ROAD conditions abroad are very different from those which prevail in this country, while the long distances often covered by the continental driver in a single session call for a car which will glide along at high speeds without tiring the man at the wheel. Independent springing and an engine of large capacity are two items almost essential in order to achieve these ideals, and so apart from the glamour which attaches to the marque of Mercedes, we felt a great technical interest in trying the latest sports car which the famous Stuttgart factory produces.
The five-litre car retains a strong resemblance to the famous ” 38-250 ” and retains the striking V-radiator, the outside exhaust pipes and the general clean and efficient lines which distinguished the older model. The engine is still a slow-speed unit in spite of being a straight-eight, and 3,400 r.p.m. is the maximum engine speed. With this point the resemblance ends, for instead of being a full sports model requiring continual use of the gear-box and having rather harsh suspension, the five-litre is practically a two-gear car, and is as comfortably suspended as one could wish for, while still capable of exceeding 100 m.p.h.
The slow-running engine and the unique method of using the supercharger called for driving technique rather different from that required with an English sports car. Bottom gear is only used climbing mountains, we were informed, and a start is made on the high second ratio. We changed up to third gear, which is the direct ratio at 2,500 r.p.m., and except in very dense traffic or for starting never dropped below it, since the car will crawl along at walking pace on third if required. Instead of dropping down a gear in order to accelerate rapidly, the driver simply presses the accelerator pedal firmly as far as it will go, which engages the supercharger drive through a plate clutch at the front of the engine, and the resulting acceleration is all that one can desire. The supercharger still makes the stirring syren note which was characteristic of the older models.
Meanwhile the gear-lever has been transferred from third to the over-top position, and on releasing the accelerator pedal for one or two seconds, this ratio is automatically selected, and the driver can again use the supercharger if he wants to continue the rapid acceleration. If the occasion does not call for haste, of course, the accelerator is kept short of the ” blowing” position. junction with a large rigid steering wheel gives the driver every confidence at high speeds, while a useful amount of caster helps to centralise the wheel after corners. The car can be held at speed on corners without the tendency to ” hop” which we have occasionally experienced on the ” S.S.” cars, and in spite of the car’s weight the tail can be slid round in moments of exhilaration without any
By using the supercharger firmly, therefore, the car is quickly brought to a fast touring speed and the flexible engine then maintains the pace without further recourse to forced, induction. At a cruising speed of 62.5 m.p.h., the engine is doing only 2,000 r.p.m.. while at 75 to 80 m.p.h., a pace which one may maintain indefinitely on many Continental highways, and in England too on some of our less frequented main roads, the Mercedes sweeps along silently on twothirds throttle. The car that we were testing had been used as a service car when the Mercedes team went to Spain to take part in the Spanish Grand Prix, and the journey of 1,720 kilometres from Paris to San Sebastian was covered in 17 hours, which gives an average speed of 63 m.p.h. The maximum speed can seldom be attained in England, but on two occasions during our run we exceeded 100 m.p.h., while without the blower the car continued to surge along at ninety-five. It is one thing to drive a fast “battleship,” if one may be pardoned for so describing a car which weighs over two tons, along fast straight highways, but in the case of some of the heavy continental cars, not quite so amusing to guide them at a useful speed along the rather sinuous main roads which are found in many parts of England. The steering of the Mercedes, which rather surprisingly makes use of an English Ross gear-box, is pleasantly light and in con
fear of its getting out of control. All four wheels are independently sprung, and this makes it possible to have good road-holding without harshness at low speeds. The car may be driven on and off a kerb at 25 m.p.h. without moving it from an even keel, and we had an even more striking though unintentional demonstration of the success of the principle when passing another car at 75 m.p.h. Not being able to judge the exact width of the car when sitting
The brakes unfortunately did not quite come up to the standard of the rest of the chassis, but as they had z:eceived no attention during the 2,000 miles which the car had covered as a team hack, this would no doubt account for it. From 40 m.p.h. the car took 120 feet to come to rest, with the back wheels firmly locked. We were informed that 64 feet was about the usual figure,
behind the left hand steering, we mounted the kerb and came down again, and without the rather perturbed expression of out passenger, would not have realised what had happened. The massive chassis is in fact almost entirely insulated from the irregularities of the road, and the maker’s claim that the “Type 500 ” will maintain 75 m.p.h. almost regardless of conditions is no idle one. and in view of the size of the drums and the efficiency of the Lockheed system, this seems quite a reason
able figure. The brakes come on smoothly and a vacuum-servo mechanism lessens the effort required to apply them. Third and top gears, as has already been explained, are the only ones used in normal travel, and attention has been concentrated on making them as easily changed as possible without touching the clutch. When changing up the lever is moved right and forward, pre-selecting the gear as it were. The actual change takes place when the foot is removed from the accelerator. A vacuum servo-motor engages the high gear when the speed of the driving shaft drops the necessary amount, while when changing down the gear-lever is moved in the reverse direction and the direct gear engages when the accelerator is released and then depressed again. The three top gears are silent-running, and second is engaged in
the usual way by freeing the clutch and accelerating. Until one gets used to the semi-automatic mechanism the change is rather slower than with an orthodox gear-box, but when one becomes accustomed to it, there is little to choose as regards the time taken.
