RDB968004/97401, a nearly true story

[Wolf27]

In 1972 when D832 was withdrawn it was sent to Derby for use by the RTC. It was to be used as a dynamic test vehicle for the APT-P drive system and anti tilt pantograph mechanism. It was chosen due to the fact it had two power units and transmissions. One was stripped out with the other being retain to provide propulsion. The end which was removed was replaced with the BP17 APT power bogie, gearbox, cardan shaft and one traction motor. This was a new design with the traction motor mounted in the body, transmitting power to the wheels via a cardan shaft and gearbox. It was also decided to install a basic version of the proposed anti tilt pantograph system, which was linked to the power bogie. 

 

To accommodate the new transmission and anti tilt pantograph some structural changes were required to the frames and body. The most noticeable change is the addition of the roof well to house the pantograph and the relocation of the cab access doors. These were moved further along the body as the linkage for the anti tilt system would foul the doors if they remained in their original positions. As it was the crew would have to step round the traction motor on one side as it was very close to the new door aperture, but this was deemed not to be an issue as it was a test development vehicle.

 

The rebuilt locomotive was renumbered RDB968004, christened Laboratory 24, decked out in the distinctive Derby RTC red and blue livery and fitted with air brakes. Consideration was given to retaining the Onslaught name but this was not to be. 

 

The installation of the anti tilt system was a part of the design that nearly didnt happen due to the fact that the locomotive could not tilt while out on the rails as it was built to the full loading gauge and the retention of one transmission also ruled this out. However it was possible to tilt the BP17 bogie on the bogie test rig at Derby RTC, which provided limited ability to prove the system worked so it was deemed worthwhile to install the system complete with pantograph. 

 

The traction motor and pantograph did not draw any power and was solely installed to prove the concept worked in the environs of a live railway vehicle. As the motive power was provided by the one remaining power unit and transmission, it was limited to 100mph, the design speed of the BP17 transmission was 150mph but this was not possible in this configuration. Consideration was given to replacing the power unit and transmission with a second BP17 but the concept had been proven and the new APT-P power cars were already under construction. 

 

RDB968004 ran from mid 1974 to late 1978 and was renumbered to 97401 at the beginning of 1978, being the first departmental loco to carry the 97xxx number series. On becoming 97401 it was repainted with some subtle difference to the lettering and given domino headcodes, the only Warship to ever have these. After withdrawal in 1978 the locomotive was subsequently saved by the Bury Hydraulic Group and rebuilt to it original state over a five year period, with the assistance of Derby RTC and Kit Spackman, who designed most of the changes, and who had kept the removed transmission, bogie and power unit as spares. 

 

S4100007 by Shane Wilton, on Flickr

 

S4100008 by Shane Wilton, on Flickr

 

S4100003 by Shane Wilton, on Flickr

 

S4100001 by Shane Wilton, on Flickr

 

cheers

 

Shane

[russ p]

I thought the proposal was for it to actually draw power from the overheads

In reality it's probably good that it never actually went ahead as I think the changes to it would probably have been virtually impossible to undo