Girandoni hybrid

[DT Fletcher]

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.

Went back and viewed Martin's video again and I remembered the issue incorrectly, Martin understands the basic nature of this valve. The problem is that instead of demonstrating the Bruno Is. accident, he speculates that it had to be a very low power shot. He asserts this on the fact that with his gun the air pressure has to go down to 300-400 psi before the hammer spring along will open the valve and the gun will discharge. (So, he fully understands the issue involved) Martin does not state what velocity the .41 cal bullet is propelled at with 300-400 psi other than to say it would be very low.

Martin goes on to demonstrate proper management when no decocking lever is present by backing off the tank.

With the Bruno Is. incident, however, there is no reason to assume that only the hammer spring pressure would be applied. Instead, since the person holding the airgun was not familiar with it's management, we must assume that the shooter only knew how to safely manage a flintlock rifle. To put a flintlock hammer down in safe decock position you normally move the hammer slowly but firmly all the way down. So, at Bruno Is., the hammer is not being gently rested on the exhaust valve (this guy doesn't even know what an exhaust valve is) instead it is being firmly pushed down. It is also possible that the hammer was resting on the exhaust valve and it was bumped.

So, my apologies to Martin, I'm getting old and didn't exactly remember the issue.

[mrto]

One wonders if a gun of this design when purchased in person from Signor Girandoni,he would have gone to great lengths to explain the dangers of trying to decocok the gun and would have emphatically advised against attempting to.

Of course,by the time Lewis and Clark had their example in the far flung colonies of 18th century America any advice from the maker would not have accompanied the gun.

They learned by trial and nearly fatal error!

[greenwayjames]

I spoke to Bowket on this matter because he has not only converted a modern bottle pcp to work using a trip lever mechanism in conjunction with a regulator but also possesses examples of the Girardoni system in both rifle and pistol form in his collection. He said that put in simple terms a bypass was used as a safety feature and disables the mechanism by moving part of the "power train" out of position.
He guesses the Bruno Island incident rifle was not equipped with a bypass/safety and the cocking lever was lowered so that the force of the mainspring opened the valve. The reservoir pressure was low. The trip mechanism opened the valve the normal set amount but it failed to close under the light return spring pressure much in the same way as a door is blown open and so the entire contents go down the barrel. The rifle being of large calibre and lengthy barrel would still be very effective at giving a dangerous velocity to the ball and considerable recoil when emptying the large capacity reservoir.
He finished by saying. The bypass principle is used on modern co2 pistol firearm look a likes that use a hammer to strike the valve stem. Put simply the hammer does not rest on the valve stem. There is a gap. When the trigger is pulled a bar rises and fills the gap. The hammer hits the bar which hits the valve stem and opens the valve. It was loosely based on an idea used in some cowboy type revolvers to get around having to load only 5 chambers in a six shooter. Giffard used rebounding hammers to provide the gap and as a side effect stopped hammer bounce which wasted CO2. Giffard also used an adjustable hammer stop to control the amount the main valve opened but thats entirely different.

I hope I got that right but can always go back to JB if anyone has any queries. James.

[greenwayjames]

One wonders if a gun of this design when purchased in person from Signor Girandoni,he would have gone to great lengths to explain the dangers of trying to decocok the gun and would have emphatically advised against attempting to.

Of course,by the time Lewis and Clark had their example in the far flung colonies of 18th century America any advice from the maker would not have accompanied the gun.

They learned by trial and nearly fatal error!

Who reads instructions anyway

[mrto]

Who reads instructions anyway

If Weihraich had made the gun in those days they would have engraved instructions and a safety warning in to the top of the barrel!

[DT Fletcher]

I spoke to Bowket on this matter because he has not only converted a modern bottle pcp to work using a trip lever mechanism in conjunction with a regulator but also possesses examples of the Girardoni system in both rifle and pistol form in his collection. He said that put in simple terms a bypass was used as a safety feature and disables the mechanism by moving part of the "power train" out of position.
He guesses the Bruno Island incident rifle was not equipped with a bypass/safety and the cocking lever was lowered so that the force of the mainspring opened the valve. The reservoir pressure was low. The trip mechanism opened the valve the normal set amount but it failed to close under the light return spring pressure much in the same way as a door is blown open and so the entire contents go down the barrel. The rifle being of large calibre and lengthy barrel would still be very effective at giving a dangerous velocity to the ball and considerable recoil when emptying the large capacity reservoir. ... James.

