British QF 18-pdr Mk.2 comment

[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.