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. 😀
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I did a decent string today, 26 shots from 3000psi down to 2000psi. I took the numbers of the first 20. 21-grain .22 with 150g hammer, 10mm spacer and the Blod spring.
1115
1117
1113
1110
1109
1099
1104
1099
1092
1071
1080
1079
1067
1077
1064
1061
1057
1054
1047
1044
After re-filling the bottle back to 3000psi I hit a rabbit at approx 90yds. I paced it out and it came up at 100+ yards, but after checking Chairgun (1100fps x20 mag plus milldot hold-over of 2.5) it came up as 89yds. You might imagine how pleased I was, until I watched it pick itself up from the squealing death-dance it was doing and literally drag itself out of sight and (presumably) back down it’s burrow. There was no sign of it when I got there.
Still, it was better than what I’ve got used to these last few months, hitting rabbits so fast they hardly notice they’ve been shot-through before legging it to cover. Anyone else have this problem? And if so, how do you deal with it? Anything other than a head or heart-shot isn’t making the nut at these velocities but a blunt-nosed pellet isn’t going to maintain long-range accuracy.
Test#3 Rifle#2 30-grain .25 round. 3000psi Fill. Hammer-weight 100g, 10mm spacer, Blod Hammer-spring.
Lang Valve:
1025fps
1029fps
1017fps
1016fps
1012fps
Average: 1019fps
Finishing pressure: 2725psi
Blod Valve:
1047fps
1037fps
1044fps
1038fps
1034fps
Average 1040fps
Finishing pressure: 2825psi
The Blod valve benefited more from the extra 2.5mm of spacer compared to the Lang valve.
keep up the good work, you will get thre at the end, i just hope you remember i wrote this so i can get it at a discount price, when you become L TUNER 😈
One major discovery with the Blod-valve on the .25 cal rifle was that at 3000psi it would get only 800fps. After putting in a 10mm spacer (the one out of the .22 rifle) it gave 1100fps at 3000psi.
With the 10mm spacer, if memory serves correctly (this was done yesterday and it wasn’t being carried out scientifically), the Blod-valve gave approx 50fps more than the Lang-valve on the same rifle (.25 cal).
We’ve only just remembered this. Another test is about to be carried out on both valves this very minute with the 10mm spacer in the .25 rifle instead of the 7.5mm, to see if yesterday’s results can be repeated. Going by yesterday’s results we’re now thinking that the Lang-valve is maxed-out with either the 7.5mm spacer or the 10mm spacer, whereas the Blod-valve still has more to give. Watch this space. 😆
Tomorrow we’re going to do a long string (going from 3k to 1.5k psi) and see what we get. We’ll also compare my valve back-to-back with the Blodnob valve. Should be an interesting and entertaining shoot. 🙂
Lang, were you able to get at the comparison one valve to the other?
Looking for an update 🙂
Walter….
The test-results are in. There’s a significant difference to firing out in the cold to indoors in the warm. Outside we generally get around 100fps more across the board.
This test was indoors.
The first test (21-grain .22 rounds) gives odd results in comparison to the second test (30-grain .25 rounds), almost certainly because the bottle with the Blod-valve doesn’t screw fully into one of the rifles (the .22 one). A fibre-washer was used to make up the deficiency, but although it’s supposed to be non-compressible washer we can think of no other explanation for the odd results (.22 rounds going slower than the .25 rounds).
———————————————————————————-
Test#1 Rifle#1 21-grain .22 rounds. 3000psi Fill. Hammer-weight 150g, 10mm spacer, Blod Hammer-spring.
Lang Valve:
1121fps
1120fps
1109fps
1098fps
1098fps
Finishing fill-pressure: 2750psi
Blod Valve:
909fps
919fps
922fps
914fps
917fps
Finishing fill-pressure: 2900psi
——————————————————————————-
Test#2 Rifle#2 30-grain .25 rounds. 3000psi Fill. Hammer-weight 100g, 7.5mm spacer, Blod Hammer-spring.
Lang Valve:
1013fps
1013fps
1014fps
1005fps
1003fps
Average: 1009fps
Finishing fill-pressure: 2825psi
Blod Valve:
948fps
989fps
996fps
994fps
996fps
Average 984fps
Finishing fill-pressure: 2850psi
———————————————————————————–
Air usage of Blod-valve on test#2 was very similar to Lang-valve. Less air used on test#1 by the Blod-valve compared to Lang-valve is most likely explained by the fibre-washer, also explaining low round-speed. Test#1 therefore is pretty much fubar. Test#2 was more representitive as all conditions were equal for both rifles.
