Isakov and Walther LP400

[David Levene]

So, where can I help and which threads do I better avoid to read? ;)

There is obviously some confusion Ulrich.

I was not referring to threads on Target Talk.

I was referring to the problem of the threads in the LP400 cylinder stripping, sometimes resulting in the cylinders flying 5-6m down range.

[Europa]

I was referring to the problem of the threads in the LP400 cylinder stripping

David, I suspect that Ulrich is unlikely to reply to your comment because the topic has been, more than adequately, dealt with among all the posts. A small minority of people are more careless than the rest of us; this is a fact. If Walther thought that they were dealing with a significant problem with respect to cylinder threads, they would have addressed it by now (it's a major company with huge resources). Meanwhile, if some are intent on installing and removing their cylinders carelessly (i.e. as quickly as possible), then that's their choice. David, there are thousands of satisfied LP400 (and AP20) owners around the world who treat their pistols with respect, and are satisfied with their purchases.

[FredB]

I was referring to the problem of the threads in the LP400 cylinder stripping

.....A small minority of people are more careless than the rest of us; this is a fact. If Walther thought that they were dealing with a significant problem with respect to cylinder threads, they would have addressed it by now (it's a major company with huge resources). Meanwhile, if some are intent on installing and removing their cylinders carelessly (i.e. as quickly as possible), then that's their choice. David, there are thousands of satisfied LP400 (and AP20) owners around the world who treat their pistols with respect, and are satisfied with their purchases.

Oh, well said. Indeed it is the duty of Walther to provide punishment for that careless minority by designing unusually fine cylinder threads of dissimilar metals. And if bystanders are injured by a flying cylinder, then that too is their fault, for associating with lazy careless people. If any manufacturers are to blame for this so-called problem, it is all the other air gun makers who designed cylinder threads that even a careless fool can safely handle. They have failed in their responsibility to enforce properly respectful pistol treatment.

[Europa]

Fred, "lazy fools" (your words, not mine) should not be encouraged to go anywhere near any type of firearm. Equally, Walther don't feel the need to manufacture pistols for such people.

[David M]

A even better question is...
"Will the threads on the careful peoples tanks last the
10 yr tank life ? (still got 5-6 yrs to go)"

[kevinweiho]

David, do careful people like yourself lubricate the cylinder threads? In the Walther manual, it says to use acid-free silicone
grease on the threads for every 1,000 shots, I know it's a no-no since silicone is NOT a metal to metal lubricant, but is good to extend the life of the o-rings.

[Ulrich Eichstädt]

problem of the threads in the LP400 cylinder stripping, sometimes resulting in the cylinders flying 5-6m down range.

So, you're not satisfied with the precision of that flying tanks? Just joking...

Seriously: even if some of the approx dozen threads in the cylinder were missing, I doubt that this causes a cylinder to disappear suddenly and "fly" under pressure like a rocket. The sole cylinder, unscrewed from the gun, has still an own working and safe valve, as every owner knows. This would then have failed, too. Accidents like that would have been reported to the company immediately. Until that it's a kind of "urban rumours" for us.

Some of the first (first! 1st) LP400 Tanks had indeed some problems with the threads, which could be damaged when not carefully aligning the cylinder to the axis of the valve at the pistol while screwing/unscrewing it. Just imagine the angle of the lever, when holding the tank at the "other" end. According to our quality assurance in Ulm this should be history for guns produced after the end of 2013 (sorry, no serial numbers possible, because often parts are produced in batches and assembled later, so the serial number doesn't correspond to the selling date).

[David Levene]

Seriously: even if some of the approx dozen threads in the cylinder were missing, I doubt that this causes a cylinder to disappear suddenly and "fly" under pressure like a rocket. The sole cylinder, unscrewed from the gun, has still an own working and safe valve, as every owner knows. This would then have failed, too. Accidents like that would have been reported to the company immediately. Until that it's a kind of "urban rumours" for us.

When I picked the cylinder up from the range floor it appeared as though all of the thread had stripped. I could still see where it had been but there was not much left of it.

I then offerred it up to the gun again and, without screwing it on, it went on as far as I thought safe without opening the valve. The thread had gone.

As far as I am aware it was reported, and the cylinder was replaced.

Some of the first (first! 1st) LP400 Tanks had indeed some problems with the threads, which could be damaged when not carefully aligning the cylinder to the axis of the valve at the pistol while screwing/unscrewing it. Just imagine the angle of the lever, when holding the tank at the "other" end. According to our quality assurance in Ulm this should be history for guns produced after the end of 2013 (sorry, no serial numbers possible, because often parts are produced in batches and assembled later, so the serial number doesn't correspond to the selling date).

This could very well have been an early gun. It was certainly the first one I was aware of in the UK. It was certainly in use in 2013 so might have been one with the thread problem.

