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thinking about going hybrid... need some help, Thanks!

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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thinking about going hybrid... need some help, Thanks!

Unread postAuthor: chinnerz » Mon May 17, 2010 4:23 am

I have decided to take damage to the next level and build a hybrid. but i am not fully sure of the whole concept and i'm not super confident in my material choice and building practices. So, let me start by shooting you guys up with some questions.... But first my concept.

I am planning on having a "sawed off shottie" look. Using ally tube for the chamber and the barrel maybe 13mm., i was thinking of some king of system to fit smaller barrels inside the bigger one, for different ammo etc.
i was thinking of using a camera charge circuit for the ignition, i have played with them in the past and i think they may work but im not too sure..., i will probably end up using sticky tape for the disk, in layers if i have to. and for fuel i was thinking of using lighter grade butane, as it is cheap and readily available.

my questions, and i have looked around but i cant seem to get a clear response... also spudfiles is quite slow on me right now and times out often :\

Is butane a good choice of fuel??

Can i use an un modded camera charge circuit for ignition? and is there a way to make it smaller?? also what is a coil in terms of adding it to the circuit to make a bigger spark?? (i have done some basic electronics at school, and i think i can make a circuit if given a diagram, i am just not sure of the parts to use)

what is a good method of attaching the barrel to the chamber, i kind of want a quick open/quick close design??

Is stickytape a good disk to use? if so how do i find its bursting pressure?

is ally tube a good choice of chambers?? i can use steel but wont that rust?, its a lot harder to work with (i have almost no metal work tools):\

What kind of valves should i use for filling?? i was thinking schrader but under these pressures wont it fail??

i dont think this will be built any time soon as i have still a lot of work to do researching fuel mixes (im am absolutely abysmal at maths, and i haven't done ANY physics so this may take a little while)

Thanks in advanced

P.S. ill draw up some idea pics soon

P.P.S., does the "coil" refer to some kind of small transformer??




Also, while trying to post this the first time i got error 500? i think its 500
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Unread postAuthor: Crna Legija » Mon May 17, 2010 6:02 am

Most people use unions as the barrel and burst disk holder.

I think that galvanized steel is you best bet if you don't have tools because you get it at any hard ware store with pre cut threads and there all the fitting you need also it wont rust because its coated in zinc.

a coil in electrical term is a bunch of coiled up wire, there is a primary coil wich has less wraps than the secondary coil the voltage increases between them. i think they are called step up transformers. Im not 100 % on that tech can elaborate more. the archive has some stuff on ignition aswell.

use foil in place of tape it tears better and less messy to work with

use propane from a blow torch you can convert the threads to npt and thread it to you meter pipe. The pressure will depend on you mix and i don't think that you could make a schrader valve fail they have been tested to 3000 or so psi


thats just what i know i have never built a hybrid so it may be wrong
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Unread postAuthor: boyntonstu » Mon May 17, 2010 7:12 am

I use pneumatic and I am curious why one would consider going hybrid?

I can shoot 160 grains at 900 fps which is as powerful as a .38 Police Special.

This is on basically free air.

What gains am I missing by not going hybrid?
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Unread postAuthor: chinnerz » Mon May 17, 2010 7:14 am

Thanks!

I know the steel your talking about!

That coil sounds like a transformer.

are you talking about thin kitchen foil?? that sounds quite weak maybe bursting at less than 20psi! Also is there a way to find out what pressure a material ruptures at or is there some kind of test that must be done??

is there much different between butane/propane not in its chemical structure but in performance??

i want the filling to be done separately, not attached to the gun like some people do.... mainly because i want this to be on display my my house and having cables and tanks will detract from its awesomeness.

Also i am a novice when it comes to epoxy (if you listen carefully you can hear JSR's shrill mocking laughter in the distance) will epoxy stand up to the abuse of repeat combustion, is there a specific type of epoxy which is stronger and therefore the one to use for this application or will bunnings epoxy do (guessing they sell it)

hmm i thinks i have to do some wikiing now :P


boyntonstu wrote:I use pneumatic and I am curious why one would consider going hybrid?

