Tuning Hammer Free-Flight & Spring Results

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SteveKralsAround

SteveKralsAround

Member
Jan 27, 2020
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Gettysburg ,PA, United States
The other day I was thinking about hammer free flight and decided to try an experiment . The rifle is an unregulated .22 cal , shooting 18.52g Hunter Extremes at 900 fps . Two different hammer springs set to run the pellet at the same speed . With a 200 bar starting pressure , 2 mags for 24 shots on each trial . Spring "A" 23 #/inch 2 1/2" length . Spring "B" 28 #/inch 2 1/8" length . 

Anyone care to guess the effect found in the results ? . What do you guys think happened ?

I will post the result at 8 pm EST .






 
Normally, I would agree with Jim. More spring preload would cause the hammer to be moving faster which causes the valve to open farther and stay open longer. What I’m not sure how to figure is that even if the springs are the same diameter, one spring is stronger, it’s also shorter which would cause the results to kind of offset. 

I was posting at the same time as Scott...I agree and definitely defer to Scott’s wisdom on this one!

Stoti
 
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Had a brain fart...updated my answer :)

Assuming by “results” we mean the longest useful bell curve, my thought process is as follows…

One of the common tuning techniques is playing around with lift and dwell by changing hammer mass and spring rating. For a regulated system, the effects are fairly easy to conceptualize. It’s a little tougher in an unregulated system. Still, let’s look at regulated as a starting point. Using a lightweight hammer and smacking the valve at a high velocity opens it quickly, produces a sharper pressure pulse to help get the pellet moving. Then because the hammer is lightweight, it is carrying less momentum which allows the valve to close quickly (short dwell). The result is less air used for a given state of tune.

Meanwhile in this experiment we are presumably using one hammer. The hammer mass is constant. There is one and only one velocity for this hammer that will produce 900fps. That suggests there will be no difference between the two springs because they will have each been preloaded by whatever amount is necessary for them to deliver 900fps. 

However the one difference we haven’t yet accounted for is that the springs themselves don’t weigh the same. So I’m going to say the shot count advantage goes to the lighter of the two springs…lighter in terms of its actual mass, not lighter in terms of its spring rate. It will allow for ever so slightly more hammer velocity and shorter dwell. Probably not by much though because the spring probably accounts for only a small portion of the moving mass.

Lastly, I’m working from the assumption that both configurations have sufficient preload to satisfy the anti-bounce goals of a free-flight hammer. If not, then it will be the one that doesn’t produce a secondary valve opening.
 
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The hammer mass remains constant .

The outer spring diameters are the same , spring rates are different .

The lighter , longer 23 # spring has 1/4" of free flight .

The heavier , shorter 28 # spring has 5/8" of free flight .

The OEM spring 10# 2 3/4" no free flight .

same pellet weight , same speed , same fill pressure start .

the result turned out to be opposite of what I thought would happen ....

dwell
 
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Meanwhile in this experiment we are presumably using one hammer. The hammer mass is constant. There is one and only one velocity for this hammer that will produce 900fps. That suggests there will be no difference between the two springs because they will have each been preloaded by whatever amount is necessary for them to deliver 900fps. 



900 fps average over 24 shots (unregulated)
 
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Oh so these springs are not under any preload? I'm inferring that from the differing amounts of free-flight.
Click to expand...


What I call free flight is the measurable distance of the hammer between the valve and the spring while not cocked .

Then the heavier spring has to cause more lift and shorter dwell?

Stoti
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That is exactly what I thought the results would show .


 
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Then the heavier spring has to cause more lift and shorter dwell?
Click to expand...

If so, that means the maximum velocities will be different for each configuration. That's the only possible outcome if the hammer's mass and other variables remain constant.

Therein may lie the difference in how I was approaching the question. I assumed the 900fps was the peak velocity of the bell curve for each, but Steve has since clarified it to be the average.

Either that or the longer, lighter spring is contributing a small amount of valve bounce as a result of not being preloaded.
 
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Then the heavier spring has to cause more lift and shorter dwell?
Click to expand...

If so, that means the maximum velocities will be different for each configuration. That's the only possible outcome if the hammer's mass and other variables remain constant.

Therein may lie the difference in how I was approaching the question. I assumed the 900fps was the peak velocity of the bell curve for each, but Steve has since clarified it to be the average.

Either that or the longer, lighter spring is contributing a small amount of valve bounce as a result of not being preloaded.
Click to expand...


BINGO !

What surpised me was the extreme spread .

The lighter 23 # rate spring with slight bounce produce a difference of 16 fps . (slight bounce according to my hearing)

The 28 # rate spring had an extreme spread of 38 fps .
 
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So to me this means there are limits to be benefit of the amount of free flight and too much will have an adverse effect . As I thought the heavy spring with more free flight would produce a lesser amount of extreme spread .

I hope you all have enjoyed this experiment ; it certainly surpised me and raises another question .



" SSG or Not ? " , nope change that . Next question is "At what time do I want to go shooting tomorrow ?"

I wonder if a 25 # rate spring with a free flight length between the othe two would produce a lower extreme spread ?




 
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Yes it sounds like you've connected the dots now...the high ES with the heavier spring is a result of the large amount of free flight (0.63in). Little variations in friction over this distance from one trigger pull to the next lead to large velocity swings. To get the best of both worlds, use a somewhat weaker spring than both of them and install it with an SSG so the spring is under some preload, and position it so it has no more than perhaps 1/8" of free flight. That's what makes a fully adjustable SSG, one having both preload adjustment and gap adjustment, so versatile.
 
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If you really want to throw a curve in there , make yourself a cobra valve. Much simpler than a regulator with almost as good of a result when done right. Nice work , looks like you have your spring weight sorted out .
Click to expand...

Sending him down that rabbit hole eh ???
Click to expand...


Ok , I'll bite : What's a corba valve ?
 
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