Announced in early October 1928 the side-valve Models CN and CSD were two of an entirely new range of Triumph machines. Along with the accompanying over-head Model CO these were Triumph's first machines to have a recirculating oil system. (As opposed the the previous 'total loss' system.) The oil was pumped from a tank mounted on the saddle down-tube via a gear pump in the crankcase. It was not a high-pressure system as we would know of today, but at least there was direct lubrication to the big-end and elsewhere, rather than places needing oil being dependant upon 'splash'.
Apart from engines and carburettors these three C-Series (as I refer to them) shared frames, gearboxes, tanks, wheels, mudguards; well, everything else!
These two side-valve models looked even more alike, for apart an extra 4mm in the bore to give the Model CSD another 51cc there was no difference. Since the size of the bore is not visually detactable, only the engine number would indicate which model it was.
As these side-valve models shared the frame type with the ohv Model CO they looked a little strange with the engine sitting well below the lower cross-tube, which was raised up above them - but the extra clearance was required for the Model CO's ohv engine. But at least by having so many common parts Triumph's costs were kept down, and today missing items are more easily located as it doesn't matter which of the C-Series models the part originated with.
If anything, these new models were 'over engineered' for frames were very substantial and wheels and muguards were quite wide.
The original 1929 sales catalogue pictures of these models showed the oil pipes to the crankcase routed in a quite impractical manner, which is why above I show a 1930 model.
The 1929 models had 'standard' handlebars, while the 1930 models had Triumph's Patent 'clean' bars with a twistgrip at each end and the control cables ran through the bars and exitted at the centre, to be discretely routed away to wherever their other ends were to go. I great sales feature, and the 'out of sight' cables concept was appreciated by owners - until the nipple pulled off the throttle twistgrip on a dark wet night!
The Model CN was catalogued for the years 1929 to 1931, while the
Model CSD continued on through 1932.
Reliable engines in very solid frames.
Model CN 498cc side-valve 80mm bore X 99mm stroke.
Model CSD 549cc side-valve 84mm bore X 99mm stroke.
Another new Triumph 3-speed gearbox. Full of needle roller bearings!
Good, every-day 'workhorses'.
An extra 50cc was considered necessary in those days to be able to haul a sidecar, although in practice there was probably little difference between the two.
7 inch twin shoe brakes front and rear.
Fuel tank capacities were increasing and the C-Series had 2½ gallon saddle tanks, with a separate oil tank of 4 pints in 1929 and 3½ pints in 1930 - a different design of tank.
From my current researches it would appear that approximately 6,700 Models CN were produced, and around 4,300 Models CSD.
Models CN and/or CSD still survive in Australia, Belgium, Britain, Chile, Czech Republic, Ireland, Germany, Holland, Hungary, India, Italy, New Zealand, Norway, Portugal, Poland, South Africa, Spain, Sweden, Switzerland and the USA.
For more details, technical information, performance figures, and much more, you really need to refer to the booklet I have written covering these models.