One of those often overlooked details. The trolley carries a 110V AC-driven air compressor, which is hooked up to each wagon in turn to power the pneumatic rams which drive the covers over the china clay before departure. Seems a bit labour intensive, but I'm sure they know what they are doing. (Photo taken on a guided tour, courtesy of Imerys) see image 26480 [Ref query 6565]
Location: Goonbarrow Junction
Original line: Cornwall Minerals Railway
Photographer: Ken Strachan
Contact photographer: Ken Strachan
Date: 28/11/2014
Image number: 49759