Talk:Divided drive (locomotive)

Hammer blow

I'm sorry, but I must dispute the phrase 'in order to reduce "hammer blow"'. Hammer blow is the vertical force resulting from over-balancing the reciprocating masses. See

• Semmens, P.W.B.; Goldfinch, A.J. (2003) [2000]. How Steam Locomotives Really Work. Oxford: Oxford University Press. p. 197. ISBN 0 19 860782 2.

"With multi-cylinder locomotives [i.e. those with three or more cylinders] the problem [of hammer blow] becomes easier to deal with. ... Locomotives with three or four-cylinders of similar size phased at equally-spaced angles are not far from being fully balanced throughout, particularly if all the connecting-rods are the same length and drive on the same axle" (my emphasis). It should be noted that Nigel Gresley was keen on locomotive balancing with the object of not just reducing, but entirely eliminating hammer blow; and in his three-cylinder designs he avoided the use of divided drive in all designs except the LNER Class B17. --Redrose64 (talk) 19:04, 26 March 2011 (UTC)

What you say is true, the problem of 'hammer blow' was later addressed by Gresley with some success without using divided drive, but he created other maintenance problems in doing so. Other designers (e.g. Maunsell with the Lord Nelson class), Vincent Raven Edward Thompson used it to solve the same problem, without the complexities of Gresley's valve gears . However, the article is only a first draft which I created because the article on the duplex locomotive stated that the idea of dividing the drive began in America with Baldwin in the 1930s. Please feel free to amend or improve the article. I am away for a week and so will not be able to do anything more.--86.168.252.30 (talk) 21:08, 26 March 2011 (UTC)

Thompson and Peppercorn

Re Gresley's successors Edward Thompson (engineer) and Arthur Peppercorn both adopted divided drive on their larger designs as a means of overcoming the maintenance problems with the Gresley conjugated valve gear.

This is something of an oversimplification, and the reference given does not completely back up that statement. Whilst it is true that Thompson and Peppercorn both used divided drive (and the ref states as much), and that Thompson wished to get rid of the Gresley conjugated gear by using three sets of Walschaerts' motion, the latter change in itself did not force him to use divided drive. Although the leading axle would have got in the way of the middle set of valve gear, this problem could have been overcome by steeply inclining the middle cylinder or the use of rocking shafts, both of which Thompson wished to avoid. Therefore, the middle cylinder was made to drive the leading axle instead of the centre axle. Thompson also wished to have all three connecting rods the same length as each other - in this he was in agreement with Gresley - but by moving the middle crankpin to the leading axle, this in turn meant that the middle cylinder had to be moved forwards. Peppercorn used divided drive for the same reason as Thompson (to prevent the middle connecting rod and valve gear from fouling the leading axle) - but in contrast, he allowed the connecting rods to be of different lengths, which allowed him to move the middle cylinder backward, and the outer cylinders forwards, so that all three were in the same vertical plane.

Some books to read:

• Boddy, M.G.; Neve, E.; Yeadon, W.B. (1986) [1973]. Fry, E.V. (ed.). Locomotives of the L.N.E.R.. part 2A: Tender Engines - Classes A1 to A10. Kenilworth: RCTS. pp. 143–4. ISBN 0 901115 25 8. {{cite book}}: Unknown parameter |month= ignored (help)

&Rogers, Colonel H.C.B. (1997) [1979]. Thompson & Peppercorn - Locomotive Engineers. Book Law Publications. p. 78. ISBN 1 901945 02 2.

Since the divided drive was a consequence of, rather than the means of overcoming the maintenance problems, the statement should therefore be rewritten accordingly. --Redrose64 (talk) 14:04, 1 April 2011 (UTC)

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Summary in multiplex locomotive

Pechristener (talk) 15:17, 30 October 2023 (UTC)