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PostPosted: Wed Nov 06, 2013 2:05 pm 
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Sorry I have to bother you, but I'm only just considering getting into airguns.

-No scuba shops around
-Don't have 800$+ for a shoebox compressor
-I weigh 118 pounds so 3000+ PSI with a hand-pump without assistance is out of the question

Is there any reason I can't take an HPA hand-pump and rig it up to a bicycle-powered crank?
Could I fill a 40+ Cubic Inch (paintball sized) tank or larger in any reasonable time?

I read 15 minute cooldown for 5 minute hand-pump session... what then? I pedal at 5x hand-pump-speed for 1 minute then 15 minute cooldowns?

What kind of unobtainium are the 14,000$ HPA compressors made of then that they don't overheat?

I've read around and people have tried refilling paintball HPA tanks by hand... taking about 40 minutes by hand-pumping.


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PostPosted: Wed Nov 06, 2013 2:14 pm 
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That gets me thinking too. I don't weigh much more than you at still under 130lbs on a good day (actually I like to keep my weight low). Thinking of getting a PCP next year as well.

I think one of the members here posted a picture of the pump handle attached to some kind of lever arm/cheater bar, that's probably much simpler to rig than any kind of rotary crank.

Worst case, you can strap 30lbs of weight to your waist and build some muscle that way in the process, or put 30lbs of chocolate and ice cream and steak and beer in your stomach :)

For cooling, I don't have any personal experience but I wonder if putting some cooling fins and an active fan on the pump cylinder might be helpful.

edit: it was joe hickey in this thread with the cheater bar - and a little extra, but if weight is your only concern then I think you could get by with just the extra leverage.


Last edited by gctkaz on Wed Nov 06, 2013 3:07 pm, edited 1 time in total.

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PostPosted: Wed Nov 06, 2013 2:22 pm 
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Seriously though, how do the HPA pumps that cost more than a car not overheat?

You should think you could buy just the pump and build the rest yourself.

Liquid cooling? Like those old water-cooled machine guns with a water tank around the barrel.

Could you get enough torque from a bike-gear ratios such that you could rig up a cheap electric motor (IE 120v box fan) for a sufficiently slow pumping such that it won't overheat?

I wouldn't mind either 5 minutes of pedal-pumping if it was large (paintball tank) volume uninterrupted (but can I add cooling systems that efficient?)
OR
I wouldn't mind hours of wall-outlet powered pumping if I didn't have to worry about it ever breaking (but can I rig it up from cheap fan motors and scrap bike parts?)


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PostPosted: Wed Nov 06, 2013 2:42 pm 
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Which pcp rifle were you thinking of getting and why. I have a detuned XSB50 that is very pump friendly so I rarely have to pump more than 40 times to fill it to less than 1500psi. I believe Discos don't need 3000psi to shoot. Hand pumps over heating comes down to people not using them properly. Good posture is the key to easy pumping and not being in a hurry helps.
Due to the nature of high pressure air, home made pumps and mods sounds dangerous for anyone who isn't trained to work on such equipment.

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PostPosted: Wed Nov 06, 2013 3:04 pm 
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Quote:
Which pcp rifle were you thinking of getting and why.

Actually I was thinking less one-specific-HPA-pellet-gun and more everything-that-uses-HPA. Hence I'm more interested in filling a small paintball tank rather than just a single PCP. If I could have an HPA pump that's affordable and uses no or minimal effort... Whole floodgate of the very best of airguns open.
Airsoft, paintball, pellet guns, you name it.

Still looking at pellet gun reviews and I'm more or less decided on upgrading my Airsoft to HPA rigs assuming I could build a decent HPA source that's not an hour long workout.

Reason I posted here is because these hand-pumps are generally PCP pellet gun specific.

Quote:
Hand pumps over heating comes down to people not using them properly. Good posture is the key to easy pumping and not being in a hurry helps. Due to the nature of high pressure air, home made pumps and mods sounds dangerous for anyone who isn't trained to work on such equipment.

I don't plan on mucking around with the pump itself. Just a crank to pump the pump. Adaptors, regulators, etc I'm not dumb enough to modify.

I'm starting to think I should be less focused on a 5-minute stationary bike ride, and more on building a gear train for cheap electric motors? If it's pumping slow, it can pump constantly for hours without overheating? The scrap bikes and motors I literally have laying around. I just don't want to ruin a 200$ hand pump, or waste the investment in one.


