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Jim Gillilan's Custom 1322 Carbine

Jim Gillilan's Custom 1322 Carbine w/Custom Stock

Here's one I'm especially proud of and is modded all over, doing 12fpe at 15 pumps.
Stock is Teak from Thailand and super light weight 1322 Carbine!

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SSP pump unit demonstration...Video...

June 11 2017 at 5:48 PM
Phil  (Login Duane35)
Crosman Forum Member
from IP address 76.120.212.220

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


    
This message has been edited by Duane35 from IP address 76.120.212.220 on Jun 11, 2017 7:36 PM


 
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robny
(Login robnewyork)
Crosman Forum Member
74.194.81.148

very Nice

June 11 2017, 8:00 PM 

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?

 
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Phil
(Login Duane35)
Crosman Forum Member
76.120.212.220

Thanks, Rob. Could be with a little redesign....

June 11 2017, 8:35 PM 

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.

 
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Robny
(Login robnewyork)
Crosman Forum Member
74.194.81.148

knowing how youtube audio is

June 11 2017, 9:41 PM 

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

 
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Phil
(Login Duane35)
Crosman Forum Member
208.87.234.201

The piston design...

June 12 2017, 6:39 AM 

...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.

 
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Steve in NC
(Login pneuguy)
Crosman Forum Member
162.198.201.47

You make it sound like weeping is a bad thing.

June 12 2017, 6:33 PM 


 
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Phil
(Login Duane35)
Crosman Forum Member
76.120.212.220

Oh, now!!

June 12 2017, 9:01 PM 

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!

 
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Steve in NC
(Login pneuguy)
Crosman Forum Member
162.198.201.47

As I'm sure you know, I'm only kidding. Actually I'm a big fan of O-ring checkvalves...

June 13 2017, 10:04 AM 

...in other contexts!

[linked image]

 
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Phil
(Login Duane35)
Crosman Forum Member
208.87.234.201

You bet! Very creative THAT is!

June 13 2017, 11:16 AM 

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.

 
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Steve in NC
(Login pneuguy)
Crosman Forum Member
162.198.201.47

Roger. Different different context.

June 13 2017, 9:18 PM 

happy.gif

 
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LD
(Login lhd)
Crosman Forum Member
172.243.154.216

IF it works as shown in the video

June 15 2017, 6:34 PM 

There is likely no need to "redesign" to avoid the vaccuum on opening "problem". Just pull the trigger as the lever is opened to relieve vacuum, then release before pumping.

 
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Phil
(Login Duane35)
Crosman Forum Member
208.87.234.201

Actually, LD, the valvepin is one way....

June 16 2017, 10:25 AM 

...in its sealing design. The system functions in the same manner as the Sharp guns, just bigger. Though, there is no sliding sear plate with a hole drilled for the pin to 'pop' through. Instead, the valve pin is 5/16" diameter with a reduced tip to 1/4". On the reduced tip is where the sealing o'ring resides, instead of being seated in the valve.

The pin is then machined out and edges rounded. The trigger pin pushes up into the channel cut out of the pin. The trigger pawl pulls down, releasing the valve pin. On the rear of the valve pin, there is a spring which returns the pin home in its rested, seated, sealed state.

Simply pulling the trigger on the open stroke doesn't assist in releasing the vacuum. Pulling the piston out actually pulls on the valve pin causing a tight seal.

The piston works wonderfully. I just machined it pretty much the same as the FX Independence. Pull the piston out, vacuum pulls on the o'ring enough to expose a hole that was machined in the inner radius of the o'ring gland through the piston face. A Delrin buffer ring sits in front of the o'ring to prevent too much movement, as I found the o'ring liked to stick in the open position up to about 1.5" of closing movement, which equated to loss of swept volume.

The way it is configured, permits the operator any stroke sweep within its lever range. So full power, half power, quarter power, etc., can be achieved.


 
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