18 Pounder query

[leaddriver]

Sorry if this has been asked before, but can anyone tell me what the mechanism between the traverse gear and the shield pawl is on the right hand side of the carriage of this 18 pounder? It isn't mentioned in Len Trawin's book on Early British QF Artillery so I assume it was later addition?

[leaddriver]

Maybe clearer from these...

[trajan]

I'm just boosting this up as it looks an interesting question and I am surprised nobody has answered it! I am not an artillery buff but they are around GWF so hopefully it will be picked up soon!

[Spaceman]

It's possible that it is linked to the operation of the clamping gear for the gun which is normally operated by the handle just in front of the lever in question. The handbook talks about the clamping handle having two stops, one of which is adjustable. Maybe the lever in question is used to provide that adjustment - in other words, it adjusts the position of one of the stops for the clamping handle. 

If you look at the schematic from the handbook, it's possible the lever in question moves the fore-aft position of the cross-hatched plate that may form the stop(s) for the clamping handle? It's difficult to see any other purposed for this lever?

[leaddriver]

Thanks Spaceman! I think you’re correct re its purpose. The illustration you posted is from the 1915 handbook? So I guess that this mechanism was a wartime modification which lasted until at least 1918?

[Spaceman]

Yes - there is no mention of an adjustable stop pre-War. I'll see if I can work out why this lever was needed from other drawings. Maybe, it was needed to lock the clamp in place with wartime experience showing that the original clamp could become undone as a result of harsh cross-country use?

[Spaceman]

To revise what I said earlier, the lever in question seems to have been added prior to 1913 and so is pre-WW1. It's not clear why the original stop provided to limit movement of the clamping lever in the locked position proved inadequate requiring the extra bit of mechanism to provide a second stop. It may simply be the original stop proved not to be strong enough and, rather than altering the design of  the original clamping clutches and cradle lugs, it was easier to add the extra bit of mechanism. The pictures at the start of this thread are for a Mk II carriage and therefore this mod must have lasted at least to the end of WW1.