Assuming that we could start from scratch, a manufacturer could build in enough clearance between the trigger group and the piston to avoid coil bind in the full power setting.
thumper,
You mean, like this - images below? Except the design I am playing with has 6 positions, at 6 mm increments. Rather than just two, like the HW45. So, tuneability via small increments, but lots of them, to provide a larger power range.
With so many increments, if all 6 sear notches were in line, one would get confused about which you are using. So, the spring guide can be rotated to select the stroke length you want to use, and you just cock it back until the mechanism clicks.
I have yet to add the 6 rotational position detent features I have in mind. This would be to keep the piston rod from rotating unintentionally. Back to the OP; If spring preload is variable via a threaded feature, that will need a detent or locknut to keep it from drifting in use, from vibration.
Simply unloading the spring via preload adjustment is great for small tuning changes. For a halving of power, the spring would need such a low preload that the spring would float off its rear support (unless the spring rate was much lower, with much greater preload applied).
More significantly; the piston motion would be sluggish. Lock-time would increase and it would become harder to shoot well, rather than easier. (a HW30 at 7 FPE has a much better shot cycle than a HW95 detuned to 7 FPE)
By shortening the effective stroke length along with the spring preload, such sluggishness and long lock-time can be largely avoided. As the swept volume is also reduced with this concept, the power would probably drop off faster than proportional with stroke length changes. So, the increments should probably not be equal in size for the sear notch positions, unless the increments are very small. Rather, some sort of square root function in sear notch position, to increment power in more equal steps would probably be better.
I was not quite ready to post this, but thumper beat me to expressing the same root idea, that occurred to me two days ago. Anyway, it saves me from spending too much time polishing the design, to add missing elements, such as the trigger sear and selection detent. Never mind the compression tube cocking slot...
One could use a single piston sear notch, and use a movable trigger sear, but somehow that seems less elegant, but is probably feasible. Either way, achieving a good and consistent trigger pull between settings is likely to tricky. So the images below should be seen as conceptual, rather than "production ready".
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subscriber, a well thought out approach as usual! I've been pondering similar designs over the last 3-years: one using a rotatable piston skirt, such as yours, as well as multi-latch sears, similar to how a bear-trap works. That said, I like the rotatable skirt better and recently I've been thinking about the advantages of combining a variable stroke length solution (like yours) and spring pre-load adjustment into one, while being externally accessible to the user.
Fixed spring rate & preload .... Change stroke to differing positions within the cocking cycle to have trigger connect to piston is the ideal solution I would agree.
Indeed, I think the combination of the stroke length adjustment and preload fine tuning should allow fine enough adjustments to eliminate potential slamming or bounce, in theory!There is a fine line .. well not necessarily fine but a line none the less, Where the piston in an ideal tune when released and making pressure to launch a pellet has said piston decelerate and come to rest on a cushion of compressed air preventing piston slam, and hard enough to not have bounce as it bottoms out.
Now with a fixed spring rate .... if we back off far enough to see the power drop away many Ft Lbs on the preload we're at risk of piston bounce, and if preload increased, Slamming of piston into roof of compression chamber becomes a risk.
More preload also risks the spring going into coil bind causing other issues mechanically.
Just a viewpoint and some FYI
I agree with that statement. However, there is always room for a niche, reason people love the FWB300s and D56s.
I agree with that statement, however the title of the thread is "why aren't springers externally adjustable", not "why doesnt someone make a niche model that has multiple power settings". There are springers with multiple power settings. If you want one you can buy one. If you think you can do it better than they do, then do it. The answer to the title question is exactly what I posted. Nothing more or less.
Yes, I did get a bit ahead of myself and forget what the title of the thread was. That said, I think you extrapolate too much about my thinking. I agree that businesses usually cater to profit margins and to the largest addressable market. That said, there is room for niche products at appropriate prices (just check out etsy). An adjustable springer would be a niche product that would probably be priced double of a typical springer.
