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second chamber for more power

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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second chamber for more power

Unread postAuthor: Billy Bob » Sat Apr 07, 2007 4:10 am

Hi,

i have an idea and need your help. I dont know if anybody make that before on an spudgun. I want to make a second chamber which ignite a few mili seconds later than the first chamber.

The advantage is that chamber 1 pushes the Ammunition from stood to speed an the second chamber mustn´t make the hard work of acceleration from stood. So the second chamber can give the Ammunition more acceleration.

But there are much questions and problems. :roll:

Gas explosions are very short so that the pressure peak will be not long.
Will the pressure from the explosion in chamber 2 fill the first chamber before the pressure pushes the Ammunition usefull. :?
Non-return valve for this size will be not very cheap :D

I will only ignite the first chamber and the second should ignite from the hot flames of chamber 1. How to get the optimal ignite time because the Ammunition must have pass the bypass.

I have put the things together so you can see what i want to do.
But i don´t know if it will work rational so i ask you for give me your opinion or some new ideas.

Don´t tell me about your safety distrust because of the fire exthingusher.
The cannon should become a distant ignite. :wink:


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Unread postAuthor: From_Hamsterdam » Sat Apr 07, 2007 4:18 am

I think 1 large chamber is better and a lot simpler. 2 chambers would produce no noticeable effect.
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Unread postAuthor: jackssmirkingrevenge » Sat Apr 07, 2007 4:25 am

sounds good in theory but hard to produce in practice, i think your biggest problem will be the second chamber igniting prematurely and actually reducing performance.

It has, of course, been tried before:

Image

This is the principle behind the WW2 Nazi V3 "high pressure pump" designed by Conders to bombard england from France in such installations

This site is in French but if you scroll down there's plenty of pictures of the protoype.
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Unread postAuthor: CpTn_lAw » Sat Apr 07, 2007 4:56 am

this principe is also used in multi-stage coilguns. but they are way more powerful than single stage ones and easy to make with the right knowledge and materials.
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Unread postAuthor: sandman » Sat Apr 07, 2007 9:02 am

hehe, but rail guns are so much cooler
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Unread postAuthor: boilingleadbath » Sat Apr 07, 2007 10:28 am

Eh, how could the second chamber fire so early that it'd hinder performance?
I mean, until the potato passes, there should be very little flame ahead of it (if any), and very little motive for it to propagate into the second chamber.

On the up side, this should provide a very effective jet-type ignition to the second chamber. (which is good... jimmy's pressure data shows that, otherwise, it'd basically smolder for the entire time the projectile was in the bore.)
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Unread postAuthor: Billy Bob » Sat Apr 07, 2007 11:46 am

sounds good in theory but hard to produce in practice


Yes at the moment I think the same :roll:
The high pressure pump is where i get my inspiration from :wink:

there should be very little flame ahead of it (if any), and very little motive for it to propagate into the second chamber.


Yes thats another big problem !

My neighbour and I come to the point that we say thats convicts to fail because of missing technical and electronical Equipment. Especially Electronic time ignition parts. And if we would have it it would become a very long gun :D

Thanks for your help we can make the discussion go on but I will not build the gun. :wink:
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Unread postAuthor: CpTn_lAw » Sun Apr 08, 2007 11:06 am

sandman wrote:hehe, but rail guns are so much cooler


Made one mini about 10 months ago. Railgun are fun, but...if you find rails that don't corrode in less than 10 , 120 joules shots...my mini coilgun fire well...
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Unread postAuthor: Scope » Sun Apr 08, 2007 11:50 am

to do it the best you would 2 stunguns
one of each chamber
the bottom chambers would be actived by break beam which would trip the 2nd chamber with a relay...

thats simplily how a multistage coilgun runs. the differences is that they use really expensive relays, 2 break beams for each coil, and a micro controler to tie it together.
http://www.anothercoilgunsite.com/nf-multiple-news.htm
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Unread postAuthor: boilingleadbath » Sun Apr 08, 2007 6:07 pm

I repeat:
Jimmy's <a href="http://home.earthlink.net/~jimsluka/Piezo_Spud.html">data</a> shows that it takes a LONG time for the combustion rate to ramp up, when lit by a spark... as in maybe a dozen ms.

A spark based system, therefore, would require you to ignight the second chamber before the potato had passed the opening to that chamber - which worries me, besides being complex.

Rather, I'd just leave the port to the second chamber open.
Such would mean that, once the potato passes, the hot gasses can force themselves through the feed pipe, in effect forming a jet-ignition system,
which should light the fuel very effectively, bringing the second chamber 'online' in rapid order.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 08, 2007 11:38 pm

boilingleadbath wrote:Eh, how could the second chamber fire so early that it'd hinder performance?


This was the problem with multi-chambered guns built by professionals ever since the idea was tried - hot gasses blowing by the projectile would ignite the advanced chambers prior to the passage of the projectile, this creating a pressure in front of it and slowing it down.
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