Why do hot guns jump violently?

[dafi]

In many sources it is mentioned, that guns recoiled and jumped violently when getting hot in an engagement.

 

Any reasons known why?

 

Cheers, Daniel

Edited November 27, 2013 by dafi

[SpyGlass]

If you are talking about a "cannon ball" loaded gun - they jump about fairly violently always  - cold or hot!.

 

But as engagements progressed several things probably made things a bit bouncier.

 

The crew would not be making such a careful job of loading and tamping everything down nor managing the ropes so well.

 

A hot gun will expand  so that the shot will have more chance of being a looser fit and ricocheting down the barrel.

Also the size selection would get sloppier. Also there may be escaping gas around part of the shot which would add instability.

 

I suspect however that your sources were mainly just using more colourful wording to carry the atmosphere

Edited October 17, 2013 by SpyGlass

[jud]

Agree with Spyglass, Guns recoil, cold or hot when fired. Often after ships guns were heated up, they would double shot them. Double shoting a cold gun often caused a failure, double shoting would cause more recoil. Getting sloppy when using black powder can cause a a gun tube to fail. The reason projectiles are rammed hard against the black powder charge is that the power curve of black powder goes high quickly and there needs to be a instant reaction on the projectile to get it moving before that power peak is reached, if not rammed hard against the charge, voids will fill up with pressure before the projectile starts to move and the short time to do that  delays projectile movement enough to make a bomb out of the  gun.  Smokeless powder takes more time to peak, that time gives the projectile time to start moving after the voids are filled  with pressurized gas and before the pressure peak. Pick up a black powder cartridge and shake it, because the powder fills the case and often is a compressed charge, shaking will not create the sound of powder moving around. Smokeless powder seldom fills the case and not often compressed, shaking the cartridge will produce the sound of powder moving around inside  the cartridge case.  Sorry for the windy response.

jud

Edited October 17, 2013 by jud

[dafi]

Here some more entries from my Vic-Build:

1

Hi Daniel

 

Two possible explanations:

 

Powder burning produces gases and heat. It's that heat that makes the gases expand and increases pressure within

the barrel eventually expeling the ball.

the metal of the barrel absorbs some of that heat. As it gets warmer and warmer less and less heat it absorbs leaving more

to expand the gases leading to increased pressure higher muzzle velocity and higher recoil.

 

That's one

 

Another would be that as the gun heats the outside diameter increases and the inner diameter decreases as the muzzle wall

expands and you have a tighter fit with less pressure loss.

 

 

But sincerely....... I really don't know

 

 

All the best

Zeh

 

 

 

The last one is not correct: when an iron ring increases temperature, both the inside as well as the outside diameter increases.

Is a nice experiment at highschool: copper sfere with a diameter slightly below the inner diameter of an copper ring. Sfere won't go through Heat the ring, and the sfere will fall through.

 

My guess is a more violent explosion as the powder heats.

 

Jan

 

 

On the guns... I have no clue.... but..... the guns would heat from within the barrel, toward the outer surface. Heat energy always transfers from hot to cold. The powder end would also heat faster then the barrel end as it would be more exposed to the reaction and for a longer time. I visualize the barrel bore becoming teardrop shaped as it heated, at least within the expansion rate of the cannons material at a given temp.

 

Thermally conductive substances such as metals usually transfer heat efficiently, unlike ...say... glass. Thats why a quick change in glass temp on one side causes breakage. The barrel overall, to my thinking at least, would expand radially from the center and more at the flint end.

 

In rocket fuel trials early on. there were early problems in uneven burn causing the launch to be throw off its center of mass causing wobble, which usually lead to mishaps (ie big BOOMS). On a cannon, the walls attempt to prevent this wobble, but as clearances expand the wobble would cause the recoil to be less symmetrical or straight back. A small shift of momentum to the left or right could increase the force on a single sides breeching rope, possibly to its breaking strength, hence a second rope picked up the slack. 

Symmetry of burn would also be critical. In an internal combustion engine the spark plug placement is key to maximizing efficency in torque and HP. Thats why Fords Boss 429 had a semi-hemispherical head and Mopars had a full Hemispherical head design. This forced the redesign of the plug placement in the valve cover center, but creates a more centered push on the piston top. In comparison the cannon has two issues... the flint fires on top (center of the back would be optimal) and the compression surface (ball) is not flat. If the burn reaches the top of the ball before the bottom, I can see a cannon recoiling with a downward thrust as the unsymmetrical burn would cause the ball to spin which could cause lift at the back wheels. Combined that with any side to side action and I'd want a preventer rope. To avoid these issues engines are build to be at tolerance when at temp, but this wouldn't work with cannon as the clearance would be to close on cold fightings.

