Identity swapping between vehicles of identical make and model went on from the time
that the LGOC moved its overhaul systems to the new Chiswick works in 1922. This
meant that as a vehicle went into works for overhaul its identity was taken over by
a freshly overhauled vehicle. The system operated through the London Transport era
until the mid eighties when rules were changed in the run up to privatisation of the
bus industry. During the war, the normal system of overhauls was suspended and
afterwards, the Ministry of Transport & Civil Aviation (as it as then known) decided
that they would tighten up on vehicle testing regimes and in order for LT to carry
on with the pre war system they had to be able to identify each chassis so as to
trace its history. The system was created by a Mr Charles at Chiswick and was
initially known as the 'Charlesian' system. It came into operation part way through
the first cycle overhauls of RTs in 1951 but pre war vehicles were not affected as
there were no plans to extend the 'works float' system to them due to their being
life expired and due for withdrawal. This meant that the majority of STLs and
earlier classes did not receive 'chassis unit' numbers (cu for short). It was later
extended to cover the last two batches of the T class, T769 - 798 (14T12 & 15T13),
the 131 TDs, STD 112 - 176 (the 4STD3s) and the GSs, RLHs and RFWs and this despite
the fact that each of these classes was not involved in works float identity
swapping. Specifically excluded because of their date of origin being 1940/41 were
the 2RT2s and the Utilities which dated from 1942 - 46.
The first chassis to receive a cu number was that of RT 426 which received the
number 1001 when it went in for overhaul on 11th April 1951 (the chassis was sent to
Chiswick for overhaul on the 18th, a common practice with RT family vehicles until
well into 1954). As vehicles arrived for overhaul, the chassis' were allocated their
cu numbers and these are, therefore not in sequence with any of the other
identifcation numbers i.e bonnet no, chassis no, body no etc. They are, however, for
the most part in sequence with the date of first but, in the case of some RTs, their
second overhaul. This resulted in some RTs with low chassis or bonnet numbers being
given cu numbers in the 3xxx range as they did not receive their next overhaul until
1954. When the full blown works float system started in early 1955, Aldenham began
working on the principle of 'a bus in today goes today', perhaps an over
simplification of the system as it didn't always happen but it meant that the
licences were in use for the maximum amount of time. The RTWs, RTLs and RFs had
their cu numbers applied in almost the exact sequence of their date of first
overhaul, the only exceptions being where a vehicle went into works late for some
reason. There are, however, two exceptions to the above general rule and the first
was the SRT class, which was, for some reason, allocated a series of cu numbers
which commenced at 101 for SRT 1 and ran in sequence with the bonnet numbers with
SRT 160 being allocated the cu number 260. Most SRTs were not overhauled but
evidence suggests that these cu numbers were not actually applied to any of the SRT
chassis. The other exception to the rule concerns the 160 RT chassis (RT 4397 -
4556) which were purchased to take the bodies from the SRTs when they were
withdrawn. These were allocated the cu numbers 2401 - 2560 and they were the only RT
family chassis' to carry cu numbers from new as they were affixed when the vehicles
were delivered to Aldenham or Chiswick for fitting of the bodies. The cu numbers ran
in four separate sequences within this batch but within each sequence they are in
the correct order with the bonnet numbers. Paradoxically, this is the only batch of
RTs where the body numbers are not in sequence with the bonnet numbers as delivered
new. Very fortunately for us, meticulous records were kept of both chassis and body
changes on the rolling stock record cards so that we can not only trace the full
history of every RT body but also each chassis as well. These were not the only
records that LT kept as each major component of a vehicle carried its own
identifying number on a plate which also gave the date of last overhaul of that
component. This covered engines, gearboxes, dynamos, compressors, radiators, front &
rear axles, cardan (prop) shafts, springs and even wheels. When a vehicle was sent
out after overhaul it carried a card with details of all the major units and any
changes would be noted by the garage staff on this card. Unfortunately, very few of
these cards survive or we would be able to trace this history of every major
component of every London RT family bus. The one item that has survived are the
original LT engine numbers which are shown on the rolling stock record cards and
also on the daily variation sheets and from these we can ascertain the origin of
many of the surviving engines, always supposing that their identity plates still
survive.
I have attached a facsimilie of the front of the rolling stock record card for NS 144 which shows that for the most part NS 144 went in and out of works for overhaul in a maximum of four days throughout its life with the LGOC. The same principle applied to the vast majority of London bus overhauls from 1922 until the mid 1980s.
Alan Bond
04/2012
13/04/12 - 17:44
Alan - Amazing!
Thank you for your explanation of cu numbers; although I was aware of body
swops within Aldenham, I had no idea that chassis were also swopped.
Bob Gell
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