Author Topic: made an adjustable piston for the 880 (Read 48411 times))

Rob M · « **Reply #20 on:** September 18, 2016, 11:44:48 PM »

is the valve the same as the daisy?/ im not familiar but the daisy valve has proven to hold 2200psi

bhh · « **Reply #21 on:** September 19, 2016, 12:34:14 AM »

No, it's not the same.

Not mine, but here's a pic:

http://www.gatewaytoairguns.org/GTA/index.php?topic=81275.msg776203#msg776203

Rob M · « **Reply #22 on:** September 19, 2016, 11:37:05 AM »

pretty cool.. the similar" abutement "plug is threaded,, I cant tell how the air is retained( how it gets into the valve) i see the checkvalve to release the air..

bhh · « **Reply #23 on:** September 19, 2016, 11:02:07 PM »

I took a couple pics of mine:

Exploded view:

Where air enters the valve:

Rob M · « **Reply #24 on:** September 19, 2016, 11:27:44 PM »

so the check valve is much like a crosman, all inline.. Im not seeing why its not sealing.the rubber grommet on the compression tube side needs to sit quite flush to get a good seal..wayy simpler smarter setup than the 880

Rob M · « **Reply #25 on:** September 19, 2016, 11:28:59 PM »

is there anything retaining the rubber grommet in the forward position to ensure a seal

Rob M · « **Reply #26 on:** September 19, 2016, 11:31:00 PM »

i guess thats the reason for the spring shape to seat the grommet

bhh · « **Reply #27 on:** September 19, 2016, 11:47:37 PM »

Quote from: Rob M on September 19, 2016, 11:31:00 PM

i guess thats the reason for the spring shape to seat the grommet

Yes, the spring seats in that cup-shaped grommet. I think the reason it started failing to hold full pressure was because the o-rings were cheap and soft. They looked like air was blowing past. I ordered some Viton o-rings in the proper metric size as well as some -113 size in Viton/90.

I'm also going to polish the holes/slots in the tube again and make sure I didn't leave any rough edges.

Rob M · « **Reply #28 on:** September 19, 2016, 11:56:42 PM »

yea, thats a factory leak.. once u get it sealed i bet the gun can push 800 fps

Rob M · « **Reply #29 on:** September 19, 2016, 11:59:55 PM »

looks like u have 880 valve volume or more

Rob M · « **Reply #30 on:** September 20, 2016, 12:02:30 AM »

heck thread the cap to the valve where the check grommet is and u have a tethered pcp!

Rob M · « **Reply #31 on:** September 20, 2016, 12:09:33 AM »

http://www.ebay.com/itm/G7-HPA-paintball-tank-regulator-One-Way-fill-nipple-1-8-npt-Stainless-10400-/171410216987?hash=item27e8d8581b:g:azMAAOSwBLlVQTxS

bhh · « **Reply #32 on:** September 20, 2016, 12:35:01 AM »

Hmmmm....I don't know if I should thank you for that suggestion or not.

First I want to build an adjustable piston and see what it will do with good seals.

Rob M · « **Reply #33 on:** September 20, 2016, 12:38:22 AM »

yep, agreed.. i could have tethered my 880 once i had the 1/8th npt threads in it , but its more fun to see what u can really squeeze out of the pumper. I really think thise valve has more potential for power than the 880.. So if i got to 910 fps the skies the limit here.Im being the devils advocate but i wonder if the factory installed weak seals to regulate the max pressure in the valve?

?

bhh · « **Reply #34 on:** September 20, 2016, 01:01:32 AM »

Quote from: Rob M on September 20, 2016, 12:38:22 AM

yep, agreed.. i could have tethered my 880 once i had the 1/8th npt threads in it , but its more fun to see what u can really squeeze out of the pumper. I really think thise valve has more potential for power than the 880.. So if i got to 910 fps the skies the limit here.Im being the devils advocate but i wonder if the factory installed weak seals to regulate the max pressure in the valve??

The seals that failed were cheapo -113 sized seals from the local hardware store. The factory seals were cut badly from installation and I didn't try them with my modified piston. Every slot and hole in the tube had razor sharp edges.

But, yes, I wonder how much pressure this valve will hold safely and how much I'm generating? Obviously I want to stay on the safe side.

Rob M · « **Reply #35 on:** September 20, 2016, 01:11:35 AM »

Whats the piston size, and whats the pump arm made of ?? I caN telll you really fast what pressures u wont hit!

Rob M · « **Reply #36 on:** September 20, 2016, 01:13:11 AM »

so the pump tube wasnt holding air , and the valve actually was ?? im confused now

bhh · « **Reply #37 on:** September 20, 2016, 01:24:55 AM »

Pump arm is plastic, piston size is about .765. IIRC

Valve was holding air but I think my leakage was between the pump tube and piston and pump tube and valve body.

Rob M · « **Reply #38 on:** September 20, 2016, 01:25:50 AM »

I will share a tid bit with you that sounds odd.. MOST people dont understand pumpers AT ALL..Yes, we all get swept volume, bore diameter, piston facial pressure, camover, material strength, pump arm geometry, valve volume, transfer port flow, flat top pistons etc. But theres a good reason why Guys like LD and Phil are currently building pumpers that bend the rules. I could list all the misconceptions I know of , but thats really scratching the surface/

Rob M · « **Reply #39 on:** September 20, 2016, 01:29:12 AM »

Quote from: bhh on September 20, 2016, 01:24:55 AM

Pump arm is plastic, piston size is about .765. IIRC

Valve was holding air but I think my leakage was between the pump tube and piston and pump tube and valve body.

sounds like u need more radius wall engagement from ur orings, i had the same problem with early designs on the 880.. the natural tendency for the piston to "yaw" or "cant" during higher pump numbers seems to cause some back leakage.In other words if the 113 has an i.d of .625 and o.d of .750 , u kinda want the oring gland to be .640 in diameter so that wall engagement is a bit more.. Hassle to load the piston sure, but same ease of pumping with a better seal

Thank you to our advertisers!

made an adjustable piston for the 880

Author Topic: made an adjustable piston for the 880 (Read 48411 times))