 

Something I did notice, previously you had one of the breeching ropes wrapped araound the lower back of carraige, but not so in the most recent modification (I think the rings make sense, as some slack helps absorb recoil). That carriage wrap, to me, seems important as it would help force a more symetrical recoil

 

Of course this is all hypothesis and I could be completely mad.

 

 

 

Thank you all, Daniel

Edited October 20, 2013 by dafi

[dafi]

Amateur, rybakov, SpyGlass:

 

I agree the diameter will change with the heat.

 

The mast-hoops, and also train-wheels are done the same way: heated up they get larger, inside and outside diameter, the get forced over the mast/wheel and give a tight grip once cooled down and shrunk.

 

Is this also the same with the tick walls of the guns? As they have far more material that wants to expand, can it be, that in this case the inner diameter actually decreases?

 

Thank you all for you input, intriguing facts and discussion as always!

 

Daniel

[fnkershner]

In addition to building period models I am also a fan of fiction from the Napoleonic period, Hornblower etc. All of these novels do mention the increased risk of injury from "jumping" guns once the barrel gets hot. I don't know the details or why, but I suspect there is something here we still have not uncovered. Everything I have read seems to indicate that the recoil is more violent once the barrel is hot.

[SpyGlass]

Now the question may be better answered by querying land based guns.

Much more stable basis for comparison

 

My view is that at sea, with an heeled deck  and confusion of a battle guns are not things to be close to when they go off - hot or cold.

[dafi]

One question I do have is the jumping: Is this result of the shot itself ot is it due to a more violent "normal" recoil and the jumping resulting from the breeching rope and tackles forcing the gun upwards?

 

Some sources mentioning them really jumping high ...

 

DAniel

[Beef Wellington]

I suspect its a combination of things, as always. Two additional factors that I would have thought played into this quite significantly would be properties of the burning powder being significantly more violent in an above normal temperature chamber (likely more condensed in time period and hence a more sudden (violent) transfer of energy to the shot - powder being a "low" explosive meaning that it burns, rather than truly exploding like modern "high" explosives). I wonder also how the heat of the barrel would also affect the barrels metallurgic properties, expansion is a given. Would there also be a softening and distortion caused by the non-uniform shape of the barrel, some areas expanding more because they are thicker (assuming safely I think a pretty uniform heat transfer in metal).

 

I would speculate that this phenomenon is also related to the catastrophic failure (exploding) of barrels after years and years of repeated heat stress (?)

Edited October 21, 2013 by Beef Wellington

[craigb]

Ramming a new powder charge into an incompletely swabbed gun can result in premature explosion if bits of burning embers are left in the bore.  This could be most unexpected, injuring people. 

Edited October 21, 2013 by craigb

[jud]

Need to keep in mind that the object of firing a gun was to maim or kill your opponent, not your own gun crews. Injuring your crews or blowing up your guns would be counter productive and everyone knew that. Because powder cartridges were made up in the powder rooms and taken to the guns one at a time, we know much thought went into the preservation of the ship, its gun crews and its guns. It is reasonable to assume that if a hot gun produced excessive pressure because of a heated propelling charge, that would have been taken into consideration when the powder charges were measured and made up into a powder cartridge. I know that their powder was regularly tested for the energy it would produce, the devices were kind of like a pistol of the time but instead of propelling a projectile, the pressure generated was measured by how far a hinged but restricted paddle was moved by each measured charge, crude but would detect changes in the conditions of the powder. Black powder has more in common with blasting chemicals used today than smokeless powder, in fact black powder was used as an explosive. Double shoting was not uncommon, that would produce greater recoil with the standard charge and move the gun to the full limits of the breaching ropes at a higher speed than normal and cause a jump, another thing that might allow that recoil to appear greater in a hot gun, could be,  the axles and wheels would smooth out and offer less friction as they were used.

I was a Gunners Mate in the Navy for about 8 years and have fired thousands of rounds, small arms up to 8" 55's, safety was always taken into account, even in combat. Those safety rules were said to have been written in blood, I question that those ship cannons were intended to jump around when fired normally. It is normal for guns to get hot when being fired repeatably, so I can't believe that a hot gun was not taken into account and the proper safe charges were not worked out long before those guns were placed on any Navy ship.

jud.

[realworkingsailor]

I think you also need to look at the physics of the breeching arrangement...

 

Through the breech ring (above the centreline of the gun), down to an eyebolt and ring on the gun carriage (way below the centreline of the gun) and back up to an anchor point on the bulwark. In tension, the rope will want to straighten out as much as possible, resulting in a downward force on the breech of the gun, and an upward force on the carriage, the result is a torque about the breech of the gun, making it "jump".

