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hybrid cartridge protoype without burst disk

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: CpTn_lAw » Sun Mar 14, 2010 5:25 am

Very nice Jack ^^;
I'm more into thinking that your ignition doesn't have enough "juice", than that your mixing was not right. Is you ignition a large piezo like on bigger combustion guns, or is it the mini you posted as size comparison?
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Unread postAuthor: zomgwtfbbq » Sun Mar 14, 2010 5:47 am

jsr,

Thanks for all the tips! Looking forward to posting my own hybrid cartridges soon. :D
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Unread postAuthor: jackssmirkingrevenge » Sun Mar 14, 2010 7:24 am

CpTn_lAw wrote:Is you ignition a large piezo like on bigger combustion guns, or is it the mini you posted as size comparison?


The piezo in the picture was my ignition, I know it's not the best in the world but there are a number of hybrids on this forum that use piezos (with small spark gaps) successfully so I don't think it's the problem.

Thanks for all the tips! Looking forward to posting my own hybrid cartridges soon.


Hope you have better luck than I did :)

I think this is a more workable idea, much simpler and lighter cartridge at atmospheric pressure, if only I could be bothered to find an oxygen source :roll: it's not so much laziness as reluctance to play with an oxygen bottle. I could always go the electrolysis route...
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Unread postAuthor: CpTn_lAw » Sun Mar 14, 2010 9:09 am

I mean i used a piezo, but a small one like that comes in the cigarette lighters, and the only succesful launcher i could manage to build with a mini piezo, was a mini combustion launcher. Such small piezos have problems with even small spark gaps when you increase the mix number. I can't ignite my hybrid with a mini like yours. The bigger one (that worn off...) could however light it.
For the mixing issue, you really think it could be that? With a syringe you can only do small errors in the gaz volume you inject, and at only 5x, the margin is still acceptable. SO even is the resulting mix wasn't perfect, it would still be in he relative flamability of propane/butane.
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Unread postAuthor: zomgwtfbbq » Sun Mar 14, 2010 8:05 pm

I think this is a more workable idea, much simpler and lighter cartridge at atmospheric pressure, if only I could be bothered to find an oxygen source it's not so much laziness as reluctance to play with an oxygen bottle. I could always go the electrolysis route...


Well, it would definitely be easier for ignition but then there's the trouble of finding oxygen, and I just don't think it's sustainable in the long run. Besides, I'm inclined to think that oxygen is rather dangerous, too.

Oh you might also want to look at http://www.spudfiles.com/forums/viewtopic,p,279882.html#279882 because I have a feeling you know how to do it. :roll:
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Last edited by zomgwtfbbq on Mon Mar 15, 2010 1:18 am, edited 2 times in total.

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Unread postAuthor: jackssmirkingrevenge » Mon Mar 15, 2010 1:16 am

CpTn_lAw wrote:I mean I used a piezo, but a small one like that comes in the cigarette lighters


The ones I use are from cigarette lighters, I've never seen smaller ones. Are we talking about the same thing?

Well, it would definitely be easier for ignition but then there's the trouble of finding oxygen, and I just don't think it's sustainable in the long run. Besides, I'm inclined to think that oxygen is rather dangerous, too.


Fair points, and it is dangerous, one of the main reasons I haven't been inclined to get a bottle.

However, there are a couple of notable benefits:

- no need for a filling valve, so less weight and complexity

- no need for a pressure resistant seal, or cartridge, since it only has to withstand pressure at the moment of firing therefore it can be relatively weak but supported by a strong breech as in firearms.

I'm looking into the possibility of making a simple electrolysis apparatus which would allow me to deal with only the small and therefore safe quantities of oxygen that I need.
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Unread postAuthor: CpTn_lAw » Mon Mar 15, 2010 2:52 am

I think we are, I mean that you should use a BIGGER piezo. Small piezos like the one you are using (from a cigarette lighter) don't do good when mix is high, even with small gap.
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Unread postAuthor: jackssmirkingrevenge » Mon Mar 15, 2010 3:52 am

Where does one find bigger piezos? Alternatively I could cut up a disposable camera flash...
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Unread postAuthor: chinnerz » Mon Mar 15, 2010 3:58 am

jackssmirkingrevenge wrote:
I'm looking into the possibility of making a simple electrolysis apparatus which would allow me to deal with only the small and therefore safe quantities of oxygen that I need.


12 volt laptop charger works well, or so ive heard
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Unread postAuthor: CpTn_lAw » Mon Mar 15, 2010 4:29 am

jackssmirkingrevenge wrote:Where does one find bigger piezos? Alternatively I could cut up a disposable camera flash...


Bigger piezos come off barbecues.

I tried something else:

Yesterday i took apart all the lamination of a small battery charger transformer. It had a step down factor of 24, counting 130 rounds on the secondary , so i reversed it, took the 130 rounds off, put a much bigger wire, and wound only 3 turns. I replaced all the ferite laminations, and tested it on the airsoft battery at 9.6 volts making approx. 10,000 volts. it worked , the spark was blue, thin. So i thought I'd give it a try shorting the camera flash....I have a 330 cap, the new step-up factor is 1032 give or take, that makes approximately 330,000 volts. I quickly realised the transformer did not like it. The spark between the secondary leads was bright yellow-ish , there was this strong ozone smell, and the very thin wire of the secondary melted at the end. Oh and the lamination didn't like it aswell. There was this strong "hit-like" vibration on my desk.
It was very much like the plasma generated with microwave-ovens on youtube. (a wee bit smaller though :D)

I'd so love to have an ignition coil.....


EDIT : photos of the arc. Sorry they're blurry, but i had to make a 0.4" openning time, and have no tripod to rest the camera.



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Unread postAuthor: JDP12 » Mon Mar 15, 2010 12:00 pm

hmm... I haven't looked at spudfiles in forever. So to understand, you rely on a friction fit to seal the cartridge?

I may have to try this with a 3/4" size, I'm looking to make a big revolver pistol after being disappointed with my combustion cartridges.
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Unread postAuthor: jackssmirkingrevenge » Mon Mar 15, 2010 12:36 pm

Interesting setup CpTn_lAw, stunguns aren't an option for me so I might try alternative ignition. Still, I want to play with electrolysis first.

JDP12 wrote:So to understand, you rely on a friction fit to seal the cartridge?


Pretty much, with the right seal you can get to fairly high pressures.
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Unread postAuthor: ramses » Mon Mar 15, 2010 3:50 pm

I hate to say it, but ignition coils are kind of overrated. I use one on my hybrid, and on a new battery the most I can do is one spark every 5 or so seconds. That sounds really fast, but if it misfires (frequent occurrence, sadly) you have to wait, then do it again, etc. It is really powerful, if I leave the piston valve open, I can hear the spark come out the 5' long barrel. In air, the spark is around 1 inch long and bright yellow, really scary. If you were to get shocked by it, I can imagine it would hurt quite a lot.

I am looking to convert to an electronic BBQ or stungun for safety, portability, and speed.
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Unread postAuthor: Zeus » Thu Mar 18, 2010 4:50 pm

JSR, if you are interested I can post a very simple ignition coil driver which will produce more than 200 sparks a second.
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 19, 2010 1:15 am

Be my guest, especially if it's something that can be made with easily obtained parts.
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