Steam speed records including City of Truro and Mallard

Not quite 100, but close.

The MNA's Dave Gouldthorpe and Paul Riley blagged a footplate ride on 46240 City of Coventry on 2 August 1964, just one month before the class was withdrawn. Dave Gouldthorpe later reported that it was driver Jack Cartmell's last turn on a Duchess and he wanted to go out in style. In Dave's words, Jack pointed to the speedo and asked "where do you want it?", pointing at 100 mph. In the event they reached an indicated 98 between Lichfield and Tamworth. Photo (hand held!) by Paul Riley.

 

Wouldn't know what one of those was, sorry!

 

Don’t complain


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Look and laugh... https://en.wikipedia.org/wiki/British_Rail_Class_700#Interior_design

 

ugly bloody things, like most modern trains, and cars, and buses

 

That is now but limited by electric supply which didn't apply in 1899. According to my notes Highflyer 4-4-2 1397 powered the 14:51 Liverpool Exchange - Southport service on 15 / 07 / 1899 and passed Milepost 17 at 15.03.75 thus taking 12.75 minutes to travel 17 miles and reportedly attaining 100 mph en route. At that time the Liverpool - Southport line operated express services to Southport and local services to Hall Road which differs from today's standard electric workings with stock limited to 75mph operation.

 

This is a really interesting idea. I think you’re right and the description, though short, seems to bear out that analysis from the translation.

I can’t see that we did an equivalent set of tests at the NPL for the LMS/LNER/SR designs tested. Needs further reading.

 

Agreed, but the question was the current limit.


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96 at Harrow ! i would have liked to have seen that , re 4

if the 105 run you mention is the 46255 run , Nock himself was the recorder

6244 and the Caley , 96 was reported going over Tring Summit . an old memory (but not faulty ) reminds me that a log in TI or RM around 1959 by U NO WHO credits 46255 with 105 mph going down to Glasgow .
the Lizzie gradient - 1/330 ????

 

Inspired by that I had a look through the TIs of 1959 and 1960. I guess 1959 may have been a top year for post war steam. Anyway, I didn't find any Duchesses over the magic number ( lots in the 90s). the four fastest runs I found were ;

TI Feb 59 60003 reported doing 107.5 max at Arlesey
TI May 59 60030 reported doing 98 at Tollerton ( level track, 325 tons)
TI Sept 59 7018 reported doing 102 at Little Somerford 260 tons
TI Feb 60 60125 reported averaging 100.4 from Little Bytham to Essendine max 102. Said to be the first recorded ton by an A1. 285 tons

 

Just looking at some dimensions of the German 05 today - this stood out to me on its wiki page: https://en.wikipedia.org/wiki/DRG_Class_05

Driver dia. 2,300 mm (90.55 in)

Am I reading this right, the 05 has 7ft 5in driving wheels? So 7in bigger than Mallard’s driving wheels? That sounds ridiculous. Have I done the maths wrong?

 

I make it 7ft 6.5in

Tom

 

That’s madness. These driving wheels are huge.

 

I agree with your calculation Tom but he A4s had 6' 8" driving wheels so the difference is 10.55". Thus the 05's driving wheels were only rotating at about 88% of rpm of Mallard's

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Same size as the ones fitted to 18 201. Seems that when the Germans wanted speed, 2.3m diameter drivers was how they went about it.

 

Putting it into perspective, some of the UK’s single driving wheel locomotives have wheels not much bigger than this - and this has six of them…it’s a big beast this 05!

 

Why madness?

For a given speed, all else being equal larger wheels means slower piston and valve speeds - so reduced frictional losses from the pistons and valves; and also reduces the risk of the loco being throttled by the valve events. (i.e. slower revolutions means that - again, all else being equal - the valve ports are open for a longer duration on each stroke, allowing more time for steam to enter and exit the cylinders). Of course, larger wheels reduces the tractive effort, but for a loco designed to go fast with comparatively light loads, that's not too much of an issue.

By my calculation of various high speed claims, and including a couple of others (a Merchant Navy at 106mph, and a 9F at 90mph, which I believe are the highest speeds believed for each class) the wheel revs per minute and revs per second;

Mallard, 6'8" wheels at 126 mph = 529 rpm or 8.82 rps
9F, 5'0" wheels at 90mph = 504 rpm or 8.40 rps
Merchant Navy, 6'2" wheels at 106mph = 481 rpm or 8.02 rps
Coronation, 6'9" wheels at 114 mph = 472 rpm or 7.88 rps
DRG 05, 2.3m wheels at 200.4 km/h = 462 rpm or 7.70 rps
City of Truro, 6'8.5" wheels at 102.4 mph = 427 rpm or 7.12 rps

In general, large wheels is part of the route to high speed. I believe that Bulleid deliberately designed the West Countries and Merchant Navies with short stroke pistons (only 24 inches stroke) to minimise peak piston speeds at high wheel revs expected given they have rather small driving wheels by normal standards.

Tom

 

Just in awe of the size - putting it into perspective against something like the A4, you really get a feel for just how much bigger this locomotive is.

Fascinating!

 

The largest diameter coupled wheels on a British locomotive were 7'7" on the NER Q1 (LNER D18) which were built in 1896 specifically with a view to the resumption of the Race To The North, which then never happened.

 

No, they went way bigger than that in the earliest days. The LNWR built 3020 Cornwall in 1847 with 8' 6" wheels. Mind you, that meant placing the driving axle above the boiler . . . Others had different ways to overcome the necessary high boiler pitch and therefore high centre of gravity: Thomas Crampton placed the single driving wheels behind the firebox allowing 8' diameter and above.