 

Anyone who's fired a pistol (or seen on fired) is well aware of upward swing of the barrel after the shot has been fired, the recoil is directed to the shooter's hand through the grip which is below the barrel. Same thing as above, only smaller scale.

 

As to whether hot guns jump more than cold ones.. I think it was more to do with stretching of the breech rope, which would allow the gun to recoil further, (thus being able to develop more momentum) before being checked.

 

Andy

[Beef Wellington]

Don't think anyone is suggesting that crews WANTED them to kick, quite the reverse, it was a simple adverse consequence of the limited technology at the time and the way they were required to be used. Put yourself in the shoes of a typical gun crew in the 18th century - likely illiterate, deafened, blinded by smoke, crews moving between port and starboard guns, shorthanded because of injuries to other gun crew members, being driven to keep up rates of fire etc. It has to be doubtful that the level of sophistication outlined was consistently possible.

 

Ultimately, suspect the question was simply a matter of balancing the risk and cost of accidental casualties vs the risk of casualties imposed by the enemy - kill or be killed. Also pretty sure this equation changed significantly depending on the scenario, one on one ship vs strategic fleet action...

 

...equivalent tragedies continue to happen even in recent history...with highly educated crews and arguably much more luxury in the way of safety protocols and benefits of modern technology.

 

http://en.wikipedia.org/wiki/USS_Iowa_turret_explosion

Edited October 21, 2013 by Beef Wellington

[SpyGlass]

Andy

 

Good practical point on the breech rope - gets my vote for sensible likely cause of increased movement.

[realworkingsailor]

Andy

 

Good practical point on the breech rope - gets my vote for sensible likely cause of increased movement.

 

And if anyone has any doubts... put a large heavy-ish weight at the end of a moderately long rope, shock load it (ie go from slack to fully taught as fast as you can) and watch the craziness happen.

[Beef Wellington]

This is a fascinating topic! I'm wondering, if the breach ropes were stretched, would that have also meant that the guns's would have similarly kicked in the next action (starting with cold barrel again)?

 

It sort of raises another question, assuming that the breach ropes 'stretched' then wouldn't their structural integrity fail as well. How often would breach ropes have been replaced, and how would that have been done at sea (apart from very carefully)?

[realworkingsailor]

This is a fascinating topic! I'm wondering, if the breach ropes were stretched, would that have also meant that the guns's would have similarly kicked in the next action (starting with cold barrel again)?

 

It sort of raises another question, assuming that the breach ropes 'stretched' then wouldn't their structural integrity fail as well. How often would breach ropes have been replaced, and how would that have been done at sea (apart from very carefully)?

 

A lot of rope will stretch naturally under load. That is not a sign of imminent failure. Even natural fiber ropes do have some elasticity and will regain some of their shape when the load is removed. I'm sure breech rope renewal was fairly frequent, and it would not have been that hard. Run out the gun and lash the tackles, replace breech rope and retract the gun.

 

Andy

[fnkershner]

Andy - I think you are close. But the question still remains. Why does it jump more when hot?

[realworkingsailor]

Andy - I think you are close. But the question still remains. Why does it jump more when hot?

 

I'm wondering if in the sources that make this claim, there was not some literary liberty taken in the name of adding extra drama to a situation....

[SpyGlass]

Lets be clear - which sources were actually written by guys who had actually taken part in a sea battle with this type of gun - any at all?.

 

 Perhaps some quotes from sources would help?

 

 

I think this is descriptive writing for atmosphere.

[dafi]

The sources are wide spread.

 

Bodo from our german forum had some nice findings. 

 

- The inside bore gets smaller when heated as the barrel is not a thin ring but has massive walls. Also the barrels can loose their straightness.

German wikipedia: http://de.wikipedia.org/wiki/Rohrkrepierer

(about squib load)

 

- Apparently the more violent recoil can also happen with old fashioned hand held guns.

 

- Some more info/discussion also here

 ttp://www.go2gbo.com/forums/blackpowder...ly-hot-or-cold/

http://www.segelschiffsmodellbau.com/t1216f220-quot-Violent-recoil-on-hot-guns-quot.html

 

Thanks Bodo!

 

DAniel

Edited October 22, 2013 by dafi

[realworkingsailor]

I don't think you're as likely to get a squib on a smooth bore, muzzle loading canon, they are more likely on breech loading rifled guns with prepared charges.

