Quote Originally Posted by ccdjg View Post
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

Quote Originally Posted by Garvin View Post
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