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Mallard record run

8226 Views 22 Replies 13 Participants Last post by  pedromorgan
I must admit I am finding it difficult to find my way around this site. I have only just joined and all I want to do is ask a couple of question about the Mallard train during It's record breaking run.

Please can you tell me what type of coaches were used during the record run ?
How many were there in the train ?
Does Hornby or Bachmann or any manufacturer make the coaches for sale ?
Is the special coach (I don't the correct name) that housed the recording equipment also avalible to purchase, even if it is only in kit form ?

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Hello and welcome to the Forum.

Most questions about the real-life railways we tend to handle in the 'Prototype' section of this Forum. - Topic now moved.

The 'special coach' you refer to is a 'dynamometer car'. This measures the pull of the loco upon the train and its speed - from this the power output of the locomotive at any instant can be calculated. Various other measurements can also be taken to assist looking at the efficiency of the locomotive at various speeds and loads.

The LNER dynanometer car from 1906, used during Mallard's famous run, is preserved at the National Railway Museum at York. I recall there were some 5 other coaches in Mallard's train but I don't know the details.

John Webb

PS Doug beat me to it in greater detail!
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QUOTE Gresley mobilised one of the double chimneyed engines, No 4468 Mallard, to head the 244 tonne test train of dynamometer car and three articulated twin units from a Coronation train set - P44 "The Fastest Trains in the World" by G. Freeman Allen published 1978 ISBN 0 7110 0889 2

Neither Hornby nor Bachmann make the articulated twin units, so all the coaches will have to be kit built. I'm not even sure there is a current kit of these?

In 4mm there are plastic kits available for the Coronation articulated twins, although they are something of a job to make up. The bodysides are one piece transparent mouldings which require very careful masking to enable painting: but which are thereby capable of replicating very well the flush exterior of the prototypes.

There may well be etched brass kits available, but I have to confess boundless ignorance on that score.

But is there a kit of the Dynamometer car? Don't recall ever seeing a model.
D&S did a kit of the dynomometer car but its now as rare as hens teeth (as is the rest of the D&S 4mm range.)

QUOTE (Doug @ 10 Dec 2008, 21:30) <{POST_SNAPBACK}>Mallard broke the speed record with six coaches plus a dynamometer car.

Going downhill...
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The real claim for the A4 class is how small they were (due to the UK loading gauge constraints) yet still able to get into the 110+mph club in company with larger wheeled and grate designs such as the 05 and Hiawatha. If, at this late date, there is to be a historical revision, it should go to the Hiawatha 4-6-4. They worked the fastest regular schedule assigned to steam, and did it reliably: daily achieving speeds in the 100 - 110mph range as a necessity to keep time.
QUOTE (ME 26-06 @ 12 Dec 2008, 07:59) <{POST_SNAPBACK}>Going downhill...

& (AFAIK) suffered serious damage !
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QUOTE (Brian Considine @ 13 Dec 2008, 12:34) <{POST_SNAPBACK}>& (AFAIK) suffered serious damage !

Mallard was not the only steam loco to suffer serious damage following a high speed record run, the damage usually happening after steam was shut off at the end of the attempt. The most common explanation I've seen is that when the regulator was closed the exhaust steam's cushioning effect at the end of the piston stroke was removed and the unrestrained momentum of the reciprocating masses led to the bearings overloading. I understand it became the practice not to close the regulator completely to prevent this occurring.

Although specifically in the case of the Gresley pacific design, the centre big end was simply understrength for half of its' duty cycle at higher power outputs. The flat back strap of the big end bearing stretched during the inside piston's forward power stroke, causing the big end bearing to pinch on the crank journal, leading to overheating. The failures occurred on power, or more precisely when high power was being produced. Mistakenly this was ascribed for a long time to lubrication failure, and that was where the effort was directed. It was eventually rectified by putting a reinforcing rib around the back strap to increase its' stiffness (now a 'T' shape in cross section); and the problem was fixed.
Another major factor in the improvement of the reliability of Gresley engines in the 1950s was the introduction of optical alignement of the frames etc. by K.J. Cook who transferred from Swindon. If I remember correctly O.S.Nock in his book on the Gresley Pacifics stated this proved very effective even when used with the original big end design.

