A Coarse Guide to the Steam Locomotive for ‘N’ Gauge Modellers

[martyn]

The RCTS history of the Duke tells a different story of the ashpan.

In late 1961, the Crewe North shedmaster instructed the shed to cut extra slots in the ashpan to improve airflow. This improved things, but too little too late.

In preservation, it notes that it was found necessary to replace the original ashpan. With no drawings available, a copy was made of the original. But just as this was completed, the original drawings were found, and it was discovered that the ashpan damper door air space was 72 sq in too small in the original one. The new ashpan was modified to this new, (correct?), arrangement.

The blastpipe and draughting arrangements were modified to Kylchap at the same time; trials were carried out to optimise the exhaust dimensions.

It was found on trials, if I've understood the text correctly, that these combined alterations improved the boiler steaming capacity by around 40-50%. The loco also has had modification to the cams, which combined with other detail changes, has transformed the loco's performance on the road. Trials had shown in BR days that the valve gear gave a better, more efficient, cylinder performance than piston valve types.

As an aside, tables within this loco's history seem to show up what has been said before in this thread; that though the King class could produce cylinder horsepower of around 2000, the drawbar hp was about 1190. Was this loss of power due to the 'internal resistance' mentioned earlier? It also shows that the Duke had a power output similar to, or slightly above, that of a Duchess when on trials, and post preservation runs have shown the loco capable of 'extremely high' drawbar horsepower, close to the maximum recorded in the UK (which, I think, was a short lived 3,300hp by a Duchess).

Martyn

 

 

[chrism]

close to the maximum recorded in the UK (which, I think, was a short lived 3,300hp by a Duchess.

Yep - 6234 Duchess of Abercorn, 26th February 1939, on a test run with a 20-coach train (including a dynamometer car) after having a double chimney and blastpipe fitted.
This was a repeat test, following one a few weeks before which showed that the locomotive's power was compromised by its single blastpipe.

Drawbar horsepower on the second test was frequently over 2,000 hp (1,500 kW) and a maximum of 2,511 hp (1,872 kW) was recorded.
The horsepower at the cylinders could only be estimated; Cecil J. Allen thought it to be 3,333 hp whilst O. S. Nock was more conservative at 3,209 hp.
This could not be expected on day-to-day workings as it required two firemen to shovel the coal, one couldn't have done it.

Following this test, all subsequent new build Coronations were given a double chimney and blastpipe, whilst all those already in service had them retro-fitted during overhauls - the last to be converted being 6220 Coronation in 1944.

BR performed a similar test some seventeen years later, using 46225 Duchess of Gloucester, which established that a continuous drawbar horsepower of 2,000 hp was readily sustainable.

[Hailstone]

when the Duke came to Didcot, it was to enable it to be tested by BR as it was the first Caprotti locomotive on BR metals since the end of steam. it is many years since this happened so please excuse my inability to remember which year the following happened. the Duke was to do a loaded test of I believe 10 coaches plus the ex Western Region Hawksworth dynamometer car the the Duke group owned, to run between Derby and Sheffield (to this day I cannot remember which direction!) the net result of this was that the Duke managed this in a time that was only 5 minutes outside HST timings for that route! the chief engineer at the time Gary Shannon later asked me on a day that I was driving it at Didcot to run the water down to one third of a glass but keep as much pressure as possible after coming off the demonstration line so that he could test the rate that the injectors were working at, as it seemed that on the test run it was getting through a lot of water, and both injectors had needed to be employed to maintain the water level. I cannot remember now what was decided, but they were thinking of increasing the cone size on one of the injectors.
the picture below is a very happy Hailstone about to leave that shed



Despite being labelled a Western man, I love Standards!

Regards,

Alex

[cmason]

John,

Catching up here after a few busy days and unable to check in.

Firstly, hope all has/is going well at hospital.

And secondly, as always fascinating info - I am learning so much from this thread which makes for such a pleasant from focus on a work on a "desk day", when I stop for morning coffee (since in this time zone your updates arrive perfectly as "morning reads" - worst case being, if there are interrupts, I get to it by elevenses... ),

Best Wishes,

Colin   

[martyn]

@Hailstone


That was an honour, and it must have been a fantastic experience.

The RCTS history says that (BR trials post preservation) 'trials....showed that the steaming performance performance of the engine had been so improved that the injectors could not keep pace.....these have subsequently been uprated'

Martyn

[Cols]

Please forgive my naivety, but I'm wondering whether an N-Gauge no.71000 would prove a popular addition to modellers' collections - and don't tell me that it's a "one-off", rarity of a loco, and that it would never sell (it could be marketed as in its original condition and in its preserved state) - what about Bachmann/Farish's popular "Deltic" prototype and the delightful (even more popular?) ex-LMS "twins"... and to a lesser extent, the "Brighton Belle", or the (original) "Midland Pullman"..?

Rant now over! Phew!

[Foxhound]

Please forgive my naivety, but I'm wondering whether an N-Gauge no.71000 would prove a popular addition to modellers' collections - and don't tell me that it's a "one-off", rarity of a loco, and that it would never sell (it could be marketed as in its original condition and in its preserved state) - what about Bachmann/Farish's popular "Deltic" prototype and the delightful (even more popular?) ex-LMS "twins"... and to a lesser extent, the "Brighton Belle", or the (original) "Midland Pullman"..?

Rant now over! Phew!

I for one would be interested, and I don't have any tender engines on my layout.