Flying Cinders

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Timed Runs

As there were only ten Clans the chances of an outstanding run by of one of these 'Cinderella' pacifics being recorded by a student of locomotive performance was pretty low compared with its far more common big sisters the Britannias which were often hauling prestige named expresses. The official test runs were made under the scrutiny of a traction inspector who was not interested in spirited bursts of speed but consistent time keeping and economies of fuel and water and his very presence would have ensured the crew were on 'best behaviour'. However there are one or two chance unofficial records which give a glimpse into what the machines were capable of, when necessary. Luckily one of these chance timings was made over a route that may be considered in recent years as the enthusiast's bench mark for locomotive performance, the Settle and Carlisle, so those expert in loco performance over this route can draw comparisons with a whole variety of other loco types.

72005 'Clan MacGregor' Settle and Carlisle

Synopsis of an article 'Classic Runs' in the 'Railway World' Magazine published by Ian Allen March 1995

A most impressive run timed over the Settle and Carlisle by A. Wood was made by 72005 'Clan MacGregor', standing in for a failed Jubilee 45673 'Keppel' and 'Black Five' 45171 pairing, the 'Clan' took sole charge of the eleven coach, 420 ton, 'Thames-Clyde' relief, which was 50 minutes down and despite three temporary speed restrictions and two severe signal checks made up 18 minutes. The 6MT cleared the summit before Low House at 40mph, up Griseburn never falling below 46m.p.h., through Birkett tunnel at 35.5, Ais Gill at 34.5, across the Pennines at 63, a 70 m.p.h dash between two of three temporary speed restrictions on the descent, 75 m.p.h. through Steeton, 62 on Keighley curve, before a signal stop just outside Leeds. A total of 141.5 minutes from Carlisle and over the Pennines to Leeds including the temporary speed restrictions and two signal checks one of which brought the train to a complete stop, 45 m.p.h average.

Today's quickest schedule, with modern diesel units and without T.S.R.'s and signal checks, is 149 minutes.

Fastest Acceleration

Synopsis of an article in 'Trains Illustrated' Magazine published by Ian Allen August 1954 also 'The Railway Magazine' 'On Your Marks' Jun 2006 published by IPC Media

C. J. Allen compared the time/distance various locomotives required to attain a mile a minute average from a standing start and published his findings, 'The most Rapid Starts in Britain' in 'Trains Illustrated', August 1954 in his report the fastest accelerating steam engine was not an 'A1' or a 'Britannia' but a 'Clan' out of Gleneagles which very quickly reached 80mph with its eight car train (it is a downhill start) and covered 6.95 miles in 6.95 mins; 'even time', i.e. basically in just under 7 minutes from a standing start the Clan hit and passed the mile a minute average with a 280 ton load and the train was still accelerating, (Gleneagles to Perth is 15.8 miles which on this occassion the class 6 covered in 15.5 minutes).

Just ponder these figures a while, the train and engine combined weigh about 400 tons, now think of somewhere you know to be about seven miles away, then think about shifting 400 tons there in under seven minutes! Or, reflecting on that Gleneagles to Perth start to stop timing, think of somewhere about 15 miles away and shifting 400 tons there in quarter of an hour!

Just For Fun

You cannot determine the relative acceleration performances of different steam engines, on different routes, with different loads, its all speculation, the weather, even the attitude of the crews could make a difference. So although C. J. Allen's bench-mark of 'even time' when the train hits a mile a minute average from a standing start is a great way to accurately measure an individual performance it would only return a truly comparative analysis if conducted under strictly controlled conditions.

However for all those who like to speculate, calculate and debate such imponderables, in his article discussing the various fast accelerations he quotes an unidentified Clan out of Gleneagles as the fastest;

It approximately covered 6.95 miles in 6.95 minutes on a downhill grade of 1 in 100 to 1 in 121 for six miles which then levels out hauling an 8 car/280 ton load.

Amongst the many records of impressive performances, many against the grade, the second fastest acceleration he quotes was an A1, 60141, out of Hitchin;

It covered 11.5 miles in 11.5 minutes on a downhill grade of 1 in 200 to 1 in 400 for 5 miles which then levels out after a slight rise hauling a ten car/340 ton load.

The Clan achieved a mile a minute average from a standing start approximately 4.55 minutes quicker than the A1. Thereafter the Clan was clocked at 78-80 m.p.h. and would have travelled up to 6 miles in that 4.55 minutes, so when the A1 hits a mile a minute the Clan would have been over 1.5 miles ahead, just a plume of steam on the distant horizon. A fair margin even allowing for the apparent advantage.

Ah! But the Clan's performance was gravity assisted and two coaches lighter.

Ah! But the A1 was also gravity assisted and it is a far more powerful machine with only a 2 coach handicap.

A1 Power class 8 - Three 19 x 26 in. cylinders - Boiler pressure 250 lb. sq. in. - 6 ft 8 in drivers - Tractive Effort 37,400 lbs.

Clan Power class 6 - Two 19.5 x 28 in. cylinders - Boiler pressure 225 lb. sq. in. - 6 ft 2 in drivers - Tractive Effort 27,520 lbs.

Which one was showing the cleanest pair of heels? We shall never know. Whatever, railways are not run as a series of races there are signals to obey, timetables to stick to and loads to shift, its just that a driver coaxing that extra degree of effort from his engine's reserve to pull back lost time sets the pulse racing as the regular traveller notices the quickening landscape and change of note to the exhaust as the machine is worked harder.

It would have been interesting had C. J. Allen chanced upon a similar opportunity to time a 9F, similar boiler, virtually identical cylinders and motion but smaller wheels, almost certainly even quicker off the mark? The Old Oak top link found this out and were conducting their own trials until management put a stop to it, freight engines on express passenger services!

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