Yes. Sounds completely correct.

Comments:
"power train" in Baker/Currie speak is the "latch."

Bypass/safety: the English version (per Baker/Currie specs) of the "Girandoni" rarely has the bypass/safety, there are some such as Mortimer that have it. The Staudenmayer example in Milwaukie Public does not have one. So, yes, almost certainly no bypass on Lewis airgun.

"The reservoir pressure was low" Yes, Lewis describes that he had, after a full fill, already taken 7 shots.

"The trip mechanism opened the valve the normal set amount but it failed to close under the light return spring pressure much in the same way as a door is blown open and so the entire contents go down the barrel. " Not sure about this. I think more likely is that the valve opening cycle was fully executed, slowly, by hand. Which means that the valve was slowly opened as normal and slow enough to dump the entire contents. Remember that the guy who was handling the gun had no idea about how to manage it. Which means he would have been conditioned by his use of firearms (flintlocks.) So, when he went to de-cock the gun, what happened is that the hammer did not go all the way down, because it's now sitting directly on the exhaust valve! What does a flintlock expert do when the hammer does not return to full de-cock or even half cock? I'm no expect in this area but it seems that what they would not do is just leave the hammer hung up in some intermediate position. They're going to gently grab the hammer and push it forward towards decock position.

"The rifle being of large calibre and lengthy barrel would still be very effective at giving a dangerous velocity to the ball and considerable recoil when emptying the large capacity reservoir." I completely agree. This is why is seems that the "very low power" comment by Martin Oro in his video seems to be seriously misguided. Martin states that in his experiments that, hammer spring tension alone, the gun can discharge at 300 to 400 psi. And, instead of showing us what a .41 caliber lead ball does being shot with 400 psi air, he speculates "very low power."

Can somebody work out the energy level of a lead .41 cal ball propelled by 400 psi air?

[DT Fletcher]

One important element of the Austrian Butt Reservoir battery that seems to get overlooked is the latch spring. In many of the diagrams and schematics the latch is usually just there hanging in midair with no support. Instead, the latch is pushed upwards by the latch spring against the tumbler wedge. If this spring is removed. The gun cannot fire.

When the safety/decock lever (if present) is pushed down, it pushes down on the latch and latch spring which moves the latch out of the way of the tumbler wedge, making it impossible to fire the gun. The hammer can now be safely moved to full decock.

I think one thing that made this safety issue so insidious in it's day is that the people using these guns were, by necessity, flintlock shooters. And, presumably they've been trained in how to make a firearm safe by decock of the hammer. With the Girandoni, however, doing what made a flintlock safe would result in the gun discharging of the air rifle.

[DT Fletcher]

The trip mechanism opened the valve the normal set amount but it failed to close under the light return spring pressure much in the same way as a door is blown open and so the entire contents go down the barrel. ... James.

Thinking this over some more, this is right that the valve is going to swing open and release the full load; however, this is not because of the light return spring pressure. instead, once the hammer moves to the point of opening the valve and it swinging away, it doesn't matter how strong the return spring is because the hammer is still in position to keep the valve open; in fact it probably is still moving to open the valve even more. And, once the air is all gone, explosively released, the hammer will easily move to the full decock position because there will now be zero resistance against its movement.

[DT Fletcher]

I want to personally thank Mr. Bowket for his insight into the operation of this valve. What I didn't have was the concept of the valve "swinging door" I knew from experience that this was the case but didn't have the right words to express it.

From a theory standpoint, it seems to me that the Bruno Is. accident has been fully explained. All that is needed now is confirmation experiment that demonstrates what happens when a large lead ball is propelled by 400 psi air. Very low power? or Deadly power?

[greenwayjames]

I want to personally thank Mr. Bowket for his insight into the operation of this valve. What I didn't have was the concept of the valve "swinging door" I knew from experience that this was the case but didn't have the right words to express it.

From a theory standpoint, it seems to me that the Bruno Is. accident has been fully explained. All that is needed now is confirmation experiment that demonstrates what happens when a large lead ball is propelled by 400 psi air. Very low power? or Deadly power?

I will pass those thanks on when I speak to him next. It should be soon because I have to chase him for fresh info for the fanpage in the next day or so.

[Jerry Cornelius]

From a theory standpoint, it seems to me that the Bruno Is. accident has been fully explained. All that is needed now is confirmation experiment that demonstrates what happens when a large lead ball is propelled by 400 psi air. Very low power? or Deadly power?

