Girandoni hybrid

[Geezer]

Normally, I avoid any contact with Beeman's fiction writing

lol.

[DT Fletcher]

He's using it with CO2 and since Lawrie is 'Mr CO2', I'm sure it's very safe.

Nonsense. The safety issue with these airguns has absolutely nothing to do with what is being used to power it. These guns, if not properly understood, can be deadly. And, the problem is exactly as you allude to, people think that they know airguns so well that there is nothing new to learn.

The lack of understanding of this type of airgun is near universal today. Beeman clearly doesn't have any idea how these guns work. I've talked with guys who have made reproductions of these airguns and they have no clue how dangerous these airguns are.

I can only do so much. At some point, somebody is going to get killed or seriously hurt if a better understanding of these extremely dangerous airguns is not achieved.

If somebody would make a video demonstrating how dangerous this airguns are, I would back off a bit and just point to that video,. Until then, I will continue to be a pest about this.

[mrto]

I would have thought gunsmiths who have made reproductions of this type of gun have a very clear understanding of the design's inherent flaws and potential dangers.After all,the valving design is very simple,just a knock open valve against valve spring tension and ambient reservoir air pressure.

https://www.youtube.com/watch?v=5fRu5tYH-4Q


Have you fired one of these?

I do wonder if the decocking,(because of the design I agree should not be done) of the mechanism when the cylinder is at 'full' pressure will always result in an unintended and dangerous discharge or if the likelihood of this happening increases only after shots have been fired and cylinder air pressure has decreased allowing hammer spring strength to overcome valve spring and cylinder air pressure resistance,if the hammer is inadvisedly decocked?

Whether and at what point this may happen would vary from gun to gun by maker depending on the balance of the valving mechanism employed?

I'm sure Lawrie Amatruda is fully aware of the dangers of this gun whether it is powered by compressed air or indeed even maybe especially in Co2 because of the lower cylinder pressure.

Possibly Lawrie could comment?

[DT Fletcher]

I would have thought gunsmiths who have made reproductions of this type of gun have a very clear understanding of the design's inherent flaws and potential dangers.After all,the valving design is very simple,just a knock open valve against valve spring tension and ambient reservoir air pressure....

You have demonstrated exactly what I'm talking about: Because you understand modern airguns, you also think you understand these old airguns. But you don't. I know this is so because your description of the valve is completely wrong. It is NOT a knock open valve, which is what a modern airgun valve is. It's what Wolff calls an indirect trip battery. The hammer action does not rebound off the valve stem like a modern gun, instead it first strikes open the valve, always the exact same amount, and then travels past the valve. This is nothing like a modern airgun, no modern airgun has this type of battery action (with one or two very rare exceptions.) Has inherent dangers completely different from modern airguns.

I have seen animations of this valve on Youtube where they have the hammer bouncing back off the valve. Nonsense, the hammer always travels past the valve stem. Note: this is one of unique characteristics of the indirect trip battery, no matter how fast the hammer is traveling, the valve always (repeat ALWAYS) opens the exact same amount (there might be some variation due to tank air pressure and resistance of the valve to being moved) but, in general, the valve opening is set. There are variable power versions of this airgun but only one example is known to exist ) in Girandoni's home town no less.

[DT Fletcher]

Note: this video ( http://youtu.be/5fRu5tYH-4Q) looks okay. Note how the tumbler, after opening the valve, proceeds past the valve stem; i.e. an indirect trip.

Now reimagine this action with the hammer being moved very slowly, as slow as possible, note that the valve will be moved the same as if it was going full speed. Where this valve has been used in modern airguns is with target guns (described to me, I have not seen these myself) where the designer used exactly this type battery. The purpose was to use it as a means of power regulation. No idea if the designer of the modern version even knew of the old version.

[mrto]

Note: this video ( http://youtu.be/5fRu5tYH-4Q) looks okay. Note how the tumbler, after opening the valve, proceeds past the valve stem; i.e. an indirect trip.

