Expired cylinder dying?

[conradin]

First of all, Rover is not allowed to answer this one, since he has a standard answer for all PCP.

I have recently purchased a brand new Steyr cylinder, while I still have two 14 years old ones. Everything seemed to be fine and they all work. However out of curiosity in preparation of an upcoming tournament I decided to compare both, without throwing the old cylinder for a water bubble test.

My scuba tank is currently at 165. The new cylinder took in 160 when I pulled it out. But the old one only has 140 when I unscrewed it from the tank. Being the old style one, I have to use a manometer to check it.

I suspect the old ones are going, but I want to check with you guys if this is a sign of them going, such as metal fatigue. I don't feel any leakage. The old one just cannot fill up as much as the new one.

Another thing I cannot tell is consistency. I found out my two 20 years old ones, while they did not leak, and actually could hold the correct pressure, were extremely inconsistent when it came to giving out air, FPS all over the map. Hence they ended up in the garbage bin.

I think I am rambling here a little bit, but the basic question is, what is the first, minute, sign of a cylinder dying? (and I don't mean kaboom).

[David Levene]

Have you tried using the separate screw in gauge in the new cylinder. Does it agree with the inbuilt gauge.

[rmca]

Some manometers don't read as accurate as other's. For example I have a friend who owns a pardini K10 and it's manometers always read about 20 bar less than my LP10, when filled from the same tank.

If it's compatible, check both tubes with your manometer and see what it read's. You can also compare the number of shoots you get with one cylinder vs the other. There should be a +/- 20 shoot difference if those readings are correct, which I suspect they aren't.

There's no reason for your older tubes to give you a variation that big unless they were leaking on there own or when screwed to the gun.
Think about it.
If the cylinder holds pressure and doesn't leak as you said, and your gun doesn't leak, because if it did it would leak with all your cylinders, were did the pressure went?
My guess is to do the water test and look for bubbles...

Now to answer your question, one of the first signs would be the loss of pressure, but that doesn't mean that a non leaking cylinder is ok... It's very hard to tell if there is fadige on the metal without a test that would cost more than a new cylinder.

[David Levene]

Another thing I cannot tell is consistency. I found out my two 20 years old ones, while they did not leak, and actually could hold the correct pressure, were extremely inconsistent when it came to giving out air, FPS all over the map.

I don't know what anyone else thinks but that doesn't sound right to me.

As your gun has a regulator it is extremely unlikely that the cylinders will be causing inconsistent velocity.

[PaulB]

Pressure gauges of any kind, just like any measuring instrument, periodically need to be calibrated against a known standard, if you want (or need) to get an accurate measurement.

http://www.tecsis.de/en/service/calibra ... libration/

http://www.veronics.com/wp-content/uplo ... 4-6-11.pdf

Since the accuracy needed on air gun cylinder gauges is not very high the best way is probably to check as many detachable gauges as you have on the same tank and trust the pressure that shows up most often, or take an average, throwing out any readings that are clearly way off. Mark each gauge with the 200 bar point, or 150 bar point, or whatever pressure you are using for your test (as best you think you know it). I personally don't trust in-cylinder gauges at all and would not use them.

[Tycho]

I don't know what anyone else thinks but that doesn't sound right to me.

I agree with David. You're not shooting with 200 bar from the tank, so as long as more than 80 bar are available, the regulator will "fill up" to that pressure and then release it to the barrel. Velocity variances usually come from the regulator. As you seem to like to throw things away, I'd therefore scrap the whole pistol.

I also agree about the comments regarding the tank manometers, they are not more than indicators and far from precise. I've never seen the metal part of a tank leaking, it's one or several of the seals, and any old tank can be rebuilt with new seals and silicon grease. Works like a charm, as long as you don't go to the olympics, or live in the land of class action lawsuits where a whole state might be traumatized when they hear of what you're doing.

[Rover]

So there!

Save your breath, guys. We beat this to death in another thread, but Conradin will not have his phobias soothed except by hearing what he wants to hear; telling him to buy new (and he's nervous about that).

But here ya are: viewtopic.php?t=40860

Now you can have two and eliminate all fear of compressed air.

Contact Conradin and see if he has a couple of Steyrs (we know what crap they are) for sale, cheap.

[william]

Oh, Rover, you are so crewel!

[conradin]

So there!
But here ya are: viewtopic.php?t=40860

I saw that ad, and actually checked it out. But why do I need THREE FWB65 anyways, especially for a mechanic special for $400? I am willing to offer him a fair price if it is a leftie though. I still need to find a leftie match grip without paying rink 175 Euro.

[conradin]

Contact Conradin and see if he has a couple of Steyrs (we know what crap they are) for sale, cheap.

Come to think of it, I wonder should I list my expired cylinders for sale?

[conradin]

re: non leakage.

I don't know what anyone else thinks but that doesn't sound right to me.

As your gun has a regulator it is extremely unlikely that the cylinders will be causing inconsistent velocity.

I think you are right. I do not feel any leakage, and I am sure even with a water bubble test they would not show leakage. Yet with a full cylinder, it is done after only 70 shots. Also some shots are like dead ducks.

You are right, PCP has a regulating system inside the pistol. So what that means is probably the leakage occurred only when the cylinder is screwed on to the pistol completely. It might or might not also leak at the time of intake from the cylinder to the pistol. Most of the dead ducks were towards the end. What was puzzling was that one shot would be perfectly fine, then the next a dead duck, then waiting for awhile we have another perfectly fine strong shot, then a dead duck, etc.

[David Levene]

I do not feel any leakage, and I am sure even with a water bubble test they would not show leakage. Yet with a full cylinder, it is done after only 70 shots.

You don't need to put a cylinder anywhere near water to check if it's leaking. Just fill it up, check the pressure after ten minutes and put it in a drawer. Check the pressure again after 3-4 days. If it's dropped then the cylinder is leaking.

So what that means is probably the leakage occurred only when the cylinder is screwed on to the pistol completely.

If the cylinder isn't leaking (see above) then fill it up, check the pressure after ten minutes and put it on the gun. Leave it for as many days as you can stand not shooting then check the pressure again. If it's dropped by more than the very small amount lost when you unscrew the cylinder then the gun is leaking.

It might or might not also leak at the time of intake from the cylinder to the pistol.

That's unlikely as when that o-ring goes it usually lets you know quite loudly. For the small cost involved, change it anyway.

What was puzzling was that one shot would be perfectly fine, then the next a dead duck, then waiting for awhile we have another perfectly fine strong shot, then a dead duck, etc.

It sounds to me that your gun could do with a good service and adjustment. Depending on what is found, it sometimes results in the recommendation to remove all tools from the owner's home.

[conradin]

It does not matter now. The pistol and the new cylinder works perfectly. The above mentioned c20 years old cylinders had since been trashed.

[Rover]

Bingo!

[robf]

Leaks can vary depending on fill pressure. I've had a cylinder leak at 200 bar but stop leaking at 100.

Just fill it, drop it in a bath and watch for bubbles. Or as said, fill, leave alone and look again in a few days.

There's nothing in a cylinder to control pressure. The valve opens by being pushed onto the nipple on the gun. It's either open or closed/leaking.

The regulator should do the job of controlling pressure. That either works, or can fail to do so if too much pressure is on it. To check a reg though you need a reg tester.