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Hybrid build thread

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: Heimo » Tue Aug 31, 2010 11:17 am

Dave_424 wrote:If I was you, I would just go with a burst disk design and use the steel chamber. It should be much quicker to build and allow the higher mixes that you were looking for.

Seeing as though the aluminium is the weak part, removing it from the mix will increase your maximum pressures.

I would say that, if there were no defects/cracks in the chamber and the end plates were over engineered enough, it would withstand 50x quite easily

Dave


OK point taken the valve goes...

from this point on this will be a burst disc cannon (since my chamber allows it I will still be able to upgrade later to a valve if I feel it's necessary)

the chamber have got no cracks or defects at all

the end plates were over-over engineered, this pic proves the point

Image
the end plates (actually its more like end plugs) are 40mm from end to end talk about overkill...
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Unread postAuthor: Dave_424 » Tue Aug 31, 2010 11:55 am

I didn't/hadn't seen the end plugs and they definatley will take the pressure

Good luck with the build

Dave
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Unread postAuthor: Fnord » Tue Aug 31, 2010 12:19 pm

You should anneal the valve before you do anything...

Once I needed some large 1" thick aluminum plates for heat sinking purposes, and since I didn't have any I cast them myself. The first time I tried they didn't come out the way I wanted(a few air bubbles formed on the plate bottom) so I broke them up for recasting. Using a 5 lb sledge it was fairly easy to break these 1" thick plates. Cast aluminum can be very brittle.

As long as you aren't standing by it when you do the initial testing I wouldn't worry though. If you can make a copy with steel I'd recommend it for handheld use. Aluminum eventually fatigues regardless of the heat-treatment.
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Unread postAuthor: Heimo » Tue Aug 31, 2010 12:49 pm

Fnord wrote:Aluminum eventually fatigues regardless of the heat-treatment.

yes that is correct and I did not think about that when I made that valve body, and since I would like this to be hand held, I guess I am going to go with burst disc for now and I am going to make the build the burst disc part from some 1/2 steel sheet I got
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