Slo-mo footage!

[ptdunk]

Posted some of this in general...

I had a very productive visit to a high speed studio and got some interesting footage.


First stuff I cobbled together is some footage of 1800's gallery gun darts firing, demonstrating Gerald Cardews 'pop gun' and 'blowpipe' compression characteristics with a volute spring piston and V-spring Bellows airgun:

https://youtu.be/VfvLJgDHgY4

I did a 'barrel movement before pellet leaves barrel' comparison on a few recoiling and semi recoiling match rifles with interesting result.
Done against a scale I will be able to measure how far the barrels move and so give them a scoring on how much they actually move before the pellet leaves the muzzle.

Annoyingly the Diana Mod.60 failed to cock and the Anschutz 250 failed to close after cocking (both worked fine last time I shot them) so it won't be a conclusive mechanism comparison but interesting nonetheless. Maybe that's a non accuracy related indication why these weren't as popular as the ultra reliable FWB300 series?
The HW55 is a surprise....as is the first recoiless match rifle the Anschutz 220....I'll cobble together those clips as a non-public video for viewing by forum members to see what you all think, before I make a better video in the future.
Same test on my tuned 97 vs boingy bog standard one and some great footage of a FWB124 spring in cocking slot on firing.
Also tuned britannia & original spring minty Britannia.

Thanks for peoples suggestions, made for an interesting days filming.

Not that he'll ever read this but thanks to Martin for filming this all, what a star.

Cheers,
Matt

[ccdjg]

Excellent footage Matt, and lots to mull over. Presumably a first for airguns?

It is interesting to see that in some instances there is a lot of initial air turbulence in front of the dart, showing that compressed air is getting past the dart flight fibres in the barrel. It seems to be more pronounced in the "pop gun" mode. I wonder why this is?

It would be worth posting your video heads-up also in the General Airgun section, to get the reactions of the technical bods.

Cheers,
John

[Garvin]

Interesting stuff, Matt. It's impressive how quickly the bristles recover their shape after the initial blast of air, suggesting turbulence is only immediately around the muzzle, at which point the body of the dart is rapidly moving beyond this 'zone of instability'.

[ccdjg]

Apologies Matt - I didn't read that you had already put your post in the General section.

Cheers,
John

[ptdunk]

Apologies Matt - I didn't read that you had already put your post in the General section.

Cheers,
John

No problem John.


For those that don't know the late great Gerald Cardew wrote about the four stages of spring piston guns, concerning amounts of pressure.

Blowpipe
Popgun
Combustion
Detonation

Read here:
https://studylib.net/doc/7683295/car...-vs-detonation

Interesting stuff, Matt. It's impressive how quickly the bristles recover their shape after the initial blast of air, suggesting turbulence is only immediately around the muzzle, at which point the body of the dart is rapidly moving beyond this 'zone of instability'.

I think you've hit on a big difference between the two guns, I don't think the Bellows has a 'zone of instability' as you put it (great phrase by the way, I may nick that)

The 'pop gun' compression of the spring piston Hebelspanner causes the dart flights to flare out immediately after leaving the muzzle, presumably due to the build up of air pressure before the dart is 'popped' out of the barrel.

[IMG][/IMG]
[IMG][/IMG]


With the bellows gun though the flights are pretty much unaffected by the steady flow of air of the bellows, which precedes the slightly looser fitting dart in a straight line.

[IMG][/IMG]
[IMG][/IMG]

Quite a difference, also the dart fired from the bellows gun looks much more stable, while the piont of the spring piston hebelspanner dart is slightly off centre as it travels towards the target, probably pushed off course slightly by the sudden blast of air behind the dart in the 'popgun' compression. Although it would probably stabalise itself on the way to the target this initial wobble would take it fractionally off course.

My own shooting with these airguns shows the bellows to be more consistantly accurate, while the Hebelspanner spring piston gun although accurate has a fair few flyers.
I would say the bellows gun uses the blowpipe action to very good effect.

So if the spring piston 'popgun' builds up the pressure behind the dart until it overcomes the darts inertia and pops it out, then how does the bellows compress air? is it a constant pressure from the moment the bellows start compressing? Physics is not my strong point.

As some of the first types of target spring airgun I find the difference very interesting.



Cheers,
Matt