British QF 18-pdr Mk.2 comment

[Mike Cecil]

This was posted by a museum recently, about their 18-pdr QF Mk.2 gun. Anyone care to comment?

"This is our British Ordnance QF 18-Pounder Mark II. This field gun was key om providing sustained artillery barrages against the enemy. Roughly 10,500 18-pounders were produced by the end of the war. Its quick-fire system was enabled by its recuperator, located above the gun barrel and wrapped in a thick asbestos rope to prevent overheating. The recuperator allowed the barrel to recoil within a fixed cradle, then return to its firing position without manual intervention."

Mike

[Tony Smith]

My only comment is that there is no such thing as a "Quick-Fire System".

QF refers to the format of the Ammunition types.

[motto]

The comment about the asbestos rope preventing the recuperator from over heating must refer to radiated heat from the barrel. The 25 pounder has the barrel above the recuperator so that consideration was apparently reduced or eliminated.
The barrel must get extremely hot under sustained fire.
Are there any restrictions or recommendations on the number of rounds fired in any given time?

David

[Mike Cecil]

I agree with Tony that QF relates to ammunition. In the case of the 18-pdr being referred to, 'QF' in the nomenclature stands for 'Quick Firing' which indicates the means of obturation, that is, the method by which the propellant gases are prevented from escaping to the rear. In the case of QF guns and howitzers, this was primarily a brass cartridge case that expanded tight against the wall of the breech while the projectile is in the barrel, but then relaxes slightly once the projectile has exited the barrel and the pressure within has returned to 'normal', thus allowing easy extraction. (QF cartridge primers have an internal ball which blocks the primer flash hole, preventing gas escape back through the primer pocket). In any event, 'QF' has nothing to do with the means of buffering the recoil or returning the ordnance to the firing position - what the museum is calling the recuperator. In fact, it is the buffer that controls the barrel recoil and the recuperator which returns the barrel to the firing position.

The comment about asbestos rope is a little more perplexing, and one I cannot find a definitive answer for. The use of asbestos rope around the buffer and recuperator is not referred to in either the 1913 or 1923 manuals and handbooks for the 18-pdr, or the 1923 textbook of service ordnance. Trawin's 'Early British QF Artillery' - a highly detailed reference - does not mention the use of rope. Various forums have comments which range from the prevention of overheating to protection from shrapnel, but none provide any reference to a source. So if an MLU member has an official reference to wrapping the buffer and recuperator (B&R) in asbestos rope, please share it here!

We might explore this a little further. Dave has pointed out that, if it is to prevent the B&R from overheating, then it must be heat from an external source such as the barrel. Good observation, as such a wrapping would not assist in reducing heat generated from within the B&R - quite the opposite, it would retain the heat, as the action of the buffer piston and the movement of the mineral oil back and forth must generate a certain amount of heat. I don't know how much heat is generated within the B&R, but it is possibly not all that much given that, in an extreme emergency, pure water can be used as a short-term substitute for the oil. So as far as I'm concerned, Dave's comment that the asbestos rope is there to insulate the B&R from the rising heat of the barrel is looking like the most likely. Perhaps it is also there to prevent the mineral oil from becoming more viscous in cold climatic conditions when the gun is not firing, ie it acts as an insulator under all conditions?

Mike

[Damien Allan]

There is no mention of asbestos rope in any of the 18Pr Mk.1 & II references I have either.
The original Mk.I recoil system was smooth except for the 8TPI threads so that it could be wound into the supporting bracket loops cast into the top of the manganese bronze cradle. There were no rope bindings of any sort in the early photos of the gun.
The AIF's RGF 1911 guns sent to Egypt before the Gallipoli campaign were the same, but the smooth front ends of the cylinders were bound with 1 inch diameter hemp or sisal rope. The only reason I can think of to do this was to protect the thin cylinder walls from damage such as dings during shipping or shrapnel balls. BTW, 1 inch diameter was huge compared with other rope bindings seen elsewhere and later, which were half or 3/8 inch diameter generally.

The later Mk.I carriage recoil cylinders had a modified design where the external 8TPI threads were continuous from one end to the other. While this may have been a manufacturing expedient (or not), it gave the cylinder double the radiating surface to dissipate heat from the workings inside, made the cylinder a bit more rigid, and maybe a tiny bit more resistant to dents that would impinge on the springs sliding back and forth. So if the purpose of the continuous threads was to dissipate heat, then why bind it with a good insulator like rope? The problem with the continuous thread from a maintenance perspective is that it would be a nightmare to unscrew the cylinder out of the bronze cradle if the treads were even slightly flattened or burred. Hence, i think the rope binding was there to protect the cylinder's external threading as much as anything else.

The only recoil system asbestos rope I have seen for 18 Pr was on the Mk.IV, which used a few feet wound inside the annular oil reservoir (around the barrel) to prevent the barrel heat from killing the hydraulic fluid.

cheers,

D.