Class A1 Trolleybus Diddler
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Click here to see brief notes about this vehicle and technical notes about this particular drawing >>


Notes About This Vehicle

The development of London’s famous Routemaster continued decades of tradition for bespoke vehicles designed by London Transport and its predecessors for use in the capital.
The desire for the next generation of London bus was conceived in 1947. Legislation of the time did not permit vehicles of two axles to exceed 27 feet in length and within this restriction the maximum carrying capacity was the aspiration.
What emerged was far-sighted in so many ways, with lightness of construction being almost an obsession. An aluminium alloy body was constructed with sufficient integral strength to negate the need for a chassis, with the former mounted on two sub-frames instead.
Every last drop was squeezed from the length restriction and even the radiator was mounted beneath the engine to gain a few more inches. Perhaps a stage too far, the destination displays were meagre and soon replaced with more meaningful and conventional ones.
The new 64-seater bus was first shown in its prototype form as RM1 at the Earls Court Motor Show in 1954. Over the next few years it was extensively tested, and, as to be expected, modified during its development phase. Soon afterwards a further three prototypes were built, two with different engines and one of these as a luxury double-deck coach. Three different body builders were used across the four vehicles.
RM1 was put into passenger carrying service in February 1956. The bus was in a state of almost continuous modification until long after it entered service, with on-going modifications being made as a result of experience gained.
During this time, legislation was relaxed to permit vehicle lengths of 27 feet 6 inches and advantage was quickly taken to mount the radiator in the conventional position in front of the engine; this helped solve the problem of over-heating.
After extensive testing of the prototypes, the first production Routemasters entered passenger service in 1959. Reverted to an early outward appearance, RM1 is now preserved by the London Transport Museum.

Notes About This Drawing

This drawing attempts to show RM1 as closely as possible to how it looked in spring/summer 1956, though as noted above, the bus was in a state of continuous modification.
It is based on a Chiswick Works ‘general arrangement’ drawing of later production vehicles (‘RM001.Z.1’) which differed considerably in outward construction. This type of black & white sketch drawing, as implied by the name, is not intended to define detail but as a specification guide to builders.
All the fine detail in this particular interpretation has been sourced from contemporary black & white photographs, mostly from January 1956. None of the detail here can be regarded as definitive.
It should be understood that all four elevations are seen here as one would see all parts of the vehicle at a truly perpendicular angle. In real life this is of course impossible.
drawing copyright Douglas Rose March 2018
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