I can shoot 160 grains at 900 fps which is as powerful as a .38 Police Special.

This is on basically free air.

What gains am I missing by not going hybrid?


I enjoy building these more then i do shooting... wel currently any ways Also, this seems to be more portable as as i do most of my shooting away from my house and often away from power.... a hand pump gets old fast.

P.S. im a student who doesn't have a lot of money, and compresses are expensive, i currently can only afford 120psi max
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Unread postAuthor: c11man » Mon May 17, 2010 7:29 am

fridgys are often free.

but as stu pointed out pneumatics can be very powerful and his is like your "average" copper spudgun.
i can see how you want some more portability and hybrid is probbably the best bet.
for burst disks aluminum foil proably is the best and it hold more pressure than you think
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Unread postAuthor: boyntonstu » Mon May 17, 2010 7:51 am

chinnerz wrote:Thanks!

I know the steel your talking about!

That coil sounds like a transformer.

are you talking about thin kitchen foil?? that sounds quite weak maybe bursting at less than 20psi! Also is there a way to find out what pressure a material ruptures at or is there some kind of test that must be done??

is there much different between butane/propane not in its chemical structure but in performance??

i want the filling to be done separately, not attached to the gun like some people do.... mainly because i want this to be on display my my house and having cables and tanks will detract from its awesomeness.

Also i am a novice when it comes to epoxy (if you listen carefully you can hear JSR's shrill mocking laughter in the distance) will epoxy stand up to the abuse of repeat combustion, is there a specific type of epoxy which is stronger and therefore the one to use for this application or will bunnings epoxy do (guessing they sell it)

hmm i thinks i have to do some wikiing now :P


boyntonstu wrote:I use pneumatic and I am curious why one would consider going hybrid?

I can shoot 160 grains at 900 fps which is as powerful as a .38 Police Special.

This is on basically free air.

What gains am I missing by not going hybrid?


I enjoy building these more then i do shooting... wel currently any ways Also, this seems to be more portable as as i do most of my shooting away from my house and often away from power.... a hand pump gets old fast.

P.S. im a student who doesn't have a lot of money, and compresses are expensive, i currently can only afford 120psi max


This is a converted 66 cu in M6 Aluminum cylinder.

It weighs about 2 pounds.

It was a challenge to tap a 1/2" pipe thread into it.

I twisted the cylinder with a homemade strap wrench while the tap was held fixed in a vice.

No drilling, just forced it through the existing threads.

It took about 20 cycles of in out turning to get it done.

A 1/2" > 1/4" bushing and it was finished.

I can pump it up to 700 psi in 80 seconds.

No leaks.

The Trom-Boyn chamber uses 50 psi per shot.

It is a 6 shooter to 400 psi.

I haven't maxed out the compressor because I am afraid of messing up a good thing.

You would probably get at least 20 120 psi shots out of one of these 2.5 pound aluminum cylinders. How much do your fuel canisters weigh?

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Unread postAuthor: chinnerz » Mon May 17, 2010 7:57 am

c11man wrote:fridgys are often free.

but as stu pointed out pneumatics can be very powerful and his is like your "average" copper spudgun.
i can see how you want some more portability and hybrid is probbably the best bet.
for burst disks aluminum foil proably is the best and it hold more pressure than you think


Yeah they sure can be powerful and lots of fun too :P but i have always wanted to make a decent combustion launcher... And i may as well take that 1 step further.

Also over here where i live, you probably cant get a free fridgy.. Cheapest would be a few hundred... And you may as well get a woking compressor then a maybe working/ on its last legs fridgy :p
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Unread postAuthor: chinnerz » Mon May 17, 2010 8:06 am

fule?? Less then 1kg?? For a large can, plus small hand pump 250 grams max.
I agree that i can get a heap of shots if i made a new gun with maybe some kind of hammer sysem and used a reg, but thats not the point of this thread. The point was i am thinking about making my first hybrid, can i have some help\ what are some things i should know and not doing those thing may result in death...

