When did engine capacity start being measured in CC?

[jansens]

Bit of an odd question. When did they start using CC (cubic centimetres) to measure engine displacement in Britain and why? 

It seems odd it is in metric when everything else (bore, stroke, bearings, crank diameter, etc) was imperial (in Britain at least). 

The 750 motor club was started in 1939 it seems so they were using it then at least. I am guessing it is something to do with a lot of the early cars being French and German and they used metric measures.

I was curious since I am looking at the specs for Brooklands mufflers and they mention the volume must be at least 6 times the volume of one cylinder. I am working all the dimensions out in imperial and so had to convert 750/4 into imperial too. 

Simon

[Mike Costigan]

It may well be due to the international racing classes which were formulated by the French. Certainly all races at Brooklands from the opening in 1907 were run to classes either by capacity in ccs or cylinder dimensions in mm.

[Bob Culver]

Britain was a late starter in the automative world. France was regarded as the leader. Roads were available for racing. It would be interesting to know the first competition defined by capacity.Bore was more commonly the limitation.

[jansens]

Looking into this I did find this fascinating period account of the first race day at Brooklands in 1907.

https://www.gracesguide.co.uk/1907_Brook...ce_Meeting

It doesn't seem to mention CCs, classes seem based on RAC power ratings, but it does list the engine dimensions in both mm and inches, I guess depending on where the car was made.

Amusing it mentions problems with spectator traffic getting into the event as well as the costs of entry. Some things never change it seems! 

Simon

[Mike Costigan]

As Bob says, most early Brooklands races were based on RAC horsepower classes, but the very first race was for cars with cylinder dimension less than 85mm bore and 110mm stroke. The first mention of capacity classes was in 1912 when the RAC introduced Classes A-J for record attempts (Class A up to 1639cc, up to Class J over 13,929cc!). The earliest reference I can find for a race with a capacity class is the 3-litre Scratch Race at the Easter 1921 meeting, but there had been races specifically for Light Cars before then, and I believe the definition of a Light Car was already well established as a car of less than 1500cc ...

[Mark McKibbin]

In retrospect it seems silly that anything other than capacity would be used as a racing formula but certainly Voiturette racing of around 1905-10 was something like One cylinder cars 100mm bore, two cylinder cars 75mm bore and 4 cylinder cars 65mm bores.  So those  like the Sizaire Naudin mono or later the Peugeot V twin  had crazy long strokes and won everything, a capacity rule would have fixed it.

[Bob Culver]

Straying a bit but the topic is not uninteresting. The RAC formula is distorted by few cylinders and by short strokes. The shortish stroke 2.9 litre model T was 22 hp. With tax of one pound per hp p.a it left a market for Brit 10s, 12s. Our Sevens are really 8s. Early Jowett twins were larger than A7s and only 6 RAC but advertised as 7 to not deter buyers. My favourite is the 1911 Lion Peugot twin racers 80x280 2.8 litre but 8 RAC. Probably the driver trained with a jack hammer. The ohv Anglia was about 1 litre but 16 RAC hp.

Re Brooklands, compared wages of the time, prizes and prices formidable. I guess a kept chauffeur only got 2 pound or so.

[John Mason]

Bob mentions tax at £1.00 per hp. Is that the reason British car makers favoured the long stroke engine as a way of keeping the road tax in a relative low class but keeping a reasonable amount of power.

John Mason.

[merlinart]

Apparently, the 1926 Grand Prix season defined a maximum capacity of 1500cc under AIACR rules. Association Internationale des Automobile Clubs Reconnus was founded in 1904 in Paris, as an association of recognised national motoring clubs under the auspices of the FIA also founded in 1904.

This appears to be the first definition of racing cubic capacity perhaps?

Arthur

[Mark McKibbin]

Then you have French Horsepower, they have much bigger horses over there. As an example a UK Citroen Light 15 (15 RAC HP) is sold as a 11BL (11CV or 11 French Horsepower) I assume they use Percherons as they need less horses to do the same job!