Early Douglas Compatibility

[gsx1100s]

I was wondering how compatible the parts of the early models of the Douglas range are between about 1915-25.  As a "newbie"  they seem on the surface quite similar. I own an 1100 katana ( thus the name gsx1100s) it is compatible with parts from the GS to the GSXR range, Is the TS similar ?
I would guess that the answer may invite such phrases as "how long is a piece of string" , but there's no  shame in asking.....I suppose Thanks for your time ,

cheers Michael

[Chris]

Compatibility within a model range over the period 1915 and 1925 is pretty good. If we look at the 2.3/4hp models, apart from the CW model of 1924 to 1926 which had chain drive and therefore used a different rear hub (taper splines to drive the sprocket), in terms of running gear, engines, gearboxes, many cycle details etc. very little changed from as early as 1912 to 1926.
 
There were detail design changes in things like finning of cylinder barrels but the barrels remain interchangeable over the period. Certainly there is a huge amount of compatibility between the TS model of say 1923/1924 and most of its two speed predecessors.

The new forks introduced in 1916 (although they continued to issue the old forks until as late as 1920) and used on the TS were carried through to many models in the 30s. Thus commonality, or standardisation was extended to some extent across model ranges as well.

This was even more noticeable in the 30s where it was sometimes carried out to a ridiculous level. For example the 150cc Bantam 1933 to 1935 had 8" brakes in common with the rest of the range up to 750cc and utilised gear handle knobs from the teens and 20s to retain the engine panels. Interestingly, unlike with the post war models, it is not easy to identify common items in the earlier designs from parts lists as these often have different part numbers for different models.

Unlike the modern GS range, I doubt if the approach by Douglas was quite so scientific. It was more a matter of continuing manufacture of anything that was still selling, of not throwing anything away and using up old stocks on a new model if at all possible. Perhaps a cynical view but part of the quirky nature of the marque we love.
Chris

[gsx1100s]

Thanks Chris , that gives me great comfort as I believe my Douglas ( 1921 ) is a true "Bitza" 

cheers Michael