Copyright © 2015-16 Stan Bell. All rights reserved.   stan.bell@systemsoft.co.uk

NVR 40t Steam Crane

Drive Mechanism


The pistons drive flywheels located at each end of a cross-shaft. Gear wheels on this shaft drive subsidiary shafts, selected by controls operated in the crane cab.  


















The operations that can be performed are:


Derricking

The Jib can be raised and lowered at up to 6’ per minute.


Hoisting.

Two speed ranges (called 10 & 40 ft/ minute) are available.


Slewing.

The superstructure of the crane can be slewed through a full circle in under 2 minutes

When travelling in a train, a heavy key locks the superstructure in a facing-ahead position to avoid inadvertent rotation.


Travelling.

The crane can self-propel for short distances at less than 1mph.


Fine-control of the speed of all operations is exercised by modulating flywheel speed using the regulator.







Weight-relieving bogies


The NVR Steam Crane is an early example of a breakdown crane incorporating “weight-relieving bogies”. This is a scheme invented at Ransomes and Rapier to solve a perennial problem for Breakdown Crane designers.


The problem involves resolving the tradeoff between the need for a very solid base for the crane and the conflicting need to keep the axle loadings below limits imposed by the railway’s Civil Engineer.  The obvious solution, simply spreading the crane over more axles, doesn’t work because extending the length of the crane means that it becomes impossible to get close to the object to be lifted.  The longer reach reduces the lifting capacity.


The weight-relieving bogies are connected to the crane chassis by cantilever arms and, by raising or lowering the arms, more or less of the crane’s weight can be transferred onto the bogies for travel to a job. Once the crane has arrived at the job, the arms are lowered, returning all weight to the crane chassis. If necessary, the bogies can be detached and the crane can be positioned very close to the load.


Although patented in 1904 and a crane of the type supplied to the Great Indian Peninsular Railway in 1906, the scheme was not used in the UK until 1916 when one was supplied by R & R to the Midland Railway. No further examples were constructed until the LMS ordered 6 similar cranes (3 from Cowans Sheldon, 2 from Craven and 1 from R & R) in 1930.


The bogies have 2 indicators to help operators understand how much weight they are carrying.  The first scheme was a simple measurement of the spring deflection alongside the axlebox:














Technical Description


A more sophisticated method using linkages, again driven by spring deflection, to guide operation was devised and uses a sector plate to indicate how the bogie is configured:

















Note the many holes in the plate, suggesting that the settings have been adjusted over the past 80 years.