That will work at low pumps numbers, because you will gain pressure faster.... However, at high pump numbers, when the pressure is higher and the volume of air expanding into the barrel is more important, you will lose power.... Somewhere in the middle, there will be no change in velocity at "X" pump strokes....Adding a partition as a spring seat, and fitting a lighter check valve spring, along with a shorter valve spring, will reduce the pumping effort.... The very heavy valve spring in a 39X means that it takes quite a bit of pressure just to open the check valve, which increases pumping effort.... This is not a 39X valve, but you will get the idea....IIRC, there is a shoulder down inside the 39Xvalve that you can fit a washer against to create the spring seat for the two springs.... Not my idea, of course, but a well known mod for the 39X's to reduce pumping effort.... with no loss in performance....Bob
You do not want to decrease the volume inside the valve. If you can increase the available volume of air compressed air inside the valve at the same pressure, the available energy will increase.
Volume and pressure are proportional to energy.
Quote from: Robert 5mm on March 02, 2019, 03:43:25 PMVolume and pressure are proportional to energy.In other words, you don't want to run out of compressed air before the pellet is halfway down the barrel.
Quote from: Robert 5mm on March 02, 2019, 02:03:54 PMYou do not want to decrease the volume inside the valve. If you can increase the available volume of air compressed air inside the valve at the same pressure, the available energy will increase.Robert I do understand your thoughts, but each pump has only x amount of air and the larger the air container the more pumps to get that same pressure.. if I wanted max velocity and did not care about the # of pumps, yes for sure I would work hard to increase volume as much as I could.I'm trying to get a balance of about 16fpe ish and the least # of pumps which for the fpe I want will most likely be 8.Here is a pic of the valve with a thinner hammer spring fitted to the valve, MUCH, MUCH less force to open the valve and being a thinner spring I have increased the potential of air volume. The black rings are electrical tape that I may use as a space filler instead of grooving "O" ring groves in the valve. ... Did I mention how lazy I am ;- )wll
The black rings are electrical tape that I may use as a space filler instead of grooving "O" ring groves in the valve. ... Did I mention how lazy I am
Quote from: wll2506 on March 02, 2019, 03:12:15 PMThe black rings are electrical tape that I may use as a space filler instead of grooving "O" ring groves in the valve. ... Did I mention how lazy I amTovarish, it works!
Took apart my 392 this am and the compression tube is .764+ish ID Some of that ID is paint I think, the valve is measuring .765 and yes the valve barley fits in ... no room for any tape or ? for sure. That Idea is a no go for sure !!It is back to see if the new adjustable piston that comes in Wed I think and a few valve tweaks will boost the speed up just a bit. A lighter valve spring should make a difference, the stock spring IMHO is way, way to heavy. That heavy of spring may have been put in for liability so no sharp hit could possible set it off, I don't know.wll
Quote from: wll2506 on March 03, 2019, 02:11:49 PMTook apart my 392 this am and the compression tube is .764+ish ID Some of that ID is paint I think, the valve is measuring .765 and yes the valve barley fits in ... no room for any tape or ? for sure. That Idea is a no go for sure !!It is back to see if the new adjustable piston that comes in Wed I think and a few valve tweaks will boost the speed up just a bit. A lighter valve spring should make a difference, the stock spring IMHO is way, way to heavy. That heavy of spring may have been put in for liability so no sharp hit could possible set it off, I don't know.wllIf you go too light on the valve spring, the hammer spring will overcome it when uncocked. The hammer could rest too far forward for the bolt to catch causing the gun to be uncockable. I know from experience....Have fun!
After following this post and reading the 3 easy to do steps posted by TIMMYMAC1 I decided to try doing a Mini valve mod job on my own 392 ( purchased 14 months ago ). I had previously purchased a valve off of Ebay for this purpose, it has two o-rings on one end - I did not add any - I do not know who added one, maybe Crosman. 1) Using a dremel I cut off two to three threads ( 1/8 inch ) from the male end of the inside of valve.2) I cut off approx 1/4 inch from flat end of the plastic check valve insert.3) I did not use a #113 O-Ring - I used the original #112 - so I did not lengthen the valve assembly or do step 3.After disassembly - looking in at piston head - it looked very dirty, black stuff. So I cleaned, then took it completely apart to really clean piston and tube.Re-assembled and performed 1 and 2 pump small initial tests, had to cock prior to pumping to hold air. I want the blue thread lock to dry and my major lube job to sit overnight, so did not pump higher then two pumps.Gun cocks easy, and pumps good. Shortening the check valve reduced the strength of the exhaust spring by reducing the initial compression of the spring by the 1/4 inch reduction in the check valve. So I am hoping it will allow complete emptying of the air at 10 pumps. Tomorrow I will find out.Prior to this mod the gun completely emptied at 8 pumps, maybe some air left at 9, definitely air left at 10 pumps.