Managed to grab a little bench time this evening and fitted the MG mounting cradles and pipework (not sure what it's actuially for though?).
The central one is the sheathed cable to the tachometer (rev counter). The two outer ones are the sheathed cables to the trigger motors on the guns*
This is an lMG08/15 with the trigger motor and flexible drive in place:
https://www.maximgun.de/deutschland/lmg-08-15/The lMG and the Vickers both work in similar ways. Cartridges are drawn from the belt passing through the slot at the top, lowered and pushed into the breech. The cartridge is fired, the empty case is pulled out the breech, lowered and ejected through the tube sloping down to the left.
The trigger motor is the lump on the bottom of the casing with the flexible drive hanging down
The difference between the lMG08 and the Vickers is that the Vickers has the triggering mechanism turned upside down, so a Vickers has the trigger motor on the top:
Constantinesco trigger motor on top of case
There's a fascinating article here on rates of fire:
https://riseofflight.com/forum/topic/30921-few-words-about-synchronizers-and-version-1026/Richard
*you don't want to know they have flexible steel sheathing