question for all you pneumaddicts out there.. problem solved

Message

killercrow · #1 Post by **killercrow** » Wed Nov 23, 2005 5:20 am

k... so i went and built myself a brass pump piston for my 1377. im working with pretty tight tolerances. the face of the piston is flat, and so is the intake on the valve. the piston im using has 2 o-rings, whereas the valve only has the one outer.

i seem to be having some problems with blow by... or something... maybe i need to do some polishing where the o-rings sit on the piston. most of the time i seem to get a good seal, but every now and then it wont pump... just goes "psst psst psst..." and then it'll start pumping again, but with lower resistance... then i shoot and repump and everythings normal gain...

anybody familliar with this?

one other thing... what exactly regulates how much pressure the valve will let in? does it just depend on the outer seals? would i benefit from using them other o-rings... not sure the name... poly urethane? the white ones you see on co2 tanks and such. i was thinking they might help to produce more pressure...

anyhow... any help would be much appreciated!

later.
al.

DoctorFrankengun · #2 Post by **DoctorFrankengun** » Wed Nov 23, 2005 9:16 am

When it goes"psst psst psst" try to find where the air is coming out. Mine was going the same thing and, as no air was coming out of the end of the barrel, I traced the problem to the cheak valve in the valve body.

I think that if it was a problem with piston seal it would do it all the time.

killercrow · #3 Post by **killercrow** » Wed Nov 23, 2005 11:35 am

well, im not so sure its the check valve. it does it wether theres pressure in the valve or not... could try changing the check valve, see if it helps.

#4 Post by **webstien** » Wed Nov 23, 2005 12:07 pm

try different hardness o-rings. DUROMETER 90, BUNA-N is the type used in airguns. They are harder then run of the mill o-rings.

killercrow · #5 Post by **killercrow** » Wed Nov 23, 2005 12:38 pm

nice... where might i be able to find these? hydraulic shop? canadian tire? i need some, badly!

killercrow · #6 Post by **killercrow** » Wed Nov 23, 2005 8:18 pm

alright!!!

i found my o-rings! i got myself a bunch of them durometer 90 o-rings. put one on the outside of the valve, and 2 on my new piston. had to enlarge the races since i bought the thicker ones... spent some time and got a perfect fit. also put an oil wiper kinda seal thingy behind the o-rings on the piston, i used pretty pink yarn!!!

had to have the pink...

anyhow, it doesnt seem to leak. works awesome. everyone should have this mod for their 1377... or any pumper for that matter! it makes a difference...