First off credit is due to a few members over on the GTA forum for there vast sharing of design ideas, drawings and some mighty exhausting threads on the subject of Balanced valves.
You may know who they are ... Thank them !
This was for me an exercise of prototyping a design idea based on what i had to work with for a valve body. All the parts to make this work were fabricated via machine shop tools or by hand etc ... Some not pretty, but remain functional for the task of testing etc ...
Started out with a bare Gen-1 M-rod valve body with the internal sleeve removed. Next fabricated a dished / concave poppet seat being o-ring sealed to I.D. bore and slightly self centering having a bit of radial motion possible. Picture #1
Next was fabricating the poppet which was done using a .052" drilled stem having cross holes @ mid throat position. Poppet head made from PEEK having the stem be a TIGHT press fit w/adhesive. The .052" hole threw stem continues out the balance chamber end. Because we have the very real possibility the pressure within the valve ripping the o-ring & tip of poppet right off decided to scale down the 0-ring size and groove depth required leaving more thickness at the chamber end of poppet. O-ring a very small 1mm x 3mm 70 duro buna/n.
Up next came the balance chamber & did much pondering on what material was actually required ? ... this based upon knowing the balance chamber is at atmosphere and the pressure within valve is trying to CRUSH IN INWARD. Steel, brass etc likely best ... BUT having dug around in my Misc plastics found a stick of 3/4" glass reinforced acetal polymer, Huh perhaps that would not crush being this material is super stiff and really tough. So that's the route went ... fabricating a screw in balance chamber where the poppet and o-ring end would reside at minimal radial clearance ( running @ .004" ) Chamber depth JUST ENOUGH to allow poppet to lift @ .100" and become flush with valve body if bottomed out. Small shallow secondary bore to get in the small stiff return spring and just going to coil bind same as previous distance specs.
Poppet down in throat you see the balance end and vent hole. Assembled with balance chamber screwed in and tightened the 3 Radial intake slots line up and valve can actually take in air.
The last picture looking THREW a hogged out m-rod gauge manifold at the air path as seen from the plenum side of the system.
Now you likely wondering, Did it work ? How well did it work ... Whats the reduction in cocking force, Reduction in energy to actually crack the valve open etc
With the sizes chosen in Poppet head diameter at sealing margin and the balance chamber diameter we're at a 41/59 area ratio. The opening force required has dropped to 64% ( Thanks Bob S for the math work )
Am able to get my previous 940 fps with a .177 JSB 10.3 using a 14 gram hammer and a much shorter spring which as eased cocking effort and sped up the shot cycle ( lower lock time )
Dang it if it don't work, seals up just fine and appears to have no sticksion issues. Came out this AM after gun sitting all night ... 940 first shot
Now @ 150 shots done, head of the peek poppet stem has not sheared off, o-ring is not leaking ... now we let TIME and shooting tell the tale if balance tubes going to crush and seize poppet or any other catastrophic failures.
Fun stuff !!
PS. thread is simply DOING what many have talked about within numerous threads using the base information contained within such threads.
While commercial balanced valves do exist and can be purchased, this was not about whats out there commercially, but what one can build using ones creative & mechanical skills without breaking the bank.
Come end of the day ... Does a 22 ft lb .177 M-rod NEED a balanced valve ? Heck No ..... Will the gun operate more efficiently ? Not likely ..... Will it cock easier, make equal power with less mechanical effort ? Well actually YES ..... Is it fun to build stuff, think outside the box and actually apply ideas into reality ? Yes it is and that's the point, No less no more.
Scott S
Motorheads AG Tuning Services
You may know who they are ... Thank them !
This was for me an exercise of prototyping a design idea based on what i had to work with for a valve body. All the parts to make this work were fabricated via machine shop tools or by hand etc ... Some not pretty, but remain functional for the task of testing etc ...
Started out with a bare Gen-1 M-rod valve body with the internal sleeve removed. Next fabricated a dished / concave poppet seat being o-ring sealed to I.D. bore and slightly self centering having a bit of radial motion possible. Picture #1
Next was fabricating the poppet which was done using a .052" drilled stem having cross holes @ mid throat position. Poppet head made from PEEK having the stem be a TIGHT press fit w/adhesive. The .052" hole threw stem continues out the balance chamber end. Because we have the very real possibility the pressure within the valve ripping the o-ring & tip of poppet right off decided to scale down the 0-ring size and groove depth required leaving more thickness at the chamber end of poppet. O-ring a very small 1mm x 3mm 70 duro buna/n.
Up next came the balance chamber & did much pondering on what material was actually required ? ... this based upon knowing the balance chamber is at atmosphere and the pressure within valve is trying to CRUSH IN INWARD. Steel, brass etc likely best ... BUT having dug around in my Misc plastics found a stick of 3/4" glass reinforced acetal polymer, Huh perhaps that would not crush being this material is super stiff and really tough. So that's the route went ... fabricating a screw in balance chamber where the poppet and o-ring end would reside at minimal radial clearance ( running @ .004" ) Chamber depth JUST ENOUGH to allow poppet to lift @ .100" and become flush with valve body if bottomed out. Small shallow secondary bore to get in the small stiff return spring and just going to coil bind same as previous distance specs.
Poppet down in throat you see the balance end and vent hole. Assembled with balance chamber screwed in and tightened the 3 Radial intake slots line up and valve can actually take in air.
The last picture looking THREW a hogged out m-rod gauge manifold at the air path as seen from the plenum side of the system.
With the sizes chosen in Poppet head diameter at sealing margin and the balance chamber diameter we're at a 41/59 area ratio. The opening force required has dropped to 64% ( Thanks Bob S for the math work )
Am able to get my previous 940 fps with a .177 JSB 10.3 using a 14 gram hammer and a much shorter spring which as eased cocking effort and sped up the shot cycle ( lower lock time )
Dang it if it don't work, seals up just fine and appears to have no sticksion issues. Came out this AM after gun sitting all night ... 940 first shot
Now @ 150 shots done, head of the peek poppet stem has not sheared off, o-ring is not leaking ... now we let TIME and shooting tell the tale if balance tubes going to crush and seize poppet or any other catastrophic failures.
Fun stuff !!
PS. thread is simply DOING what many have talked about within numerous threads using the base information contained within such threads.
While commercial balanced valves do exist and can be purchased, this was not about whats out there commercially, but what one can build using ones creative & mechanical skills without breaking the bank.
Come end of the day ... Does a 22 ft lb .177 M-rod NEED a balanced valve ? Heck No ..... Will the gun operate more efficiently ? Not likely ..... Will it cock easier, make equal power with less mechanical effort ? Well actually YES ..... Is it fun to build stuff, think outside the box and actually apply ideas into reality ? Yes it is and that's the point, No less no more.
Scott S
Motorheads AG Tuning Services
I'm just gonna live vicariously through you and sell my gun! Lol