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Railgun Injector V2 (all metal QEV)

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Railgun Injector V2 (all metal QEV)

Unread postAuthor: rp181 » Mon Oct 19, 2009 8:23 am

Here is the new injector for the railgun. The valve is a .5" QEV, the chamber is a modified propane tank. The barrel is the railgun, but I made a adapter for .5" PVC. The red wire is for remote triggering, it is for a railgun after all.
The first picture consists of the Injector, the railgun bore, the pull cable, and a 100mw laser I made for sighting (very accurate when just layed in that space). Also, the tank looks much bigger compared to the bore due to the angle of the shot, and the length.
Image

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[youtube]http://www.youtube.com/watch?v=Y4nwZiIU3Qk[/youtube]
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Last edited by rp181 on Mon Oct 19, 2009 7:19 pm, edited 2 times in total.
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Unread postAuthor: Ragnarok » Mon Oct 19, 2009 8:30 am

Neat. What's the injection velocity going to be like?
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: rp181 » Mon Oct 19, 2009 8:32 am

Do not know, plan on testing that today with a old railgun projectile.

EDIT: Delay on that. Won't have a laptop available for a week.
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Last edited by rp181 on Mon Oct 19, 2009 7:13 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 19, 2009 8:45 am

Looks formidable enough without the electric element, the final result should be impressive :) Surely you can afford to go a bit higher with the pressure though, given the all metal construction?
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Unread postAuthor: Ragnarok » Mon Oct 19, 2009 8:48 am

jackssmirkingrevenge wrote:Surely you can afford to go a bit higher with the pressure though, given the all metal construction?

It may be all metal construction, but the chamber is a propane tank, and they're not notable for their strength.

Also, it's questionable whether he does want to go higher - it is after all simply feeding a railgun, and too high a pressure could cause the projectile to enter the rails unstable (thus doing more harm than good).
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Unread postAuthor: Technician1002 » Mon Oct 19, 2009 11:36 am

Ragnarok wrote:It may be all metal construction, but the chamber is a propane tank, and they're not notable for their strength.


I noticed that with the Marshmallow cannon, the disposable propane cylinders are very thin. It is the reason I have no gauge on the cannon. The extra length adding a T and gauge to the fill pipe would provide too much leverage.

In building the 2.5 inch QDV with a refillable propane tank, I noticed the metal is MUCH thicker and stronger. To bevel the end of the tank for the pipe required a severe beating with a hammer instead of the mild shaping blows the little tank took.

As far as the disposable tanks holding pressure, they have to be able to hold the pressure of liquid propane in normal temperature ranges from room temp to desert heat without bursting. Unless you do something to weaken the metal, the tanks should be good for 240 PSI, the listed service pressure for propane.

Refillable Propane tanks are supposed to remain sealed up to 315 PSI minimum on the safety pressure vent for DOT approval. I'm not sure the vent pressure on the disposable tanks. I'll have to test one sometime.
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Unread postAuthor: rp181 » Mon Oct 19, 2009 6:52 pm

The projectile instability would not be a problem, as these are close fitting dimensions. In fact, higher speed would be beneficial, due to the rate of current rise, with too slow, the current is already low again before the projectile is fully in the rails. Too fast, and the rails are pointless, as jack said on my earlier injector.
I really did not compromise the tanks strength, there is still a thick wall where the fitting is glued on, and the thin parts have not been modified. I only go to 60 PSI, because I can't go higher. My pump has "high volume steel barrel" printed on the side :?

Originally the entire pilot assembly was connected via tube (14'), but the pilot volume was way too high, and the tank vented through the pilot rather than the barrel.
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