I'm really starting to think that these 21/22mm bores with their longer strokes...

[Shed tuner]

Hi Jon

Is it too secret to bring along to the bash?

Might be interesting to compare yours and mine.

BB

It's not mine mate, I will ask the developer... I believe he's planning on coming to the bash. Would be a good conv between you two

[Black Beard]

Excellent. Would love to see someone else playing with this stuff.

[Shed tuner]

Excellent. Would love to see someone else playing with this stuff.

He's also playing with accelerometers

[TopDog]

Not really, as the small bore has less air to compress, and that air presses back over s smaller surface area, reducing the decelerative force, so the piston is decelerated less, so it's overall journey time is actually shorter... however, see below...


Been running some numbers on the top secret funky recoil simulator:

Bore & Stroke / exit time / piston bounce dist / action dist / max piston bounce
25mm & 78mm / 10 / 5.9 / 4 / 28.4
22mm & 92mm / 9.7 / 7.7 / 3.8 / 36.9

lock time (pellet exit time) is actually a fraction quicker on the 22, but the difference is tiny.
the action dist recoil is 0.2mm less, but also a tiny difference.

The far more significant numbers, I'd suggest, are the piston bounce distance (at pellet exit) - the 22s piston has bounced back 7.7mm, the 25s only 5.9 Still not a huge difference, but definitely the most significant so far. Max piston bounce (ie after the pellet has left) is also a fair bit great too...



Maybe this is why ? Maybe we should make our 22mm pistons heavier....

Interesting results there Jon. What were the other parameters used in the model besides Bore and Stroke by the way? Pellet Type, TP Dims, Spring Stiffness and fixed and moving masses etc. If I send you some rifle parameters for which I have oodles of test results, could you plug them into your TSS (Top Secret Simulator) and let me have a copy of the output data file to compare with my measured results? I can use you as the simulator driver!! Tee Hee!

atvb
David

[Shed tuner]

Interesting results there Jon. What were the other parameters used in the model besides Bore and Stroke by the way? Pellet Type, TP Dims, Spring Stiffness and fixed and moving masses etc. If I send you some rifle parameters for which I have oodles of test results, could you plug them into your TSS (Top Secret Simulator) and let me have a copy of the output data file to compare with my measured results? I can use you as the simulator driver!! Tee Hee!

atvb
David

Yes David, happy to do so.. will take it to email....

The dev would very much like to correlate to empirical results; I recall your piston displacement measuring potential divider...

ATB - JB

[TopDog]

Yes David, happy to do so.. will take it to email....

The dev would very much like to correlate to empirical results; I recall your piston displacement measuring potential divider...

ATB - JB

Hi Jon

That's very kind, thank you!

Will try to get down to the Bash if I can hitch a ride since it's a helluva hike from here!

atvb
David

[Shed tuner]

Hi Jon

That's very kind, thank you!

Will try to get down to the Bash if I can hitch a ride since it's a helluva hike from here!

atvb
David

I forgot how far "north" you are - I can recommend a decent B&B very closeby if you want top ensure a decent night's rest with all that travelling...

[BTDT]

It's not mine mate, I will ask the developer... I believe he's planning on coming to the bash. Would be a good conv between you two

I think you'll find they've already met, Jon.

I introduced them to each other at the last Boinger Bash I attended.

[Shed tuner]

I think you'll find they've already met, Jon.

I introduced them to each other at the last Boinger Bash I attended.

Yes mate, they have indeed... you coming to this event ?

[Snooper601]

Congratulations to Jim on another excellent article in the latest AGW, including this very subject.

Also to Tony on his boinger article in the same issue.

Boingers are the new cool airguns.

Cheers

John

[BTDT]

Yes mate, they have indeed... you coming to this event ?

Looking very doubtful on two counts, Jon.

First - no lift. Second, the Saturday will be spent setting out a new 30 target HFT course for the Nomads shoot, which will be held on the Sunday.

[TonyL]

Looking very doubtful on two counts, Jon.

First - no lift. Second, the Saturday will be spent setting out a new 30 target HFT course for the Nomads shoot, which will be held on the Sunday.

'Tis a shame, Jim, as it would have been really nice to meet there again.

The lift would never be an issue.....a mere trifling diversion, young sir

But I appreciate the commitment and hard work required in getting the new Nomads shoot sorted and established.

Next one, hopefully?

[TonyL]

Congratulations to Jim on another excellent article in the latest AGW, including this very subject.

Also to Tony on his boinger article in the same issue.

Boingers are the new cool airguns.

Cheers

John

Will see them tomorrow John; thank you.

Boingers have ALWAYS been the cool dude's weapon of choice, young sir!

[rockdrill]

...are actually more hold sensitive that the 25s
Shooting today with a 22mm TX, around 90mm stroke, benched. Was getting an inch of vertical stringing. Then realised it was because I was getting lazy with my technique, letting my RH pull down on the pistol grip, the buttstock being supported by the rear bag.
I then shot few a strings much more attentive to position, and the stringing disappeared to give some lovely groups...
Now, the short stroke 25s (78mm), simply would never have that issue.
Going to test the 23 (86mm) tomorrow, but I think that's OK too...
I guess that whilst the longer, smaller bore strokes are more efficient, there comes a point when the extra stroke simply can't be made up for in efficiency and the overall "lock time" suffers ? Going to look at a rather funky recoil simulator and see what it thinks...

To be honest your findings do not surprise me, it seems logical that there is going to be an optimum set of dimensions for a balance of efficiency and ease of obtaining accurate performance and straying outside that envelope gives rise to unwanted variances.

[Shed tuner]

To be honest your findings do not surprise me, it seems logical that there is going to be an optimum set of dimensions for a balance of efficiency and ease of obtaining accurate performance and straying outside that envelope gives rise to unwanted variances.

Agreed, although I'm slightly surprised that's it's so "detectable" within a fairly small variation of those parameters;
- 26mm OK (slightly hold sensitive) and a little too much recoil / surge
- 25mm good but can be a little "aggressive"
- 24mm very good and quite soft
- 23mm very good and soft
- 22mm OK (slightly hold sensitive) and very soft


Spent rather a lot of time in the shed lately, so I have built all of these now - bringing them to the bash if folks want to compare, although the 24 is in .20. I think Tony / Nick have 21s too...

Maybe I need to try 23.5 ?