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how much pressure does your bike pump delive each 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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how much pressure does your bike pump delive each pump

Unread postAuthor: Darkside 6ix » Wed Jun 28, 2006 8:16 pm

well the title basicly explains everything. im saving up for a air compressor, so in the mean time i use a bike pump. i did a graph and it showed right from the start that it delivered 5 psi per pump. and about after 70 psi i find it terribly hard to pump. :oops:
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Unread postAuthor: frogy » Wed Jun 28, 2006 8:52 pm

It all matters with the chamber... With my pneumatic with a
4" of 1" it took about 4 pumps to 110psi
With my bigger pneumatic chamber (the stock) it takes more than 4 to get to 70psi...
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Unread postAuthor: carlbelcher » Wed Jun 28, 2006 8:57 pm

There’s not a set pressure that any pump delivers per pump. There are just too many variables. It all depends on the size of the pump the size of the chamber and even how much air is in the chamber.

There’s also not much you can do about how hard it is to pump. You have to think that your creating "pounds per square inch" that means if your pump is just 1/2" in diameter it’s going to take 78 pound of force to make 100psi.
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Unread postAuthor: Nereth » Mon Aug 07, 2006 2:49 am

bike pumps dont work that way... they just deliver a set volume of air at the pressure of their intake (usually STP). If you have a chamber the same volume as the pumps input, it will add 1 atm (14.696 psi) per pump.

If your chamber is twice the volume, it will add 14.696/2 = 7.348 PSI

If your chamber is half the volume, 14.696 X 2 = 58.7840 PSI per pump/

The reason it gets harder as you pump is that the pressure on the inside of the chamber is pushing back against the other side of the pump, so it fights you pushing air in.
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Unread postAuthor: carlbelcher » Mon Aug 07, 2006 3:14 am

bike pumps dont work that way...


Oh really?!

Because I thought that PSI meant Pounds Per Square Inch(it does). So if that is true (which it is) that means to create 100 PSI with a pump that has a 1" diameter piston is would take 157.5 pounds of force.

I calculate the area of a 1" piston I get 1.575 square inches so if I have 1.575 square inches and I want to make 100 pounds per square inch (PSI) it would take 157.5 pound of force.

The reason it gets harder as you pump is that the pressure on the inside of the chamber is pushing back against the other side of the pump, so it fights you pushing air in.


And know you know how to calculate how much force that air pressure in the has, based on the size of your pump.

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[Comments Removed] I'm sorry I misunderstood your post!
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Last edited by carlbelcher on Fri Aug 11, 2006 6:57 pm, edited 1 time in total.
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Unread postAuthor: FiveseveN » Mon Aug 07, 2006 12:31 pm

Nereth lives in a world without friction and leaks, and Carl is forgetting that the pump is connected to the chamber. So you're both right and wrong.

If you have a chamber the same volume as the pumps input, it will add 1 atm (14.696 psi) per pump.

True, in theory. But there are some losses. And from I've noticed, the bigger the pressure, the higher the losses. Plus, there's that point where you just don't have the strenght to add more volume (thus pressure).

to create 100 PSI with a pump that has a 1" diameter piston is would take 157.5 pounds of force.


Also true. But it doesn't contradict what Nereth said.
Best thing one could do is get a foot pump or some other pump with leverage.
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Unread postAuthor: carlbelcher » Mon Aug 07, 2006 9:56 pm

bike pumps dont work that way...


I believe that contradicts what I said in my post.
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Unread postAuthor: Nereth » Thu Aug 10, 2006 7:26 am

carl, seriously, i wasnt even talking to you, i was talking to the original poster, trying to explain why you cant say how much PSI a pump puts in. It doesnt put psi in. it puts air in. the amount of psi it puts in is dependant on the volume of waht its putting it into.

Infact your reply to me was really quite stupid, in your first quote of me, you point out that it takes 157.5 pounds of force for 100 psi, and then your second quote has me saying pretty much exactly the same thing, without the numbers. Not only that, but you failed to realise i was making exactly the same point as you in my post. One would assume your illiterate or something.

dont tell me i dont know what im writing about, unless you have the literacy level to read what im writing about.

oh and fiveseven, i know theres losses, but for the sake of this discussion, im ignoring them. What im trying to get across to the guy is just that that the pressure a bike pump delivers is dependant on chamber volume compared to the displacement of the bike pump. The leaks are too minimal for me to care about in the explanation.
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Unread postAuthor: carlbelcher » Thu Aug 10, 2006 8:48 pm

I explained how the calculation works because it appeared to me that you were contradicting what I had said. In fact my entire post was based on the fact that you were contradicting what I had said. Here's a hint since you're a noob, if your talking to the poster above me then you should make it clear by quoting him/her.

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Unread postAuthor: Nereth » Fri Aug 11, 2006 4:09 am

carl, when you misread something, say something stupid to someone, and then get told you said something stupid, cant you just suck it up like a man?

Your entire argument just then was based on me being a 'noob' and me being inexperienced on the use of forums. In other words, you had no actual argument against me. I dont think my ability to use a forum has particular relevance to my knowledge of basic physics. Maybey your just nettled because a "noob" got you worked up when your a long time member.

I dont know what the mods are like on this forum, but theres a good chance they wont be liking us going this far off topic. Why dont you get over it?
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Unread postAuthor: SuperSonic » Fri Aug 11, 2006 6:24 am

I'm going to evacuate my pressure chamber with a vaccum pump then insert my wang in the barrel and pull the trigger, because I am in serious need of a blowjob. 19 y/o sister not putting. I have a pretty fucked up life.
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Unread postAuthor: carlbelcher » Fri Aug 11, 2006 6:43 pm

I don't know what your problems are! I'm glad you feel better attacking me, and not contributing to this forum.

Nereth, I don't know what I did to piss you off, but give it a break. Yes I misunderstood your post... big freakin deal, I didn't go off calling you illiterate! I just explained my post!

SuperSonic, I hope you get banned!
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Unread postAuthor: BC Pneumatics » Fri Aug 11, 2006 7:32 pm

Props to FiveseveN for being the only one here not acting like an idiot.

Everyone else, seriously, grow up.
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Unread postAuthor: Velocity » Fri Aug 11, 2006 8:12 pm

supersonic is a dumbass though

back on topic anyway...

I can get 180 PSI in 1 pump on my tiny tiny tiny tiny thing (its not really a cannon, rather a cannon accessory...)

On my big cannon, however, it takes 150 pumps to get it to a measly 20 PSI :? . Thank god for air compressors!


EDIT: whoa, I though the poster of this topic was benstern, because they have the same icon thing!
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Last edited by Velocity on Fri Aug 11, 2006 10:26 pm, edited 1 time in total.
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Unread postAuthor: MrCrowley » Fri Aug 11, 2006 9:47 pm

what about 12v air compressors? would it take long to fill a 4" chamber 30" long?i know someone with a proper air compressor but i dont want to keep bugging him every time i need it.
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