Ray,
The option for electric lighting was designed into the EW350 right from the beginning. An alternate timing cover was utilized that carried a BTH PA series pancake dyno.
The 350EW came out in late 1925. There seemed to be plenty about by September that year and reported being used in events. But generally 1926 is considered their debut. They had a number of problems; mainly related to the oiling system loosing prime and having been built down to a 200 lb weight limit to be eligible for reduced road tax. Over time these were addressed
In 1927 the frame and transmission mounting was redesigned to be more robust. (The 600EW was also introduced)
This continued into 1928 unchanged,designated as the A28. However it was joined by the B28, which was much the same but instead of blind cylinders had detachable heads. They were not plate heads; that would come later. The C28 was a B28 with aluminum rather than cast iron pistons. Aluminum pistons had been available since 1926 in the Deluxe (or Sports) version of the EW.
The now dated flat tank was last offered in 1929 as the A29. Certainly to use up old inventory. It was being superseded by a 350EW with the engine sitting on a oil sump and a frame with a saddle tank; the B29. Was this the end of the 350EW? Maybe, maybe not.
These saddle tank, sumped EWs carried on into 1930 as the L3 and H3. The H3 was a slightly heavier version with larger tires intended for touring or Colonial markets.
But the 350EW 'Sports' was back in 1931 as the A31. Essentially the detachable head engine with a stylish saddle tank. The sump model was carried on more year as the B31.
Little change for 1932 other than the A31 (now A32) also being known as the Terrier. The sumps were gone and the B32 became a touring version of the B32. It did not get a doggie name.
1933. Factory bankrupt and nill output. Only a few 600cc models produced apparently. So was this finally the end of the 350EW? Maybe, maybe not.
1934, Douglas are back with a full and even expanded model range. The A32 is back with the only significant difference in that the engine now has plate cylinder heads and the headlamp had 4-brace mounting (rather than archaic headlamp irons). Now called the model Y1. There is also a model Y (250cc) and Y2 (500cc) that we will not consider as EWs, though they were basically the machine, built on the 350cc crankcase with different sized barrels and heads.
Carried forward into 1935 as the model 5Y1. Now with a more bulbous saddle tank in keeping with the big twins and named "Cotswold" and two frame tubes passing under the engine in conformance with the big twins. The engine now clamps to the frame tubes, like the transmission since 1927.
Carried forward to 1937 essentially unchanged except the catalog illustration shows a reversion to the previous style saddle tank. Assuming any actually ever were fitted with the more bulbous tank in 1936. Some gas welding started to replace frame lugs.
Only the 600cc was listed for 1938, other than a two-stoke that may or may not have gone into limited production. So 1937 was the last of the 350cc models. Given the minor changes from year to year, it is difficult to say when it ceased to be 'The EW' and became something else; and the threshold is subjective. Would it be when they altered the frame. When it lost the flat tank? Acquired detachable heads or when it changed to plate heads? When they gave it a new model name?
Nor was the 350EW influence limited to the 350cc models. After a diversion with the Dixon inspired S6 big twin models from 1930-33, and 1934-35 without the oil sump, the much simpler 500cc Blue Chief engine was introduced in 1935. This was essentially a scaled up Cotswold motor. It was a little ahead of its time in using aluminum for the cylinders and heads, and essentially this same engine was used in the Endeavour. The aluminum caused problems and it and the Blue Chief and Endeavour were gone by 1936. To be replaced by the Aero models with iron barrels and heads. The Aero lasted to 1938, so a bit of the EW heritage lasted right up to WW2.
-Doug