Air Compressor as First Stage for Hand Pump

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J

jpbrewer

Member
May 27, 2015
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Georgia, United States
Ok, don't have the funds yet for a shoebox, but 140 pumps between fills on my Benji hand pump for my FX Wildcat seriously cramps my style trying to shoot tight groups.

So I had an idea... Could I use a regular shop compressor as the first stage to a hand pump much like the shoebox compressor uses a shop compressor as the first stage of its process? 

After a little research, I found this video… 


Before you call BS, I went to Lowe's today and spent $20 on a set of parts to connect my hand pump to a shop air compressor. It turns out on the Benjamin pump there is a little air inlet on the same side as the hose that you can unscrew. It is a one quarter inch connection. Same with Hill and others I think. Just like he showed in video.

The results: if I supply 30 PSI of pressure to the first stage of the pump, I can fill my wildcat from 140 bar to 230 bar in 25 pumps. Yes the pumps are a bit more strenuous, but not terribly so. The pump handle rises as you apply the air pressure just like in the video. It does not rise on subsequent compressions and you actually have to work just a bit to pull it up.

I have no idea what the long-term implications are for the longevity of the pump, all I know is that it is much better to do 25 pumps instead of 140. Anyone else tried this? 
 
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WTF!!!!!! Yeah, thats a hell of a mod. I have OBA (On Board Air) on my truck. 200PSI to be exact. I wonder if there is any math on this or gains depending on the PSI. 


so he said it was regulated air input of 50psi, he went form 0-2000 psi in 13 pumps. So thats about 154psi in per pump. My attention is officially peaked. 
 
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this got me interested too. I wonder why start at a lower psi why not the full shop pressure of 125psi...hell you'll be done in like 5 pumps! I'm gonna have to try this out. But my shop compressor is a oil piston pump, it would be best to use a oil less pump so you don't get dieseling in your gun and blow up the air tank. Also make sure to connect various filters to keep the air as dry/clean as possible.
 
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"jpbrewer"Actually he went from 1000 to 2000 with 13 pumps, but that still beats 60.

Over that range you could go 50 psi. On mine, I am going from 2000ish to 3335psi. I could only physically press down at 30 psi. 50 was difficult. I am 240 and 6-0.
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See, I thought the same. He started by saying it was at 1000. then when he hooked it up and looked at the gauge again. He says 'it's empty' - also says it is 200 psi per pump. Really the math would be if it was 1k psi starting. 1000 / 13 = ~77psi per pump. or something. I know it is actually EXPONENTIAL but I do not have all the variables. 
 
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Please keep us informed about how your system works over time. You wonder why someone has not built a pump with these two components. Right now I am pumping my Disco and MRod .25-in part because I need the exercise (6-1/250--I can afford to shed a few!). And it would be at least an hour round trip in heavy traffic to get a tank filled. Seems you are working on a middle a middle way---a practical approach if the system lasts over time.
 
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May I ask what kind of fitting did you use to connect the compressor to the Benjamin hand pump? I compared sizes between that, which is 0.375 inch, and I could not find a standard size fitting which would have a nominal OD of 0.375.

For NPT 1/16, the nominal OD is 0.313 and 1/8 is 0.405. Also NPT is tapered, and the one on the pump is parallel.

Thanks.
 
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I was going recommend the marauder forum as well. Aj beat me to it. You have to be careful of input pressure. The Hill pump for example uses plastic where the input from the moisture filter takes in air. I think its limited to about 15 psi input from to shop compressor. Heck the Shoe box is limited to 85 psi. Also you should use a good size dessicant moisture filter because shop compressors will put out a lot of water. More than you might think.
 
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I also pump my MRod 25 and Disco .22. I think one possible road to dealing with the air barrier is simply making these pumps more efficient. I don't find the problem is effort--more a matter of time. And worry about moisture. Like one of the respondents above--I weigh over 200. That really helps. Just have a big frame and let mass do a lot of the work. If I was 130 I just do not know.
I know he is topping off fast---but I wonder what wear and tear that has on the pump? And the pump with me to the county (cannot shoot here in the city).
 
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