Spring return system for hammer strike control

[corerftech]

If a hammer in a pcp was to have a variable rate return spring opposing it to generate a control for hammer return and dwell would that be helpful? Could that assist in control waste air flow?

I was contemplating rallysharks clear tube mod to the at44 hammer.
The compression rate is not variable, it only controls hammer bounce and dwell in a single point. The rate can't be changed. Not having looked at the at44 valve receiver up close today but having the thought, of the vale receiver were able to be drilled and have two pins added that are spring loaded with rate controls, coupled they've used to control or assist with the slew rate of the valve closure ??

There would be a fixed air pressure acting on the valve.
A fixed but adjustable rate of stem spring.
A n adjustable hammer spring.
Lastly an adjustable twin stand off pin that resists the hammer blow.
That is four points of variable control and the duration curve potentially could have four controls manipulating the dwell curve shape.

 Not saying it can be applied to a valve and valve receiver effectively but that would be as close
To electronic control as one could get in a mechanical state. It also would defend against hammer bounce and accidental leaks if the hammer spring was set very loose.

Anyway I was having coffee and contemplating life and had the thought. Maybe someone has already done it on Airgun's. Maybe an answer to a problem that doesn't exist.

[Motorhead]

While not a physics guy .... my thoughts are that if in a lab where one could fit pressure transducers and related monitoring means you very likely could achieve a very well balanced self regulating state of tune.

Sadly springs are NOT constant in there energy rate over time and cyclic motion.
If one spring in the system changes spec it upsets the whole balance.
If we had a system based upon the spring rates of MANY springs don't see how one could honestly get a long term balance to happen

Just thoughts and like you ... over a cup of Joe 

[rsterne]

I'm not following most of your description.... but if you use pins to control the forward limit of the hammer movement, you will also limit the maximum amount the valve can open.... After the hammer hits the pins, any reduction in pressure inside the valve after that will result in declining velocity for the pellet.... You will have cancelled any possible self-regulation at that point....

PCP valves self-regulate by opening more as the pressure falls.... This is what causes the bell-curve in velocity we strive for in an unregulated PCP.... Sometimes, after the velocity peaks, that process happens too quickly, and wastes air, causing a compounding effect (pressure drops more quickly, valve opens even further, wasting even more air).... The bstaley O-ring buffer system is intended to correct that by working like a very high rate progressive valve spring.... However, completely eliminating the possibility of the valve opening further as the pressure drops (with a rigid stop) will guarantee declining velocity as the pressure falls....

Bob

[Rallyshark]

My clear tube mod is basically a variation of the bstaley o-ring mod.  I'm just using silicon tubing, instead of o-rings, but the same principle applies.  I have tried different variations of the rc car fuel tubing, and some manufacturers of it have in varying levels of wall thickness.  You can't see it in the picture, but the tubing currently in there is one of the thicker wall types.  I also filled the hole in the tubing with a cut rubber o-ring, so in theory, the resistance to compression increases a lot after a certain point.  Of course, that resistance to compression requires the hammer spring to adjusted accordingly to a certain extent depending on power level. 

For those who haven't seen what Mike is referring to, this is it below.  I've found it to be far more beneficial mid-low power settings(under 35-40fpe).  It is still the simplest way to apply the same principle in the AT-44 at least in my "testing".


Mike, your idea is good, but applying it reliably in the given space you have to work with may be an issue.  I think what the experts above are saying is that is a lot of effort to essentially accomplish the same thing as the bstaley mod?  Heck, I even toyed with the idea of a damper system in the hammer with different rates of bound and rebound.  While in theory it can work, the execution of it is a whole other ball of wax... 

In my case, I've learned the hard way that the simplest is usually the best.  I have all kinds of neat ideas in my head, but after its all said and done, I usually end putting stuff back the way it was.  The complication of it tends lend it self to less reliability and not nearly enough benefit to justify it.  K.I.S.S.  always comes back to bite me in the rear 

This isn't to say don't try it, of course!  If you come up with something that works better, that would awesome.  So far the best way of not wasting air in a while has been Bob's SSG concept, and it can be done on most guns.  The only reason I haven't adopted it my self is because I'm a 'one gun for most things' type of guy, and it doesn't lend itself to easy adjustments on my particular guns. 

[corerftech]

Rsterne the intent was not fixed pins but ones reinforced with springs beneath. Identical to the hammer spring in basic operation except they impede hammer travel at a rate based on their spring tension. They would add a step to control dwell.

I never mentioned fixed pins stopping the hammer, simply rebounding it away from the valve while still traveling forward. Basic rebound control with a variable rate and kicking in at a particular valve stem height (lift). Think variable intake valve can lobe.

I could change the rate and change the valve open position at which it operates.

Was a thought. Complicated and counterproductive I'm sure.
Certainly NOT fixed metal pins opposing the hammer strike.

[rsterne]

I didn't understand that the pins were spring loaded.... If you use two pins (or more) with different spring rates and heights, you can achieve a progressively higher spring rate as the hammer travels more as the air pressure drops.... While this could work, I think it is just a more complicated way of achieving what a stack of O-rings do.... As they compress from round to oval and eventually to nearly flat, they work like a progressive spring.... You can use different O-ring cross sections and diameters if you want even more control over the progression, should it be required....

Bob

[corerftech]

Yes one requires complete disassembly of the gun the other simply removing the reservoir  and adjusting the two screws

 Probably not even feasible I haven't looked at the valve body and I'm sure that I've completely missed something

 But I see you did grasp the idea of having very fine and precise control over the hammer strike and rebound with multiple springs multiple pins and varying their rates

That was the idea that was driving the topic

[rsterne]

You can change the O-ring stack by hooking them from the back and withdrawing them, once the hammer is removed, as they simply sit against the back of the valve.... Usually that does not require removal of the breech or trigger group, and sometimes not even the stock, depending on a few variables.... If you are not familiar with the bstaley mod, I suggest you investigate it.... It works well for low to medium powered PCPs, the drawback is that it starts operating too soon, limiting the peak power available for any given setup....

Bob