[David M]

David, do careful people like yourself lubricate the cylinder threads? In the Walther manual, it says to use acid-free silicone
grease on the threads for every 1,000 shots, I know it's a no-no since silicone is NOT a metal to metal lubricant, but is good to extend the life of the o-rings.

Yes, I lube the threads every couple of months with a small amount of Festo Pneumatic assembly grease wiped on the threads when filling.
The only tank I have seen fail was another brand, when the lady filling it unscrewed the tank off the bottle without closing the bottle valve.
When the tank had only a coulpe of threads left it blew off the bottle destroying the thread and flew a couple of metres cross the clubhouse.

[william]

So, you're not satisfied with the precision of that flying tanks? Just joking...

problem of the threads in the LP400 cylinder stripping, sometimes resulting in the cylinders flying 5-6m down range.

So, you're not satisfied with the precision of that flying tanks? Just joking...

Ulli, flying tanks? Don't give any ideas to the Bundeswehr.

[Ulrich Eichstädt]

Upps, somehow a Freudian error...

Always these synonyms in different languages, cylinders, tanks, capsules, bottles, whatever.

But I'm not afraid of flying tanks in the german army. Our helicopters don't fly, the ships don't swim, and with our assault rifles you can't hit (sometimes).

[j-team]

Flying tank... AC130 Spectre

https://en.wikipedia.org/wiki/Lockheed_AC-130

[shaky hands]

"Flying tank" was a nickname for the Soviet IL-2:
https://en.wikipedia.org/wiki/Ilyushin_Il-2

[Pheyden]

Ref: tank threads and lubrication.

Lubricated threads are a "boundary lubrication interface", albeit a very slow motion one. Generally, in these types of interfaces dissimilar metals are specified where there is at least a Rockwell hardness difference of 5-6 points in the two materials. Using the same material for both elements, particularly with a lubricant not designed for boundary interfaces, will tend to cause galling, causing either seisure of the treads and/or thread failure. A good example of this is racing wheel lugs and spindle, both made of magnesium. At least one or the other should be coated and/or lubricated.

The other issue may be the choice of aluminum alloy used. From a tensile strength perspective it would appear that 7075-T6 would be the correct choice. However tensile strength may not be the ultimate factor. Other alloys such as 2024-T3(or T6) have very similar strengths, however have much higher levels of ductility and are much less notch sensitive.

The removal of the cylinder, under pressure, will test the ductility of the metal used and metals lacking adequate ductility may develop stress cracks. This is exascerbated by the very design of threads and their method of manufacture. If threads are machined (cut), using either a die or single point tool the root of the threads may have a very sharp corner. This could lead to stress cracking when the cylinder is removed/installed under pressure, particularly if only a few threads are initially engaged.

The best combination would be a more ductile grade of alloy, with coarser threads which are "formed", rather than machined, with an adeqaute number of threads engaged when coming under pneumatic pressure. Forming threads creates a radius at the root of the threads and due to the compressive nature of the process, increases the strength of the material in this high stress area.

[therider]

Ref: tank threads and lubrication.
The removal of the cylinder, under pressure, will test the ductility of the metal used and metals lacking adequate ductility may develop stress cracks.

NO WAY!
Ductile behaviour of metals only interveens after yielding! No way one would design the thread so that under pressure or under unscrewing the yield stress is attained!

[Pheyden]

Yield stress probably is not attained, or surpassed, but stress cracking, particulalry at the root of the threads is a distinct possibility. This can be particularly true if the alloy is not properly heat treated.

All of this is quite academic, without knowing the alloy used, the heat treatment employed, and whether the threads were machined or formed.

[therider]

This is not academic, it's simply wrong!
I'm sorry but Continuum mechanics, fracture mechanics and plasticity theory is science and for professionals, not something to be reinvented in here!
Of course you are free to fantasize... But all this is far away from reality.

[Pheyden]

Obviously, there are those more learned than I in the field of failure analysis and I will bow to their immense knowledge and wisdom. Whenever a feasible explanation is promulgated, rather than simply saying it is a problem with how the cylinder is removed/installed by the pistol owner, then I would be pleased and delighted to consider it. To date I have not seen such an analysis of the apparent problem, as Walther is loathe to admit that there may be a problem, and no one else is willing/capable of performing such analysis work.

So, what we are left with is conjecture and opinion.

[Europa]

Pheyden, Ulrich has already accepted that there was a cylinder thread problem with some of the very first cylinders. This has now been remedied, and it's no longer an issue. With the greatest respect, your posts have added nothing useful to the cylinder debate. The LP400 is a top gun, and I'm very pleased I bought mine.

[Pheyden]

I am pleased to hear that the problem has been resolved. Yes, I agree it is a good gun. I compete against several in my local club.