I will continue making gas guns, i just wanted to give this a try because i have always wanted to


On a side note, how much will a tank like that set me back??
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Unread postAuthor: boyntonstu » Mon May 17, 2010 8:57 am

chinnerz wrote:
c11man wrote:fridgys are often free.

but as stu pointed out pneumatics can be very powerful and his is like your "average" copper spudgun.
i can see how you want some more portability and hybrid is probbably the best bet.
for burst disks aluminum foil proably is the best and it hold more pressure than you think


Yeah they sure can be powerful and lots of fun too :P but i have always wanted to make a decent combustion launcher... And i may as well take that 1 step further.

Also over here where i live, you probably cant get a free fridgy.. Cheapest would be a few hundred... And you may as well get a woking compressor then a maybe working/ on its last legs fridgy :p


Most folks throw away window A/C units every few years here in FL.

I suggest that you ask any a/c company for their takeaways.

IMHO an 8,000 BTU a/c compressor is superior to a fridgy.
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Unread postAuthor: saefroch » Mon May 17, 2010 10:04 am

Butane, in theory, is a better combustion fuel than propane. However, propane is much easier to come by in large quantities, fill a meter with, and also diffuses quicker than butane. Overall, I advise using propane, but if you can find an effective way to use butane, you will actually get more energy output for the same amount of fuel than with propane.

By some good use of ball valves and/or quick disconnects you can remove the entire metering assembly from the gun for display purposes.

If you've got basic knowledge of stoichiometry and gas laws you can run mix computations yourself, or you can look around on the hybrid fueling thread for the standard "X" mix computations.
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Unread postAuthor: chinnerz » Tue May 18, 2010 1:23 am

hmm i see,

So far,
I should use steel for my chamber,
Use some kind of transformer in my ignition system,
Use foil for my burst disk.

To do: work out my ignition, add remove caps etc
Find how to attach barrel to chamber.

Questions, can i use ally for my barrel?? Or should i use a steel one
Is epoxy ok to use instead of end caps??
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Unread postAuthor: MrCrowley » Tue May 18, 2010 1:53 am

What gains am I missing by not going hybrid?

Supersonic for one. Portability for another. A hybrid can achieve 1000PSI spike pressure and you don't even need a compressor.
You can really go quite a bit past supersonic with decent projectiles, such as ball bearings. You can get pretty amazing performance from small valves (say 3/4" union) and short barrels (say 3 feet). They can be quite versatile. Of course, there are down sides.


As for the topic at hand, I'll try and comment a bit later when I have more time. :)

edit:
I can shoot 160 grains at 900 fps which is as powerful as a .38 Police Special.

With a hybrid, you can out-peform most handguns fairly easily.
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Unread postAuthor: Crna Legija » Tue May 18, 2010 3:43 am

what mix do you wanna use?
You could use epoxy as a plug but wouldn't it be ezyer to just thread on a cap.

alu should be fine to use as a barrel but its all depens on the thinkness
and yeah i ment use kichen foil as a burst disk most people use it and it worked lots better on my pneumatic burst disc gun
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Unread postAuthor: chinnerz » Tue May 18, 2010 4:08 am

-_- wrote: (1)what mix do you wanna use?


(2)You could use epoxy as a plug but wouldn't it be ezyer to just thread on a cap.

alu should be fine to use as a barrel but its all depens on the thinkness
and yeah i ment use kichen foil as a burst disk most people use it and it worked lots better on my pneumatic burst disc gun


(1) i was thinking of starting with a simple 1X and moving it up to maybe a 3X?? when i get to a computer i will have a play with HGDT and see what figures i get.

(2) yeah i could.... but for looks having a flush plug (epoxy plug) would be better :P :P
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Unread postAuthor: Crna Legija » Tue May 18, 2010 6:06 am

to test the burst pressure just mount a schrader valve and fill up with a shock pump. do it a few time to be sure
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