CLASS 25 SPECIFICATION

South Devon Diesel Traction, SDDT





"Class 25" or "British Railways A.E.I. Sulzer Type Two" To give them their original rather long winded name, were introduced in 1961 as general purpose light engines. Some were fitted with steam generator boilers to allow them to work winter passenger trains and all of them were used for small freight trains, summer passenger trains and often two of them were coupled in multiple to work bigger trains.

Most were built at British Railways' Derby & Darlington Works and a few were sub contracted to Beyer-Peacock at Gorton. Ours was built in Derby, April 1966 .It was originally numbered D7612, then 25 262 under the BR "TOPS" numbering system and finally in Dec 1985, 25 901. One of twelve specially renumbered for the new chemical & minerals sector.




Early 25
Early type class 25

GENERAL DESCRIPTION

The Wheel arrangement is 'B-B' (i. e. the locomotive has two bogies, each of which has two individually-driven axles). The locomotive may be operated singly, or may be coupled, to form a two-unit or a three-unit locomotive, with other locomotives which carry the 'blue star' coupling symbol.

Earlier Locos were fitted with nose end corridor doors, so that traincrews could change over on the move. This was not a succesful practice, consequently later ones were built without. Earlier locos had other differences including electro-mechanical power contol whereas the later ones were electronic. Ours is a later one.

GENERAL DATA

Weight in running order: 70 - 73 tons
Number of traction motors:4
Continuous tractive effort:20,500lb at 18mph
Maximum Tractive Effort: 46,500lb


Length over buffers: 50ft 6in Height:12ft 8in, Width:8ft 9in.
Wheelbase:36ft 6in, Wheelbase of one bogie: 8ft 6in
Distance between bogie centres:28ft Oin
Minimum curve negotiable: 4. 5 chains radius


Total fuel capacity: 510 gal
Total coolant capacity:186 gal
Maximum permitted speed: 90 mile/h

ELECTRICAL MACHINES

MAIN GENERATOR Type A.E.I. RTB15656;
Rating (continuous) 780volts at 1050amps

AUXILIARY GENERATOR Type A.E.I. RTB7440;
Rating (continuous) 54 k.w.

TRACTION MOTORS Type A.E.I. 253AY
Rating (continuous) 650 amps at 315 volts, Gear Ratio 67:18


Later 25
Later type class 25 (like ours)




25 layout
Class 25 layout

COMPONANT LAYOUT

Although this is an electrical componant diagram, it also shows the layout of the loco's major componants.




25 Engine
Class 25 Engine

DATA OF ENGINE

Type: Sulzer 6LDA28-B
Cylinder Formation: 6 cylinder inline.
Continuous Rating: 1,250bhp at 750rpm
Bore: 11.02 inches
Stroke: 14.16 inches
Lub.Oil Capacity: 100 gallons