Advice (N) of energy for opening co2 valve

[supersniper]

As some of you have seen i have been custom building a co2 air rifle the gun is almost complete.I have recently been testing hammer and spring combinations but have found all the springs i have are too weak to open the valve.The valve is a basic co2 pin valve with very light return spring( I have even tried it without the return spring)

I have been trying to source a spring to fit the action i have built would rather buy the right spring first time instead of loads trial and error...!

IF ANYONE HAS ANY IDEA TO THE AMOUNT OF ENERGY(Newtons if possible)REQUIRED TO OPEN A PIN VALVE OR SOMEWHERE THAT MAY HAVE INFORMATION THAT WOULD HELP ME SOURCE AN APPROPRIATE SPRING I WOULD BE VERY GREATFULL...
REGARDS
SS

[Titchgamer]

I would imagine it would depend on the valve?
What Valve have you used? Have you tried a crosman hammer spring?

[JimmyRiddle]

The Hammer cocking effort of a stock 2240 is a bit less than 3.5 kilos, that might give you a rough idea to work from.

The amount of hammer travel before it strikes the valve pin is going to be important, and the surface area of the valve opening.

[supersniper]

No Titch not got one handy the vavle is custom made with 4mm stem,I have made a one peice valve body bored out of solid this attaches the cylinder to The hammer chamber.The seal is on a 11.5mm stem body. Atm i'm trying to calculate the force of co2 gas acting on this diameter
I decided to make it all from scratch (apart from the barrel) rather than buy loads of bits......The "O" rings have been the only expense so far..
crossman spring's a good idea cheers Titch..
SS

[supersniper]

Cheers kackwurst...

[jetski]

there is going to be so much variation depending on so many factors. what sizes will fit? I have a few springs I could send you if they fitted. shimmimg it with a couple of washers or cutting a coil or two off will give you some considerable adjustment

[supersniper]

Cheers for the offer jetski, I'd rather not just keep chopping springs up because i have found quite a few online and there pretty cheap and come in various wire diameters and Newton's ratings it may be that i have to buy a couple to get the set up right but im looking at somthing around 20mm o/d x 75-80mm long with a 1-2mm gauge and coiled at 24mm or less ......there's plenty of movement on O/D an I/D i can probaly accomadate a spring from 4.5mm I/D with same gauge and guide's but the lengths are pretty much set
I've been doing some calculations and i think i need to achieve just over 5.6N/mm/2