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PostPosted: Wed Nov 06, 2013 4:58 pm 
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Some folks have had great success with replacing the human bits.
http://www.youtube.com/watch?v=Q2laNybPzDI


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PostPosted: Wed Nov 06, 2013 6:12 pm 
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blarg wrote:
Some folks have had great success with replacing the human bits.
http://www.youtube.com/watch?v=Q2laNybPzDI

That is a great idea, and well made it seem,s. I wonder if putting a hose on the desiccant filter and then submerging the pump foot in coolant would allow it to run long enough to fill a scuba tank without getting even warm.

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PostPosted: Wed Nov 06, 2013 9:05 pm 
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Another latest trick to help hand pumps is to pressurize the intake with a compressor set at about 20 or 30 psi. I have seen a video on that and heard of others doing it and it works, makes for easier pumping and less pumps required.

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PostPosted: Wed Nov 06, 2013 10:07 pm 
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GarthThomas wrote:
Another latest trick to help hand pumps is to pressurize the intake with a compressor set at about 20 or 30 psi. I have seen a video on that and heard of others doing it and it works, makes for easier pumping and less pumps required.


Hmm, that sounds feasible! Already have a filter on my shop compressor.

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PostPosted: Wed Nov 06, 2013 11:55 pm 
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joe hickey wrote:
blarg wrote:
Some folks have had great success with replacing the human bits.
http://www.youtube.com/watch?v=Q2laNybPzDI

That is a great idea, and well made it seem,s. I wonder if putting a hose on the desiccant filter and then submerging the pump foot in coolant would allow it to run long enough to fill a scuba tank without getting even warm.


very cool idea but please pay close attention to what the guy says about the lubing of the pump, at around 14:30 in the video. :shock: i know most of you know but just in case.

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PostPosted: Thu Nov 07, 2013 2:45 am 
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Ace wrote:
joe hickey wrote:
blarg wrote:
Some folks have had great success with replacing the human bits.
http://www.youtube.com/watch?v=Q2laNybPzDI

That is a great idea, and well made it seem,s. I wonder if putting a hose on the desiccant filter and then submerging the pump foot in coolant would allow it to run long enough to fill a scuba tank without getting even warm.


very cool idea but please pay close attention to what the guy says about the lubing of the pump, at around 14:30 in the video. :shock: i know most of you know but just in case.[/quote
External lubrication or coolant is not a factor. The heat comes from 2 layers inside where the final stage compression takes place.

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PostPosted: Thu Nov 07, 2013 9:35 am 
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I would question whether biasing input pressures is worth doing by hand.
Regardless of input pressure, your pump still requires weight to compress and the differential is small in comparison to the output.
That is, it will take more effort to compress 14+20 then 14 alone. It may take less time, but will require more effort using a body.
Pumping to 1500 makes a lot less heat then the higher differentials do.


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PostPosted: Thu Nov 07, 2013 10:18 am 
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sorry Joe wasn't talking about that part of your quote guess i should have removed that section.
just the (great idea part) and it is a cool idea just be very careful is all i was trying to get at even with a regular hand pump with out the pumping aid just don't use combustible lubricant's, just putting the word out there. :wink:

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PostPosted: Thu Nov 07, 2013 11:37 am 
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When you add air to the inlet side, the pressure in the first and possibly the second stages of the pump increases for the first part of the stroke, but in the third stage, which can never exceed gun pressure, all that happens is that the high pressure part of the stroke (while the check valve in the gun is open) gets LONGER because you are adding air to the gun for more of the stroke.... Basically, the resistance you feel at the bottom of the stroke is over a longer distance when you pressurize the inlet.... More heat is produced, of course, because you are compressing more air per stroke.... but the maximum FORCE doesn't increase, just the TIME you have to apply that force.... and hence you have to input more horespower (peoplepower) per stroke....

Bob

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PostPosted: Thu Nov 07, 2013 5:00 pm 
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blarg wrote:
I would question whether biasing input pressures is worth doing by hand.
Regardless of input pressure, your pump still requires weight to compress and the differential is small in comparison to the output.
That is, it will take more effort to compress 14+20 then 14 alone. It may take less time, but will require more effort using a body.
Pumping to 1500 makes a lot less heat then the higher differentials do.

I have my shop compressor hooked up to mine and set to 75 lb,s. Even with my lever assist it is still hard to push down. By hand would be nearly impossible at 75 lb input. Even 25 lb input would speed up filling.

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