Lightweight hammers, pros and cons?

[rkr]

I've been thinking of making a lightweight delrin or nylon hammer for my Evanix, mainly to reduce friction but I'm also interested in other benefits it may provide. To my understanding it provides faster shot cycle and faster valve opening but dwell is reduced. How does it go in practice, say if I cut the hammer weight in half do I need more hammer spring force to keep the power level in max. power configuration (.257 Evanix at 160 fpe)? What are the real pros and cons of a light weight hammer, is it for air efficient pellet shooters or is it also useful for higher power bullet guns?

[Motorhead]

In larger caliber and high power guns .... likely not going to work well unless combined with the use of a balanced valve configuration.
Here on the GTA i was one of the first major contributor to the R&D that took place what was in the time HEAVY HAMMER use and looked at what a Lighter & faster hammer would take to get equal result in power while reducing air use by actually reducing dwell when it was excessive.
This lead to gains in air efficiency that in that time was pretty ground breaking.
The original post goes back 8+ years and can be viewed here ...

See:  https://www.gatewaytoairguns.org/GTA/index.php?topic=38088.msg354519#msg354519

[triggertreat]

You're going to need enough hammer energy to crack the valve open, regardless.  You can trim the weight of the hammer some, and that may still work for your tune with the current hammer spring.  There comes a point of dimensioning returns with hammer weights before needing more hammer spring for the same tune.

It's true, the lighter the hammer the faster the valve dwell.  I use some MDS hammers, but with my higher powered tunes I have hammered in a JSB 34gr or two to up the MDS hammer weight on those tunes to avoid the need for a higher rated hammer spring.  In other words, it's a balancing act to get the hammer weight as light as possible without too much heavy hammer spring for a particular tune with a particular weight projectile.

[nervoustrigger]

A pure MDS nylon / Delrin / PEEK hammer will not be a good match for a 160fpe rig unless, as Scott says, it gets paired with a balanced valve.
 
For a conventional valve, you could go with an in-between approach…a hybrid hammer paired with a PEEK poppet.   By hybrid I mean a plastic hammer with a metal core or slug of some kind to bring up the weight.  The PEEK poppet will make the valve noticeably easier to knock open relative to a more common Delrin poppet, so more of the hammer’s energy is conserved (in the form of momentum) for the purpose of providing dwell.

[rsterne]

If your current tune is wasting air from too much dwell, then a lighter hammer can improve efficiency with no power loss.... If you are already tuned so that increasing hammer spring preload gives more power, then installing a lighter hammer will very likely reduce power, and require even more spring to get back to where you were....

This means that without a balanced valve, if you are trying for more power, typical for a Big Bore, fitting a lighter hammer will likely make the gun even harder to cock, and in fact going heavier on the hammer may be advantageous.... Since there are very few balanced valves available in the aftermarket, or used in factory PCPs, fitting a balanced valve so that you can use a lighter hammer in a Big Bore will generally mean making it yourself.... The exception is the Cothran Powerhouse, which drastically reduces the hammer strike required.... but it cannot be easily tuned for a bell-curve, so is best fitting in a regulated PCP.... again, not often the reality in a Big Bore....

Bob

[rkr]

Thank you for your comments. I think I'll make a delrin or nylon hammer and see what happens. I need to make a steel face for it anyway and I can always add weight if needed. In Evanix the sear drags against the hammer belly and there's wear marks at hammer skirt as it rubs against the aluminium frame so softer self lubricating material should reduce the drag and help in shot-to-shot consistency.

As for the balanced valve, I made one for my .45 sniper and while it allowed much reduced hammer strike it also tends to start leaking after few shots - so I decided to keep this gun simple with traditional valve as I need reliability and tight fps spread.

[bear air]

Following

[rkr]

One more question, do I want Delrin/POM, Nylon or PTFE as the material for the hammer body? The face where sear engages will be steel but the hammer will be pulled back from a slot in the hammer body by a 3mm steel stud in a sidelever system. The hammer sides will be only 1.5mm thick.

