classic motorcycle forum

I think your uncle is on a mid 1920s Triumph Model P.

If we take stock of what is in the pic, the engine is a sidevalve (angle of exhaust pipe), the tank is between the frame rails, magneto low mounted in front of engine, the forks are sidespring trapezoidal, mudguards are plain curved c-section,  front brake is small internal expanding, primary chain cover appears to be alloy, the rear wheel has a belt drive style of brake band, but no sign of a belt (chain drive was on the other side). And the tank has a Triumph style of paint and lining, although the emblem is not as standout as you would expect.

I reckon you are right R because I looked through the other possible candidates and the model P has the same front mudguard as the subject one shown in the above picture. The other candidates like the model SD has a wide lower front mudguard although the N and W all seem to have the uniform width front mudguard like the one in the picture.  The front light must have been a later addition because most of the pics of Model Ps I've looked at have old style acetylene type lamps with a hooded peak over the lens although the one in this attached picture has a front light almost identical to my Uncle's Triumph.  I notice all triumphs seemed to have that peculiar shaped front numberplate holder with a rounded bit at the rear, presumably for the tax disc.  My uncle's bike hasn't got one of the rounded thingys at the rear of his number plate maybe because it was registered in India, albeit British India.

Here is a picture of my Uncle Richard on what I think is a Triumph. It was taken in India during WW2.  I reckon looks a bit like an old 1920s or early 30s Triumph but I'm not sure of the model. I've got good pics of a 1923 Type R Fast Roadster and a  1923 Model SD but they don't quite match the one in the attached picture.
I'd like to know the model and the engine capacity etc and whatever else anyone can tell me.
Any help greatly appreciated.

Thanks Andy. That works a treat. I can indeed find out a lot for myself.

Can someone explain how an acetylene light worked and were they any good for night riding on unlit roads at speed? What was a carbide light? Was it similar to acetylene?

Leon, do you know how many cc the Rudge TT Roadster was? I know you said it was 3.5 bhp.

Thanks so much Leon & John for your expertise. I have found another photograph which I’m including and it seems to show my great uncle Arthur Blair-White (1891 – 1975) in the foreground on the Rudge (eg LF2275) with the Villiers Sun (Reg IF1187) in the background with his older brother Charlie on it. I am almost certain these photos are pre-war because Arthur got married in 1919 and he had a bad war and probably wasn’t in the mood for riding much after he got back from France.  I was thinking the pics were taken in 1911 or 1912 but I’m guessing.  I’m glad that some of you guys can tell from a magneto or a gearbox what month of what year the model dates from.  That’s what I call expertise!
The house, incidentally, was called Ashton Park and it later became a boys prep school called  Brook House which existed until recently when it merged with Castle Park school and the site was developed for housing.  They look like a couple of toffs in their blazers I must say but their lives was soon to change drastically when they went to war.
I know from my Encyclopedia of the Motorcycle that there were literally dozens of British motorcycle makers at this time.  I know that many of them used the Villiers engines before developing their own and sometimes going back to Villiers or JAP again.  I also know that JAP and Blackburne made a lot of engines for many makes of motorcycle.
I do know that all Irish registrations had an I or a Z in them and any reg with I or  must be Irish.
I know that IL was a Fermanagh plate and IA was Co Antim etc.  Didn’t know IF was a Cork plate John.
I presume the LF plate is an English or Scottish plate.
Leon, how exactly can you tell it is a Villiers engine and how can you tell it’s a 2-stroke? Is it a valveless 2-stroke with disc valves because I’ve read about those.  I trust any expert eye but am always intrigued to know how you identify things.  I hope the new picture helps you to further define your diagnoses.
I’m interested to know what the top speed of these bikes might be and what brakes they had.  I make motorized bicycles myself using Honda, Subaru, Mitsubishi and other engines and they don’t look that unlike the ones shown in these pictures.  Their top speed is about 34 mph max and they are chain driven and usually single geared.  I can only get horizontal springer forks these days & they can’t be trusted that much but I would kill to get hold of a real vintage bike for close scrutiny.
These pics are the best resolution I can get but I can’t see a way of attaching images to a PM.  I can email the best copies to anyone who gives me an address.
I really am grateful for your help Leon and John and I thank you for it.