Now reimagine this action with the hammer being moved very slowly, as slow as possible, note that the valve will be moved the same as if it was going full speed. Where this valve has been used in modern airguns is with target guns (described to me, I have not seen these myself) where the designer used exactly this type battery. The purpose was to use it as a means of power regulation. No idea if the designer of the modern version even knew of the old version.

On this page can be found about halfway down excellent diagrams of the Girandoni mechanism,which clearly show it as a type of knock open valve,

https://www.beemans.net/Austrian%20airguns.htm

The slightly more elaborate design of the mechanism necessitated because the air source and valve are positioned to the rear of the lock which is of relatively conventional flintlock design.

Also,I have found this youtube video of the Girandoni replica being decocked which is consistent with my understanding of the mechanism and answers my questions admirably.

https://www.youtube.com/watch?v=qvy2OunCu9w

[Benelli B76]

Thanks everyone for your input, it has made me quite impressed with the skill of these early designers and engineers.

Baz

https://www.youtube.com/watch?v=2dZLeEUE940

[DT Fletcher]

Like previously stated, I don't expect folks to understand or believe me. But, you might want to consider for a moment that I'm not the only one with these views. I direct your attention to "Air Guns and Air Pistols" by L. Wesley 1st ed. pg. 28-29: "A Repeating Air-Rifle of 1792- (b) The lock is provided with a small knob which was not fitted to the military weapon.

This job (located on the left lock-plate) when pressed downwards disengaged the mechanism connecting the striker-pin and the hammer. The hammer was then allowed to fall, releasing the tension on the spring, without any air being emitted from the reservoir.

This was undoubtedly a very useful device since, when hunting, the opportunity of taking a shot may pass as quickly as it occurs.

Provided the shooter presses down the small knob, the hammer may be lowered, either with the thumb or by pressing the trigger, without discharging either air or bullet, Half-cock and full-cock positions are provided. The hammer could, of course, be lowered from half-cock without using the knob, as the air-releasing mechanism is not set until the hammer has been raised to the full-cock position.

To appreciate fully the utility of this knob, it must be remembered that a peculiarity of nearly all the old multi-shot pneumatics was the once they had been fully cocked, they had to be fired. The reason for this was the (unlike in spring air-rifles) the pin which depresses the valve, and thus allows the air to escape, completes its full travel irrespective of whether the hammer is allowed to fall quickly or slowly."

[DT Fletcher]

On this page can be found about halfway down excellent diagrams of the Girandoni mechanism,which clearly show it as a type of knock open valve,

https://www.beemans.net/Austrian%20airguns.htm

The slightly more elaborate design of the mechanism necessitated because the air source and valve are positioned to the rear of the lock which is of relatively conventional flintlock design.

Also,I have found this youtube video of the Girandoni replica being decocked which is consistent with my understanding of the mechanism and answers my questions admirably.

https://www.youtube.com/watch?v=qvy2OunCu9w

Yes this video is consistent with your understanding because Martin doesn't understand how these airguns work. The "concern" he talks about is me, the only reason he did this was because of me. The problem is, when it comes to actually demonstrating the Bruno Is. accident he chickens out and just talks it through... expressing exactly what Beeman wrote... by the by.

You wil find my comments on this video. And I made Martin fully aware of how poorly I thought of his "demonstration" on the AVA.

The Bruno Is challenge stands. Just waiting for some brave soul to standup and accept the challenge. Nothing but a bunch of chickens trying to talk their way through it at this point.

[DT Fletcher]

Besides Wesley, another well known airgun expert, Eldon Wolff, also fully understands how these airguns work and is in total agreement with what I've stated; I can state this because his understanding of the dangers of these airguns is fully documented and he pointed out in detail how it is that the Bruno Is. incident was a clear indication of what type of air rifle was involved.

So, on one side there is Wesley, Wolff and Fletcher. On the other side .... Beeman.

