI wrote:You would need a gauge so accurate that you could buy 3 of my non-volumetric systems for the same price, but sure, if that's what floats your boat, go right ahead.

Really! tell us your secret metering system. You cant just post crazy numbers like that with out a link or term to search...
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