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self-contained hybrid pistol concept

A place to ask general spud cannon related questions.
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Unread postAuthor: nature-boy » Fri Feb 25, 2011 6:31 pm

The problem with your solution is that the dual piston mixing relies on the fuel being at atmospheric pressure, but it's stored at higher pressure in the reservoir.

Yeah, I thought of that issue (pressure in the fuel-reservoir aka lighter), but I don't understand why this would only be a problem in my idea.
Or would you let the fuel slowly drain out of the small pump-shaft (where I would have added a seal), to keep the fuel-pressure (before the compressing) in the pump cylinder at atmospheric? Sorry I'm a bit lost... :?


Edit:
but there is nothing to block the flow of fuel to the chamber...
When you start compressing the fuel in the pump-cylinder, the pressure there would be higher as the pressure in the fuel reservoir, and the check-valve would stop the flow.
Or did I misunderstand you?
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Unread postAuthor: POLAND_SPUD » Fri Feb 25, 2011 6:48 pm

I'd rather have *click-click* bang as opposed to *click-click-click-click-click-click-click-click* bang
I don't think there is any other way than *click click click click click*
any gun with a one stroke pump would offer pathetic performance

besides IIRC you've got a regulated HPA setup :wink:


When you start compressing the fuel in the pump-cylinder, the pressure there would be higher as the pressure in the fuel reservoir, and the check-valve would stop the flow.
Or did I misunderstand you?
yeah, I know but there is nothing to stop the flow from the pump to the chamber...

of course most spring loaded check valves act as regulators at the same time... unfortunately, the OD of the part exposed to pressure is so small it won't be a very accurate reg... so there are two options here:

1. either get a proper reg and feed the pump with it or you might as well go for fully manometric metering

or

2. let the fuel purge the chamber
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Last edited by POLAND_SPUD on Fri Feb 25, 2011 7:07 pm, edited 1 time in total.
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Unread postAuthor: mark.f » Fri Feb 25, 2011 6:59 pm

jackssmirkingrevenge wrote:Do we get to see your pump action in progress?


When it's built. So far all I have is a well thought out and organized list of materials and a diagram. Just no money... :P
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Unread postAuthor: Fnord » Sat Feb 26, 2011 10:55 am

It would have been nice if you labeled the diagram...

But anyway, although this is plausible your main problem will be servicebility; you'll need to make sure you keep everything completely removable. It has a lot of small moving parts so you'll be maintaining and evolving it constantly until you get it right, much like the modern IC engine.

Now personally, what I would do is make a short 'rifle' design and have a single stroke pump running the length of the barrel. With a 20mm x 500mm copper pump and a single stroke to power it, you could expect perhaps 100 J energy per shot with an efficient design. You won't need to vent the chamber if you run it at a high mix, but beware of dieseling effects.
You might want to look at that... thing... I sent you a diagram of a few months ago. Basically a manual version of that is what I'm suggesting.


Remember, there is about 4000J per liter of prop/air mix, and 20% efficiency is the maximum most practical designs can achieve.
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Unread postAuthor: jackssmirkingrevenge » Sat Feb 26, 2011 1:11 pm

Fnord wrote:It would have been nice if you labeled the diagram...


I figured it was self explanatory ;)

But anyway, although this is plausible your main problem will be servicebility; you'll need to make sure you keep everything completely removable. It has a lot of small moving parts so you'll be maintaining and evolving it constantly until you get it right, much like the modern IC engine.


The point of this was really to show the ":idea:! you know what you could build next!" part of my brain that while it sounds great, it would be far too complex an undertaking and push me back down the cartridge route.

In that regard, I've made yet another prototype for 3/8" bearings with a friction breech, made out of *gasp* PVC! Should be a blast, not literally I hope :D
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Unread postAuthor: POLAND_SPUD » Sat Feb 26, 2011 1:34 pm

The point of this was really to show the "Idea! you know what you could build next!" part of my brain that while it sounds great, it would be far too complex an undertaking and push me back down the cartridge route.
I find it really surprising... dude you're the guy building the most over complicated launchers ever

Is some russian girl taking all of your free time ?? :wink:
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Unread postAuthor: jackssmirkingrevenge » Sat Feb 26, 2011 1:46 pm

POLAND_SPUD wrote:dude you're the guy building the most over complicated launchers ever


Please tell me you're being sarcastic, I strive for the oppposite!

Is some russian girl taking all of your free time


Not anymore, decided (yet again :roll:) that I'm better of alone :D
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Unread postAuthor: POLAND_SPUD » Sat Feb 26, 2011 2:19 pm

uhmm no, actually I am not... sure some of your recent launchers are pretty much as simple as it gets... but I still remember all of your fullauto valve guns


Not anymore
ohh sry... anyway let us not forget that:

linky
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