supercharged pumperFebruary 20 2012 at 8:00 AM
|Ron (Login oo7fuzz)|
Crosman Forum Member
from IP address 220.127.116.11
A couple years ago I scratch built a pumper and have dedicated it to bench rest for smooth bore expiriments. It is a .25 cal and has a 30" smooth bore barrel. The exhaust valve is inline and blow open. The pump volume is 2.6ci so thats a pump tube diameter of 5/8" X 8 1/2" sweep. The pump handle is 19" long. The reservoir is quite large and it generally takes 25 strokes to send a .25 cal JSB Exact King 25.4 grainer out at 875fps plus.
When I built this gun, I designed the air intake hole for the pump to be a 1/16" hole thu with a 3/16" counter bore anticipating future experimenting such as I describe.
Well, this weekend I FINALLY came upon a neat little 12 volt air compressor at the local secondhand store. Set me back $3. Removing the compressor unit from its plastic case, I discovered a compact piston compressor driven by a small DC motor which has a 3/8 gear in the motor shaft that runs against a 1" nylon bull gear on the compressor.
The unit has a gage on it and will easily pump to 60psi. I removed the cigarette lighter adaptor from the cord and found the compressor to run well using a 9.6 volt rechargable battery. Next I coupled a length of 3/16" vinal tubing to the hose of the unit. Now I am in business.
End of story is that by precharging the pump tube, ~45psi near as I could determine, I could now fill the gun in four strokes instead of 25.
So I am thinking. To hell with the multi-stage pumps which are generally minimal swept volume and o-ring intense. If the tiny air compressor and battery were concealed in the buttstock, I think one could get many shots per battery charge and greatly minimize pumping strokes.