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Hammer weight Physics confusion

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Avidrob

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Mar 25, 2019
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Netherlands
Can somebody help square me this circle please.

Can somebody please explain why increasing hammer weight would aid its ability to open the valve at higher pressure.

Surely the energy stored in the cocked hammer spring in constant, so the only difference between a light or heavy hammer is that the velocity of the hammer, the energy and valve opening potential is the same no?

if this is correct why does adding hammer weight help open the valve at high pressure? would you not need a stronger spring also?

I guess the only thing i can see being different is the dwell time on the heavy hammer is longer, thus letting out more air?

What am i missing?
 
Don't miss / forget that this MASS that is the hammer once in motion opening the valve must stop and then get turned around and moved the other dirrection to enable valve to close.

Heavier the hammer harder & slower it is for the poppet stem to push it back "Quickly"

All this time from open to close is what we call Dwell. There is a point where more dwell does not gain a thing in power and just creates air waste. Sadly as a crutch to make power many guns are equipped with hammers of excessive weight and thus has been for many tuners the inspiration to go the other way and lighten the hammer of many PCP's not only finding equal power but much greater efficiency.



It is a balance that only in more recent years have some manufactures grasped and actually applied to there newer models / designs.
 
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Scott, I read the other thread, a lot of great information. Thank you. What are your thoughts on adding hammer weight to the Impact when using high reg. pressures? I'm wondering if the valve adjuster, helping stop the forward momentum, after the valve has opened will give you the best of both worlds. More mass to hit harder and open the valve fully but also shorter dwell time because the valve adjuster stops the forward momentum so the valve can close faster than it normally would? You know a lot more about it than me... your thoughts?

Thanks, Stoti
 
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While i do service IMPACTS have not really gotten into power mods on them. Thus have no opinion on your inquire. What trend I do see in some of the more efficient PCP's while still having great power is the use of a LIGHT hammer ( Or generally lighter than average ) being thrown with really stiff hammer springs with the hammer in free flight.

Now as noted of a higher BAR setting on reg, that indeed is going to create a poppet less willing to get opened. "IF" there is sufficient weight in the factory hammer and it is running with some free flight ... STIFFER Spring. "IF" adding more spring still can't open the valve sufficiently leaves you 2 choices ... ADD weight to the hammer or make valve open easier ( less poppet head diameter or perhaps a different valve configuration ) * that of a reduced opening force / balanced valve design. 



Taipans / Steyr / Daystate / JSAR and a few other production guns have figured this out. Issue with Heavier hammers or More spring while in some preload against poppet stem ... Guns over dwell and get hammer bounce more readily.



Again JMO ...

Scott S
 
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Scott, I read the other thread, a lot of great information. Thank you. What are your thoughts on adding hammer weight to the Impact when using high reg. pressures? I'm wondering if the valve adjuster, helping stop the forward momentum, after the valve has opened will give you the best of both worlds. More mass to hit harder and open the valve fully but also shorter dwell time because the valve adjuster stops the forward momentum so the valve can close faster than it normally would? You know a lot more about it than me... your thoughts?

Thanks, Stoti
Click to expand...

My name is not Scott but I will chime in anyway. :D

The impact is a different gun:

1- Is designed / engineer to be multi caliber, ergo all will depend on the caliber you have or calibers, tension on the spring is not maxed out, since is a multi caliber. You can adjust it a lot. I believe that spring and hammer is made for the average (between .22 and .25), but if you shoot an specific caliber you might need less (for example 0.177) or more 0.30 (and wait for the 0.35 will bring lots of changes ... and I bet you can not use the 0.177 with that one...nothing official, just thinking out loud here) in order to have the perfect harmony, but still will shoot good on those calibers.

2- Hammer on the impact is +- 19.5grams (from X to Mk2 first edition ... I have not take the weight of others, FX changes a lot of things on latest versions)

3- Hammer Weight on the impact besides the weight, has a pretension to max out the tension on the spring 

The Valve Adjuster helps?, hell yes! (IMO) with the spring and hammer you control the opening, with the Valve Knob the closing both very important.

If you use reg pressure over 150 bar, you need more force to open the valve, and if you have a bigger Valve Seat 6.5mm+ you also need more force to open it (from like 130bar + - ) Chrony numbers do not lie ;) (if you increase the reg and you find no increase of power then and usually you know is a problem on the hammer/spring not fully opening the valve)

my 2 grains of salt ;)
 
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Kinda like a when a bicycle hits the back of your car going 15mph (spring tension) compared to a car (heavier hammer) hitting you from the back at the same speed. A lot more stored energy.

jk
Click to expand...

But this is not the same, 

A car pushed with the same energy to propel the bike at 15mph would only propel the car at maybe 0.2mph.

