The following notes give details of the variations in the class.
||Build dates, names, and withdrawal dates, together with the fifteeen locos rebuilt as Castles (4000/9/16/32/37 in 1925-29 and 4063-72 in 1922-1923), can be found here.
||4000 was built with 'square drop' framing at the front, 4001 onward had the curved style.
|Front cover for inside cylinders
||'Square box' on 4001-20, the remainder 'scalloped'.
The prototype 'North Star' loco, renumbered from 40 to 4000 in 1912, had a footplate 2½" higher than the rest of the class, and remained so even when rebuilt as a Castle.
||Boiler type was No 1. Initial locos fitted with superheater no 1, but superheater type no 3 soon became the standard for the class, with older locos being updated by May 1913.
(The above is a considerable simplification, the very early boilers having non-superheat. Also, the process of replacing early 'half-cone' boilers with the later standard 'full-cone' version was probably not completed until c 1921.)
||Initial locos had backhead-fed boilers, very soon replaced by top feeds, which first made their appearance from 4041 onward in 1913.
||Fitted with 4-cone ejectors from 1914 (4046) onward, with earlier engines being similarly re-fitted thereafter. All had been so fitted by 1919.
|Lubricator pipe cover style
||The right-hand side was initially of early pattern. The later pattern was fitted probably from 4061 onward, with earlier locos being updated on works visits.
On the left-hand side, most locos did not have a lubricator pipe cover, but a few locos did. The presence of a lubricator cover on the left-hand side probably indicates the later fitting of a 'five-sight' feed lubricator rather than a 'three-sight' as would originally have been fitted.
||The Princesses were initially fitted with fluted rods of special steel but later fitted with standard fishbelly. 4061/2/7-72 had I-section coupling rods.
||4001 and 4002 were initially fitted with non-standard I-section slidebars without the vertical strap, but these had reverted to standard T-section with vertical straps by 1909.
||Began to be fitted to the right-hand side rear driver from c 1937.
||Initially fitted with Churchward standard taper. Collett tapered type started to appear in the 1930s (see here in a later BR era), and Collett parallel types were seen in BR days.
||Tall safety valve casings were fitted initially, but most of the class migrated to the low type, introduced in 1927, in later years. Dated prototype pictures should be consulted.
||The first batch of ten locos initially appeared with a 1'6⅞" body diameter chimney, but all later batches (from 4011 onward) were fitted with a chimney of 1'8⅞" body diameter and 1'11¾" high, which became the standard for the class. Following the 'austerity' period of WWI, many * locos were fitted with a tapered cast-iron chimney from 1919-24. From 1939, a few locos received the Grange type of shorter 1'9" chimney. (These quoted heights do not include the 1¾" capuchon.) None received the fatter 1'10" diameter Castle type, short or tall (except of course those rebuilt as Castles).
||4002/8/9 were fitted with front steps, but these were a hinderance to accessing the inside motion, and were removed later.
||The first batch of ten locos was fitted with swing-link bogies, but all later batches were fitted with the Swindon version of the de Glehn bogie, and these were retrofitted to the first batch.
||4001-20 have apertures in the bottom section, 4021 onward are solid.
||The first members of the class were coupled with the then standard 3000g, very soon thereafter (probably starting with 4031 in 1910) 3500g flush-riveted (normally) or (later) snaphead riveted was the typical mid-period look, most of the class starting receiving 4000g after 1938. Two of the class ran with Hawksworth flat-sided 4000g, including Malmesbury Abbey, although this also ran with 4000g in late days. (4045 and 4022 ran with Great Bear's 8-wheel tender for a while in 1936.)
Some engines ran with 3500g Collett tenders. It is also reported that some locos ran with the rare Dean 4000g tenders. 4043 ran with the unique Collett 8-wheeled tender at one stage.
|Brass beading on splashers
||Removed during WWI and never replaced.
||Fitted from new, removal started November 1923 (and quickly completed, probably by 1925).
|Cab front portholes
||Plating over started c 1924.
|Reversing lever cover housing
||A few late surviving locos had a cover housing in front of the cab on the right-hand side. These seem to have appeared sometime during WWII.
||Initially flush riveted, smokebox snaphead riveting started in 1922 with the appearance of 4061-72, and older locos started to show snapheads from c 1924. A Queen in 1932 has rivets on the back ring but the front ring still flush-riveted, and a rarer form is the converse. The late-surviving Stars ended up with rivets on both front and back smokebox rings. The early external smokebox damper mechanism was removed between 1917 and 1924 and plated over.
||Fitted from 1927.
||Originally all inside-piped, outside pipes started to be fitted from 1929, either elbow type or 'Castle' type. Some were never fitted with outside pipes.
Dates of outside steam pipe fitting: 4000-4029 and 4030-4072. These dates are tabulated below.
The difference between types of outside cylinder can be seen well here, which shows the top of the cylinder casing of the traditional Star being at the bottom of the footplate valance, whereas the top of 'Castle' type cylinder casings were at the middle of the footplate valance.
|Front lamp iron
||From 1932, the upper lamp iron was transferred from the front of the chimney to the smokebox door.