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Over pressurising a floor pump.

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Mitchza89 » Mon Jan 07, 2008 7:06 am

How the hell can you manage to get a 160psi pump that high? :| Man you must weigh a ton more then me....I'm 67kg and can only manage 150 tops with my pump :(
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Unread postAuthor: Hotwired » Mon Jan 07, 2008 7:12 am

Er... I weigh about 70kg.

I obviously have a superior pumping technique :blob2:
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Unread postAuthor: mopherman » Mon Jan 07, 2008 4:39 pm

jackssmirkingrevenge wrote:
shud_b_rite wrote:I over pressurized a 160psi floor pump once and it broke the check valve inside it and now it only acts as a pneumatic ram.


If the attachment doesn't physically open the schrader it can still be used,
until the dead space maxes out the pressure available. souldnt be a problem if you cut down the hos though.
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Unread postAuthor: DYI » Mon Jan 07, 2008 4:48 pm

I weigh 130 pounds, and I have no trouble pushing El Cheapo 160 psi pumps past their breaking point. It's all in the technique.

Bike pumps aren't really the way to go for larger high pressure guns. Bulk compressed gas supplies (like nitrogen, helium, SCUBA tanks etc...) are the cheapest way to go. You can get high quality 0-500 psi nitrogen regs for about $200, and tanks that weigh more than you do for about $70/year.
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Unread postAuthor: Hotwired » Mon Jan 07, 2008 5:03 pm

Personally I physically lean over my hands on the pump handle so it is justabout my whole weight on the ram. You'd kill yourself trying to pump using your arms only.

Bulk gas is the cheapest way...??

I think not. Probably the quietest, fastest and easiest way to get high pressure but it ain't scoring on price.

A custom floor pump is the cheapest one unless you find a mini tyre compressor that can actually do the 300psi it claims without turning itself into molten slag.
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Unread postAuthor: DYI » Mon Jan 07, 2008 6:26 pm

I meant something more along the lines of bulk gas being the cheapest way without going to a tremendous amount of work. Filling a cannon the size of the SCTBDC or bigger to 500 psi would be quite a bit of work with a homemade pump. Certainly possible, just not pleasant.

I used the wrong wording though: bulk gas is a better way, not a cheaper way.
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Unread postAuthor: potatoflinger » Mon Jan 07, 2008 6:35 pm

If you overpressurize a pump, the first thing to go will probably be the hose, at least it was the first thing to go on the ones that I broke. I guess the hose kind of acts like a failsafe.

Actually, you can get a SCUBA tank for 50 dollars or less, then fill it with a shock pump to around 400 PSI and you have a pretty cheap source of high pressure air*.

* I would call that high pressure air, but it is probably nowhere near what others might think of as high pressure air.
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Unread postAuthor: DYI » Mon Jan 07, 2008 7:01 pm

You could try a 3-4kpsi homemade manual pump and fill the SCUBA or equivalent tank with that. You'd get a high pressure air source, as well as a workout roughly similar to running a half marathon on your hands with your head underwater and carrying a 50 pound backpack, while breathing through a straw...

Or... you could just pay a few tens of dollars to have the tank filled.

And the first thing to go on all the hand pumps I have broken was the gauge, which usually fails completely and irreparably at 170 psi. Although I did bring one up to 200. It seems as though the gauge is the failsafe on those pumps.
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Unread postAuthor: cwazy1 » Mon Jan 07, 2008 8:07 pm

hey DIY, for the nitrogen tanks, its 70$/year just to rent the tank right?? how much is it to fill it once for you??
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Unread postAuthor: DYI » Mon Jan 07, 2008 8:31 pm

My tank (Type 16) is only $56/year, because it's one small enough to be carried. A full size (Type 50) tank weighs several hundred pounds, and costs about $100/year.

One "fill*" of my tank cost me $40, a little over 50 with added charges. Per unit volume, gas becomes cheaper as it is bought in larger quantities. For the volume of gas involved, I could do the same with a Type 50 tank for relatively less, but practicality reasons prevented this.

*the term fill is misleading, since my tank is not filled and sent back to me. I simply receive another full tank of the same type on its way back from the filling station. It can take more than half a year for a tank to cycle all the way through the system, since the main fill station is several hundred kilometres away
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Unread postAuthor: cwazy1 » Mon Jan 07, 2008 8:36 pm

ahh okay gottchaa
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Unread postAuthor: Ragnarok » Mon Jan 07, 2008 9:40 pm

DYI wrote:A full size (Type 50) tank weighs several hundred pounds, and costs about $100/year.

Use the savings to make a suit of power armour so you can move it!
That's still quite a bit of money to pay for gas. As a guess, that sounds of the order of $0.50 a fill to me (WAG at SCTBDC's chamber size, probably completely off)

I try to keep my cost per shot to a minimum, maybe £0.02 to £0.05 for a "plinking" shot*, for a rare-ish fancy shot - maybe 50 pence, and for a very special once or twice only shot (which I will film to refer back to) - I might pay a couple of quid.

*Actually I picked up around 8 or 9 lbs. of potatoes the other day for a measly 20 pence because they were about to exceed their shelf life. That's over 100 shots I reckon based on my bore (or I might just destroy some with paintballs, I haven't got much longer to fire them in before I'm at uni again) - they're sprouting a bit now, but that's hardly a problem if I'm firing them!

The thing is I spend so much on the cannons I then don't really have the cash to be very lavish on the ammo or targets.
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Unread postAuthor: DYI » Mon Jan 07, 2008 10:20 pm

Well, the the SCTBDC has 170ci of chamber, which, at 500 psi, is 3.46 cubic feet of gas. The tank stores 90.5 cubic feet of gas and costs $50 for a complete fill, which means that I spend 1.93CDA per shot for the SCTBDC. The ammo is usually composed mostly of ice or Pykrete, and is therefore free, as are my targets, which are recovered from the dump, and the backstop*, which a friend gave me. Of course, a day with all the daylight hours devoted to shooting, with no problems, would maybe see 10 shots, maximum, so the high cost per shot is balanced out to some extent by the low shots/unit time. Or at least that's how I rationalize it :roll:

*a steel dart that I shot a few months ago which I just recovered after the snow melted further reinforces my theory that the plate is a hardened alloy; the dart was bent 180 degrees with the point completely mashed, and the steel plate wasn't even damaged, not even a scratch.
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Unread postAuthor: dongfang » Tue Jan 08, 2008 9:14 am

Hi,

In my limited experience, the problem with overloading pumps is the compression heat rather than the pressure itself. I always had plastic parts melt and hoses pop off when taking a pump beyond specs.

(On my current floor pump, I replaced the check valve with an all-metal one and I have a metal pipe intercooler between that and the hose. Works ok).

How about using 2 pumps; first a bike pump for the first 8 bar and then a shock pump for the final 4 ;)

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Unread postAuthor: jackssmirkingrevenge » Tue Jan 08, 2008 9:29 am

I agree that bottles are convenient ways to fill but in many ways a pump is a good excuse for a decent workout, better than pumping iron pointlessly in a gym.
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