Beyer Peacock type hydraulics. The type 3 locomotive classes with between 1,500 and 1,999 bhp engines have proven the most useful rating band in British service. The type 3 hydraulics were a design by Beyer, Peacock and company with a single, larger Maybach engine than the two-engined type 4s and Mekydro transmission, leading the the Hymek name. After initial de-bugging of the locomotives the Hymeks settled down to be reliable performers on secondary passenger, parcels and general freight duties and, like class 37s, capable of standing in for a type 4 in a crisis. Phased out with the planned withdraw of the diesel hydraulic classes in 1976, with 4 examples surviving in preservation.