Why do hot guns jump violently?

[NMBROOK]

I realize from the above posts that a cannon does recoil and jump about a fair bit .The recoil was certainly taken into consideration as to the rearming of the weapon. So many considerations come into play. Can the crewman reload with all his attendant procedures taken into account ? The swabbing of the barrel and the reloading of same and having the room to accomplish the task ? I have seen so many models that have deck supports and other furniture that would be at extreme risk when a cannon fires. Just my thoughts but I always build my ships with a degree of common sense with what works and what does not.

 

Chris

Totally agree with you on this one Chris.Many of the models I build have internal decks but no accurate drawings exist for the layout.I try to calculate the serviceable area required for the armament and develop the interior around this.This not only applies to obstructions,but also to deck levels as several of the works by Van de Velde I use for reference do compromise feasability.

 

Kind Regards

 

Nigel

[mtaylor]

Due to obstructions, such as hatches, etc. might not a shorter breeching rope be used and basically pull the gun up short on it's recoil?   Yeah.. I'm reaching here...

[NMBROOK]

I maybe inclined to say yes and no Mark   Invariably the breeching rope is sized to give the minimum amount of space required to load the cannon,shortening the rope any further would result in no operational space.Generally I would say there is generally no additional 'spare' space to afford to shorten the rope.

 

Kind Regards

 

Nigel

[mtaylor]

Nigel,

 

While I agree with you in principle, I've seen some contemporary paintings where the gunners (some, not all even on a given ship) are hanging out the port to load.   Makes me wonder.....

[NMBROOK]

I see where you are coming from Mark I would say that would be a rarity rather than common practice.We discussed something similar on Michael's Vasa log,looking at the 1/10 model pictures he posted with the incredibly long cannons,I would have said that would be the case for those.

 

Kind Regards

 

Nigel

[mtaylor]

I do agree Chris and Nigel.  As I said, I'm reaching here.  I'm still wondering about the double-shotting, double-charging or even just the double-shotting, if that would do it.  And records do indicate that many times they double-shotted at close range.   Recoil, as has been pointed out is a function of windage, gun weight, shot weight, etc....

 

Hmm... I wonder where I can find a naval 32 pounder and carriage that I could borrow for some "testing"....???     We'd need some balls, powder, and a gun crew also.

[mtaylor]

Mark. When you get the required provisions to do your experiment give me a shout. While I am not willing to lend a hand with your fact finding expedition I will most certainly send some flowers to your sudden demise.

 

Chris

 

Spoilsport....   :P  

[mtaylor]

Forget the test, I don't want to deal with Homeland Security, the local constabulary, or the ATF...

 

Rethinking this... the accounts do not say WHEN the gun bucked or jumped.  Was it while run out of the port?  During the actual recoil? Or at the end of the recoil?  

 

Logic would say near the end of the recoil.  On an English/American ship, the breeching runs from the casabel, down to the ring and then up to the ring on the bulwark.  So as the gun got to the end of it's recoil (or rope, literally) the rope would tighten and try to become straight from the casabel to the bulwark ring.  The net effect, the muzzle and front of the carriage would go up.

[mtaylor]

Add this one to the "What are some mysteries that you are dying to know?" in Shore Leave.... I guess we won't really ever know.                      

[wq3296]

Folks,

 

The original question related to guns jumping when hot. The jumping may not be due to excessive recoil at all - just that the force from the fired gun is not directed straight back.  Of course any gun will recoil more if the projectile weight is increased. Go to a gun range with rounds of the same caliber and powder charge but with different bullet weights and you can feel it in your hand or shoulder. All the peripheral stuff that has been discussed here does not relate to the original question. The laws of physics govern. There are (were) so many variables that it is silly, but fun, to speculate on the tension of the breech rope, double shot, etc. I believe that the all things being equal, it is possible for guns to jump violently when hot if changes in the barrel alignment, caused by excessive heat, affect the blast such that it is not directed along the centerline of the gun. If the recoil does not go straight back, a y axis force (vertical) will result instead of just the horizontal x axis force. This y axis force would cause the jumping.

 

wq3296 

[Lieste]

I am going to offer an alternative risk, that of the gun in loading condition has a casualty from the heated bore setting off the powder charge, during loading or after the shot is rammed. The worm and sponge are supposed to pull and extinguish any embers from the wad or cartridge, but they can't do much against the heating of the gun over time. The Vade Mecum suggests that the first 20 rounds can be fired in just under an hour, but the prolonged engagement cannot safely exceed 5 minutes between rounds (12 rounds per hour).

In the run out position, the gun recoils, losing some energy to a coefficient of friction of ~ 0.1 between trucks and deck/axles - In the loading position and with a single breeching, the slack is already taken up, so the entire ~15kN of recoil energy (55cwt 32lb) is delivered immediately and impulsively to the breeching rope/side *before* any movement happens - this could risk the eyebolt pulling, or a rope failing, especially if any damage has been done to it (by age and neglect) or by injury within the action. A second preventer breeching would reduce the risk of a damaging recoil from the loading position (halves the expected average loading - but in practice may only act as a backup once the one which is carrying the bulk of the initial load fails - but after some momentum is taken out of the recoil.

Even without this risk, shot damage to the side could easily pull a breeching ring or cut a breeching rope - a second rigged might just permit the gun to continue in action until such time as it can be repaired, or further damage causes a dismounting of the piece.

Both firing rapidly and often, and taking damage from enemy shot are expected on going into fleet action, so either or both of these could be the reason.

Carronades and shell guns are especially called out as 'never to be fired double' unless a preventer breeching rope was mounted, so this makes me think that recoil sharpness is the factor - Carronades recoil at very nearly the 'full' gun of their own calibre's energy already, and are checked in a shorter distance,and slide, elevation screw and breeching casualties seem to have been common enough for this warning against doubling the shot to be repeated.