[nervoustrigger]

Probably not PTFE due to its softness.  MDS nylon (molybdenum disulfide impregnated, Nylatron is a trade name) Delrin, or PEEK would be better choices.  I don’t think any of the 3 is distinctly superior for the job you have planned.  All are tough and have high self-lubricity.

[rsterne]

If the cocking pin only engages in a 1.5mm wall made of plastic, you may have a strength issue....

Bob

[nervoustrigger]

If the hammer sidewall is only 1.5mm thick, that means most of its weight is at the business end of the hammer? 

If so I’m picturing a sandwich hammer assembly.  The thin back portion with the cocking slot in steel, a slug of plastic on that, followed by a steel disc on the face to support the sear.

The plastic portion could be through-drilled and the whole thing assembled with a screw from the front end.  Crudely, picture a slotted flat head screw with a fender washer going through the plastic slug and threading into the back end of the hammer.

[Motorhead]

When I had my Gen 1 rainstorm with a regulator, was very successful using a 100% Aluminum hammer made from 7075 grade.
IIRC had inserted a short round slug of tungsten carbide to be the strike surface while adding a bit of weight.
Good polish and gentle radius on the sear to hammers holding edge and across the top where dragging all was well and no wear was present.

Had done this 5-6 years ago and Sadly don't have any pictures ... BUT DID FIND the original post ... post #17 talks about the hammer.
See: https://www.gatewaytoairguns.org/GTA/index.php?topic=67566.msg643145#msg643145

[Hack21]

I am surprised the following link wasn't yet shared. Good stuff courtesy of rsterne on the subject.

https://www.gatewaytoairguns.org/GTA/index.php?topic=99949.0

[mackeral5]

All of the previous responses are giving you great input.  I followed Scott's light/ultralight hammer posts and applied the concept to many of my guns. 

Early in the process I made a peek hammer for my P15.  The OEM p15 hammer weighs in around 18 grams.  My all peek hammer weighed a whopping 3 grams.  it didn't work so well, obviously. 




I use a 17gram hammer on a 90fpe .30 pellet shooter.  It is in freeflight, and very easy to cock, however it is opening a Cothran valve. 

I have a 60fpe .25 QB build that is opened by a 17gram all peek hammer.  But mods were performed giving that hammer a pretty good running start.....

Running the same 17 gram hammer in my Gauntlet required excessive cocking effort to get sufficient dwell from the small plenum.  Ultimately settled for a 26gram hammer. 

In my .457 Extreme I reduced hammer weight by 40 grams and delivered a tighter string at higher fpe. 

In my Bulldogs, when equipped with conventional valves and unregulated, reducing hammer weight is not helpful at all. 

Even with a balanced valve we may need more hammer mass to facilitate adequate valve dwell. 

All of my .257 testing has pointed towards needing dwell to build power.  Heavy hammers provide dwell.

There is no perfect answer, every gun and application is different.  160fpe out of an Evanix is indeed a unique application.

Some of us have to physically see something fail to learn from it.  My all peek p15 hammer is a good example of this. 

Best of luck, whatever you do please share the the story and results.

[rkr]

I started making a delrin body with steel bolt through it as the face of the hammer. Skirt of the hammer ended up at 1.7mm and it doesn't look too flimsy. Weight is 22 grams vs. 37 grams of the original hammer. I need to set up my lathe for milling next and the gun needs some other mods before I can put it together so testing won't happen anytime soon. I will report how it works when I get to testing phase.

[rkr]

Some results in the gun related thread https://www.gatewaytoairguns.org/GTA/index.php?topic=147066.msg156086756#msg156086756

[JPSAXNC]

Hi All, Another thought on hammer speed, is having a vent hole in the tube for the hammer. So that the hammer isn't compressing air going forward, It can make a big difference in hammer speed. hth

[nervoustrigger]

That’s a good reminder.  Note the same can apply to a vacuum behind the hammer.  For example, the old BAM B50 platform is susceptible.  It tends to cause wild velocity fluctuations.

[triggertreat]

That is a good point, James.  I drilled for venting in all of my hammers.  Venting the hammers will also improve the ES.

[Motorhead]

I had addressed hammer venting issues many years ago and still keep aware of this issue with some designs.  Indeed compression on the forward side and vacuum on the back side can really screw with ES stability.