OK I've come to this one nearly 2 years late, but had to report that that's me driving the Croc at Tan y Bwlch and I was involved in the construction of the beast. It was indeed the brainchild of Brian Hollingsworth who built the body. The bogies were the work of Don Fifer (Pfeifferbahn), the beautifully metal bashed and distinctive bonnets were by Warren Shephard (7mm modeller of note these days) and I was charged (!) with the electrics. As I recall each bogie had a 1hp (I think) 36v motor controlled by a commercial chopper style control box amidships with the lead acid batteries. All conrol was from a cable connected hand held box which controlled air brakes, air whistle, forward/reverse and power controller- all of which presented quite a challenge design wise as it had to fail safe in the event of the controller being disabled..
The piece de resistance were the RhB station bell sounds recorded to a ROM chip (in 1987 !) and donated by a Swiss gentleman I believe and this necessitated the Croc to have its own sound system!
The intention was to have the battery charging done by way of the pantograph (which Brian lovingly crafted mainly from Meccano) from catenary contained within its shed which Brian had speciallly made and was installed on its own siding alongside the Cafe but this was never finalised.
The railway itself ran for several seasons and all the equipment was Brians and later returned to his home to enable completion of his Croesor Junction and Pacific Railway. Other locos of Brians that ran there were :-The EAR Garratt "Mount Kilimanjaro" lately with its sister at Weston Park, "The Queen of Clorado" ( D&RG K27 2-8-2), The Darj- Darjeeling B class and briefly "White Fire", a Bullock Pacific ( Originally "Monarch", then "Audrey" and when Brian aquired it, "Bubbles"- he gave me one of the plates!) regauged from and now back to 10.25" at Eastleigh.
Happy days pre H&S police and Safety Cases!! Nobody got run over, burnt or electrocuted.