As may be gathered from what has been already said, speeds on the gears do not worry the driver of the Mercedes very much, but at the maximum of 3,400 r.p.m. they are roughly 38, 64 and 109 m.p.h. on second, third and over-top. Unfortunately Brooklands was closed for record attempts so the maximum could not be determined.
The petrol consumption is about 10 m.p.g. with ordinary fast touring and the car we tried had a compression suitable for Esso, the well-known Continental ” doped ” petrol. During our test we ran on 50-50 straight petrol and benzol, but with a slight reduction in compression the car runs happily on Pratt’s Ethyl or Cleveland Discol. One of the joys of the big car is that there is
plenty of room in the driving compartment, and the pedals and the steering wheel of the Mercedes were arranged just where one wanted them, so that the car could be driven at full speed with the minimum of effort. The car we tested was fitted with left-hand steering, but the ones to be sold in this country have the wheel on the right. The windscreen though quite shallow gave good protection and a useful range of vision. while one sat high enough to see both wings over the high bonnet._ The dash equipment comprised all the usual instruments, and we liked the button switch for the indirect lighting, which put on the lights at the first pressure and extinguished them on pushing it a second time. The car was fitted with large Bosch headlights, which however did not give
as powerful a light as one would have expected, owing to having to conform to the strict regulations in force in Germany. However in combination with the two fog lamps also fitted, the road was completely illuminated from side to side and we Were able to run safely at 70 m.p.h. The dimming mechanism is controlled by a button on the floorboard alongside the driver’s left foot. Turning to the chassis details, the engine is a straight-eight With push-rod operated overhead valves. The cylinder block, and the head which is detachable, is made of cast iron, with one plug per cylinder, and the alloy crank-case holds 11 gallons of oil. The crank-shaft is carried in five plain bearings and is balanced, and also provided with a damper, with small ends lubri cated under pressure. Plain bearings are also used for the big-ends and the thin alloy pistons have three plain and one scraper rings. Coil ignition is used, and the petrol is drawnfrom the 24-gallon rear tank by a large Mercedes electric petrol
pump. A reserve supply is carried in a tank on the dash. The carburetion system is One which has been used for many years on supercharged Mercedes cars. A double carburetter supplies the front four and the rear four cylinders, and when the supercharger is brought into action, it produces its effect by forcing air at pressure through this same instrument. In order that fuelmay pass when the induction pipe is under pressure, the float chamber is also connected to the blower, and the electric pump is specially built to force in petrol against the pressure it meets. The blower, which is of the two-vane Roots type, is driven through a plate clutch and a train of gears from the front end of the crankshaft, and is, of course, only in operation when the accelerator is fully depressed ; it draws its air through a large cleaner mounted on top of the engine. The dynamo, distributor and water-pump are accessibly mounted on the near side of the engine, and a ther
mostat is fitted. The engine and gear-box are rubbermounted in one unit and the clutch is of the single plate type. The gear-box has four gears and reverse with a direct third gear and a geared-up fourth. The open propellor shaft has two flexible disc joints, while owing to the independent rear springing the differential casing is
mounted on a heavy cross-bracing at the rear of the chassis. Each wheel has its own half-axle attached to the casing by a metal universal joint, and two large coil springs are used on each side of the chassis. At the front of the car the king-pins and their stub-axles are carried on two A-shaped links which rise and fall at right angles to the axis of the frame. A single spiral spring is used for each side, and is fitted in the middle of the A’s bearing on the lower of the twr;
Hydraulic shock-absorbers are used back and front. A box-section chas.sls frame is used -and cross-members of the same type brace the side-members beneath the engine and behind the gear-box, while the rear part, which is upswept to clear the swinging axles is further braced by boxmembers and the sturdy pressing which carried the differential, casing. The stripped chassis which was shown at Olympia was almost classically simplein
outline, and might well be copied by some of our manufacturers, whose frames can only have been inspired by writhing serpents.
The specification is completed by Lockheed brakes,. servo-assisted, and the unusual wire wheels with their massive knockon hubs, and numerous balancing weights.
The car we tried was fitte4 with a handsome seater body painted red, devoid of frills, but with its familiar plated exhaust pipes, looking the complete ” Sportwagen.” The front seats, which were well upholstered in leather, were adjustable, and a large dickey at the back provided ample room for two more passengers or a quantity of luggage. Two spare wheels are carried on a single support at the back of the car and serve to round off the sporting outline. Summing up -one’s impressions of the. Five-litre Mercedes, one may say that here is a massive unbreakable ” car capable of 44 travelling. indefinitely at high speed and yet not difficult to handle, a man’s car in a period when chromium plate and snowplough radiators are making ever increasing inroads into the ranks of the thoroughbred sporting vehicle. It should be the ideal car for anyone living in the remoter parts of these Islands who wants to make fast non-stop journeys to the urban centres, while an owner who has to make long journeys abroad would, of course, find the Mercedes an ideal means of
transport. British Mercedes-Benz Ltd., Who have an extensive Service Station at 111, Grosvenor Road, London, S.W. 1, are the representatives in England of the parent factory at Stuttgart, and we are indebted to them for this opportunity of trying this unusual and distinguished car.