primotipo…

(Popperfoto)

Engineers building a production run of these very successful T20/23 series of cars which were important in helping launch the careers of Mike Hawthorn and Jack Brabham amongst others. And positioning Cooper as just not builders of 500’s…

The photos were taken in Cooper’s Surbiton workhop in early 1953, the cars are the CB Mk2 or T23.

The essential difference (there were other improvements as well) between the T20/23 is that the latter used a spaceframe chassis, clear in shot, the earlier car a more traditional box section frame. Note the stack of frames, not yet stove-enamelled on the lower right of the shot.

I wrote an article about the T20 a while back so I won’t repeat myself, click here to read it;

https://primotipo.com/2015/02/10/stirling-moss-cumberland-park-speedway-sydney-cooper-t20-wm-holden-1956/

Australian Gold Star Champion 1959, Len Lukey’s Cooper T23 Bristol (chassis CBR/2/9/53)  pictured at Mt Druitt, a circuit west of Sydney on 25 May 1958, the car did a 13.53 seconds standing quarter to take FTD. Shot shows the handsome lines of these cars to rather good effect as the gent looking on would attest. Later fitted with a Holden 6 cylinder engine, restored, for a time part of the Donington Collection and still extant (John Ellacott)

The workshop shots are great, the unclothed cars show the Bristol engine, the chassis and the suspension mix of wishbones and transverse leaf springs front and rear.

Cooper were somewhat maligned over the years about their ‘curvy spaceframes’ by engineering purists but in comparison with other cars of this period, the Cooper is a paragon of modernity if not a perfect example of triangulation!

Doug Nye credits Dante Giacosa’s design of the 1946 Cisitalia D46 for Piero Dusio, as the first modern customer spaceframe car ‘the production racing car trendsetter for an entire generation of designers’.

Cisitalia factory drawing of the D46 voiturette and its lovely, stiff spaceframe chassis, Fiat 1100cc 62bhp OHV engine. Suspension F/R lower arms/live axle with transverse semi-elliptic springs front and rear, hydraulic drum brakes. Drivers of the cars included the elite, Tazio Nuvolari and down

Robert Manzon’s 14th placed Cisitalia D46 during the 330Km GP du Comminges, St Gaudens 0n 10 August 1947. Race won by Louis Chiron’s Talbot Lago ’39. The caption with this shot simply says ‘1947 French GP’, which it is not. I have arrived at the above driver/car/event by elimination, some French readers will be familiar with the background, the other hint is the ‘team badge’ on the cars side, let me know if i am wrong or right for that matter! (GP Library)

As stated above the Cooper Bristol Mk1 (T20) used a simple fabricated box-section single plane-ladder frame with tacked on body supports and was very successful.

John Cooper and Owen Maddock’s (Cooper designer/engineer/draughtsman) 1953 Mk2/T23 used a multi-tubular frame which took advantage of the entire cross-sectional area available inside the body ‘and looked more like what would become known as a ‘spaceframe’ design though still sparsely triangulated…this new welded-up chassis frame employed all the same sized round section tube, and it was effectively the forerunner of many more British GP cars ‘spaceframes’ to follow’ Nye said.

So, if the car isn’t the trendsetter Giacosa’s was the Cooper lads were certainly spaceframe ‘early adopters’, very successfully so.

Note the beautiful light alloy Cooper wheels, rudimentary independent rear suspension set up of lower wishbones and top transverse leaf spring which would serve Cooper well till the end of the decade. Double wishbones and coil springs at the front appeared a bit earlier but the transverse top leaf is in use here.

New Cooper T23 on what is perhaps its first test at Goodwood in late ’52 or early 1953, triple Solex fed 1971cc circa 155bhp spec engine as per text. Frame, neat throttle linkage and beautiful hand formed aluminium body also clear in shot (Popperfoto)

The Bristol/BMW engine develops around 155bhp from its 1971cc in BS4A spec, the engine is worth a paragraph or two. What follows is a summary in relation to the engines race application, not a chronology of the many variants fitted to road cars.

As demand for aircraft and engines eased towards the end of WW2 the Bristol Aeroplane Company decided to diversify into cars. The history of this great company is interesting, click here to read about it; http://www.bristolaero.org/bristol-built/

One of its directors, HJ Aldington, had impeccable BMW connections, another of his companies, AFN Ltd were both the constructors of Frazer Nash cars and the pre-War importers of BMW. The 2 litre engine the subject of this article, was fitted to BMW’s superb 328 sports car, famously the winner of the 1940 Mille Miglia in Huschke von Hanstein’s hands..

