Keith,
Here is a picture of an old Thames Ditton hose.
The maker is 'Tubano' not as you spelt it, although your rendering is more sexy. The part number on this old hose is 'TR 37' which I suppose might indicate 37 mm. However the size is also shewn thus: 1 3/8 - 1 5/8. The Thames Ditton elbow, still in situ, has an O.D. of 1 5/8" - I cannot give you a definite answer to your question as my application is LM5000 which has a different radiator to an Ace Bristol, however the 'Tubano' in 37 mm (slightly more than 1 3/8" and slightly less than 1 5/8") fits the spigots on the Bristol water pump. This is not in accordance with Luke's post, but the bottom hose does include an elbow and I am not sure that the radiator to elbow section was 'Tubano' but may have been a short straight section, with the 'Tubano' joining the elbow to the water pump inlet spigot. This might account for an increase in hose diameter part way along the bottom hose.
So far as length goes it was just cut to fit, you can clamp the convoluted section just as well as the short plain ends on the 1 metre lengths. As it is expensive stuff I suppose the real question is, "Can you get one car done out of one length ?"
For what it's worth I did LM5000 using only a one metre length and if anything the radiator is further from the engine than is the case on an Ace Bristol.
And here is a lovely old pic that has nothing whatsoever to do with the thread (sorry Robin) but it is snowing outside here and it brings me a smile.....
