M12140 Mk3 coach bogie trials
Mk3 coach No: M12140 was unusual in that it was
chosen as a test bed for a number of different bogie types including the
BT7 and the SIG bogie BT7 The BT7 bogie was fitted with Clouth rubber primary suspension and vertical stiffness testing of the BT7 bogie was carried out in the Vehicles Lab at the RTC. The spring included a shaped mandrel and housing to give a non-linear, rising, characteristic. The spring was circular in plan view and therefore gave equal lateral and longitudinal characteristics. The BT7 springs were fitted in a pedestal configuration with no additional traction rod. They incorporated their own lift stop or would otherwise just ‘ooze’ apart. It is not clear how much inherent damping they provided or whether an additional vertical damper was fitted (or added later). What made the springs a bit impractical was that having so much rubber in shear led to a lot of vertical creep leading to a possible need for frequent re-packing dependent on the application. Needless to say they were not adopted for Mk3 coaches |
BT41 SIG bogie
It was also used to trial the SIG bogie prior to selection for the Mk4 coaches
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M12140 fitted with the SIG bogie Dave Bower |
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M12140 fitted with the SIG bogie Unknown |
T4 bogie
Not yet come across any photos of T4 fitted to M12140
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The T4 bogie pictured in
Litchurch Lane works - note the International coach in the background unknown |
BT17 bogie
BT17 bogie was a BT10 but with coil/rubber pedestal primaries and was fitted under Mk3 coach No: M12093.