Potential wear related to power tunes.

[TF89]

The question is a general query on the down the road wear relating to power tunes.  To get this started I will throw out what I know (which isn't much).

For example using the Discovery as an example of a very modified platform.  The .22 I own has been worked to produce 36fpe from a 2300 to 1600 psi fill which is not a real power mod as my fill pressure is still on the low side.  Throwing in a stiffer hammer spring to achieve that certainly has it down side as I mention below.

The one that I'm most aware of when using a heavier than stock hammer spring is the hammer tipping and galling the air tube.  That last one can even happen with stock spring I have found.  The fix for that is often going old school and buttoning the hammer with the same methods used on Springer pistons.  Using a nylon sleeved (or some self lubricating material) hammer also works.   I combine the buttoning with a better hammer pin which seems to reduce tipping during the cocking cycle.

Going outside of my actual knowledge and only what I have read would be the poppet extruding if the valve throat is opened to the extreme and/or fill pressure is increased.  That seems to be fixed by using a denser material such as Peek. 

What other things happen to the poppet?  Does the poppet stem start to mushroom from the heavy hammer strike?   Anything else?

How about the valve itself or other items?  Regarding the poppet stem and the hole in the back of the valve, does that wear or elongate (out of round)?

Well that exhausted what I think I know and now hope to hear from the people who actually power mod on a regular bases.

[nervoustrigger]

My engineering mind is forever devoting CPU cycles thinking of such longevity considerations but unless you are doing heavy, heavy modifications, there’s not much in the way of wear or stress-related failures to be concerned about.  I mean we all know O-rings and other seals eventually fail, particularly dynamic ones (abrasion).  Regulator valve seats gradually wear and introduce pressure creep.  But as far as metal parts failing, that’s way down the list. 

I’ve never had hammer binding severe enough to actually damage a tube/receiver.  It is possible but I think if you are conscientious enough to be mindful of the possibility, there’s no chance you would ever let it get that bad.

Never had a sear failure but that’s a possibility if pushing way more hammer spring preload than the system was ever expected to see. 

One time I did have a torsion spring break and fall out of a trigger group.  Nothing to do with a power tune, just fatigue from its role in sending out several tens of thousands of pellets. 

Never had a valve stem wear out the valve body in a noticeable way.  I seem to recall Ribbonstone citing an example of it though.  Pretty easy to drill it out and set a stub of brass tubing with some threadlocker if it ever does.

I’m sure others can cite isolated examples but it does not seem commonplace in my experience, this coming from someone having roughly half my guns producing between 2x and 4x the energy they did in OEM form. 

[TF89]

Thanks Jason.  I never even considered the sear, yet all the extra stored energy could potentially cause a breakage or wearing down the bearing edges.  I have seen the rounding off of edges on my stock Crosman 140 1st variant sear. 

As far as the tube galling, it happened to me and once it starts only gets worse unless it is addressed.  To be fair it happened after I installed the BNM Breech and I actually ended up replacing the air tube on my Disco because of it.  Not to mention, making cocking very gritty and unpredictable. 

I'm enjoying the read on the extruding poppet thread, very informational and kind of ties into this thread.

[rsterne]

I have never seen and peening of the end of the valve stem, either, even with hugely heavy hammer strikes (eg. a .457 cal).... and all I use for valve stems is normalized O1 tool steel (ie as purchased, no heat treating)....

Bob

[JPSAXNC]

Hi Dave, The wear related to power tunes depends, in my experience if the gun is tuned for just velocity and not consistency, the wear will be less. If tuned for power and consistency, the wear will be greater, because the opposing forces are greater.

[nervoustrigger]

If memory serves, valve stem mushrooming was a problem with the early Puncher Breaker.  Largely unheard of otherwise.  I got into the habit of heat treating the stem when I’m making a poppet because the OEM ones always seem to be, and I sometimes use 2mm which is at risk of bending pretty easily when pressing it into the poppet.  It’s easy enough with W1 steel rod using a small can of propane, a pencil torch, and a bucket of water.

[Motorhead]

JSAR valves with the 2 piece "Brass" poppet head suffer peening issues.  That simply because the poppet stem must be drilled with a .052" drill for venting and material soft enough to allow this.  They hit it with the end of a hardened bolt.  weaker of the two take the damage of this impact.
Not a big deal .. but present.


NOW AS TOO the original question
It generally will be the COCKING, TRIGGER & FIRING mechanics that will see greater wear & tear with power tunes within a conventional juiced up PCP.

EXCEPTIONS being Electronic firing system such as Daystate, Those with Balanced valves such as JSAR, Cothrin valves etc ....  This due to LOWER cocking forces and Lower hammer loads to fire the guns.  * This just a general statement !!!