PCP air rifle depinger

[Ischgl99]

I bought a Benjamin Marauder air rifle a couple months back, every time you shoot it, there is an annoying ping in the air tank from the valve closing, similar to water hammer. The air rifle forums have many innovative solutions to problems, and a device to stop the sound wave causing the ping is called a depinger. There were some interesting 3d printed devices being used, and some recommended putting a nylon bristle brush in there, not doing that, but since I have machine tools, I settled on a simple design I could turn on the lathe.

This was a simple turn the OD to the same size as the cylinder end plug, groove for an o-ring to keep it in place, drill and bore to about 2mm wall thickness, add a 1/4” center hole, and part off. Installation is simple, push it all the way down into the air tube with the small hole side facing out. I pumped the rifle back up to pressure and tested it, ping completely gone, and more enjoyable to shoot.

 

[pontiac428]

So does it just create an air space with a baffle to soften the impulse from resetting the lock?

Depinger is an interesting term, I thought it might be the opposite of an impinger and got curious.

 

[Ischgl99]

Exactly, this design is to place the baffle a short distance away from the valve at the end of the air tube. The back gets machined as large as practical so you take up as little of the available pressurized air space as possible to keep your shot count high. Pretty much anything that interrupts the shock wave will work and why some people use a bristle brush. I’ve seen some designs that have multiple holes in the end on the theory that the shock wave will continue if the hole is centered, but that doesn’t seem to be the case. I may try making a couple more with different size holes to see if hole size makes a difference, but I have enough projects on the back burner already, so I will probably never get to that.

 

[pontiac428]

It's like the muffle bar on a piano, the hole is a restrictor for the pressure front and breaks the wave. Size and location can probably be optimized as well as volume, but who cares- you've effectively put a rubber band around the tuning fork!

 

[Ischgl99]

Yup, if I was selling these, I might spend the time to optimize it, but this is good enough, until I get the bug to tinker with it lol. I'll have to see if I still have my compressible fluid dynamics textbook from college to see if there are any formulas that would predict what would happen with different size holes.