Air Gun Home :: View topic

rsterne · Moderator

I took apart a spare JDS regulator today, and compared it to a Ninja.... They are virtually identical, to the point that I think the pistons would interchange, I used Ninja O-rings to rebuild it.... The Belleville washers and the shims are the same sizes, the only difference I really noticed is that the screws holding the bonnet on are different, Metric I think.... The reason I stripped it down was I wanted to see if I could convert it to be adjustable.... I borrowed Lloyd's idea of adjusting the position of the HPA inlet seat instead of shimming the spring.... It was actually a pretty simple conversion.... Here are the parts....

I drilled the housing 17/64" straight through, removing the original HPA seat.... and then tapped it 5/16-24 NF in about 3/4" from the bottom.... I then drilled in from the top 9/32", stopping level with the shoulder on the regulator.... The adjuster is a simple 5/16" bolt with the end machined flat.... It pushes on a small shuttle (center bottom) which is 9/32" OD and carries two #007 O-rings.... The lower portion, and the waisted area in between the O-rings are 1/4" OD.... There is a cross hole drilled through the waist, intersecting a 0.040" hole feeding the seat (the small bump sticking out visible on the right in the photo of the shuttle).... The piston is unmodified, although I ended up using a different belleville stack to get the pressure range I wanted.... The bonnet of the regulator had the pin valve removed, it was drilled 11/32", and tapped 1/8" NPT for the female Foster fitting.... Here is the assembly....

The male Foster (no check valve) connects to my SCUBA tank.... The female Foster connects to a fill whip I have that has a gauge, bleed screw, and female Foster to attach to the gun.... Basically, the regulator is an inline device that could be put in any place there was a Foster QD fitting.... To adjust the pressure you simply turn the bolt.... I machined flats on the regulator shank so I can use a wrench on it.... I had to add a nylon pin through the adjusting bolt to prevent it from moving too easily.... To get the pressure range I wanted I had to use a fairly stiff Belleville stack.... but with no shims there was lots of room.... I used 0.022" and 0.032" bellevilles as a pair (total thickness of 0.054") which should have a flat load of about 365 lbs.... Here is the stack.... Each pair is one 0.022" plus one 0.032".... )) (( )) (( )) (( ))

There is a total of about 0.11" adjustment available before the O-rings run out of surface to seal on, either at the top end near the piston, or near the holes for the foster, gauge, and HP burst disc.... As it turns out, I ended up with an adjustment range from about 700 - 2300 psi.... It takes about 1 flat on the bolt for each 100 psi.... That is certainly practical for my purposes.... I set the regulator for 2000 psi and marked the flat that lined up with the flat on the regulator shank, which I also marked.... Unscrewing the bolt increases the pressure because the piston has to move further, compressing the bellevilles more, which takes more pressure to balance the spring force.... I find it easiest to bleed the regulator before adjusting.... Since the gun has a check valve, and the tank has a shutoff, all you have to bleed is the regulator and lines.... so no great air loss....

I'm pretty darned pleased with my afternoon's work.... It will make it a snap to tether any gun to my SCUBA tank.... The first honours will fall to my Millenium Pumper....

Bob