 

Not saying they're impossible, just much less likely

 

In a muzzle loader,  if the gun crew failed to notice the logged ball in the bore initially... as soon as the sponge and worm where sent down the barrel, someone would surely notice something was amiss. And even if they didn't, another loaded charge would sit in front of the lodged shot and might fail to ignite altogether.

 

As for your other two forums.... I can't access the first one and the other... nicht sprechen... sorry...

 

Andy

[jud]

  In guns the heat is produced in the bore and chamber, it radiates outward rapidly, ever see the paint on a large weapon burn because of that heat or a small arms barrel burn the oil, the heat generated does not remain where it was created?  Don't think that the bores of muzzle loading cannons get smaller with heating, there is enough time for any heat to radiate out between shots, which would allow for a  constant temperature in the whole gun tube. The slow firing rates of muzzle loading guns allows for some cooling time between each shot and the wet swab will add some cooling water, a side benefit of drowning burning embers. I would not be surprised to find that the heat those old cannons had to deal with, would be considered cool  in modern rapid fire guns. Nor do I believe that those guns were allowed to jump around under normal use, recoil was a factor,  provisions were made to control the effects of that.

   I don't know how the gun tackle was handled, was it thrown off or allowed to run with recoil acting a brake. Were it allowed to run, any slack in those tackles would tend to destroy that tackle when the gun was fired and if the slack was controlled and the tackle allowed to run, there would be a bitter end whipping around. Need to find some gun drill instructions written at the time to answer that. Perhaps someone here has read some gun drill instructions that could shed some light about what was done with the tackle when the gun was actually fired.

jud

[realworkingsailor]

The gun tackle probably would have been cast off after running out the gun. Like you suggested, the recoil would destroy anything heavier than the breach rope. Most modelers do capture this detail, in that they try to have the gun tackles hooked onto the truck, rather than seized.

 

The more I think about it, the more I feel that the whole idea of hot guns "jumping" more than cool ones is simply Georgian literary hype. Hollywood is not the first to go about exaggerating for dramatic effect.

 

Andy

[SpyGlass]

There are a number of manuals around giving the detailed sequence for working a  muzzle loaded gun.

 

There are lots of discussions around various forums on this subject but until someone points to a source from the actual period I shall go along with Andy.

The breaching rope may ease a bit with successive shots and gradual chaos with attend errors increase as battles proceed.

But apart from those I think all the other descriptions arise from the imaginations of armchair naval authors.

Edited October 22, 2013 by SpyGlass

[dafi]

Apparently Boudriot mentions for the side tackles to be taken off before firing.

 

In the british gun instructions there is no mention of that as far as I know. If one looks at Master and commander, the guns do not run back too fast, due to their own weight. If I am not mistaken, the side tackles could have be loosened a bid before firing.

 

Another thing I realised, is that todays Victory is displayed with left hand laid breeching ropes istead of the normal right hand ropes. Another of Goodwins small mysteries ?!?

 

After long research I found in Nares the following

http://archive.org/stream/seamanship00acadgoog#page/n34/mode/2up

page 25

 

I chose this too for my build even though it was written down some 60 years later. But this would even give further stretching to the ropes when under strain.

 

XXXDAn

Edited October 22, 2013 by dafi

[Jim Lad]

In "The Seaman's Vade Mecum" by William Mountaine, published in 1756, there is no mention of unhooking the tackles in his list of words of command in the section on the 'exercise of the great guns'.  The only mention of the tackles is in his notes on the positioning of the tackles for the lee and windward guns, and I quote,

"If you exercise the lee guns, and it blows fresh, you must keep one tackle hooked to the ring-bolt on the deck, near the coaming, and the other tackle hooked to the ring, in the train of the carriage.  But if you exercise the windward guns, keep both tackles hooked to the ship's side, and the train of the carriage."

 

I think I'm with Spyglass on this one - are there any factual contemporary sources that mention the guns 'kicking' when they got hot?

 

John

[dafi]

I think the Vade mecum is just before the time that Goodwin mentions that the third tackle was issued as a standard.

 

XXXDAn

[AntiSpiral]

i think its simply because there's more heat = more pressure = more recoil = more momentum, and if the ropes are stopping it from going further back it only has one place to go, much like when a you pull the brakes on a motorbike the back end goes up.

But i'm not a scientist..

[mtaylor]

I posted this in Daniel's build log... I'm still looking (as time permits) for the video. 

 

At first I thought the "hot guns jumping and recoiling" was a bit of literary license on part of some authors.  But then, I remembered seeing some videos of American Civil War (aka, The Recent Unpleasantness) where the gunners were firing for effect (load as fast as they could).  I believe it was a competition to get 10 rounds off, points for speed and accuracy.  Last several shots made those cannon jump also.