BDŽ class 75

The BDŽ class 75 is a series of Bulgarian narrow-gauge diesel-hydraulic locomotives.

BDŽ class 75
BDŽ class 75 006-7 at Belitsa station
Type and origin Power type Diesel-hydraulic Builder Henschel – Kassel Build date 1965 Total produced 10
Specifications Configuration: ​  • UIC B'B' Gauge 760 mm (2 ft 5+15⁄16 in) Bosnian gauge Wheel diameter 900 mm (2 ft 11+7⁄16 in) Minimum curve 40 m (130 ft) Wheelbase 8,400 mm (27 ft 7 in)  • Bogie 1,900 mm (6 ft 3 in) Pivot centres 6,500 mm (21 ft 4 in) Length: ​  • Over couplers 13,040 mm (42 ft 9 in) Width 2,470 mm (8 ft 1 in) Height 3,520 mm (11 ft 7 in) Axle load 12 t (11.8 long tons; 13.2 short tons) Loco weight total: 48 t (47 long tons; 53 short tons), empty: 44.5 t (44 long tons; 49 short tons) Fuel capacity 1,800 L (400 imp gal; 480 US gal) Prime mover Maybach Mb 820 Bb four-stroke Diesel engine RPM range 1.500 min−1 (nominal) Cylinders 12 Transmission Hydraulic
Performance figures Maximum speed 70 km/h (43 mph) Power output Engines: 1,100 hp (820 kW) Tractive effort 147 kN (33,000 lbf)
Career Operators BDŽ Numbers 75 001 - 75 010 Disposition 7 preserved, remainder scrapped

The first 760 mm track-side diesel locomotives of the BDŽ were built by the German company Henschel & Sohn of Kassel, and were put into operation in Bulgaria in the beginning of 1966. As soon as they arrived, they became the main narrow-gauge locomotive series at the Septemvri depot, took the passenger (from the series 81 and 82) and the freight (from the 600.76 series locomotives) service on the railway lines Septemvri - Dobrinishte and Varvara - Pazardzhik. Moreover, due to the higher power of the locomotives, the trip from Septemvri to Dobrinishte was shortened by more than 1 hour.

The locomotives were constructed under the technical conditions of BDŽ and consisted mainly of: a diesel engine with a power of 1100 hp, a hydraulic gear and the wheelset formula is B'B'. At their creation (the 1960s), they were the world's most powerful diesel locomotives for the 760 mm gauge. For the first time in Bulgaria the concept of using the cavities in the main locomotive frame for fuel tank was applied.

The first scrapped locomotive in the series was 75 007.5, which derailed on January 16, 1991, due to a broken track on the open line to the closed stop "Dryanov Dol". The damage to the locomotive was not so great to force it to be scrapped, but due to the sufficient number of locomotives it was not required to be recovered quickly. Thus it became a "donor" for spare parts for the other locomotives of the series and eventually in 1994 it was scrapped.