Page
Rational Supercharging
Like most other practical features of the motor car, supercharging is
matter of compromise, that is." compromise in regard to the ex- tent to which it should be carried
That "clrcumstances alter cases" is particularly true in regard to this, and many erroneous ideas ori the subject exist, due to the fact that supercharging originated in application to racing ears, the usage conditions of which differ from those of other caps.
The most Important fundament- 31 difference in these conditions of use is that, whereas a racing car Is concerned often with power out- put under full throttle opening. the everyday car calls for high average efficiency at all speeds and throttle openings.
Until such time as an engine with automatically variable copa- city combustion chambers" comes into being, it is impossible to get high average eficiency with a high pressure supercharge. '}'
As we are dealing with "every-" day car requirements, I am as- suming that only standard fuels as obtainable from roadside pumps will be used, and therefore any figures I may give do not take into account the special "dope" fuels provided with abnormal anti-" detonative and valve-cooling pro- perties which, at extravagant prices, permit racing engines to run with compression ratios quite Impracticable for ordinary use.
Roadside pump fuels permit the use of compression ratios limited to maxima ranging from 54 up to. 7 to 1.
CHARGES LARGER THAN NORMAL
Now, it is obvious that 11, by supercharging, a substantially lar- ger than normal charge is forced into the combustion chamber, then the chamber must be enlarged proportionately or detonation due to over-compression will result. It is here that the matter of com- promise comes in.
An enlarged combustion cham- ber proportionate to the "increased engine requirements at full" throttle naturally produces a lower com- pression ratio, and therefore re- cuced compression of the charge. under
part-throttle conditions. The power developed by a given amount of fuel being proportionate to its compression at the moment of ignition, low compression means both high fuel consumption and lack of "vim" under normal road-«
conditions. With
of reasonably good power-weight ratio really full throttle is used comparatively little.
use
a car
As the very remarkable success of M.G. Midgets on doped fuels and pressures as high as 28 lb., for track races and records, has tended to create a false impression in regard to normally desirable supercharge pressures, consideration of existing practice's on noted Continental racing cars of the immediate past.
affords, useful data on this sub- ject of supercharge values. The outstanding names are undoubted- ly Alfa-Romeo, Bugatti Maserati. Auto-Union, and Mercedes, none of whom employ pressures as high as the above.
The most popular foreign super- charged cars as supplied to the public have pressures of from 2 lb. io 8 lb. only, while American cars have less than 2 lb., and even this "only comes into operation at high engine speeds. Having much lar- ger engines than are usual in this country, there is sufficient power for their requirements at low speeds, and the supercharger acts primarily as
a. compensator to make good the volumetric in- efficiencies of the engines, at the higher r.p.m. By this is meant that whereas, with moderate-rised valves and induction passages to promote good low-speed perform- ance, engines suffer from inade- quate Alling of the cylinders at the bigher rp.m., a mild supercharge coming into operation as speed in- creases makes good this potential deficiency.
产
This is an opportune moment to refer to one of the great merits of supercharging, namely, that the power curve of the engine con- tinues to rise proportionately to the engine speed far beyond the point at which the power of the, normal engine begins to fall off. The supercharger, therefore, haa, an effect beyond that of providing the power of an engine larger in cylinder capacity.
THE BEST COMPROMISE, 3 LE. TO 6 LB.
The question now arises as to what is the best compromise în re- gard to supercharge pressures, as epplied to existing care, this would appear to be from 3-16 to 4 lb.,
according to the idiosyncrasies of the engine in question.
Some engines are more efficient in regard to valve cooling than others, while others may have rather fine margins in regard to transmission factors of safety which accordingly may render a very great increase in power un- Besirable.
Working on the basis of 4-5 lb. average, we obtain an increase in power of approximately from 30 per cent. to 35 per cent., which, as only a few pounds weight is added to the whole, obviously will give Immensely improved performance.
Restriction to this figure is ad- vacated for the following reasons:
(1) The majority of cars can be sately improved to this extent...
(2) The benefits of relatively high compression are maintained under all conditions.
(3) The use of Ethyl or similar standard fuel" renders it unneces- sary to make any alteration to the existing compression ratio, as most engines are designed to run with- "straight," detonation On
.
out
petrol.
(4) Normal types of sparking plugs at popular prices can be used.
(5) If power be increased undu- is one or more weak links will be discovered in the chain comprised by engine unit, clutch, gear box, propeller-shaft, differential and
axle shafts.
Finally. It is unwise and costly t attempt to give a touring car really racing-car performance, but its performance may be immensely improved at little expense, and at no sacrifice in rellablity or fuel. efficiency by a reasonably proper- tioned supercharge.
