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Flint ignition

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: jackssmirkingrevenge » Fri Feb 15, 2013 10:16 am

The obvious question is "why?"

You can ignite a hybrid with fuel mixtures up to 15x easily and reliably using the piezo ignitor from a cigarette lighter...
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Unread postAuthor: Happy » Fri Feb 15, 2013 10:21 am

Im trying to make a cannon that is small and portable. The main idea is efficieny. Also could you link me to a post that has the piezzo ingniter info I'm interested in how it works. But anyway ile think of something though having no experience in Hybrids apart from what i have gleaned from wiki and such I'm in desperate need of advice though I have to warn you I like to experiment.
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 15, 2013 10:26 am

Have a look through my own hybrid "journey", this is the first succesful hybrid I made: http://www.spudfiles.com/forums/mini-hy ... 21655.html

It's a long thread but there are plenty of videos and diagrams as well as fuelling and construction advice.
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Unread postAuthor: Happy » Fri Feb 15, 2013 10:31 am

Thanks also is there anyone who has tryed to make a true Hybrid. One that can both independently run of Pnematics and combustions efficiently without the use of burst disks?
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 15, 2013 10:37 am

A piston hybrid can serve this function. Here's a tiny one I made: http://www.spudfiles.com/forums/0-22-mi ... 22465.html

If you fill it only with air, it's basically a coaxial pneumatic and will fire if you dump the pilot through the schrader.
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Unread postAuthor: Happy » Fri Feb 15, 2013 10:43 am

Amazing thx! Btw i have some more questions are you willing to answer them, they are about ammunitions (also im not sure if im aloud to talk about ammo here).
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 15, 2013 11:21 am

we have a whole forum section for construction and ammunition discussion: http://www.spudfiles.com/forums/constru ... n-f19.html

I suggest you spend a couple of hours browsing the forum before asking more questions, you will find that some of your questions will be answered, and also that you will have new questions you didn't think of before ;)
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Unread postAuthor: MrCrowley » Fri Feb 15, 2013 4:28 pm

Happy wrote:So the problem here is the ignition will take to long. Ok ive come up with a soloution. Would it be possible to place a tight fitting concave piece of copper atached to the piston, that has been covered in iron facing the inside of the barrel. Then have the flint placed around the inside of the barrel. So the piston will essentially have a lip that is placed in the barrel and when vented will strike the flint igniting the mix? I know its fiddly and highly improbable but do you have any ideas of making this work?


The problem in both instances is that, even if you get the mix to ignite, you're not allowing the fuel:air mix to remain compressed in a closed-chamber during ignition so the resulting combustion will not reach its full potential. You seem to know a bit about hybrids but you are a little confused about a few aspects of its operation and design, especially with the piston hybrid.

The whole point of a burst disk or a piston valve in a hybrid cannon is to prevent the combustion gases from escaping down the barrel until they have reached the peak of their combustion. We can tell when they reach their combustion peak because that's when the pressure generated by the combustion is the highest. Thus, we set our valves to open at a pressure near this estimated peak combustion pressure.

In a burst disk hybrid cannon, one may have to do a few tests using the cannon as a pneumatic to see at what pressure a chosen piece of materail used as the burst disk will burst at. If we have a 3/4" disk cut from a soda can in a 3/4" union and that bursts when 300PSI is pumped in to the chamber, we can probably assume that 3 or 4 layers would be suitable for a 10x mix as this will result in a peak pressure of about 1000PSI when ignited and contained momentarily.

The same goes for a piston hybrid cannon except instead of fiddling with the number of burst disks we need, we instead alter the pressure in the pilot area behind the piston. Beforehand, one may calculate the forces generated by each fuel:air mix (2x, 3x, 4x, etc) on the front of the piston so we can then find out how much force we need behind the piston so that the piston wont open until the peak combustion pressure has been reached.

Opening the valve at the moment of ignition, or before ignition, is just wasting potential power that could have been utilised had you constructed a valve that doesn't open until the ignited mixes reach peak pressure. Download HGDT and alter the pressure at which the burst disk will burst and you can see how drastically the performance will drop when you have the disk bursting at too low of a pressure.

edit:
While there is a fair amount of info in the Wiki, you should really trawl through the countless hybrid cannon topics in the 'Hybrid Showcase' section as members may divulge information about their cannon that may not appear elsewhere on the forum unless someone has asked a specific question about it. Such information may be things like what material a person uses for a particular union size and how many layers of that material they use for each mix or they may have a novel method for their ignition system or other things like that.

Other topics to keep an eye out for are the ones in the 'Hybrid Discussion Section' where people are about to build a hybrid but they have some questions they would first like answered. Before I built my first hybrid I found these topics quite useful because sometimes they asked seemingly simple questions that weren't in the Wiki or had been talked about before but the information too ambiguous. However, hybrids have come a long way the past 5 years so we have a lot more information on this forum than we used to and you may find it easier to obtain this information than I did back then.
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Unread postAuthor: POLAND_SPUD » Fri Feb 15, 2013 4:50 pm

MrC consider changing you member name to mr lenghtyresposes
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Unread postAuthor: MrCrowley » Fri Feb 15, 2013 4:57 pm

POLAND_SPUD wrote:MrC consider changing you member name to mr lenghtyresposes

Can't argue with that :oops:

Comparing my post to JSR's several recent posts in this thread shows why one of us has only ~10,000 posts and the other over 20,000 :D
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Last edited by MrCrowley on Fri Feb 15, 2013 9:30 pm, edited 1 time in total.
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Unread postAuthor: Happy » Fri Feb 15, 2013 9:25 pm

Thx and im sorry for posting pointless questions, I now understand Hybrids better. It seems it would extremely complicate the system i have in mind if i undergo a hybrid. Though now i have a few ideas to still utilize the flint lock method in conjunction with a piston valve.

I will be back and i will find a way of intergrating a flintlock with a piston valve and perhaps make a stock standard hybrid and a piston piezzo one too.
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