Foot Pump for PCP?

[Noah]

One of the major reasons for not even thinking about going into the PCP world is the hassle of manual pumping unless you spend a lot on compressors and such. Although I haven't looked, is there such a thing as a pump that can be used with the ease of your feet rather than arms and upper body? For me, that could be a game changer. 

[CraigH]

Standard HPA pumps have about 17.5 inches of travel.    There have been airgunners that have motorized single and double pump arrangements.    Perhaps stirrups could be designed over the handles to use with leg power.

It seems a simple short travel foot pumps with HPA capability would require a gigantic number of pumps to get even a small volumn filled.

[Noah]

Standard HPA pumps have about 17.5 inches of travel.    There have been airgunners that have motorized single and double pump arrangements.    Perhaps stirrups could be designed over the handles to use with leg power.

It seems a simple short travel foot pumps with HPA capability would require a gigantic number of pumps to get even a small volumn filled.

Thanks, Craig. 

I am no engineer, but there has to be some kind of tweak that can be made to the design of an air pump to allow it to be powered by our feet opposed to arms and upper body. 

[DHunter]

I saw a video somewhere of an arrangement where a motor had a belt-drive system to drive hand pumps, where the pulley on the motor was very small compared to the pulley on the pumps, in order to get the lower speed and higher force required by the pumps.  There might have even been a double reduction, so the motor could spin at a couple thousand RPM or more while the pumps would work at manual speed so as not to get them too hot.  A similar thing could be done with bicycle pedals and a reduction driving a hand PCP pump, although it would probably be more practical to use a bike chain and related parts, since they're readily available (instead of using a belt and pulleys).  I would use the smallest granny chainring available for the crankset which might be about 20 teeth, and the largest chainring available which might be 55 teeth connected to the wheel that drives the pump.  Attached is the idea.  I don't see any way to inline it, and the picture doesn't even show up in the preview.  I'm not sure you'd save any pumping time though.  The pumping speed is limited not by how fast a human can pump, but by the pump's ability to get rid of the heat so you don't destroy O-rings.  If the whole system were 25% efficient, and I were pumping up an airgun that could do 16 shots at 50 foot-pounds each, that's 800 foot-pounds, which divided by 25% efficiency means I'd have to put 3200 foot-pounds of energy into it.  A horsepower is 550 foot-pounds per second, or 745 watts.  I as an avid, strong cyclist could do that much in five seconds of all-out sprinting (at 900 watts output).  Top pro sprinters could do it in about two seconds (at 2000 watts output).

[arkmaker †]

That just might work. 👍
I do like the motorized versions that all you need to do is flip a switch better. Me...lazy.


That said- I paid 250 for my compressor on flea bay. Works fine so far. Only hassle is needing to use a water pump for cooling. There is a newer version by air venturi that does not need water. Cost is doubled.

[Noah]

That said- I paid 250 for my compressor on flea bay. Works fine so far. Only hassle is needing to use a water pump for cooling. There is a newer version by air venturi that does not need water. Cost is doubled.

Thanks Rich (and. DHunter). I will keep an eye out. 

[CraigH]

Look for videos like this:

https://youtu.be/q_22dphYB_k

[KevinP]

That's a nice setup. I don't see and auto shut off however.
What happens if you walk away for some reason and
forget that it's running ?

[CraigH]

I've seen a number of these motorized hand pumps in videos.   I don't think it's a good idea to let them run, for say, more than 50 strokes at a time (maybe less) before letting them cool.    I also think they run a bit too fast for the hand pump.

Point being, the mechanism would then be in cool down much more than pumping.

OTOH, if left to run rather longer, they will probably overheat the o-rings and fail.   Hopefully before over pressurizing the tube or small tank.     

[BillK]

The nearest & best fill station is 20 Min. away and costs $12. (dive shop)  Sure is easy & there is a McDonalds across the street for coffee while waiting.  Just a thought.....

[DHunter]

There's this site http://www.airfillstations.com/ , but it's not giving any information now.  I've been checking for the last week or two, but there's nothing.  It just says, "This site hacked and it has to be rebuilt.  This is going to take me a week or two.  Sorry for the inconvenience.  When the site is rebuilt it will be better than ever with much faster searching."  I wonder how long it has been saying that.

[CraigH]

The nearest & best fill station is 20 Min. away and costs $12. (dive shop)  Sure is easy & there is a McDonalds across the street for coffee while waiting.  Just a thought.....

If a tank is affordable and the logistics are good, this is the best solution.   Guaranteed clean, dry air.

[DHunter]

If a tank is affordable and the logistics are good, this is the best solution.   Guaranteed clean, dry air.

Can anyone tell of problems they've had that were caused by water condensation in the compressed air, or can you give links?  I've seen a lot of water come out of the gas-station air hoses you use to put air in car tires when the water wasn't bled out of the bottom of the compressor tank regularly; but I don't know what the implications are for airguns.  Obviously when we pump something like the Crosman 1377 or 1322, there's no air dryer in the system.

For running your own compressor, one idea I've had is to run the air through tubing submerged in ice, and make sure the output has to go uphill so the condensed water doesn't get into the gun.  It would be most effective on the high-pressure side, but that raises a couple of challenges you wouldn't have on the low-pressure side.  The ice bath may be a bit inconvenient, but maybe not nearly as inconvenient as having to go to a far-away dive shop or even a fire station.  Everyone has a freezer.

[BillK]

If a tank is affordable and the logistics are good, this is the best solution.   Guaranteed clean, dry air.

Look for a Dive Shop in your area.  They fill divers tanks and are usually inexpensive.  A good place to go as they have experience with HPA & fittings needed to fill your tank.

[DHunter]

Here's another cool mechanism: