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what do you think about this piston systeme ?

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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what do you think about this piston systeme ?

Unread postAuthor: ceizz » Thu Nov 12, 2009 2:14 am

all in the subject title :
what do you think about this piston systeme ?

i need your comments !
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PISTON SYST1.JPG

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Unread postAuthor: SpudBlaster15 » Thu Nov 12, 2009 2:27 am

It should work, but it's more complicated than it needs to be. What's wrong with a pop-off valve on the pilot chamber?
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Unread postAuthor: ceizz » Thu Nov 12, 2009 2:40 am

i am french and my english is not full, what do you meane about ''What's wrong with a pop-off valve on the pilot chamber? '' ???
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Unread postAuthor: SpudBlaster15 » Thu Nov 12, 2009 3:26 am

Sorry about that, I didn't realize English wasn't your first language.

It seems like you want to vent the volume of air in 'Chamber A' as the fuel mixture burns and the pressure in the combustion chamber rises. To do this, I would suggest mounting a safety pop-off valve in 'Chamber A'. As the pressure in the combustion chamber increases, it will push the piston backwards, increasing the pressure in the chamber behind the piston. When the pressure reaches a certain point, the pop-off valve will open, and allow the air behind the piston to vent.
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Unread postAuthor: ceizz » Thu Nov 12, 2009 9:17 am

ok thank you for your comment i thinking about this idea !

i need more comment some one else ??
you read but you don't poste, come on every body !!! loool
:D
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Unread postAuthor: Ragnarok » Thu Nov 12, 2009 9:31 am

I think I'd better point out the error in the third image.

If the "piston" is moving, the main chamber is clearly at a higher pressure than chamber A - so the air flow wouldn't be from Chamber A, it would be INTO chamber A.

Yes, you ideally need to get chamber A to vent, but it needs to be to atmosphere - for which SpudBlaster's idea would work.
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Unread postAuthor: ceizz » Thu Nov 12, 2009 10:15 am

yes i think about non-return valve to vent the volume of air in 'Chamber A' to another chamber 'B'.
After shot , can reinject this volume in chamber 'A', its quick to set up another shot[img]C:\Documents%20and%20Settings\mam\My%20Documents\My%20Pictures\untitled.JPG[img][/img]
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Unread postAuthor: ceizz » Thu Nov 12, 2009 10:16 am

i don't know how to insert imag, i hope you understand me
[/img]
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Unread postAuthor: Ragnarok » Thu Nov 12, 2009 10:19 am

Linking to a location on your hard drive is... not the most effective way of us being able to see it. You'll need to upload it.
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Unread postAuthor: ceizz » Thu Nov 12, 2009 10:33 am

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Unread postAuthor: CpTn_lAw » Thu Nov 12, 2009 11:03 am

Hey ceizz, ton idée est super compliquée pour pas grand chose! Imagine qu'au moment de la combustion, la pression augmente dans les chambre, fait reculer le piston, donc derriere le piston, la pression augmente tres rapidement. Pour eviter trop de pression tu peux mettre une valve pop-off au bout du tube dans lequel le piston bouge. De cette maniere, quand le piston aura comprimé suffisament l'air derriere, la pression sera trop grande, la valve pop-off s'ouvre en laissant le surplus s'echapper, et les gaz de combustion peuvent pousser le projectile. A mon avis, il faudrait mesurer quelle pression tu veux utiliser (quel mix) pour determiner la pression de claquage de la pop-off ;)

If someone has issues with me replying in french to him, let me know, i'll just say somehting in english and PM the answer in french.

I basicly said that the idea is too complicated for something much simpler. Putting a pop-off at the end of the piston cylinder would be much more practical, and an adjustable would allow for different mixes to be used.
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Unread postAuthor: ceizz » Thu Nov 12, 2009 11:47 am

salut CpTn_lAw, je suis d acord avec la pop-off mais a chaque tire ya une projection d air qui sert a rien alors que ce que j essaye de trouver c'est une solution pour "recycler l air'' et c'est aussi reglabe celon les mix en fonction de la pression qu'on met a l arriere du piston. non ? lol

j ai peut etre pas compris le principe de la pop-off aussi:
quand la pop off claque elle libere toute la pression ou il en reste un peu, vu que c'est un ressort dans la pop-off ????

je suis entrain d essayer de calculer avec HGDT le mix et les dimension de la chambre c pas facil c tout en anglais et les mesures aussi super !! :?

hi CpTn_lAw i am ok with the pop-off valve, but for every shot there is a air realese in atmosphere for nothing, i try to get the solution for recycle this air volume, its also Adjustable like pop-off up to the mix and pressur in chamber 'A'. allright ? :)

maeby i don 't understand the pop-off fully ! is it relaese all the pressur in chamber 'A' or not yet because there is a spring inside ?

i trying to understand the software HGDT now, it's not easy for a french man know only "les metre et les centimetres" !!!

i like this forum its funny to write english !!
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Unread postAuthor: Ragnarok » Thu Nov 12, 2009 12:02 pm

ceizz wrote:...mais a chaque tire ya une projection d air qui sert a rien alors que ce que j essaye de trouver c'est une solution pour "recycler l air"...

In many cases, it is often actually a better solution to waste a little air than go to the effort of trying to avoid losing it. In this case, I don't think it will harm performance trying to keep that air, but it will add complexity.

Feel free to go at it either way, but avoid getting too hung up on the idea of avoiding venting to atmosphere, because in some cases, it is actually the best solution.
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Unread postAuthor: POLAND_SPUD » Thu Nov 12, 2009 12:34 pm

it's not easy for a french man know only "les metre et les centimetres" !!!
click on file and choose configuration

there you can switch units to metric units

voila!! :)
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Unread postAuthor: ceizz » Thu Nov 12, 2009 12:56 pm

thank you POLAND_SPUD :wink:
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