Mr Nock's opinions should be treated with some caution. The optical frame alignment was certainly very helpful in reducing clearances on bearings, and the locos were noticeably quieter in action when erected with this technique (something that distinguished Swindon's products from its' introduction from the other railway's workshops output); and the objective evidence in the form of reduced rates of bearing wear in service from the more accurate assembly is well attested. But the inside big end design was revised in 1945, well ahead of optical alignment; and this reduced incidences of overheating in that bearing to what was typical of all plain bearings operating at similar loading on UK locomotives.

General UK practice in loco bearings was pretty primitive up to WWII. The plain bearing was universal, fit and finish largely a matter of tradition. The wartime experiences of US designed locos with grease lubricated bearings, and the automotive bearing design of tanks and other heavy vehicles built in railway workshops had an influence on moving practise forward; rather late in the day it has to be said. Really any loco in the 2,000+ IHP class should have had roller bearings on driving axles and big ends at minimum. But the railways were all short of cash so had to concentrate on what was most urgent, and had large workforces of fitters distributed around their systems to deal with the heavy ongoing maintenance demand of steam locos...
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QUOTE The failures occurred on power, or more precisely when high power was being produced.

In the absence of a rolling road it's hard to see how you can test for a condition like that. Finding an empty stretch of mainline to run at maximum power isn't something that happens very often.

David, Quite so. And you will recall that Gresley was the prime mover in the quest for such a rolling road plant to be built in the UK. Even then without stop motion high speed photography, analysing the failure mode would have been problematic. The problem was solved the old fashioned way: careful inspection of the failed components, and engineering insight and analysis of the forces at work.

And then even a rolling road may not have been all the help that might be supposed. There are well documented instances of severe bearing heating, draughting difficulties, failures in combustion rate achievement and consequent poor steaming, and truly frightening wheelslips on such test plants; all atypical of the tested locomotive when on the rails. Some features of the basic Stephenson locomotive were a serendiptous synergistic outcome of the vehicle on rail interaction while in motion, and the different environment of the rolling road lost much of this synergy.
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I am fairly sure that both Rugby and Swindon had rolling roads, Gresley (I think) consulted André Chapelon to improve the draughting of the A4's but I am not totally sure.
QUOTE I am fairly sure that both Rugby and Swindon had rolling roads, Gresley (I think) consulted André Chapelon to improve the draughting of the A4's but I am not totally sure.

I believe the rolling road at Rugby was at the instigation of Stanier and Gresley but came some time after Mallard's record breaking run.

The Kylchap exhaust fitted to Mallard is a Chapelon design which is where the "chap" in the name comes from. Looking up this Wikiepedia article on Kylchap reveals where the Kyl comes from - a Finn Kylala whose nozzle formed the second of the three stages in the complete exhaust assembly.

QUOTE (72C @ 18 Dec 2008, 22:18) <{POST_SNAPBACK}>.. Gresley (I think) consulted André Chapelon to improve the draughting of the A4's but I am not totally sure.
Gresley and Bulleid were very much indebted to French practise in steam circuit design. Once Gresley had his A1 pacific running, most of the improvement that culminated in the Kylchap ejector fitted A4, was based on the work of Messrs Chapelon and Lancrenon, and concentrated on eliminating internal resistance in the steam circuit. The French railway engineers had obtained their pre-eminence in this field by experience with compound locomotives, which in their early days largely lost the efficiency gained by more efficient expansion in the cylinders, by the extra work the steam had to do in the more complex steam circuit. It is estimated that 70% of the drawbar horepower gain of the Kylchap A4 over the single chimney A3 derives from the steam circuit improvement, the remainder coming mainly from the increased boiler pressure and superheater area.

M. Andre Chapelon in particular maintained a strong interest in UK locomotive design, and influenced the original W1 compound; and also tried to persuade Collett of the virtues of a large trapezoidal grate 'Super King' 4-8-0 to supply the GWR with a heavy express engine of comparable power output to a Pacific, but better suited to the curvature and gradients of the lines West of Exeter.
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QUOTE tried to persuade Collett of the virtues of a large trapezoidal grate 'Super King' 4-8-0 to supply the GWR

How about trying your hand at one those Andii?

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