And there is even a well known collector of these airguns in the US (obviously not Beeman) who when using one of these airguns during a duck hunting session (not for the ducks, obviously) had the gun accidentally discharge for exactly the reason I've described. He had de-cocked the gun and in the process resting the hammer on the exhaust valve (of course dangerous, but at this point he didn't understand that) and then some time later, the gun, which was resting against something, discharged. He learned, the hard way, that these guns are deadly dangerous. And most of that danger exists because people refuse to understand how they work and the inherent danger.

It's not often one gets to say that I'm right and everyone else is wrong, but, this is one of those cases. I've been observing this for at least 15-20 years. It's quite amazing how tightly folks hold on this misunderstanding. Even those who build replicas. Note: if a mechanic can assemble an engine, does that really mean that they fully understand how it works? Obviously not.

[Shed tuner]

the diagrams on the beeman site are actually very good - would be stretching it to call that a knock open valve - more of a push open (and it's the lack of a need for hammer inertia that makes them very different from a std knock open) - and I can see why decocking would be very scary

It does lose the advantage that a knock open has in terms of power regulation though.. there may be a slight difference in valve closure time with pressure, but essentially the opening is always the same, unlike a knock open where it opens less / much shorter at higher pressures, smoothing out the power curve. With this, I'd except every shot to slowly reduce in power. One advantage however is zero hammer bounce wasting air, so efficiency should be good.

How does the de-cock button / lever work ? I guess it must push the striker latch down out of the way of the hammer tumbler notch to avoid it catching and allow it to pass freely when released ?

JB

[mrto]

I had considered describing it as a push open valve,but as there is free travel of the wedge before it strikes the striker latch which at first instance knocks the valve open or at least gets it moving I decided knock open is as good a way as any to describe it.The mechanism is a clever design intended to ensure consistency of valve dwell on each shot.

The video shows with care on a fully charged cylinder it can be decocked,but inadvisable to do so I agree.

[Garvin]

Nonsense. The safety issue with these airguns has absolutely nothing to do with what is being used to power it. These guns, if not properly understood, can be deadly. And, the problem is exactly as you allude to, people think that they know airguns so well that there is nothing new to learn.

Hmm. I wasn't pointing out that co2 was safe, just that Lawrie is using co2 and he's a real expert in using this gas, so he will understand how safe the gun is, or otherwise, probably better than anyone else alive.

[DT Fletcher]

the diagrams on the beeman site are actually very good -

How does the de-cock button / lever work ? I guess it must push the striker latch down out of the way of the hammer tumbler notch to avoid it catching and allow it to pass freely when released ? JB

I have no issues with the diagrams on Beeman's site. My problem is with the words written.

De-cock function: you are correct, the left-side plate lever pushes down the latch so that it will not be hit by the tumbler. This is also how the power can be varied; by pushing the latch down but not completely out of the way of the tumbler. That way the tumbler strikes the latch for less of it's travel. With that, the valve is pushed in a shorter distance which reduces power. (See Arne Hoff, plate 80)

It may be instructive to realize that varying the speed of the hammer (as done with modern airguns to vary power output) on these airguns has the reverse effect. That is, a slower hammer opens the valve slower so a slow hammer actually increases the time the valve is open which increases the output! A very fast hammer opens the valve quickly and reduces the power output.

[Shed tuner]

I have no issues with the diagrams on Beeman's site. My problem is with the words written.

De-cock function: you are correct, the left-side plate lever pushes down the latch so that it will not be hit by the tumbler. This is also how the power can be varied; by pushing the latch down but not completely out of the way of the tumbler. That way the tumbler strikes the latch for less of it's travel. With that, the valve is pushed in a shorter distance which reduces power. (See Arne Hoff, plate 80)

It may be instructive to realize that varying the speed of the hammer (as done with modern airguns to vary power output) on these airguns has the reverse effect. That is, a slower hammer opens the valve slower so a slow hammer actually increases the time the valve is open which increases the output! A very fast hammer opens the valve quickly and reduces the power output.

Thanks, makes sense.