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A Few Ideas...

A place to ask general spud cannon related questions.
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Unread postAuthor: Crna Legija » Wed May 11, 2011 7:24 am

jackssmirkingrevenge wrote:
shiny455 wrote:wouldn't the second ignition put at least half of its energy into pushing the piston backwards rather than the projectile out of the barrel as the area behind the piston only has whatever pressure the ignition of the 20x gives and the detent in the barrel would have to be at least more than that or the projectile will leave the barrel before the second mixture diesels


The man makes a good point, a heavy piston is a must.


or
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Unread postAuthor: jackssmirkingrevenge » Wed May 11, 2011 8:47 am

Crna Legija wrote:or


At which point it really is getting too complex for its own good.
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Unread postAuthor: POLAND_SPUD » Wed May 11, 2011 8:59 am

or just build a high mix hybrid
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Unread postAuthor: Fnord » Wed May 11, 2011 6:23 pm

edit; oh and poland, the only advantage here is that you could used shop pressure (say, 10x) to get 100x-plus perfomance. This would be good for the average spudder but may be difficult to do with off-the-shelf stuff.

Although an internal detent could be used, it would get sheared off neatly unless it was really strong. It is also a bad idea because you need orings on the piston. A detent could damage them or at least keep them from sealing as they pass over.

I don't know if auto ignition temperature would be reached- certainly not by the ignition pressure alone but perhaps with the stored kinetic energy of the piston. If not, no big deal- just add some springy electrical contacts at the front of the stroke and let the piston run into them. You could hook up a couple camera caps, and the contact arcing would be good enough to ignite the mix.


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Seriously, I don't want to stop anyone from attempting it, but I had this idea in like 2009 and didn't even bother to say anything because it was so over-engineered/complicated :)
good luck!
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Unread postAuthor: saefroch » Wed May 11, 2011 8:10 pm

Crude adiabatic gas law calculations say that you'll exceed the autoignition temperature of the secondary chamber by a factor of ~2.7. Honestly... that's a pretty safe margin, I'd say anyone with the supplies or desire should try this.

This system may work very well if you have a burst disc or a detent holding back the main valve from opening until after combustion. If you can manage that and also restrain the piston from just absorbing the energy and recoiling, this will work. :)
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Unread postAuthor: Crna Legija » Wed May 11, 2011 10:45 pm

Fnord wrote:Although an internal detent could be used, it would get sheared off neatly unless it was really strong. It is also a bad idea because you need orings on the piston. A detent could damage them or at least keep them from sealing as they pass over.


If you look closely in my edited pic, theres a little cut in the piston. it should stop right there.
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Unread postAuthor: shiny455 » Thu May 12, 2011 4:23 am

At which point it really is getting too complex for its own good.
yes i agree and i believe there is a good chance whatever you use will just break under the pressuret.. also with what i said earlier as the surface area of the piston is greater than the projectile wouldn't this effect be increased a lot.
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