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Compressing air upto 300 psi with bicycle pump.

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Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: Steverulez » Mon Mar 06, 2017 4:15 am

Hi guys. Recently I planned to build a full auto bb gun (uses 4.5mm steel balls) operating at 300 psi. Air flow is regulated by a solenoid valve which is controlled by arduino.
Here's the question, I've decided to make the air chamber out of a 2" galvanised steel pipe which is 90cm long ( about 1.6 Litre capacity)
To check whether I could pump 300 psi, I directly connected a pressure gauge to my bike pump and I actually did it atleast till 260psi. I'll build a new pump with lesser cross section area to get more psi. Then I remembered that when I went down to pump air in my car tyres, it was really really hard . Car tyres operate at about 40 to 50 psi right ?
So why did this happen. Does the the tanks volume effect the force we need to apply to build pressure or its the pressure alone which decides it. Did I check my pumps pressure output capacity the wrong way ?
Thanks
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: Ragnarok » Mon Mar 06, 2017 11:14 am

Steverulez wrote:Does the the tanks volume effect the force we need to apply to build pressure or its the pressure alone which decides it.

Force = Pressure x Area. The volume doesn't enter into the amount of force required, but it will affect the amount of work required.

Something like my own HEAL is a pretty big launcher in terms of being hand-pumped to 20-25 bar (290-360 psi), using a custom built track/stirrup pump, and that's only a 600 cc chamber, so I wouldn't particularly recommend hand pumping a 1600 cc chamber with a standard single-stage pump design.

In that kind of case, I'd say you may need to look at a multi-stage pump design if you don't want to be spending 20 minutes pumping it up each time.
I'm working on a possible 3 stage* pump design to use for high-pressure/high-volume applications, but like all of my projects, I'm not sure exactly when I'll get around to that.

* Stage 1 would be about 600 cc, using the upstroke to pre-charge a large diameter second stage to about 1 bar (15 psi). Stage 2 would be about 300 cc, using the first part of the downstroke to pre-charge a small diameter final stage to about 10-15 bar (150-220 psi). Stage 3 would be on the final part of the downstroke, with a limit of about 60 bar (~870 psi).
If I can make it work, 600 cc per stroke at up to 60 bar is pretty good going for a manual pump.
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: Steverulez » Tue Mar 07, 2017 3:15 am

Ragnarok wrote:
Steverulez wrote:Does the the tanks volume effect the force we need to apply to build pressure or its the pressure alone which decides it.

Force = Pressure x Area. The volume doesn't enter into the amount of force required, but it will affect the amount of work required.

Something like my own HEAL is a pretty big launcher in terms of being hand-pumped to 20-25 bar (290-360 psi), using a custom built track/stirrup pump, and that's only a 600 cc chamber, so I wouldn't particularly recommend hand pumping a 1600 cc chamber with a standard single-stage pump design.

In that kind of case, I'd say you may need to look at a multi-stage pump design if you don't want to be spending 20 minutes pumping it up each time.
I'm working on a possible 3 stage* pump design to use for high-pressure/high-volume applications, but like all of my projects, I'm not sure exactly when I'll get around to that.

* Stage 1 would be about 600 cc, using the upstroke to pre-charge a large diameter second stage to about 1 bar (15 psi). Stage 2 would be about 300 cc, using the first part of the downstroke to pre-charge a small diameter final stage to about 10-15 bar (150-220 psi). Stage 3 would be on the final part of the downstroke, with a limit of about 60 bar (~870 psi).
If I can make it work, 600 cc per stroke at up to 60 bar is pretty good going for a manual pump.


Well, my pump's cylinder is about 286cc. Is it enough to pump 1600cc at 20 bars withing 5 minutes ? (Sorry if I quoted incorrectly, I'm new to spud files )
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: mark.f » Tue Mar 07, 2017 3:56 am

I would jump straight to using a refrigerant compressor, speaking as somebody who's built a track pump before. :D
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: jackssmirkingrevenge » Tue Mar 07, 2017 7:28 am

mark.f wrote:I would jump straight to using a refrigerant compressor, speaking as somebody who's built a track pump before. :D


Hear hear, thought if you want to do some cardio it's a good practical application. You could avoid the strike of building one by sending a generous donation of less than 100 bucks to a team of highly skilled Asian infants who will build you one from the finest Chinesium that can go to 4500 psi.
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: Ragnarok » Tue Mar 07, 2017 2:21 pm

Steverulez wrote:Well, my pump's cylinder is about 286cc. Is it enough to pump 1600cc at 20 bars withing 5 minutes?

Unlikely. You'd have to average more than 20 strokes a minute*, and that's just not practical, particularly when trying to hit those pressures with a single stage quite that large.

* @ Jack - No. Just no.

mark.f wrote:I would jump straight to using a refrigerant compressor, speaking as somebody who's built a track pump before. :D

A major limitation there is that not all launching sites have mains power.
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: jackssmirkingrevenge » Tue Mar 07, 2017 10:26 pm

Ragnarok wrote:Unlikely. You'd have to average more than 20 strokes a minute*, and that's just not practical, particularly when trying to hit those pressures with a single stage quite that large.


The figure I heard officially quoted was 15 per second :D
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Re: Compressing air upto 300 psi with bicycle pump.

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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: jrrdw » Wed Mar 08, 2017 7:22 am

The figure I heard officially quoted was 15 per second :D


Where do you find these things... :twisted:
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: Ragnarok » Wed Mar 08, 2017 10:06 am

jackssmirkingrevenge wrote:The figure I heard officially quoted was 15 per second :D

I see that, despite the forum being quieter than before, the pyrotechnic pink pachyderm remains. :roll:
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: jackssmirkingrevenge » Thu Mar 09, 2017 10:21 am

jrrdw wrote:Where do you find these things... :twisted:


The more pertinent question is how to I manage to remember them and look them up where "appropriate" ;)

the pyrotechnic pink pachyderm


Still rampaging through the forum with flames pouring out of it :D
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: jrrdw » Thu Mar 09, 2017 4:59 pm

jackssmirkingrevenge wrote:Still rampaging through the forum with flames pouring out of it :D


L0L.... FIRE IN THE HOLE! :bom:
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: jackssmirkingrevenge » Thu Mar 09, 2017 6:05 pm

I don't think mentioning burning holes is going to do much to assuage matters :D
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: encohen » Thu Mar 16, 2017 2:13 pm

I'm a bit off topic here, but i'm thinking about buying a PCP hand pump for my homemade big bore. but i'm currently using a schrader valve in my air gun, and i guess a PCP pump won't fit.
air rifles are not sold in my country so i have no idea what kind of valve i need to get, and will I be able to connect it to a 1\2 Tee?

Will a quick-disconnect male fitting + a reducer 1/2" to 1/8" BSP will do the trick?
are most pcp hand pump will work with that?
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: jackssmirkingrevenge » Fri Mar 17, 2017 10:45 am

For something like this you will need this nipple, to my knowledge they are identical to the typical QD fitting that is used in paintball bottles and markers. Make sure you get one with a check valve!
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Re: Compressing air upto 300 psi with bicycle pump.

Unread postAuthor: encohen » Fri Mar 17, 2017 4:52 pm

jackssmirkingrevenge, you're my guru!
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