Derby Lightweight (Yellow Diamond) 1, 2 & 4-car DMUs
Single Cars
Two 'double ended' power cars (aka bubble cars) built for the Buckingham - Banbury Experiment. The vehicles had different sizes of guard's vans, resulting in differing numbers of seats.
| Number | Type | Diagram | Lot. No | Region | Seats | Weight |
|---|---|---|---|---|---|---|
| 79900 | DMBS | 514 | 30380 | LMR | 61 (later 52) | 27t |
| 79901 | DMBS | 515 | 30387 | LMR | 52 | 27t |
Diagrams
M79900: BR 514, M79901: BR 515
Works Photographs
From the Derby Works Collection, all showing M79900.
Negative 56/601
Negative 56/602
Negative 56/603
Looking from the van end.
Negative 56/604
Looking towards the van end, with the sliding van door closed.
Negative 56/605
Looking towards the van end, with the sliding van door open.
LMR Publicity Photographs
Distributed with the press release about the launch of the experiment. M79900, probably on the Wirksworth branch.
Origins
The two vehicles were originally to be built as regular DMBSs M79182/3 for the Manchester Part 1 scheme before being re-assigned to the Buckingham - Banbury experiment. This can be determined from the minutes of the LMR Light Weight Diesel Trains Committee which regularly listed the delivery status of the Region's vehicles and the schemes to which they were allocated. This appendix notes that the two vehicles were taken from the Manchester Part 1 scheme, which involved over 100 sets from five builders. The Derby sets were a batch of ten power / trailers (79127-36 and 79648-57, already delivered), and another fifteen power / trailers due for delivery April - June 1956 (79169-83 and 79670-84), the time that the vehicles for the Buckingham - Banbury experiment were authorised. This diagram of the completed power / trailer sets shows the mis-match of vehicle quantities.
Changes
When new the vehicles had ivorine tablets fitted which stated a maxiumum number of passengers to be carried. In common with other Derby Lightweight vehicles they had a joint in the cantrail above the passenger doors which led to distortion and doors not opening under heavy loadings. It was planned that vehicles would have these areas strengthened and the notices removed.
The small van on M79900 was a concern before it entered traffic, and soon became an issue when it did. At some point it was returned to Derby Works, the extra seating bay (9 seats) was removed and the partition moved towards the vestibule as on 79901.
In the image, taken south of Padbury (near Buckingham) with the 4.0pm Bletchley - Buckingham service on April 18, 1964, the changes to the small saloon immediately behind the van can be seen. The window has a wire mesh and a stack of parcels is visible. Michael Mensing.