Trying to tune my new Zelos, but the hammer spring adjustment has me confused. The regulator pressure is set to 2000 psi, and with the screw adjustment for the hammer spring turned all the way out, I'm gettin about 905 fps with 21 gr Barracudas. As I turn the screw in (clockwise) velocity goes down, not up. What am I doing wrong?
Umarex Zelos Hammer Spring Adjustment
- Thread starter Jack Hart
- Start date
First suspicion I have is the hammer may be bouncing off the rear of the valve, however I don't know if 905 fps with 21 gr should be the plateau for this gun, I don't have enough info on it and no experience. Try to turn the hammer adjustment all the way out and then test with 1/8th turns at a time to see if there is any changes in FPS output.
Hopefully someone who has more experience chimes with a concrete solution, as mine is just a W.A.G to consider while you wait.
Until then, if you want more fps from the 21gr, it may be necessary to increase the regulator beyond 2,000. That will potentially answer the hammer adjuster question as well.
-Matt
Hopefully someone who has more experience chimes with a concrete solution, as mine is just a W.A.G to consider while you wait.
Until then, if you want more fps from the 21gr, it may be necessary to increase the regulator beyond 2,000. That will potentially answer the hammer adjuster question as well.
-Matt
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Your not doing anything wrong, your at the knee of the curve and to get more FPS, you need to up the regulator.
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It seems like you do not have enough hammer spring adjustment range to get the velocity to decrease. Your hammer spring is below the butt plate, I believe. If you take the butt plate off, can you decrease it further? If you are at the knee of the curve, it should go down with more decrease in the hammer spring force. I realize you probably do not want to shoot the gun with the butt plate removed but a test in that mode could confirm what is going on.
I also agree with the "turn it up" comments. If the hammer spring is indeed too much for the current regulator that would get things in better balance. Another change that could help if you do not want to shoot heavier pellets (you are already going pretty fast for 21 grain) would be to reduce the length of the spring. I did that on my P35-177 and it worked out great. But to get back to stock would require me to find a stock spring. A shorter spring might even reduce hammer bounce improving efficiency.
I also agree with the "turn it up" comments. If the hammer spring is indeed too much for the current regulator that would get things in better balance. Another change that could help if you do not want to shoot heavier pellets (you are already going pretty fast for 21 grain) would be to reduce the length of the spring. I did that on my P35-177 and it worked out great. But to get back to stock would require me to find a stock spring. A shorter spring might even reduce hammer bounce improving efficiency.
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Thanks all for the input, but I guess my main concern is that when I turn the hammer spring screw in (clockwise), increasing spring compression, shouldn't fps increase? Just the opposite seems to be happening.
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It should, yes. However, it is possible the hammer is over-sprung from the factory for the adjustment to make any difference at lower reg pressures.
-Matt
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There is a curve you follow with each regulator pressure you choose. In this case, you are on the decline of the curve, past the "knee" where speeds increase.
You will need a higher regulator setting to get more speed.
This is tuning, turn your screw out until you reach your best speed then reduce it 5 fps more. That's all your going to get from that regulator setting.
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Same setup on the snowpeak m60b. I set mine to 180 bar on the 30 cal. It's right around 70 fpe with the spring backed almost all the way out. If I increase tension, it drops velocity. I could get more oomph out of it if I turn the reg up, but it's already getting loud at the power setting it's at, and I don't want to lose anymore shots.
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You're not passed the "knee" of your tune curve, based on your post your at the plateau since no hammer spring tension increases your velocity.
The velocity commonly referred to as "knee" is roughly 95%-97% from your plateau, meaning if you are at 905 fps, your knee of that tune is 860-877. This would be considered the 'sweet spot' to tune for efficiency.
Based on the other users experience, you're definitely experiencing an over-sprung valve as I mentioned. Tuning pcp's can be a headache, so if you need any further help chime back here and someone will help.
-Matt
The velocity commonly referred to as "knee" is roughly 95%-97% from your plateau, meaning if you are at 905 fps, your knee of that tune is 860-877. This would be considered the 'sweet spot' to tune for efficiency.
Based on the other users experience, you're definitely experiencing an over-sprung valve as I mentioned. Tuning pcp's can be a headache, so if you need any further help chime back here and someone will help.
-Matt
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It's the game we play to get the velocity we want.
I've tried the weaker spring "fix" others have recommended and have still not been able to climb past the knee for the same reg setting.
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I tried too, but I figured without getting in there and opening things up, she's going to stay where she's at.
I wonder if the ports are all the same size on these rigs, or if they're caliber specific. Considering it comes in 177 thru 357, you'd think it would be caliber based.
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Thanks again for the answers. I think I finally understand what's going on. My goal is accuracy and maximum number of consistent shots, not fps. If I decreased regulator pressure to 1500 psi, what is the chance that I can get on the right side of the curve (knee) so that tuning the hammer spring will make sense?
