SSP pump unit demonstration...Video...

Pretty self explanatory in the video, I think. As it is, it is extremely loud and has enough blast out the transfer port to move the assembly while holding it. We shall see what happens when pushing pellets. As configured in the video, it is compressing 8.5 cu.in. of air to roughly 2000psi.

Many have expressed concerns over piston vacuum on the open stroke. This design uses no weep hole on the tube to draw air in. Instead, there is a weep on the piston face near the radius. The oring gland is designed just like many, if not most, PCP pumps. Pulling the piston back on the open stroke force the oring toward the face exposing the weep hole, thus allowing air in. To achieve this, the gland is cut 1.75 times the width of the oring and then using a Delrin made spacer to fill the excess void. The spacer prevents the oring from too much movement within the gland.


https://youtu.be/89ky3M1DCIc

question.. With the ssp format and the blow open valve , would there not be a clear path from the compression tube to the transfer port for the piston to draw air from on the backstroke?

The valve pin is under spring load, which returns it home as soon as it is fired, nearly.

A few things could permit what you suggest. This approach keeps the valve pin mass down so it can be very responsive.

from posting videos of 2 guns I made, that ssp has some freaking pop!!!!!

...permits variable stroke length since there is no tube weep hole. It can be stroked anywhere between the arc of the stroke to have power variability.

Just imagine the vacuum moving the piston back to a tube weep hole! I can!

While in that point of design, decided to try moving the piston back. Boy was it a not so fun venture. Didn't feel right. In fact, made it feel broken.

At that point, it was decided to utilize the piston weep hole with a shimmed o'ring. Problem solved!

...in other contexts!

In this design, the o'ring serves as the piston seal and the check seal; two way seal.

Pulling piston out forces ring against the piston face exposing the hole, which allows air in. Closing the piston forces the seal against a seat.