SR Z Class

Infobox Locomotive
powertype=Steam
name = SR Z Class Haresnape, Brian (1977). "Maunsell Locomotives - a pictorial history". Stroud: Ian Allan Ltd. ISBN 0-7110-0743-8.]

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caption = BR Z Class 30951 at Exeter Central, 1960
designer = Richard Maunsell
builder = SR Brighton Works
builddate = 1929
totalproduction = 8
whytetype = 0-8-0
gauge = RailGauge|ussg
driversize = 4 ft 8 in (1.46 m)
length = 39 ft 4 in (12 m)
weight = 71 tons 12 cwt (72.7 tonnes)
fueltype = coal
fuelc

waterc

cylindercount = 3
cylindersize = 16 in × 18 in (40.6 cm × 45.7 cm)
firearea = 18.6 ft² (1.67 m²)
boilerpressure = 180 lbf/in² (1,241 MPa).
tractiveeffort = 29,376 lbf (137.894kN)

The SR Z Class was an 0-8-0 3-cylinder tank engine designed by Richard Maunsell and intended for heavy shunting on the Southern Railway. Only eight Z Class locomotives were built, the first entering into service in 1929.

Construction history

Designed as a specialist locomotive, the Z Class was a standardised locomotive utilising the experience gained from Robert Urie's G16 Class. The boiler was of an existing Brighton design, which meant that parts could be interchangeable with other classes of locomotives. The resultant design was a three-cylinder locomotive that incorporated Walschaerts outside valve gear and a custom-built inside gear.Banks, Chris. (2001) "BR Locomotives 1955", Oxford: Oxford Publishing Company, ISBN 0-86093-560-4.]

Due to the requirement for heavy shunting, the locomotive was provided with an 0-8-0 wheel arrangement to increase traction, and the locomotives were able negotiate tight curves that were prevalent in goods yards. Another requirement was for the locomotive to be able to have power after long periods of standing idle, as freight marshalling was an intermittent duty. A large water capacity was also required to reduce the need for regular watering, and this was provided in side tanks alongside the boiler, making the design a tank engine. The first of the class emerged form Brighton in 1929.

Steam and vacuum brakes, as well as steam heating was provided. This was to enable the locomotive to undertake the shunting of passenger stock should such a role be called for. A second batch of ten locomotives was mooted to be constructed at Eastleigh, but the economic climate in 1931 meant that the order was scrapped. [ Southern E-Group (2004) [http://www.semgonline.com/steam/zclass_1.html SEMG gallery] , Retrieved April. 18, 2007. For information on projected second batch. ]

Operational details

Throughout their working lives, the Z Class locomotives remained in their role as heavy shunters. Three of the class were loaned to the War Department, and saw service in Scotland where their abilities to move heavy freight were needed to move troop trains and war materials over winding routes. The class was considered a rarity amongst locomotive crews, and due to the customised inside valve gear, the regulators worked in a different fashion to the norm, therefore causing problems amongst those unfamiliar with the design. [ Southern E-Group (2004) [http://www.semgonline.com/steam/zclass_1.html SEMG gallery] , Retrieved April. 18, 2007. For information on war service and rarity of locomotive. ]

Another problem with the design lay with the fact that the buffer beams overhung the ends of the locomotives by 11ft in total, which was a disadvantage if negotiating tight curves in a confined space during shunting.

Towards the end of their working lives, the Z Class locomotives were moved to the Western section of the BR(S)(BR Southern Region), where their traction was put to good use in banking trains up the steep bank between Exeter St. David's and Exeter Central stations. ["Bulleids in Retrospect," Transport Video Publishing, Wheathampstead, Hertfordshire ] However, with the reorganisation of the BR regions in 1962, the Western section of the BR(S) came under the control of the BR(W) (BR Western Region). As the Z Class was not of a standard design under BR (W) control, they were withdrawn throughout 1962, and banking duties were taken over by ex-GWR Pannier Tanks. [Fereday, Glenn, D.(1997) "Rail Rover From Kent to Cornwall", Stroud: Alan Sutton Publishing, ISBN 0-86299530-2.] Because of their early withdrawal, none have survived into preservation.

Livery and numbering

Southern

Livery was black, with yellow numbering and 'Southern' on the tank sides.

Post-1948 (nationalisation)

Livery remained black in the guise of BR Freight Black, and the locomotives were provided with the BR crest on the tanks, whilst the numbering was located on the sides of the coal bunker.

The Z Class were given the numbers 30950–7 under the BR standard numbering system.Ian Allan ABC of British Railways Locomotives, winter 1958–59 edition]

References

Further reading

* Ian Allan ABC of British Railways Locomotives, winter 1961-62 edition

External links

Southern E-Group (2004) [http://www.semgonline.com/steam/zclass_1.html SEMG gallery]