Traditional valve Cracking force for .45 big bore

[BigBird]

I am slowly making a big bore.  I made a valve with a throat of .421.  The diameter is only about 64% of the bore size when calculating the stem.  The stem will be .125 using O1 tool steel.  Poppet will most likely be peek but I may start with delrin for practice.

I would like to know what weight hammer and spring I should be looking at for this throat.  I seem to recall there is a point where the throat size is too big for the average person to cock.  Also I have a raised lip on the valve.  Would it be easier to crack the poppet with a concave poppet seal area?  I know air will flow better just not comfortable with cutting it that way yet.

Thanks.  Any advice will help.

Forgot to add 3000 psi is the fill on 1.25" OD x .095 wall tube.

[Doug Wall]

If the poppet was 0.5" in diameter, it would take 589 lbs to overcome 3000 psi. That's one big hammer!

[Rob M]

as doug said , thats some cracking force.. But , I beleive Bob  Sterne built a gun with 660 lbs cracking force and was able to overcome that , so its not the end of the world.

[rsterne]

My Hayabusa .457 used a hammer that weighed over 1/2 lb. with a 2" stroke, and required 28 lbs. cocking force to get nearly full power at 3600 psi.... The poppet was 0.45" OD and the throat was 0.406" with a PEEK poppet.... The cracking force was 572 lbs....

When I installed a balanced valve last winter, I increased the throat to 0.422", and the PEEK poppet OD to 0.500".... However, the 3/8" diameter balance chamber reduced the cracking force to about 300 lbs. at 3600 psi.... I shortened the hammer stroke to 1.50", reduced the weight of the hammer to 140 gr., and the cocking force dropped to under 20 lbs.... Power was essentially unchanged....

Bob

[Motorhead]

Build the valve as a balanced configuration .... you will thank us later !!