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When I back off all the way on the hammer spring I get about 905 fps. When I turn the spring in fps decreases about 5 fps per half turn.
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You need to increase, not decrease regulator pressure. That way you will begin to enter the knee of the power curve versus the plateau which is where you are currently. Lowering will make matters worse, unless you re-spring the gun, which is the other option if you wanted to run lower reg pressure for more shot count.
As you increase pressure, the valve becomes harder to open, making the hammer work more, thus allowing the HST adjustment to work properly, lowering your pressure makes the valve easier to open.
Definitely not a good 'beginners' user experience based on what you're saying, no one should have to re-spring their gun to get an adjustment working as intended.
Lets say hypothetically your current spring is 10 lb/in, you would be best suited finding a spring of similar dimensions that were 8 or 9 lb/in instead, if you wanted to keep the 2,000 psi set point or take it below towards 1,500 psi it in its current state.
Ideally one tunes for the lowest reg pressure they can while achieving 103%~ of their desired power level, that way you can reduce the hammer strike a hair, and be at the 'knee' of your power curve, which is best for shot count/efficiency and lowered muzzle report. HTH
-Matt
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If you want a low power high shot count tune it seems like you need a weaker hammer spring. You have to have the hammer spring and the regulator in reasonable balance or things do not work like they should - as you have experienced. I've been chasing a slow leak on my P35-25 and took the regulator apart and replaced all the O-rings and put a tiny amount of silicone grease on the spring washers. When I put it back together I tried to replicate the tune it had when I took it apart but it did not work. When I took it apart I was shooting JSB heavies at about 750 fps. When I got it back together they were going about 600 fps. I tried blindly adjusting the regulator without any real benefit and then just shot some pellets I have no plans for to see where the regulator was. It was at about 150 bar. I know from past experience the hammer spring cannot open the valve when the regulator is set this high. That is why my velocity was so low. So I lowered the regulator by 1/4 turn which seems to be about 10 bar. I am back to 750 fps.
You are supposed to get more velocity from a higher regulator setting and you will if you have enough hammer spring force to effectively open the valve. If you do not, then the velocity is low until you get the regulator adjusted low enough the hammer spring can deal with it.
The OP has the opposite issue, too much hammer spring. Solutions are to find a weaker spring or raise the regulator to be in reasonable balance with the spring you have. Cheapest simplest way to have a weaker spring is to shorten it. Before I do something like this I like to have a replacement part in hand so I can go backward. But on my P35-177 I was confident I would not want to shoot a pellet heavier than about 11 grains and that meant I did not need the stock spring. Shortening the spring has the exact same effect as backing off the adjustment screw. The Zellos is made by SPA which tends to mean parts are hard to come by but you could try contacting Umarex and also Airgun Archer Fun if you want a spare hammer spring. You can also measure the dimensions and look on line for one shorter or wound with thinner wire. McMaster Carr is one source but there are others.
You are supposed to get more velocity from a higher regulator setting and you will if you have enough hammer spring force to effectively open the valve. If you do not, then the velocity is low until you get the regulator adjusted low enough the hammer spring can deal with it.
The OP has the opposite issue, too much hammer spring. Solutions are to find a weaker spring or raise the regulator to be in reasonable balance with the spring you have. Cheapest simplest way to have a weaker spring is to shorten it. Before I do something like this I like to have a replacement part in hand so I can go backward. But on my P35-177 I was confident I would not want to shoot a pellet heavier than about 11 grains and that meant I did not need the stock spring. Shortening the spring has the exact same effect as backing off the adjustment screw. The Zellos is made by SPA which tends to mean parts are hard to come by but you could try contacting Umarex and also Airgun Archer Fun if you want a spare hammer spring. You can also measure the dimensions and look on line for one shorter or wound with thinner wire. McMaster Carr is one source but there are others.
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Does pellet weight affect proper tuning of the hammer spring for a given regulator setting,
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My Zelos has the same behavior.
When I increase the hammer spring the velocity drops a few FPS.
This is with the regulator at 1750-1800 PSI.
I think the original hammer spring is too strong.
By the way these are the OEM hammer spring dimensions:
Length: 63.5mm
Outer diameter: 8.5mm
Wire diameter: 1.3 to 1.4mm (coils are too tight to measure accurately)
When I increase the hammer spring the velocity drops a few FPS.
This is with the regulator at 1750-1800 PSI.
I think the original hammer spring is too strong.
By the way these are the OEM hammer spring dimensions:
Length: 63.5mm
Outer diameter: 8.5mm
Wire diameter: 1.3 to 1.4mm (coils are too tight to measure accurately)
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Yes, but I am not sure in the way you're thinking. Pellet weight won't cure an over-sprung valve, only way to fix that are
1) Increase regulator
2) Decrease spring pre-load or spring rating
3) Run a custom lighter hammerr
4) Decrease the distance that the hammer travels
Yep, over-sprung, see above.
-Matt
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