The first batches of "modern" trolleybuses bought by Bradford were new in 1934 and 1935 and comprised a total of thirty-six vehicles:
597-617 (KY 8200-8220) new 1934
618-632 (AAK 420-434) new 1935
They had AEC 661T chassis and English Electric bodies. They were the first metal-framed trolleybuses for Bradford. Quite a few of the photographs relate to that aspect. This initial design of metal-frame body seems generally not to have been too successful and all these vehicles were rebodied from 1944 to 1947 by Brush or Northern Coachbuilders. In this form they had long lives, with many surviving into the sixties.
These vehicles had several distinctive features:
- The electrical equipment was largely chassis-mounted, rather than being in the cab. This allowed the vehicles to be fitted with an internal 'half-cab' and an additional pair of inward-facing seats located over the front nearside wheel. They were modified in 1938 to a more conventional seating layout, although 607 was modified as early as December 1935 following collision damage and 614 was done in January 1937 - suprisingly not as a result of its own accident featured in this gallery. This modification involved moving the contactors and shunt field resistors into the cab and restoring a conventional bulkhead. The lack of this bulkhead was most likely the cause of many of the early problems relating to leaking front windows.
- The circuit breakers were roof-mounted and very visible on the exterior photographs. They were reset by a Bowden cable from the cab which can be seen on the offside view of 601. This feature proved troublesome in service. They seem to have been moved when the vehicles were rebodied.
- The traction equipment had a regenerative capability which also caused some problems which were mitigated by limiting the regenerative capability (regenerative braking control was difficult in the days before electronic control was developed). This was started with vehicle 598 in February 1943 whilst it still had its original body. All others were done when they were rebodied although some of the Brush utility bodies were modified a few months later.
- The chassis featured an double-reduction differential to gain the necessary reduction. This was noisy in operation and combined with the initial use of two trolley wheels (before carbon skids were adopted) and a single skin roof made a high-speed ride such as the descent of Thornton Road a real conversation-stopper! The differentials were very troublesome at first but it appears that a modified design first introduced on the second batch improved the reliability, if not the noise.
© David Beilby