I might have a book with the necessary formula in but I can’t check before the weekend. It’s middletons book on “man powered bullets” if anyone else has it. Iirc he fabricates a simple total-loss “airgun” running at car tyre pressure (in fact I think a tyre may be the reservoir) and I distinctly remember his observation that a large bore low pressure air gun develops considerable power, the large bore giving a considerable area for the low pressure to work on, and hence allowing some force.

I’ll see if he included the maths.

[DT Fletcher]

To put it into a few more words what the insight of Mr. Boket has brought to the story. What went on in the gun the instance immediately prior to the discharge was well understood. Precisely what was going may not be known but it's without question that the hammer was resting on the exhaust valve.

We also know what happened after the shot. What we really didn't know was what happened at the instance that the valve was cracked open: the instance of discharge. As Bowket describes: "The trip mechanism opened the valve ... (then) much in the same way as a door is blown open, ... the entire contents go down the barrel."

May seem like a small bit, but, imo, it's an important part of the story of the M. Lewis airgun and the Bruno Is. accident. There may be questions about just before or just after, but at the instance of the shot, the exhaust valve of Lewis's airgun was swinging open like a door allowing all the high pressure air down the barrel.

[Shed tuner]

Found this...

http://closefocusresearch.com/calcul...ty-gun-systems

It's for powder burners, and quick play with 100 grains and a 36" barrel gives 500 fps / 58 FP, but I'd guess with the valve being held open, and therefore that pressure being held for longer, it would be a lot higher. (certainly over 100 FP). Even 60FP would be unpleasant !

[DT Fletcher]

So, this new information from the great John Bowket has been running around in my brain. One thought that kept coming back was a CO2 that I was repairing that, after a refit of valves etc, operated in a bizarre manner in that it would "machine gun" on each firing. The rifle was a single shot so there was nothing mechanical involved. But on each fall of the hammer, the gun would go "burpppppppppp" for half a second or so. Was never sure of what caused this but recall doing the typical mechanic thing and replaced some parts and the problem went away. Now, from Bowket's description of the Bruno Is. accident, I'm pretty confident that what was happening is that the exhaust valve of that Crosman 180 was "swinging away" in the high pressure flow of CO2 due to a weak valve return spring.

The Thomas Rodney Journals:
The very best (really the only) description we get of the M. Lewis gun is from Thomas Rodney. It was only through Rodney's perceptive description of his friend's air gun that we know for certain that it was of a Girandoni style. But we got more from Rodney; a description of Lewis's demonstrating the air rifle for Rodney. It didn't go too well. The first charging of the air tank only provide a single shot, another charge of the tank provided 2 shots, they tried another one got 7 and gave up. (I've provided the Rodney quote below)

This event occurred after Bruno Is. and, with Bowket's insight of the weak return spring resulting in an uncontrolled exhaust valve, it would appear to me that the likely reason for Lewis's gun behaving this way is the same weak valve return spring, now, apparently, in at least one tank, at the point of complete failure.

The next event that is worthy of new consideration -with Bowket's observation in hand- is when Lewis in his journals describes how the company blacksmith renewed the gun's main spring and it shot as well as ever. There has been speculation for many decades about what it was that constituted the "mainspring" that was repaired. Note: As far as I can recall, it has never been suggested that lewis's "mainspring" could be the valve return spring. The same spring that in now appears almost invariably to have been the cause of Lewis's earlier problems.


From Thomas Rodney's journal, M. Lewis demonstrating his air rifle for Rodney:
". . . which fired 22 times at one charge. He shewed us the mode of charging her and then loaded with 12 balls which he intended to fire one at a time; but she by some means lost the whole charge of air at the first fire. He charged her again and then she fired twice. He then found the cause and in some measure prevented the airs escaping, and then she fired seven times; but when in perfect order she fires 22 times in a minute. All the balls are put at once into a short side barrel and are then droped into the chamber of the gun one at a time by moving a spring; and when the trigger is pulled just so much air escapes out of the air bag which forms the britch [breech] of the gun as serves for one ball. It is a curious piece of workmanship not easily described and therefore I omit attempting it."

[Geezer]

It was loosely based on an idea used in some cowboy type revolvers to get around having to load only 5 chambers in a six shooter.

That would be the 1896 Fryberg patent transfer bar safety, popularised by Iver Johnson in revolvers as the “hammer the hammer” [and it still won’t fire] safety, and used to this day on Ruger revolvers.

Sounds like Girandoni had the same idea a century earlier?