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William Pickersgill and the Caledonian Railway '956' Class

William Pickersgill and the Caledonian Railway '956' Class

Donald Peddie

168 pages. 275x215mm. Printed on gloss art paper, casebound with printed board covers.

ISBN13 : 9781911038054


contents and extra information for this book »

Designed at St Rollox to work, without assistance, the heaviest passenger trains on the company’s principal routes from Glasgow to Carlisle and Aberdeen, the ‘956’ Class would be required to haul 425 ton loads, as well as operating at 75-80 mph to maintain the booked timetable. For the class of four locomotives, out-shopped in 1921, three-cylinder propulsion was chosen, using a novel 2:1 derived motion for the centre cylinder, this being associated with a large boiler where, unaccountably, a number of recognised technical imperatives, well established with earlier classes, were neglected. Initial trials results were disappointing, difficulties being found with both the steaming capabilities and the novel valve gear, which was subject to two major redesigns, with little obvious improvement. Based on the surviving records, including numerous previously unpublished historic drawings and photographs, this book analyses the failings, the probable causes and the potential modifications which could have been implemented. Unfortunately, the ‘956’ locomotives being incapable of meeting the initial objectives and unable to match the performance already achieved by the ‘49’ and ‘903’ classes, they were consequently largely used on goods workings and the last of the class was withdrawn at the early date of 1935.

William Pickersgill and the Caledonian Railway '956' Class - Sample Images

cover illustration
Right-side view of No. 957, fitted with Stephenson’s link motion, at Kingmoor shed in 1922. Again the finish is spotless. (A.B. MacLeod, courtesy Jim MacIntosh)
cover illustration
Boiler ‘proving’ by hydraulic test at 150 per cent of working pressure was an essential element of the construction process, the illustration showing one of the ‘956’ Class boilers apparently being prepared for testing. What is assumed to be the calibrated test gauge is connected to the top of the boiler and mounted to the right of the firehole aperture. The order number Y125 is clearly chalked on the boiler barrel to the right of the encircling chain. (A.E. Glen)