Locomotives

CLASS 25/1 WITH GANGWAY DOORS

Standard editions will be BR green with yellow panels, BR green with full yellow ends and BR Blue with yellow ends. The limited edition will be green without yellow warning panels and without the overhead warning flashes.

These are now all sold out with no plans currently to re-run them.

LOCOMOTIVE SPECIFICATION.

The Class 25/1 featured the new AEI 253AY traction motor, the motors were a result of the collaboration between BTH, MV and American builder Alco. This smaller, lighter motor was an attempt to market a traction motor to a worldwide audience, especially to the meter gauge lines. For Class 25 locomotives these lighter motors meant the discontinuance of other weight saving measures being built into the design. They would be highly rated, being an attempt to overcome the loss of tractive effort normally found on starting, the field divert system was also modified to allow increased capability throughout all the speed ranges.

The main generator was a 12-pole machine with the rating changed to 819kW, 780/545V, 1050/1500A at 750rpm. The four traction motors were now connected as series parallel pairs being rated at 234hp, 315V, 650A at 460rpm, with a gear ratio 18:67. Pairs of motors connected in series provided a higher maximum tractive effort (usually quoted as 45,000lb although 47,000lb could be achieved) but the downside being that a series pair connected machine was more prone to slipping that one with an all parallel grouping. Full power was available between 7 and 77.5 mph, an improvement over Class 25/0 locomotives with all other ratings unchanged from the earlier series. The traction motor’s continuous rating of 650 amps was not far removed from its one hour short term or "emergency" rating of 680 amps, and this could only be monitored manually. On heavy trains close monitoring of the ammeters was necessary to avoid motor damage. Whilst the body shell remained similar to D5151 there were a number of refinements. Relocated were the air horns to either side of the headcode panel. The cab skirt and body fairing were discontinued, though the support lugs remained. A new driving control panel was fitted. The fuel & water tanks were also redesigned with a fuel capacity of 510 gallons.

There were initially two variants of this sub-class. The vast majority were boilered and designated 251 AV. The four without train heating were designated 251BV. In due course, when it was decided to fit dual braking to a number of locomotives, those previously 251 AV became 251 CX and one of the 251 BV (25032) became 251 DX.