Editing GWR 4073 Class (section)

==Design==
[[Charles Collett]] succeeded Churchward as Chief Mechanical Engineer of the GWR in 1922 and immediately set about meeting the need for a new locomotive design that would both supplement the Stars and replace them on the heaviest expresses. Collett's solution was to take the basic layout of the Star with an extended frame, and add a newly designed No.8 boiler which was both larger and lighter.{{sfnb|Nock|1980|p=92}} The increased amount of steam that this produced allowing an increase in the cylinder diameter from {{convert|15|x|26|in|mm|0|abbr=on}} to {{convert|16|x|26|in|mm|0|abbr=on}}. The extended frame allowed for a side window cab and an increased grate area. The result was an increase in tractive effort to 31,625&nbsp;lb, and a locomotive that looked attractive and well proportioned while remaining within the 20-ton axle limit.