[modeleng] Re: Lord Nelson Class Locomotives

>How accurate is this description of the Lord Nelson class of locomotives 
-- especially the cylinder count and crank angles?  Thanks.<
According to Holcroft ( Lcomotive Adventure, Vol 1,)

P.126

'When the required output was gauged, then began the question of 
dimension. A 6ft.7in diameter coupled wheel was the obvious choice becasue 
it was an Eastleigh stock size of tyre. Clayton proposed to go for a 
boiler pressure of 220il per sq. in., and he was not in favour of a stroke 
in excess of 26 in. on account of the crank axle. This left thecylinder 
diameter outstanding and likely to be between 16 and 17 in., depending on 
how adhesive weight and boiler dimensions worked out.

further on on this page, he says

'When however the preliminary drawings to be sent o Eastleigh for 
development of the design were submitted to maunsell for final approval, 
he increased the diameter to 16-1/2 in. to give more tractive effort.'


Ibid p. 178
'Another alteration to an engine of the 'Nelson' class was made in 1934. 
It arose from an informal discussion after a meeting of representatives of 
the Running Departments of the four railways. The Great Western men tried 
to convince those of the Southern that a train was more rapidly 
accelerated by a series of tugs than by the smoother tractive effort of 
the 'Nelson's' eight impulses per revolution. The Running Superintendent 
put this to Maunsell, who said he was willing to test the theory if the 
opportunity occurred. This happened when No. 865 needed repairs to the 
crank axle, which was replaced to a setting of of 180 degrees instead of 
135 degrees to the outside cranks. In normal service the alteration had no 
marked effect on acceleration, but when the engine was worked hard in 
rough weather or with heavy load, the coal supply on the tender was 
quickly reduced. No tests of coal consumption were made with No. 865, but 
Nine Elms shed recorded that it averaged 7-1/2 per cent. more than other 
engines of the class.

So it seems pretty accurate in this respect at least.

Peter Chadwick
Swindon





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