Classic Car Catalogue

 Jowett 1953

Great Britain

Jupiter (B4 cyl, 1486 ccm, 60 bhp)
Jupiter R4 (B4 cyl. 1486 ccm, 65 bhp; wb: 7 ft.) – London 



Jowett Javelin PE Saloon replaced the PD model from October 1952 and is powered by the Series III flat-4 1486-cc engine, which is a great improvement over the troublesome earlier versions. Sturdier tapered-section bumpers are fitted and leather upholstery became standard on the basic as well as the de Luxe model.
Jowett Jupiter Mark IA (Series SC) is also fitted with a Series III power unit. This model, replaced the Mark I (Series SA) in October 1952, features numerous modifications including a proper opening boot, smoother wings, larger cockpit, curved mouldings only over the front wheel arches and metal fascia panel with grouped instruments.

Jupiter R4 - prototyp zaprezentowany w Londynie. Powstały 3 egzemplarze z plastikowymi nadwoziami.

Javelin. December '52 advert.








  In the past 12 months competition in sports-car racing has become so keen that success can only be achieved by cars designed to give speeds and acceleration considerably higher than have been thought adequate in past seasons.
  The Jowett Co. have responded to this situation by the introduction of the R.4 Jupiter, the overall design of which differs materially from the type Mark IA although the power units employed are very similar. Taking advantage of the high octane values of currently obtainable premium fuels, the R.4 engine has been given a compression ratio of 8.5 : 1 which has raised the output on the track to 65 h.p. at 5,000 r.p.m. This corresponds to a piston speed of just under 3,000 ft./min. and the peak of the torque curve lies between 2,750 and 3,000 r.p.m., that is to say, between 45 and 50 m.p.h. on the normal final axle ratio.
  As with all other post-war Jowett models, the four cylinders in two opposed pairs are placed well forward of the front wheel centre line, the four-speed gearbox lying beneath the radiator core which is placed on the wheel centre line. An unique feature of the R.4 Jupiter is an electrically-driven fan placed just behind the core and linked to a thermostat. This electric fan drive gives the designer a good deal more freedom than normal in the relative position of the radiator and the engine, and eliminates the need for driving the fan from the engine itself. There is almost no weight penalty as the weight of the electric motor is offset by the use of a smaller and lighter radiator. This in turn follows from the fact that in traffic conditions where the fan would normally be turning at low speed with the engine idling the fan comes in and runs at a high speed until the water temperature is reduced to normal. A similar situation arises when climbing hills at low speeds (as when following other traffic) and when a first or even second gear is not needed by the steepness of the gradient.
  In ordinary running on the road the air flow through the radiator is such as to keep the water temperature at the required level without the use of the fan so that those who are doubtful of the reliability of all electrical contrivances will be comforted by knowing that breakdown will not affect the normal operation of the car.
  Although the electrically driven fan is undoubtedly the most technically interesting of the changes made, the new frame design is also of particular interest. The previous tubular structure has been replaced by box-section pressings of quite exceptional depth. The chassis is further reinforced by welded-on steel scuttle, but a large proportion of the body panels are made of resin-impregnated glass fibre. This new material has remarkable qualities which are referred to in detail in the chapter dealing with technical developments. It will therefore suffice to say that the use of the material on the R.4 in conjunction with smaller dimensions and the new frame has resulted in the exceptionally low weight of 14 cwt. dry, 25 per cent. less than the Mark IA model, although the overall stiffness of the structure is appreciably improved.
  There are three more major differences between the two cars. At the front the rack and pinion steering gear hitherto used is replaced by a Bishop cam and lever, this being one of the very few instances where a manufacturer has ever discarded the rack and pinion type. A second, at the back, is the replacement of torsion bars and trailing arm plus Panhard rod for suspension and axle control, by the more conventional semielliptic leaf springs. A third, placed mid-way in the car, is an overdrive gear which is mounted between two cross members and thus divides the propeller shaft into two sections.
  The ratio of this component is such as to reduce the engine speed by 18 per cent. and the effect on overall performance may be considered by taking the speeds reached on the read at the peak of the h.p. curve. On the three upper ratios of the conventional gearbox these are 35, 56, and 83.5 m.p.h. Using overdrive third as well as overdrive top we get 35, 56, 68, 83.5, and 102 m.p.h.
  The actual top speed realized on the road will depend in part on the condition in which the car is run, since the frontal area of 16½ sq. ft. with a full screen is reduced to 13.6 sq. ft. with one aero screen, as would be used for competition purposes. A true maximum of over 100 m.p.h. can, however be confidently anticipated.
  Although, as first announced, this model (despite its exceptionally low price) appealed primarily to the competition driver the constructors are actively engaged in the development of an enclosed version, one form of which is a quickly detachable top. It may therefore confidently be expected that the R.4 will obtain a considerable fraction of the sales in the market for small sports-cars.

The Motor Year Book 1954



World Sportscar Championship entries:

24h Spa 25-26.07.1953 Entrant: Results:  
#         gen. group  
46 Javelin   Leavens / Leavens   acc. T -  
Tourist Trophy 05.09.1953 Entrant: Results:  
#         gen. class  
41 Jupiter   Lund / Robinson Ted Lund fail. S1.5 -