Editing GWR 3252 Class (section)

==Design==
===Frames and wheels===
The outside frames of the Dukes were curved upwards over each pair of driving wheels. Inner and outer frames were {{convert|3/4|in|mm|0|abbr=on}} thick.<ref name=OSN78>{{harvnb |Nock |1977 |p=78}}</ref> The first 40 members of the class were fitted with Mansell pattern bogie wheels with wooden centres.<ref name=OSN17>{{harvnb |Nock |1977 |p=17}}</ref> The first 25 tenders built also had Mansell pattern wheels, and a shorter than normal wheelbase of {{convert|11|ft|m|2|abbr=on}} so that the locomotives would fit on the smaller turntables then in use west of Newton Abbot.<ref name=OSN17/> The engine bogie was of a centre-less type designed by Dean.<ref name=OSN27>{{harvnb |Nock |1977 |p=27}}</ref>

===Boilers===
The majority of the class were fitted with [[round-topped firebox]]es of the same diameter as the boiler. The last four were fitted with [[Belpaire firebox]]es, raised a few inches above the boilers.<ref name=OSN29>{{harvnb |Nock |1977 |p=29}}</ref> Eighteen of the Duke class were later rebuilt with domeless tapered boilers and Belpaire fireboxes between October 1906 and January 1909.<ref name=OSN77>{{harvnb |Nock |1977 |p=77}}</ref> They were reclassified as members of the [[GWR 3300 Class|Bulldog Class]]. A further Duke, no. 3273 ''Armorel'', had been fitted with a parallel domeless boiler in February 1902, converting it to a Camel Class locomotive. It was fitted with a Bulldog-type boiler in October 1910.<ref name=OSN77/> By December 1923 all remaining Dukes had been fitted with flush-topped Belpaire fireboxes and domed boilers pressed to {{convert|180|lbf/in2|MPa|abbr=on}}.<ref name=OSNb70>{{harvnb |Nock |1978 |p=70}}</ref> Duke no. 3258, ''King Arthur'', built August 1895, was fitted with a [[superheater]] in December 1896. The rest of the class, with the exception of two locomotives, were fitted with superheaters between August 1911 and September 1946.<ref name=OSNb87>{{harvnb |Nock |1978 |p=87}}</ref> The class had distinctive long smokeboxes, extended to hold a diaphragm plate and net for spark prevention.<ref name=OSN17/>

===Cylinders and valves===
[[Slide valves]] were fitted underneath the cylinders, and were driven directly by eccentrics on the leading driving axle through [[Stephenson valve gear]].<ref name=OSN27/><ref name=OSN10>{{harvnb |Nock |1977 |p=10}}</ref> This position had the advantage that, when the regulator was closed and steam pressure shut off, the valves would drop away from the steam ports, thus reducing wear on the valves and port faces. Dean's earlier designs had used slide valves mounted vertically between the cylinders; the new position allowed an increase in [[cylinder (engine)|cylinder]] [[Bore (engine)|diameter]] from {{convert|17|in|mm|0|abbr=on}} to {{convert|20|in|mm|0|abbr=on}} in the Armstrong Class.<ref name=OSN11>{{harvnb |Nock |1977 |p=11}}</ref> The Dukes had {{convert|18|in|mm|0|abbr=on}} diameter cylinders, possibly due to [[permanent way]] weight restrictions and a reduced supply of steam from the Dukes' smaller boilers.<ref name=OSN17/>

{| class="wikitable" style="text-align:center;"
|+ Table of orders and numbers{{sfnb|Allcock|Davies|le Fleming|Maskelyne|1968|p=28}}
! Year !! Quantity !! Lot No. !! Works No. !! Locomotive numbers !! Notes 
|-
| 1895 || {{0}}2 || {{0}}97 || 1431–1432 || 3252–3253 || align=left | 
|-
| 1895 || {{0}}8 || 101 || 1493–1500 || 3254–3261 || align=left | 
|-
| 1896 || 10 || 102 || 1501–1510 || 3262–3271 || align=left | 
|-
| 1896–97 || 20 || 105 || 1531–1550 || 3272–3291 || align=left | 
|-
| 1898–99 || 20 || 113 || 1682–1701 || 3312–3331 || align=left | 
|}