May 11, 2008 at 8:08 pm #2128
I have something strange going on her. In an atempt to get as many shots as possible from my SS at +-30ft.lbs I have made a tiny valve with as big a transfer port as I can. It’s made of titanium stem is 4,2mm through hole is 3,2 and transfer ports are 2x2mm angeled. Tiny 2,5mm stem behind that holding a small 6.5mm poppet. New condor valve style.
I’m using a delrin hammer and stated out with 22 grams and too much preload on the hammer spring. Preload on the spring is now next to nothing and my hammer weighs a tad bit over 12 grams right now. Had to sneak of about 10 grams not to let the hammer overpower the valve!
Now here’s the strange but good thing about the setup at the moment. From a 190 bar (tank I had with me at that moment was empty) fill I get 30 shots With 30fps varience. But all downhill velocity wise. I’m using a 18″ barrel and I stated out with 1000fps and ended up at 970. So I’m bettin I could get around 50 decent shots with this tiney valve!
I’ll get some shooting time tomorrow and do a nice 50 shot string from a 200 bar fill. And post it. Maybe later I’ll post some pics!
MarcMay 11, 2008 at 8:35 pm #38984shrpshotr28Participant
sounds like you might be on to something.! 🙂 As far as overpowering the valve, the smaller diameter poppett would mean less hammer pressure required to open the valve. That in combonation with the valve being Ti (much lighter) means more of the hammer momentum is used opening the valve instead of overcoming the inertia of the valve spring/valve.
Might try lightening the hammer and using a little stiffer hammer spring/more preload and a corresponding heavier valve spring to keep the valve balanced. The lighter hammer/more spring should make for faster “lock time” possibly increasing accuracy.May 12, 2008 at 7:39 am #38992
Your comment is the point of my thread. I want to get the discussion going about those heavy hammers! Everyone states use a 80gram hammer while I’m using a 12gram! But using a small stem means I can’t even use a heavy hammer and still get good results! I know I work with my own stem and so I don’t have to use airforce valveparts but still. I think they are bull for anything upto .25 you can use a max of 30 to 35 grams.
Ok I think the Ti valve helps out more than I expected. And in my previous post I forgot to say I use a hammerspring a little stiffer than that one airforce uses. The valve return spring is on par with the one airforce uses btw. And I still need a pritty decent preload to get the velocity in the 960 region. If I would use just one turn preload and filled to where my sweetpoint would lay I think I would be going supersonic.
I think by increasing the size of the ports I could get a decent 60ft.lbs if I’d use a 24″ 0.25 barrel!
Just my $0.02
MarcMay 12, 2008 at 4:13 pm #38996vincentvangervenParticipant
ha marc, looking forward to some pics and perhaps a chrony string with fill pressure. Are you going to ochten4.5 as well? would be nice to check out the stuff you made and i can also bring my modified condor 😀May 12, 2008 at 8:21 pm #38999
No I’m not going to ochten 4,5 but we might meet 7 june on the Almelo shoot!
Here is a 67 shot string!
210 bar fill
That was shot with 14.4 grain JSB 5,5mm
Are you comming to the Almelo shoot!
MarcMay 12, 2008 at 8:22 pm #39000
Is your custom valve opening larger than the stock SS valve??May 12, 2008 at 8:36 pm #39002
Mine is about 3.2mm how much is the custom opening?
MarcMay 12, 2008 at 8:45 pm #39003vincentvangervenParticipant
Impressive, especially from shot 12 and on! Looks like it’s struggling just a bit with at first 10 or so shots , after that the valvelock is gone and it sorts itself out. Really nice since you have roughly 3000 psi behind the valve. mine’s got a stock hammer, with a new type valve; it doesn’t really kick off on powerwheel 0 before 2200 psi. Ok, can compensate with the wheel, but assuming you didn’t fiddle with it this is a nice string.
And yeh, the way things are looking now i’ll be at the almelo shoot as well. we’ll have a chat over there ! cheers, vincentMay 12, 2008 at 11:14 pm #39009shrpshotr28Participant
impressive string of shots. What was your ending pressure in the tank? I’d be guessing 1700-1800psi?May 13, 2008 at 12:04 am #39012
😯 OK, lets try this….
Is your valve (custom 3.2mm?) that your testing larger than stock or smaller than stock?May 13, 2008 at 6:30 am #39030
I typed it wrong. Here are my valve dimensions. I don’t know the stock dimensions.
As for pressure drop. It went from 210 to 150/140 bar So endpressure is about 2200/2100 psi
MarcMay 13, 2008 at 7:54 pm #39041
😯 Sweet, nothing like a drawing to make it perfectly clear…
Now i’m off to find the stock opening in the valve… 😉
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