Conclusion: No difference between the valves worth a wank. 😆
puff of air around the valve could also be because of this
Breech bounce
Tomorrow we’re going to do a long string (going from 3k to 1.5k psi) and see what we get. We’ll also compare my valve back-to-back with the Blodnob valve. Should be an interesting and entertaining shoot. 🙂
Lang, were you able to get at the comparison one valve to the other?
Looking for an update 🙂
Walter….
Today I put an x-ring in the stem-shaft, that’s improved the noise and puff of air from the breech area but no noticeable effect on fps (30-grain at 1021fps and 21-grain at 1139fps on a 3k fill).
Tomorrow we’re going to do a long string (going from 3k to 1.5k psi) and see what we get. We’ll also compare my valve back-to-back with the Blodnob valve. Should be an interesting and entertaining shoot. 🙂
I have got a taper, but the contact-point is about a 1/4mm chamfer in the brass and it’s not particularly steep (about 45-degrees). When I look at the delrin under light I can see the contact-ring shining and it really is very narrow. Hard to think it’s binding under pressure. So narrow I had to bed it in by spinning it back and forward until I got a good seal. It’s not the return-spring either, I’ve fired with it at only 1mm pre-load (19mm total length), where it’s much weaker than the stock spring.
The stem moves freely in the body, but I guess it could be binding under pressure? I’m going to put an x-ring in there, that might centralise it more effectively and make a difference (it’ll certainly stop air from blasting out of the breech area, a minor issue currently).
Baz, the threads are 1.5mm pitch (very bloody coarse). I intend to get a finer pitch tap & die (0.75mm) but until then these’ll do. They also happen to be very quick in the field, if you get my drift. 😉
Already have a milling-machine, that’s what I’ve been using for the stem-ports.
I’m not sure how the “jets” would work Sharp, but I really do need to have the top-hats swappable in a high-speed stylee. I’d hate to have somebody come back from abroad and forget to swap his hi-power setup before going for a shoot, only to find a couple of cozzers coming towards him across a field. An innocent enough mistake, but unfortunately the law here doesn’t operate in the spirit of the legislation, it goes by the letter. Used to be a cozzer could use his discretion and behave honourably, but with the system of targets today they’re all bloody robots.
Thanks for all the advice chaps, it’s much appreciated and it’s given me plenty to think about. 😀
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. 😉
could use the one piecer, then thread the inside of it for “jets” to regulate airflow, could change without discharging bottle too.
If both your valve stem seal and seat are tapered, the two tapered surfaces may be “wedging” together, from the tank pressure, especially as the derliln being softer would tend to push into the tapered seat.
Good advice Sharp.
Setscrews orifice for control of flow (power) works well.
The delrin will indeed wedge and steal power.
Here is a pic of my valve assortment that I use from .177 cal up to .458
Walter….
edit: the bottom stem is an older version Condor for comparison.
What size threads are you using on your stem and top hat? From your photo it seems you’ve used quite a coarse thread. Good to see your getting plenty of time on your laithe, next you’ll need a milling machine, very useful for boring the ports in the stems. Keep up the good work.
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. 😉
could use the one piecer, then thread the inside of it for “jets” to regulate airflow, could change without discharging bottle too.
If both your valve stem seal and seat are tapered, the two tapered surfaces may be “wedging” together, from the tank pressure, especially as the derliln being softer would tend to push into the tapered seat.
Lang, closing force occurs where the ‘differential’ pressure exists.
In other words if the sealing is 6.5mm where one side is atmospheric and the other is at bottle pressure then the closing/opening force will indeed be a result of that effective area.
There must be other issues if you are struggling to open virtually identical sealing diameters.
Cheers,
Walter….
This doesn’t make sense, going by what’s been said previously about the closing force being governed by the seal area.
On the stock UK rifle the seal is a 5.5mm delrin cup closing against a 6.25mm brass rim. Yet the very puny main-spring can open that at 3000psi.
My seal is a delrin job closing against a 4.5mm brass rim, yet it takes a Blodnob main-spring to open it properly.
The only other thing that can be affecting how it opens is the space on the barrel-side of the seal, so far as I can make it out. On the stock assembly the area beyond the seal is the 2mm/3mm bore of the stem. Is that how it actually works, the force of the vacuum against the seal seat is regulated by the size of the area beyond it? 😕
That doesn’t seem to compute either. Static atmospheric pressure is present regardless of the space in which it exists.
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I’d knock off 30grams of your hamer and see what happens.
About that rabbit shot placement. Only direct headshots stop them in their tracks.
Cheers,
Marc