preload versus heavier hammer?
after some experimentation with my stealth i have found that the accuracy increases with less preload on the hammer spring (fewer washers) but of course the fps goes down, so, adjusting the tophat back out to compensate and bring the fps back up i have noticed that the accuracy remains……so it would seem that my hammer spring has a sweet spot in terms of accuracy………..so, if a “slack” spring is more efficient would a heavier hammer be a good way to increase the fps and keep accuracy?
To recap, it seems a heavily preloaded spring produces irregular strikes (according to the chrono)
A “slack” spring produces regular strikes (according to the chrono)
Question; would a slack spring and heavy hammer be more efficient than more preload on the spring? 😕
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I like this theory, makes sence in my head also.
Most on here are set on getting the most power and some are focused on a consistant shot to shot count set up so the latter would fit into your idea for a more indepth set up.
what i would love to see is some data with ratio’s based on rifle type then power output with shot count but from a standard bottle so say a SS with standard bottle fireing at say 25 foot pounds and the hammer weight needed with any other parts needed to acheive this. clearly calibre would be a major factor and pellet two but for anyone just starting out or looking to improve on theres it would be a good starting point. it maybe that to get a better shot count you could look at the valve spring to further tweek things. could be any power you need but a simple format and combination required would be a great reference.
sorry if im stating the obvious, but im just thinking aloud really…………….i reckon the most important thing in this issue is the correlation between the hammer spring/weight and, the valve spring……this may not be as easy as it first sounds as there must be many thousands of permutations which can be alighted upon…..maybe a starting point is to somehow measure the striking weight of the hammer which may be for arguments sake, 10pounds, so maybe the the force upon the valve return should perhaps be equal to that? we can easily work out the rating in pounds of the valve return spring but how do we work out (in pounds) the pressure that is excerted by the air in the bottle? (is this simply the psi in the bottle?) if we know this figure we can surely know what poundage valve spring to use……………
In essense what im saying is if we find a good logical starting point (as just outlined) and keep notes of our tweakings from that point sooner or later a pattern will emerge from which we can make performance predictions and then test those predictions according to the found pattern to see if it works…….bingo we have a formula (based on weight increments) to find the “2 springs device” sweet spot…………..
Up until about 10 years ago, I spent 15 years as a “starving artist” and could have told u all u need to know about god, the universe (hence my username) and life………and now i m thinking about air rifles! funny old thing the passage of life isnt it! 😀 😀 😀 😀 😀
Incidently, im no mathematician nor engineer so as iv outlined the above theory it may be way out in factual detail, but within it (as outlined) i believe is the key……..so, any engineers out there care to think about that for a while?
Cheers 🙂
I think you have found the sweet spot for the spring. The power wheel is a good idea theoretically. I think practicality demands a spring made for a certain situation. Right tool for the right job?
Good topic! I am curious to hear what the rest of the boys have to say about this as “excessive preload” and “heavier hammer bounce” surely contribute to decreased accuracy….
well, my boy, youve got the idea now… lets see some strings when youve got her where you want her, i expect youll do well 😎
in looking at the hammer spring (or indeed any spring) my logic runs thus;
whatever the dimension of a spring, it is designed to work efficiently within set parameters, over compression of said spring and it ceases to operate as it should, so, at this point you should use a spring of a higher strength and start again at that point….etc etc etc.
So, in our air rifles surely the starting point of hammer spring strength should be that it is just strong enough to knock open the valve with the top hat as low as it can be……or am i just stating the obvious?
so the next point of interest is surely the valve spring and, by weakening its strength it has a direct effect on the effects of the hammer and its spring to the point where the hammer spring (or hammer weight) can be reduced still further………but why do this? well, i found that my air rifle as it came delivered seemed to be using too much force to do a relatively simple task….why use a sledge hammer to crack a nut when an efficiently placed pin hammer will do the job better not least by not smashing the edible part tp bits in the process……….the nut in our case being the quite fragile top hat, its thread, grub screws and valve stem.
My airarms s400 has a hammer action which is just a click which does not echo off the buildings around my house where as the airforce hammer action is a SMACK which does most definately echo off the buildings…… the airarms also has a less effeicient valve arrangement than the airforce in that its transfer port is beneath the barrel so the air has to first travel upwards and then turn 90 degrees before it meets the skirt of the pellet, where as the airforce transfer port (the end of the top hat/valve stem) is right there behind and in direct line with the back of the pellet, in terms of efficiency, thats exactly where it ought to be, and yet the air arms uses a much softer spring and is therefore quieter, im sure we can tone down our springs and get much better results in all respects…….. 🙂
the AF valve design relies on preload more heavily than others, the lack of preload, i would think, allows more consistent operation by allowing the valve to operate independently of the hammer/spring and their variables once hammer energy dissipates. shot strings may be improved as well and more response to TH adjustment due to quicker (valve) lock time. of course, ive been wrong before… 😥
well, bearing in mind my question, today, i fashioned a temporary hammer weight out of a brass plumbers washer which fitted nicely to the back of the hammer without interfering with the spring (cant say how much it weighs as i dont have any scales, but im guessing about 9grms) this was glued on using epoxy (just temporary for the experiment!) I then removed another half inch of preload which left me with just half inch of preload (it came with three half inch aprox preload spacers) and ran a 30 shot string with chrono and, testing for accuracy which is my chief concern. To cut a long story short i was grouping at 3/4 inches at 40 yards with fps variation of just 3fps, which, although not as accurate as my airarms s400 it is certainly a better fps spread………..the accuracy is perhaps now improved whith reconfiguring my silencer baffles/chambers and/or a better barrel, however, so far this is a big improvement………….so it does seem (at least in my case) that a heavier hammer and a “slacker” spring does make for more consistancy 🙂
Team you are woking in an area that has alot of variables! but also yes you are right! What I have found is less preload on the spring or power wheel and acctually lighter hammers have worked better for me! By the way my power wheel is set on 0, I never go behond 4 whit my power wheel, right now I am shooting and 18 inch barrel on my Condor 2600psi fill down to 1600 psi and my average is 950fps for about 25 to 30 good shots! Stock tank and high flow valve. I am shooting jsb 18.1 gr, 1/2″ groups at 65 yds
Great question!
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Interesting. Don’t forget to factor the barrel length, the size of the pellet, the fill pressure and size of the tank/tube(big factor on the closing of the valve). Once place to start is to find the tuning guide in the quick ref section. There is a tutorial on finding the sweet spot. Also on the power curve. There are many posts about it.
Here are my current numbers
– Condor valve and tank all stock. Basic debur and polish.
– Stock valve spring with retainer screw all the way it.
– TH set at .050″.
– PW at 1/13
– 85gr steel hammer.
– 18″ LW .25 cal barrel.
– JSB 25.4gr pellets
– Fill pressure 2650, End pressure 2100
– 880 – 910 – 880 string over 30 shots.
I could pull 10 more shots in the 50fps variance range. Which is still decent accuracy wise up to 50 yards. According to chairgun. I recommend downloading that tool and play with it. It rocks!