One of the things that I’ve found intriguing and often perplexing is the LT system of swapping vehicles identities as part of the vehicle overhaul process at Aldenham. On leaving the works, an RM (and RT) was given a new identity and this ultimately mde it difficult to determine the origin of a particular bus.

Whilst the body number, that used to be displayed on the edge of the nearside canopy in white transfers, enabled the origin of the body to be determined, it was difficult to tell the identity of the chassis (or sub frame in the case of the RM). LT did allocate a unit number by stamping a small brass plate on the top edge of the nearside A frame, but these do not appear to bear any relation to the original sub frames.

I did hear that whilst some records do exist by which the unit number could used to trace the original sub frame, many of theses have been destroyed. Is there anyone who could shed some light on this topic?

My bus number (if any): RM1699 - Eastbourne Regent V 69

In effect Steve, the origin of the body of an RM was as you say easily determined by its body number. This of course determined its original stock number and its various identities as other buses were also recorded. The same applies to the chassis but is not as easy to follow as the chassis number changed, as did the component numbered A and B frames.

The “chassis” number always tallied with the bus number and that was on a brass plate riveted on the bottom of the cab bulkhead window. The “chassis” (as we will call it) on an RM was made up of an A frame and B frame, these were individually numbered and identified in records as “the chassis”.

The log book of an RM as far as I know gives it’s registration plate and chassis number in the form of a RM number, so it would say originally for example for RM 300 “WLT 300 Chassis number RM 300”. I have not got one so I cannot be sure of this. However, as far as I know, these always tied up, the “chassis” number being allied to the registration plate, which was in turn was tied to the bus number. So in all its forms WLT 300 had chassis RM 300 even after its third overhaul the “new” RM 300 would still be WLT 300 - Chassis RM 300.

But what constituted RM 300 after an overhaul? I can’t find my body swaps book so we will have to make up an example

Lets say at its first overhaul our RM 300 (originally body B 300 - chassis, RM 300 made up of A/B 300), might have acquired Body B 1222, it still officially had chassis RM 300 which was originally A/B 300 but was now perhaps A/B 1222. In some cases where the A or B frame had been changed due to damage some chassis did not have corresponding A and B numbers, I recall the overhaul programme showing something like for example RM 1931 Body B 106 - Chassis A 108/B 1257

The A and B frames had AEC numbers originally allocated to these units but as with the RTs and RTLs LT ignored these numbers completely after delivery and gave them their own A and B numbers identified by a brass plate. In the case of the RT and RTL they were given a chassis unit number that never changed but this was not the chassis number recorded on the brass plate on the chassis or dumb iron, that always tallied with the original Leyland or AEC chassis number recorded in the log book, so for example as the log book for RT 520 HLX 337 showed that it had chassis 0961360, it always carried that chassis number on the plate on the dumb iron in the form of “RT 520 0961360” even though the actual chassis might have changed on each and every overhaul. The original 0961360 chassis had been given an LT CU number on its first overhaul and was now the chassis of another RT and showing a completely different 096 number !!

Records are certainly kept of the buses that were carried with various RT chassis numbers and body numbers and I am sure that they also exist for the Routemasters. The different possible identities makes the history of any LT bus that went through Aldenham very complicated to follow after even just 3 overhauls, (some RTs had five) with the original body and chassis each having 4 possible new identities and each constituent part of the second and third and fourth buses also having had a previous bus identity, so the history of just one bus can be quite complex to follow. I hope this sheds some light on what is a complex topic.

My bus number (if any): RTL 960 RML 2667 and an RMC

Thank Brian for shedding some light on the topic. It's no wonder that LT required an act of parliament for this process - no one else would be able to get away with such practices!

As a matter of interest, RM 1699 is fitted with B1043 (which is out of sequence since it sepnd over 2 years on the works float). Its A frame number is A1039 whilst the B frame number is B2419 - but this is a replacement B frame since this was fitted over 6 years ago replacing the original that was severely corroded. So it really is a hybrid of various buses!

My bus number (if any): RM1699 - Eastbourne Regent V 69