Some explanation of sources of production figures. Firstly, all published vehicle registration figures, monthly or annually, are audited by the SMMT. Note these are actual registrations, not sales figures supplied by manufacturers. For any production figures I have quoted my source is the Leyland Group documents held in the British Commercial Vehicles Museum. They are not figures that I have requested from there, but they are from actual factory records and chassis build sheets that I have personally accessed and researched, a time consuming exercise, but to me interesting and absorbing. Whatever else might have been going wrong at British Leyland it was certainly not the documentation of its products. The records are very detailed and comprehensive. To establish how many TL12 engines were built then there will be a record of the production figures at the BCVM. To find out how many ■■■■■■■ and RR powered Marathons were built then it will require a trawl of all the individual Marathon chassis build sheets, as each engine type had its own designation.
Take chassis build sheets as an example. When a sales order was received then the lorry chassis was immediately allocated a building number that became its chassis number. So, say Gingerfold Transport ordered a TL12 Marathon tractor unit in 1978 it would be identified as 2MTL3828FN. Then there was a 5 digit number beginning with a 3, and prefixed 2T25/27.
2 = Mark 2
M and T25/27= Marathon
TL = TL12 engine
38 = Design GTW in tons, (still limited to 32 tons GTW in the UK in 1977)
28 = TL12 engine BHP rating
F = Tractor Unit
N = Sleeper cab.
The 5 digit chassis number was a sequential number and by 1977 it was in the mid-30,000 range. In about 1970 Leyland had changed AEC’s chassis numbering system from a series system for each AEC model to Leyland’s sequential system. For the researcher AEC’s own system was easier to follow. For example, if my Marathon’s number was 35,611, then 35,610 could have been a Reliance coach (with its own model prefix) and 35,612 could have been a Marshal (again with its own model prefix).
The chassis build sheets are very detailed, not just for Marathons but for every model built in the Leyland group. They record the vehicle designation, chassis number, engine type and number, gearbox type and number, rear axle type and number,diff ratio, original tyre make and size fitted, wheels, fuel tank size, and every component fitted. In addition they record the customer, date of registration, and registration number. Dealer stock orders will record the name of the dealer, surprisingly not very many of these. If an order was cancelled then, certainly in the individual model series chassis numbers, there will either be no chassis build sheet and therefore a gap in the numbering sequence, or it will be marked either “not built” or “not allocated”. Guy Motors retained a model series chassis number system for the Crusaders it built. Sometimes a registration number is not recorded, usually because the vehicle was stored before going into service, a not uncommon practice with some hauliers years ago.
Annual chassis build figures by individual factories or assembly plants. Obviously the largest output plants were Leyland and AEC, with annual chassis production capacity of approximately 6,000 and 5,000 respectively. The assembly lines ran on a 5-day week 50 weeks per year. However, the capacity figures are somewhat arbitrary because it depended on what types of chassis were being built. A 4x2 tractor unit takes less time to build than an eight wheeler. Internal factory photographs of AEC at Southall show that anything and everything was on the assembly line at the same time, Mandators, Mammoth Majors, Reliances, Bridgemaster buses, Marshals and so on. Leyland was the same and sales orders dictated production schedules. Having visited the DAF assembly plant at Leyland in recent years it is still the same there, a variety of models are in production at any given time. There was a well recorded production run at Southall in the early 1960s when Harold Wood required an urgent order of 43 Mammoth Major Mk.V eight wheelers. Agreement was reached with the unions to build them as one batch over a weekend, with the normal speed of building being calculated to take the two full days. All 43 had been finished by 11.00 am Sunday morning, causing AEC to investigate if batch production was the way forward to increase productivity. but sales requirements dictated otherwise.
Scammell at Tolpits Lane Watford was not a large site and its annual production could be as low as 1,200 chassis, but some of its products were complex. In the 1970s the 6x4 military spec Crusader was a complex machine, especially the recovery vehicle variants. It was also building the Routeman eight-wheeler, again a slow build chassis compared to a 4x2 tractor unit. When it built the Marathons after Southall closed then it is entirely feasible for them to have built them relatively quickly, especially as at that time Routeman production was ending in readiness for the introduction of the T45 Constructor model.
Hope I haven’t bored you all with the above.