[external link] (5 Sept 2003) for boiler data.
Richard HN Hardy (see Locobase 2314 for a discussion of this photographer and his extensive collection of LNER images; see [external link], accessed 8 May 2006) offered a terse comparison of the relative amounts of reserve in the A3 vs the A1: "Those old A1s could time the heavy trains with their big cylinders even when down to 140 psi or so whilst an A3 or, even more, and A4 would be struggling if short of steam."
Designed by Nigel Gresley. Delivered with a distinctive streamlined casing, these engines quickly proved to be extremely fast and free-running. Marsden comments that the class was a hit from the start. In 1,952 Silver Jubilee runs before World War II, only 10 saw any mechanical problem offered by the A4. "Drivers and firemen were happy, too," says Marsden. "They found the A4s easily took the loads required of them. They also found the footplate very smooth."
Richard HN Hardy (see Locobase 2314 for a discussion of this photographer and his extensive collection of LNER images; see [external link], accessed 8 May 2006) offered a terse comparison of the relative amounts of reserve in the A4 vs the A1: "Those old A1s could time the heavy trains with their big cylinders even when down to 140 psi or so whilst an A3 or, even more, and A4 would be struggling if short of steam."
The Mallard set a steam-powered record of 126 mph in 1938. Perhaps two reasons for the class's free-steaming was a superheat ratio that was comparatively generous for British locomotive, internal streamlining of the steam passages, and 9" piston valves with steam laps of 1 5/8" and travel of 5 3/4" The Gresley conjugated gear that ran the inside valve operated well, if it was well-maintained.
Altogether, 35 engines of this class were completed and ran into the late 1950s. G. Freeman Allen (writing in Great Railway Photographs of Eric Treacy, 1987) comments that the fitting of Klychap double blastpipes and chimneys (sic) "which so strikingly rejuvenated them" was "wretchedly belated," occurring only in the late 1950s.
See http://www.gresley.org.uk/snghome.htm for details on the rebuilding of the Sir Nigel Gresley.
. Data from Bryan Attewell ([external link])'s Steam locomotive simulator (April 2000 edition), confirmed and augmented by Richard Marsden's LNER site -- http://www.lner.info/locos/locos.shtml (Jan 2004) The data show a design consistent with British practice -- a hard-worked boiler, low superheat, generous firebox area, and a modest EHS to cylinder volume ratio.
As with the older 9N/A5, these locomotives provided solid service right through the 1950s. As newer designs replaced them in the mid-1950s, A5s retired, but the last didn't go out of service until 1960.
Marsden comments thats the rebuilt A8s "could easily work the heavy suburban traffic and long-distance coastal trains on which they were put to work." Locobase considers the relatively small amount of evaporative heating surface area and wonders if the high stroke-to-bore ratio allowed every possible BTU to be wrung from the superheated steam entering the cylinders through 7 1/2" (191 mm) piston valves.
OS Nock reported (Locomotives of the NER, 1954), that the A8 conversion produced "among the smoothest riding engines I have ever travelled on.".
Once diesel railcars were introduced in the 1950s, the A8s' days were numbered and they were withdrawn between 1957 and 1960.
|Principal Dimensions by Steve Llanso of Sweat House Media|
|Country||Great Britain||Great Britain||Great Britain||Great Britain|
|Number in Class||27||35||13||45|
|Locomotive Length and Weight|
|Driver Wheelbase (ft / m)||14.50 / 4.42|
|Engine Wheelbase (ft / m)||35.75 / 10.90||32.75 / 9.98||33.25 / 10.13|
|Ratio of driving wheelbase to overall engine wheebase||0.41|
|Overall Wheelbase (engine & tender) (ft / m)||60.89 / 18.56||71 / 21.64|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||49,392 / 22,404||49,280 / 22,353||40,320 / 18,289||39,872 / 18,086|
|Weight on Drivers (lbs / kg)||148,288 / 67,262||148,000 / 67,132||120,960 / 54,867|
|Tender Loaded Weight (lbs / kg)||143,696 / 65,179|
|Total Engine and Tender Weight (lbs / kg)||374,416 / 169,832||192,416||194,656|
|Tender Water Capacity (gals / ML)||5000 / 18.94||5000 / 18.94||2280 / 8.64|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||8 / 7.30||8 / 7.30||4.70 / 4.30|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||82 / 41||82 / 41||67 / 33.50|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||80 / 2032||80 / 2032||67 / 1702||69 / 1753|
|Boiler Pressure (psi / kPa)||220 / 15.20||250 / 17.20||180 / 12.40||175 / 12.10|
|High Pressure Cylinders (dia x stroke) (in / mm)||19" x 26" / 483x660 (3)||18.5" x 26" / 470x660 (3)||20" x 26" / 508x660||16.5" x 26" / 419x660 (3)|
|Tractive Effort (lbs / kg)||32,910 / 14927.74||35,455 / 16082.14||23,749 / 10772.38||22,890 / 10382.74|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.51||4.17||5.09|
|Firebox Area (sq ft / m2)||215 / 19.98||231.20 / 21.49||141.30 / 13.13||124 / 11.52|
|Grate Area (sq ft / m2)||41.25 / 3.83||41.20 / 3.83||21.20 / 1.97||23 / 2.14|
|Evaporative Heating Surface (sq ft / m2)||2692 / 250.19||2576 / 239.41||1280 / 118.96||1085 / 100.84|
|Superheating Surface (sq ft / m2)||636 / 59.11||749 / 69.61||178 / 16.54||191 / 17.75|
|Combined Heating Surface (sq ft / m2)||3328 / 309.30||3325 / 309.02||1458 / 135.50||1276 / 118.59|
|Evaporative Heating Surface/Cylinder Volume||210.34||212.31||135.39||112.41|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||9075||10,300||3816||4025|
|Same as above plus superheater percentage||10,799||12,669||4274||4629|
|Same as above but substitute firebox area for grate area||56,287||71,094||28,486||24,955|