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Class 126 Swindon Inter-City DMU

Class 126 DMU Technical Information

Introduced: 1957 / 1959
Coupling Code: White Circle
Engines: 4 x BUT (AEC) 150hp
Speed change gearbox: 4-speed epicyclic
Reversing gearbox: Two per (power) car, driving inner bogie wheels only
Body: 64ft 1/2 in x 9ft 3in
Transmission: Standard mechanical

The introduction of the Class 126 diesel multiple units originated in a British Transport Commission report of 1952. BR’s works at Swindon were chosen to design and build express units for the ex-North British Railway Edinburgh Waverley to Glasgow Queen Street route.

These were the first DMUs to be built with the 64’6″ underframe. Swindon built a second batch in 1959/60 for use on services to Ayrshire. The second batch was closely based on the 1956 stock, one big improvement was that the guard’s van was moved to the rear of the coach giving passengers a forward view.

Originally designated inter-urban, (quickly changed to inter-city, long before this name became more widely used), the Class 126 is one of the earliest types of Diesel Multiple Units to have operated in Scotland.

Class 126 DMU at Johnstone
One of the final units in service leaves Johnstone station on its way to Ayr. The corridor connection has been removed to reduce draughts in the driver’s cab. Note that part of the connection buffing plate was retained as this carried the tail lamp bracket – the units were one of the very first types introduced and were never fitted with electric marker / tail lights.

The cars were of steel construction and featured Pullman gangways and buckeye couplings. Each power car was fitted with two AEC 150 hp. underfloor engines with mechanical transmission giving a maximum speed of 70 mph. The power characteristics of the AEC engines was such that the units were ideally suited to long fast runs.

The units had two front-end designs: either a full-width cab or a half-cab with central gangway connection. The latter intermediate driving car allowed through access within a six-car set.

Power car seating was in open saloons with compartment seating in the trailers.

A unique multiple-working control system (coded White Circle) was employed. The 79xxx & 5xxxx series vehicles had different control systems – the earlier vehicles had an electrical system similar on the Yellow Diamond (Derby and Met-Camm) vehicles, the later vehicles were almost completely identical to the Blue Square electrical system. The different coupling code also came from the fact that they had buckeye couplings, Pullman gangways and no through air pipes.