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A fuel meter problem - thoughts hugely welcome.

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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A fuel meter problem - thoughts hugely welcome.

Unread postAuthor: SPG » Sat Apr 25, 2009 5:24 am

Years of reading, thinking, doodling, mean I'm now 90% there on a BB Repeating Hybrid, but there's one thing that's got me stumped, and that's fuel metering.

The ideal would be to have seperate fuel and air tanks, with the fuel going into the chamber during the trigger pull. But here I'm stumped. I thought about ballvalves, or spoolvalves as a meter but there's the problem that there'll be a tiny bit of air in the meter to take into account of and it's this air that is puzzling me. Obviously because we're talking about tiny volumes and high mixes fueling's got to be perfect.

I also wondered about syringe metering, but then there's the problem of filling and emptying all in one movement.

So can anyone think of a way to do this, or do I have to resort to a tank of pre-mixed fuel/air and the resultant risk I might go up in a big ball of flame?
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Unread postAuthor: jrrdw » Sat Apr 25, 2009 5:51 am

Purge valves on you valves/meters. Just purge the air before you start shooting. Do a few small shoots first to be sure it's working right and your on your way.
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Unread postAuthor: SPG » Sat Apr 25, 2009 6:55 am

So you're suggesting I vent propane to air? I did think that but somehow on something that might end up a few inches from my face I didn't really fancy sitting in a cloud of propane - I like to smoke while I shoot.
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Unread postAuthor: inonickname » Sat Apr 25, 2009 7:07 am

You could consider the tippman c3:

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If that doesn't help let me know

Edit: Sorry, missed the hybrid part. I'll give it some thought and get back to you.
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Unread postAuthor: THUNDERLORD » Sat Apr 25, 2009 9:14 am

IDK what design it's for,
But if your ignition and trigger is pressure controlled, You could have two small ball valve type flow regulators an air or oxygen hose into one "Y" and propane/fuel into other.
The "Y" fitting ( EDIT:or "T" :oops: ) would go into blow nozzle, co2 tyre filler or pressure washer handle etc. for the trigger.
The JSR type blow forward bolt could be fitted with a contact (switch) on the front of the loader tube's piston.
With just the right spring (or spring adjustment), when proper pressure is reached (just before the loader tube moves off the blocker pin),
the switch closes and the the spark ignition is on...Blammo!

If you added a gas piston w/rod (maybe a "T") near the end of muzzle, when the projectile has nearly exited the barrel, the rod presses a check valve (or lever to one), venting the exhaust (inert spent gas).
Then it could go...Blammo, blammo, Blammo Blammo, blammo, Blammo,Blammo, blammo, Blammo,...etc.
Otherwise it might be like a car with a spud in the tailpipe!

For electric button trigger control (faster triggering than pressure controlled),
The switch on the blow forward bolt could be series with the trigger switch (trigger button). And a safety switch (safety)
The two tanks (oxydizer and fuel) could be contained in seperate personnally constructed (modified/homemade) tanks each loaded to proper mix pressure, with constant flow into the firing chamber.
It would fire with safety switch closed and push button trigger.

Now I am wondering though with constant flow of say propane, when the fill tank becomes low, if the correct oxygen level enters the hose (back pressure, maybe (bad)boom...Guess it needs a check valve(?)...

That's my thoughts on hybrid semi/full auto...hope it might be helpful.
IMO pre-mix is too dangerous. Also the heat from rapid fire might weaken the pipe so...stronger pipe than pressure rating(?) :wink: :) 8)

BTW, for small diameter, rather than a blow forward bolt, perhaps the trigger could pull the magazine or loader tube back (mechanically dropping shot and blocking mag opening), then press the trigger button (one switch to ignition) That would be semi-auto unless a solenoid or gear was attached though. :)

EDIT: I hadn't really read all the info as thoroughly as I thought... :oops:
I am wondering, for a mini hybrid, with a constant spark gap going and if 8 gram n2o cart (pressure controlled) trigger was used at some point you'd be bound to get the right mix ( for blammo... :P )???
EDIT2:BTW Just dreamed up a pressure switch between two propane reservoirs and solenoid valve, small flow regulator between them for more capacity.
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Unread postAuthor: sputnick » Sat Apr 25, 2009 11:56 am

Well, from what I can understand, I would say go with a premixed tank, maybe just keep it on the smallish side if at all possible, it is after-all a BB repeater. Maybe multiple precharged tanks that are easily switched out for one another could also be a possibility
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Unread postAuthor: SPG » Sat Apr 25, 2009 12:07 pm

It does sound a hell of a lot easier doesn't it? As the layout would be to have it in the foregrip logically if I put a burst disc on the barrel end of the tank, then in the event of a "bang" it'll just go down range, where no-one wants to be standing anyway.
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Unread postAuthor: sputnick » Sat Apr 25, 2009 12:30 pm

There you go, a burst disc is a great idea,

What hybrid mix are you going to be using? because you do not want to have a larda hybrid tank under your gun.

I think a premixed tank could be the best option, especially if you have as you suggested, a pop off (after all, that is REALLY what they are for, people seem to forget they are a safety feature, not a full auto triggering system :D ) or a burst disc.
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Unread postAuthor: THUNDERLORD » Sun May 03, 2009 4:26 pm

I realized my stupid error on last reply after posting and haven't been online since... :oops:

For some reason I was thinking of the flow regulators on welding torches, not thinking they vent into air rather than a chamber.

Not so useful for a mini, but your fuel line would need a pressure reg. and the oxydiser would have a flow regulator (small ball valve type) set for lower pressure. (The error in the explaination of pressure controlled action I explained last reply).

I've had a few thoughts on fueling without pre-mix, but still working on the design mostly.

Maybe something like a hammer valve with one valve for fuel and other for oxydizer.
It would take a lot of fiddling though for proper mix, but maybe a solenoid or other electro-magnet design like an alarm bell device could work.

If a premix is used, perhaps there is a way to use a pre-chamber with volume or pressure only maybe twice that of firing chamber....
Been thinking of a cylinder design with two ports and the fuel pressure presses a piston far enough to expose the air/ oxydizer port into chamber.(?) (one way valves on ports).

Too much physical labor last week though and my brain is still burnt to perfect my thoughts for now. :(

Still wondering about constant butane flow and n2o through tyre filler mix with constant spark or pressure switch? (good for mini/micro?):roll: 8)
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