The kinetic energy is the same. As they both use the same engine (hammer spring)

(forgetting about friction coefficients for the sake of simplicity)

Thats why im confused, 

Given the same kinetic energy, why can a slow heavy hammer open the valve when a fast light hammer cant?
 
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Because of the lighter hammer weight the energy required to open the valve is absorbed faster leaving insufficient residual energy to actually create the required lift and dwell to make any power. ( Simple explanation without the confusion of Inertia and momentum ) 



Too look at this in an ABSTRACT way ... Think of a Pool table and billiard balls. A stationary ball has MASS ( This your valve poppet ) and it will sit there until struck by another ball, which in POOL is a ball of EQUAL mass.

The abstract is this .... Think of the ball you wish to strike staying the same weight, BUT the ball your using to strike it being lighter and if you will progressively lighter if you were to actually apply this.



Lighter the STRIKING ball becomes HARDER & FASTER it must strike the stationary ball to get it moving. *If you send the striking ball always at the same speed ( this is your hammer spring which has fixed energy potential ) you would see less motion of the struck ball with less weight and greater motion with more weight.



If your not changing the weight of the striking ball ( Your hammer ) you must exert MORE energy to get the lighter striking ball to move Faster increasing the impact against the stationary ball to get it move more.





Hope this in a simpler form make some sense.



Scott S
 
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Simplest (as motorhead said above, not going too much into momentum, inertia etc) explanation is that energy transfer from the spring to a heavier hammer is more efficient, as is the energy transfer from the now moving heavier hammer to the valve.

Exactly the same thing is happening when you switch from light to heavier ammo in your pcp without changing anything else. The heavier pellet fliesmore slowly, but the fpe you get is higher than with the lighter projectile. Same accelerating force (air pressure) but more efficient transfer of that energy. The heavier pellet also smacks the target harder downrange due to increased retention of energy and then transfer of that energy to the target.
 
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Thanks Edosan, you know your opinion is always welcomed and valued! You're quickly catching up to Ernest as the "GO TO" guy for Impact power mods. Remember a while back I told you that you were 2nd, only to Ernest? Now I'd say you're almost tied for Impact power mods!!! ☝️or✌️? Jajaja!

The hammer spring installed on the Impact MKII must be extra stiff in order to work for a .22, .25 and .30 as you mentioned. That's exactly why I was asking. I definitely wasn't sure but would think the spring in my MKII being sufficient for the .30 cal. should be more than adequate for my .25. I'm really hoping your weight and valve combo would benefit me. Mine gun is a .25 cal. shooting phenomenally at 160BAR. It's efficient, powerful and very accurate! However, I think I'm right on the verge of needing the hammer weight and or the larger valve if I'm going to gain anymore power for testing the heavier slugs past 160-165BAR. I haven't increased my regulator over 165BAR but up to that reg. pressure there was no decrease in velocity. Now, with my gun tuned at 160BAR, shooting the JSB 33.95 and lighter slugs like the 31.5, 32.8 and 33.5, I've got more than enough velocity. I can shoot the 33.95's well over 1000fps if needed and the 32.8 and 33.5gr. slugs that I've been testing most, I can shoot in excess of 985fps. Right now, I've got the gun tuned to shoot the 33.95 MKII pellets at 975fps and the 33.5 slugs at 960fps with only about a 1/4" difference in the POI (at 50yds anyway), so close that I don't want to change anything other than for testing a few more Nielsen slugs. I want to test the heavier 38gr slugs and a couple brand new Nielsen slugs and think I would definitely benefit from the valve and weight combo. 

Anyway, I've gone on long enough... the post that Scott linked for us was superb, it was packed with very useful information that made perfect sense...after I read it 2 or 3 times! LOL. I just wasn't sure if it applied to the Impact, since the Impact has a stronger spring to begin with, one suited for use with the .22, .25 as well as the .30.

Thank you all for your help with this question. Exactly why I love this site, so many knowledgeable people with different areas and levels of expertise. Awesome!!!

Thanks, Stoti
 
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Simple answer. You are working with force not potential energy.

Force = mass x acceleration.
Click to expand...


It is a little more complicated. There is an exchange of energy between the hammer and the release valve and the energy of the hammer is proportional to the mass and velocity ( 1/2 m v2 ). Increasing either the mass or the force of the spring (that will increase the velocity) will give the hammer more energy and a higher force hitting the valve (the force will be proportional to the de-acceleration of the hammer over the distance travelled on impact), There is, however, a hidden problem with increasing the mass of the hammer. Increase in mass will cause a lower acceleration of the hammer (with the same spring) resulting in lower velocity over the striking distance, and under certain conditions will not make much difference to the vale opening. Increasing the spring force while keeping the mass of the hammer the same, will be more effective as the energy is proportional to the square of velocity. Ideally the balance between the mass, the force of the spring (and the spring factor governed by the spring shape and geometry as well as the material)) and the striking distance is matched to obtain the optimum results.
 
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