Job’s a good ‘un.
I finally have a fully viable valve. Clearly not as good as Mike’s though, I’m having to use Sean’s heavy-duty spring with 20mm of spacers. Considering I’m using the same seal-area as Mike (4.5mm) but he get’s his open with a stock spring, my design is off somewhere (AK47 vs M16 😆 ).
750psi: 700fps
1500psi: 900fps
2000psi: 1000fps
2500psi: 1050fps
All +/- 10fps or so per shot.
The internal components are prototype-rough, so I might gain some performance with everything smoothed and polished etc. But as it stands I’m getting the extra performance I was looking for (over 200fps more for the same fill), so I’m a happy bunny. 😀
All Replies
I no longer use a threaded tophat as the threads take a severe beating and disturb setup as well as the weakening you are experiencing.
I’ll try and get you a pic of some of my stems.
Walter….
I would do that very thing, but the top-hat needs to be swappable from non-FAC to FAC for when users go to countries where they can have full power legally. 😉
Lang, how about go with a one piece stem so as to dispense with the threading altogether.
I no longer use a threaded tophat as the threads take a severe beating and disturb setup as well as the weakening you are experiencing.
I’ll try and get you a pic of some of my stems.
Walter….
Cheers Walt. 🙂
In the pic above, the thread has failed. I knew I was cutting it close but I thought it was worth a go for the sake of convenience (not having to include a collar on the stem). It was fine until I got hold of some 30-grain Pile-driver pellets and put the 150g hammer in to bring the fps back up. Took a couple of shots and noticed the top-hat was squiffy. 🙁
Three ways to fix that:
a) Reduce the bore of the stem from 6mm to 5mm, so I’ll have an extra 0.5mm of wall thickness in the stem. I’m not sure how much that would effect fps though. Not sure it’d leave the stem strong enough anyway, at 6mm the thread must have been virtually through the wall already. The die was maxed-out too.
b) Increase the stem OD to 10mm, but that’d mean waiting on a wider return-spring.
c) Leave a 10mm collar on the stem. That creates two problems of it’s own; makes it difficult to mount the stem in the vice for boring the inlet-ports, and leaves no spring-tension on the top-hat when I screw it on (the collar takes it instead).
I guess I’ll go with c) for now (got a shoot on thursday with the chaps and my FAC mate wants the valve working for that) but order in some wider springs for the production items.
Fill-pressure after 12 shots: 2600psi.
Nicely done there Lang.
Good numbers for sure 🙂
Walter….
10-shot string at 3000psi, highest 1084fps, lowest 1068fps with 21-grain Bisley Magnums. Six shots were 1075fps, so pretty nice consistency. 😀
Fill-pressure after 12 shots: 2600psi.
LOL, I was gonna say “build a wrench”. But Bikini beat me to it.
Could you take some more detailed pics of the internals, and especially the valve seat on the newest one.? They look good, you shouldn’t use a p[ipe wrench to take them off though… 😛
The three I’ve made. The 1st one, far left, had a seal diameter of around 9mm and didn’t open worth a toss. Number-2 was giving around 900fps at 2300psi but using way too much air and wouldn’t open properly above that fill. Number-3 (the one in the bottle) seems to be spot-on in all regards, though I haven’t tested it at 3000psi yet. But as the Blodnob valve only works at optimum fps at around 2500psi (in a mate’s rifle at least) I won’t lose any sleep over mine if it’s the same. 🙂
YAY!!!!! 😀 😀 😀
What Lang hasn’t told you is that he now only has 4 fingers…and one eye 😮 😆 :10
you are one goofy bastard! 😀
numbers look good, now give us a sting and some pics, please..
- You must be logged in to reply to this topic.
Ooh. 1029fps with 30-grain Pile-drivers. 😯 😀
And supersonic for the first time (with the 21-grain Magnums) at 1121fps. My FAC-toting mate is a happy chappy.