MODERNISATION of power station coal trains in the 1960s demanded a wagon capable of being unloaded without stopping or being uncoupled from the locomotive. The term ‘Merry-Go-Round’ (MGR) came from this concept of an almost continuous rolling conveyor of coal on rails, which operated as continuous circuits between colliery and power station, with unloading being as automatic as possible.
The HAA wagon ( MGR), first built in 1964 as a prototype at Shildon Works and subsequently introduced in large numbers from 1965, fulfilled this requirement admirably. The large hopper enabled swift loading at the colliery, either from storage bins or loading pads, whilst the mechanical discharge controls were activated by lineside equipment (‘Daleks’) at the