0 TO 60! CLASS 59
Just how nimble are today’s locos and units, and what’s the quickest off the mark?
Our performance column gets a welcome and long-awaited opportunity to sample diesel locomotive traction as part of GBRf’s mammoth annual charity railtour in September. The loco might have been in Southern DC third rail unit territory, but that didn’t stop it pulling out the stops to put on an electrifying show.
The four-day GBRf marathon ‘This Time It’s Personal’ railtour in September 2021 (see December issue) was an endurance test for many on board, especially those who succumbed to a purported norovirus outbreak on Day 3.
Day 2 was different though. The weather was good, adhesion conditions favourable and former German exile Class 59 No. 59003 Yeoman Highlander was ticking over, in the distinctive way these General Motors products do, waiting for the road over the switchback ‘Portsmouth Direct’ route from Woking towards Guildford.
Gradients that varied from 1-in-143 ‘down’ to 1-in-111 ‘up’ over the 2.73 miles it took No. 59003 to accelerate its 14-vehicle, 635 tonne trailing load from 0 to 60mph made calculations less than ideal. However, there are not that many opportunities in a single lifetime to record a straight acceleration like this with a freight locomotive normally limited to bulk haul trains.
The Railway Performance Society horsepower calculation spreadsheet has a facility for computing average gradients. When used in conjunction
On Day 2 of the GBRf ‘This Time It's Personal' railtour, No. 59003 Yeoman Highlander approaches Havant with a 635tonne trailing load (12 x Mk.1s + 2 x '73/9's), working the 1Z25 07.26 London Euston-Marchwood MoD on September 3. with new Network Rail gradient information, which has been added to some distance linecharts by editor Ian Umpleby, much of an area formerly occupied by supposition has been removed. The result is an average gradient spanning the full distance, over which it took
No. 59003 4min 30seconds to reach 60mph, of 1-in-311 downhill.
It is a long time since we were able to sample locomotives in this column, so a recap might be worthwhile. With locomotive-hauled trains the power is obviously not provided proportionately to the trailing load so the number of seconds to reach 60mph will depend on the weight of the train. It was just such a situation which the ‘RE Factor’ was designed to overcome.
The figures used in the RE Factor calculation reflect the variables involved in estimating horsepower, but without a lot of the complications. The figure that emerges for No. 59003 is 9291, comparing favourably with the output of other diesel locomotives.