BMW 328 on Avus’ North Curve, Germany on 19 May 1938, driver and event unrecorded (Ullstein Bild)

In the post-war German mess, der Deutschlanders were keener for their technology to be shared with the ‘goodies rather than the baddies’ (the Ruskies), Aldington did a deal via the War Reparation Board which gave the engine technology to Bristol. The Brits fitted the engine to a 326 chassis and dressed the lot in an aerodynamic body similar to the 327 ‘Autenreith’ Coupe.

The first Bristol built engine was fired up on their dyno on 22 May 1946 and was soon fitted to its prototype ‘400’ car.

The engine was tall, slim and short despite its long stroke. The bores were cleverly siamesed within the cast iron block to allow the use of 4, rather than the 7 main bearings considered normal for a straight-six. The head had hemispherical combustion chambers with valves inclined at an included angle of 80 degrees with downdraught inlet ports between them.

Rather than twin overhead camshafts the valves were operated by 18! inclined cross-pushrods. For its success it demanded great engineering precision in its build, something Bristol had in spades. A steel crank ran in Vandervell ‘ThinWall’ lead indium bearings. Dry cylinder liners were of Brivadium alloy-steel so hard that for racing Bristol didn’t consider them run in until the engine had done 8000 miles!

After fitment of three downdraught SU carbs the ’85A’ engine developed 80bhp. The ’85C’ was fitted with three Solexes.

Bristols; Type 171 Sycamore helicopter and 401 Coupe in 1950 (Hutton Archive)

In 1948/9 Aldington asked Bristol to develop a high performance variant for Frazer Nash, this ‘FNS’ (Frazer Nash Specification) unit with 0.15 larger inlet ports, improved crank counter weights, Delco-Remy distributor rather than the Lucas unit developed 126bhp @ 5500rpm. In the FN Le Mans Rep the engines were very successful.

The 8th placed Bristol engined Frazer Nash Le Mans Replica of Dickie Stoop and Peter Wilson about to be swallowed by the winning Aston Martin DB3S with Reg Parnell at the wheel, he shared with Eric Thompson, during the Goodwood 9 Hours 22 August 1953 (GP Library)

Encouraged by the Frazer Nash success, Bristol built a new ‘Bristol Sport’ (BS) engine based on the ‘403’ Type 100 spec engine. These had blocks cast in chrome alloy steel. With a 66mm bore and 96mm stroke they displaced 1971cc.

The head was aluminium alloy with inlet valves made of chrome-nickel steel, exhaust valves of austentic-chrome steel. All of the valve gear was very light and polished. The crank was in aviation spec nitriding steel still running in 4 main bearings. A short duplex chain drove from the cranks nose to the high camshaft which ran in four bearings and carried a skew gear driving the distributor and oil pump shafts. High pressure lubrication was used but a wet sump retained. On ‘BS Series’ engines the head was ‘ported and polished’.

These engines, the Mark 2 version used by Mike Hawthorn’s Lavant Cup winning Cooper T20 at the Goodwood Easter 1952 meeting developed 149.8bhp@5550rpm on the Filton dyno before Leslie Hawthorn deployed his secret ‘witches brew’ of nitro-methane to produce more power still.

The ‘BS4A Mk1’ engines  developed 155bhp@6000rpm and 148lb/ft of torque at 5000rpm.

Ultimate versions of the German/British engines were Cooper Bristol driver/engineer Bob Gerard’s de-siamesed port 2.2 litre variants running nitro-methane which developed 180bhp@7000rpm. Bristol’s own de-siamesed engine which ran at Le Mans in its Coupes developed a reliable 160bhp. By that time the 2 litre F2 racing for which these engines were developed was over.

The Cooper Bristols were important cars in the rise of the Surbiton marque and formidable weapons in the right hands if not Ferrari Tipo 500 beaters…

Cooper T23 Bristol being unloaded from its trailer on a bleak, winter Goodwood day in late 1952 or early 1953. 85km trip from Cooper’s Surbiton ‘shop to Goodwood. These shots (of the mechanics fettling the engine above and the two below) are undated other than 1 January 1953 which will be an approximation, there are no details of the mechanics or driver. My guess is that its a Cooper instigated press shoot, as are the workshop ones above, probably of the cars first test, the ‘stub exhausts’, these engines not usually raced as such, indicative of a ‘quick fix’ overnight to run the car for the first time. If any of you have the details please provide them and i will update the text (Popperfoto)

Bibliography…

Doug Nye ‘History of The GP Car’, Automobile Year, John Blanden ‘Historic Racing Cars in Australia

Photo Credits…

Popperfoto, John Ellacott, GP Library

Tailpiece: John Cooper, but its just a guess…