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no burst disc hybrid revisited

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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no burst disc hybrid revisited

Unread postAuthor: nabsnoabs » Fri Dec 29, 2006 12:43 am

in one of my earlier posts, i made a design for a no burst disc hybrid


looked somethin like this

<a href="http://photobucket.com/" target="_blank"><img src="http://i40.photobucket.com/albums/e226/nabs000abs/inlinenoburstdiscconcept.jpg" border="0" alt="Photobucket - Video and Image Hosting"></a>



well after revisiting my idea, i think i have a better concept

so what do you guys think?
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inline no burst disc hybrid 2.jpg
so basically the compressed air and propane mixture is kept at the same or less than the pressure of the air in the chamber behind it. this keeps the entrance to the barrel sealed. an ignition would set off the mixture, pushing the valve between the chambers back causing the holes to align and releasing the pressure of the back chamber. this action has also released the valve blocking off the opening to the barrel and allowing the expanding gasses to fire the projectile.
pretty simple eh?

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Unread postAuthor: Flying_Salt » Fri Dec 29, 2006 1:05 am

That would take some playing around with, to get the right amount of compressed air in the back part.
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Unread postAuthor: Insomniac » Fri Dec 29, 2006 1:16 am

I see no reason as to why this wouldn't work. I wonder if anyone will build it??
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Unread postAuthor: MrCrowley » Fri Dec 29, 2006 2:56 am

that may be difficult to get a perfect seal.

I think you may need a spring as the pressure on both sides may be equal dependig how much pressure your putting in the back but then it needs to be O-Ringed
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Unread postAuthor: nabsnoabs » Fri Dec 29, 2006 2:34 pm

the only thing im worried about is that the valve that seals the barrel wont move back very far, and i dont know how this will affect the flow of the gas
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Unread postAuthor: Bluetooth » Fri Dec 29, 2006 2:40 pm

I think that should work fine but instead of compressed air behind the piston just put a sring that can hold back however much PSI your putting in so when it ignites it overpowers the spring.
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Unread postAuthor: nabsnoabs » Fri Dec 29, 2006 3:07 pm

the only reason i like the idea of the compressed air in the back was that you could easily adjust it to the proper psi level depending on the psi up front, so i could test it at different mix levels. maybe if i had a spring by itself where i could adjust the tension, but the only problem i have with a spring is that its eventually gonna force the valve closed and trap some exhaust gasses in the first chamber. also i think a spring pushing in 2 directions would have more potential to crack the pvc versus compressed air pushing in all directions.
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Unread postAuthor: singlespeed » Sat Jan 06, 2007 6:37 am

You could have a light spring to move the piston forward, to seal the barrel.

Fill the fuel into the combustion chamber.

Then fill the rear chamber, with a non return valve built into the piston to fill the combustion chamber.



Only problem could be that filling with fuel could overcome the spring ( this would depend on the size differential of the chamber and barrel, versus the spring and fuel pressure ). ballancing fuel and air pressures could be tricky
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Unread postAuthor: Chimps » Sun Feb 11, 2007 4:43 pm

why dont you just put a small hole in the piston so the aire pressure equalizes and put one of those things in the back end that will release the air at a certain pressure(the ones with an extreemely strong spring) for the exaust?

screw the two air chambers because that's just dumb, no offence, for 2 reasons:1 it's inconvienient to have to fill two schradder valves at the same time and 2 you will never get an air tight piston.
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Unread postAuthor: judgment_arms » Sun Feb 11, 2007 10:55 pm

Okay chimps,
One, you use to male quick-connects and have it continually hooked up to air, haven’t read the post in a LONG time as I thought this was dead but, if you need to stop air flow use a ball-valve.
Two, why can’t he make the piston air tight? Maybe you can’t but he may be able to.
Three, monkeys taste good deep fried with banana pudding on the side…
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Unread postAuthor: Chimps » Sun Feb 11, 2007 11:04 pm

haha dont try to eat a chimp with a loaded gun

i dont really care anyhoo since i have not and never will make a hybrid.
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Unread postAuthor: zeigs spud » Sun Feb 11, 2007 11:29 pm

many people to put a small hole in the pistom to quickly equalize pressure.
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Unread postAuthor: frankrede » Mon Feb 12, 2007 1:34 am

use a 1/8 check valve for an even better equalization hole
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Unread postAuthor: Deceiver » Fri Apr 27, 2007 4:10 pm

I cam up with a similar design back in january but due to school I haven't had the time or money to build it nor let the spudding community in on my epiphany.


The distance behind the piston would be equal to 1/4 the barrel diam. and the area of the cut-outs for blow by would need to be roughed in using GGDT to find the optimum volume. The larger area would only need to be in certain sections, you wouldn't have to enlarge the entire rear section, nor would you be able to given the piston configuration.

The basic operating principle is that the air behind the piston acts as a buffer for to slow the pistons movement so that the piston won't open until optimum pressure have been generated by the combustion. So with a 1x mix the air pressure behind the piston would need to be approximately 50psi. That way when the piston reaches the half way point of compression the air pressure behind the piston is just shy of the combustion pressures, at which point the piston self vents and the compressed air behind the piston is vented through the barrel and then offers no resistance to the combustion gasses which slam the piston back fully venting the barrel.

Sorry if that is a bit convoluted, hopefully the *.gif clears any foggy areas up.

Now feel free to tell me why it won't work






edit: Hows come the animation is all FUBAR in the attachment , it plays fine when opend on its own though
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coaxhybrid.gif
I forgot to draw in the o-rings around the outer section of the piston and I was too lazy to animate a spring that would go behind the piston to close it after firing.

The two lines coming from the T and L sections of the fill/meter tube represent 3- and 2-way valves respectivly.

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Unread postAuthor: A-98 » Fri Apr 27, 2007 4:14 pm

there is something terribly wrong with your animation.

design looks good tho.
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