# Talk:SECR N1 class

Might have missed it, but there doesn't appear to be a description of which axle was driven by the centre cylinder. It seems most probable that it was the middle axle, giving an undivided drive. The centre cylinder would then have to be raised so that the connecting rod clears the front axle; the inclined cylinder and valve would require the boiler to be set higher (as it was). On the prototype the conjugation gear would be in front of the cylinders and smokebox saddle (not behind as in the usual application of the Gresley gear) and would have been covered by that metal sheet sticking out at the front above the buffer beam. Ning-ning (talk) 08:39, 6 November 2010 (UTC)

I'll have to refer to my sources on this, but what you say makes sense, particularly concerning the clearance issues. Will clarify this soon. --Bulleid Pacific (talk) 12:24, 6 November 2010 (UTC)
I was wrong about the position of the Gresley gear- it was in front of the cylinders (apart from the first application on GNR 2-6-0s). Apparently, according to Holcroft, placing the gear behind the cylinders was preferable, but only achievable if the drive is divided (p35 of "Thompson & Peppercorn" by HCB Rogers). Ning-ning (talk) 23:08, 6 November 2010 (UTC)
The centre cyl of the N1 class drove the middle axle: undivided drive. See Bradley "Locos of the SE&CR" (RCTS, 2nd edn 1980),  p.114 also Haresnape "Maunsell Locomotives" (Ian Allan 1977), diagram on p.38
The conjugated gear of no. 822 was definitely forward of the cylinders, hence the raised footplate and deep buffer beam. Bradley 1980, fig. 89.
The GNR 2-6-0s (GNR H4, LNER K3) definitely had the conjugated gear in front of the cyls (see RCTS "Locos of the LNER" part 6A, p.91): the only GNR engine with the conjugated gear behind the cyls was the prototype O2 2-8-0, no. 461, which used a completely different conj gear in any case.
Gresley normally used undivided drive, except for the B17 class; and normally placed his conjugated gear forwards of the cylinders, except for no. 461 and the D49 class. The significant factor in conjugated gear placement is not whether the drive is divided or not, but whether the centre cyl is inclined relative to the other two or not: on the D49 class all three were in the same plane. There were several differences between Gresley's design and Holcroft's. In particular, Gresley drove the conjugated gear from the tail rods of the piston valve spindles, so the valve events of the middle cyl were subject to variation due to thermal expansion of the outside valve spindles (with wear in the pin joints this could cause overtravel of the middle valve, which caused so much trouble with the A4s). Holcroft took the drive from the rear of the valve spindles via rods outside the cylinders; to accommodate these rods within the loading gauge, the cyls had sloping sides - in this way thermal expansion problems were avoided. --Redrose64 (talk) 17:23, 7 November 2010 (UTC)
It's the old problem of me having an older edition of the RCTS publication. Thanks for the research, I'll add these details when time permits, but feel free to do this yourself if you feel so inclined. --Bulleid Pacific (talk) 17:55, 8 November 2010 (UTC)

Done. --Bulleid Pacific (talk) 23:19, 24 November 2010 (UTC)

"The rebuilding of the prototype in 1930 provided an opportunity to apply the Southern Railway's new system in which Maunsell's 2-6-0 locomotives were renumbered into one sequence." Er, how so? The renumbering was not confined to the 2-6-0s - all that happened was that all locos with "A" prefix dropped that and were increased by 1000, except for class Z which simply lost the "A". Dealing specifically with the Maunsell 2-6-0s: the locos previously A610-A639, A790-A880, A890-A900 became 1610-39, 1790-1880, 1890-1900, so the same two breaks in sequence existed before as they did after. The final batch of U1 merely followed on with 1901-10; and the 1932-34 build of class N were nos. 1400-14 so definitely outside that "sequence" - if there had been any desire to produce a sequence, those 1932-34 locos could have been nos. 1640-54 (all but one were blank in 1932, and no. 1654 became available in March 1933 with the wdl of ex-LCDR class B2 0-6-0 of that number). --Redrose64 (talk) 18:10, 7 November 2010 (UTC)

I've changed the wording to reflect this. Ning-ning (talk) 17:23, 8 November 2010 (UTC)