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Notes About This Vehicle

Despite a long and illustrious history of in-house bus design by London Transport and its predecessors, radical changes were on the way by the mid-1960s. The delivery of new Routemasters finally came to an end in 1968 but by then London streets were already home to what some called ‘off-the-peg’ vehicles.

Further changes were also taking place with the introduction of one-man-operated (OMO) buses. Experiments with one-man operation were not new, though designing a bus purely intended to operate in central London in this way, as opposed to converted vehicles and failed bespoke experiments, were.

1965 saw 15 AEC ‘Swift’ chassis with Strachan bodies, 36ft 0ins long, with front entrances and centre exits arrive; these were eventually called ‘Merlins’. The first six were XMS fleet numbered 1 to 6 and were in central area red.

A further nine were delivered in country area green with a different internal layout and fleet numbered in the series XMB 1 to 9. Eight of the nine XMBs had not yet entered service and were converted to XMS layout. XMBs 2 to 9 were re-numbered XMS 7 to 14 and XMB1 was later re-numbered XMB15.

The first XMS entered service in April 1966 on Red Arrow route 500. The Red Arrow was to become a branded network all of its own with a flat fare and limited intermediate stops. Passengers entered at the front and paid via a coin-in-the-slot and then pushed through one of two three-armed turnstiles. Exit was via the centre doors. One-man operation, flat fares, and separate entrance/exit are all routine now, but these were significant innovations then.

A further major departure was a severely reduced seating capacity of 25 and with up to 48 passengers standing. Following the experimental 15 vehicles, a further 150 Merlins were ordered. These were to a more elegant external design with bodies from long-standing supplier to London Transport, Metro Cammell Weymann.

Deliveries arrived rapidly, almost too rapidly bearing in mind there was so much new about these buses and that they had not really been tested in anger. Though for different applications and with different internal different applications and with different internal configurations, in their various guises, the MB, MBA and MBS series eventually reached number 665.

These buses were unpopular with drivers who found them too long – at the time the lengthiest in London. Innovative they certainly were, as referred to earlier. Sadly, another look to the future was that they were not particularly well put together and had a justifiable reputation for rattling profusely – just like most do nowadays, but not then.

The new buses suffered several mechanical and structural faults – some of these were quite serious with roof domes coming apart and windows popping out. Some structural strengthening was carried out to remedy these from 1969. By 1974 withdrawals were already under way.

Based on experience gained from the Merlins a shorter variant of 33ft 5ins started to appear from January 1970. The first batch of 50 ‘Swift’ types were designated SM in central area red. The only other SMs were in country area green and fleet numbered 101 to 148 and 449 to 538. The other original variant were SMSs and occupied the intervening 51 to 100, 149 to 448 and 450 up to 838.

The first and only batch of red SMs had no centre exit, as depicted in this drawing; both subsequent batches of green SMs did however include these, as did all SMSs from new.

The principal difference between the two was inside: SMs had a greater seating capacity and on SMs passengers could only pay the driver; on SMSs this was also possible but in addition they could pass through the right-hand pair of front door leaves and use the automatic ticket machine immediately in front of them.

When new the SMS variant provided for 33 seating and 34 standing passengers; the three batches of SM each had different seating/standing configurations from the SMSs and indeed each other. Built on the shorter AEC ‘Swift’ chassis, three different body builders were employed for the SMs and SMSs. Numbers 1-50 and 149-223 came from Marshall, 51-148 and 224-448 from Park Royal Vehicles, and 449-838 from Metro Cammell Weymann.

London Transport wanted as much interchangeability of parts as possible between the Merlin and Swift series, though this proved unachievable with very few body parts being the same. From lessons learned with the former, many structural changes were made for the Swifts. Three variants of its shorter chassis and consequential effects put paid to this laudable desire. Further detail variations of body parts from the three builders, further precluded meaningful standardization.

Modifications to the external body features and internal configurations occurred during the lives of these vehicles, resulting in an additional designation to the range of ‘SMD’.

In service, as with their sister class Merlins, problems routinely occurred with unreliability and relentless rattling. The final delivery of new Swifts was in January 1972 and withdrawal of the series was under way by October 1976.

Today these good looking buses are possibly regarded with rather more affection. Not especially loved in their day, only a few survive in preservation.

Notes About This Drawing

The drawing is based on general arrangement drawing ‘SM.001 Z.1’ of January 1969. 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 has been interpreted from a very few contemporary black & white and colour photographs and restored SM1, which originally entered service in early 1970. The detail should not be viewed with any certainty in terms of its appearance when new and in service; none of it can be regarded as definitive.

It should be understood that all four elevations are seen here as one would see each part of the vehicle at a truly perpendicular angle. In real life this is of course impossible.

© drawing copyright Douglas Rose – May 2023
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