CAR CONTROLS
Standard Positions
Suggested
By no means least of the useful activities of the Society of Motor Manufacturers and Traders is ita persistent endeavour to secure a reasonable degree of standardisa- tion in the many practices con- nacted of motor cars. Had it not been for the efforts of the 6.M.MT., the chances are that we should now find great difficulty
in purchasing at an ordinary gar-
age a tyre to at the rlins of our car, while even to obtain a spare valve inside." or a dust cap for a tube. would not be the simple matter it is to-day.
The Society's latest recom- mendation relates to the position of control pedals and the layout of gear changing gates. As re- gards the foriner, all manufac- turers are advised to fit the ac- celerator or throttle pedal on the right of the brake pedal. It will be remembered that in a good cases the throttle pedal many hak in the past, been arranged between the clutch and brake pedals. Not only is the foot, as a rule. more easily placed when it operates the throttle pedal on the extreme right, but there is also a very real advantage in recom- mending one position for it which does not vary from car to car. If every driver knows that in or- der to stop a car quickly his right foot must move to the left from the throttle to the brake pedal. this action becomes instinctive. and applies to whatever vehicle he may be driving. Quite a number of accidents have been' attributed to a driver on a strange car try- ing, in an emergency, to move his foot in the wrong direction in search of the break.
So far as the layout of th? gate is concerned, with very few excep- tions this has now become stan... dardised, with the first speed of a four-speed box forward on the leit, the second speed back on the same side, the third through the gate and forward on the right, with top speed back on that side, This arrangement is now official ly recommended by the 8.M.MT. In the case of a three-speed box, the reverse position recommended
is forward on the left, first back on that side, second through the gate and forward on the
HONG KONG DAILY PRESS, TUESDAY, SEPTEMBER 17, 1935.
MOTOR
› THAT OLD CAR
Smarten It Up
Now that the new senson's models, are beginning to appear on the roads, owners of older cars are faced with the dismaying rea- lisation that their cherised posses- gicns, which quite recently seem- ed to them the last word in auto- mobile design, are already a year out of date, writes M.W.D. in The Autocar. No matter that in some cases. Uttle or no alterations have been made in the latest models. It is a strange paradox that the marketing methods of the indus
The try have "brought about. owners of pre-1935 machines suf- fer this minor humillation to a 1sser degree; in fact, the older the ear the less the humiliation, That is one of the consolations of owning a really old can
Yet it is mistaken practice to allow an old car to deteriorate in
SILC appearnce
performance merely because it is old. Mistaken for two reasons, first, because there is far more satisfaction in owning a machine that looks and runs well than is generally sup- posed; and secondly, because on the resale of a well-kept car A considerably higher price can often be obtained than for one of the other sort.
The writer has had the truth" of this assertion demonstrated to him in bitter fashion. He wish- ed to purchase a venerable Cow- ley two-seater that was in more than sound condition, both ex- ternally and internally. The price was high. Yet the owner refused to haggle, because he knew, as he said that he could get his price privately. if not in the trade, without the slightest trouble.
The car was bought, at the owner's price, and it gave every satisfaction. It was always yat- tended to mechanically, but, like many other people, I hadn't the time, or couldn't be bothered, to see to its tolet. Result: when the time came to sell it, I had either to spend much money and-time in restoring its pristine elegance or accept what is called a knock- down price for it. I chosen the latter alternative,
The reverse experience has also been mine. The first car which I possessed did not give a parti- cularly good account of itself; in fact, to use a colloquialism. It was a packet of trouble, or rather, of small, irriating troubles. Yet, I tended that car lovingly from the start; and I sold it, in the end. at higher than the market price.
The moral of these two exper- iences as the title I have used." Money spent on repainting or re- cellulosing shoddy coachwork wil almost always come back to you in the long run. Besides, you will enjoy extremely the feeling of superiority which Inevitably arises in you when older and more dila- pidated models of the same make pass yours on the road. The plea- sure of such an experience is not to be assessed in terms of mere money!
ROAD TARRING
Unsuitable “Grit”
Ever since road tarring came into fashion, in the early years of this century, motorists have had good reason to complain of the manner in which the cover- ing" of "grit is applied. Some- times the protecting layer is in- 'sumciently thick; at others, t consists of small sharp' stones which cut" the tyres. The chief complaint to-day is that sur- veyors are using stones of excessive, size. These are apt to be "catapulted" up by the rubber tread with considerable violence..
Within the past few weeks two cars used by members of “The Autocar" staff have been damag- ea by these high-velocity mis- siles. On one occasion the outer sheet of glass of a safety-glass windscreen was punctured, and
1
another a "gritting" stone hit the front of a mudguard and removed the cellulose right down to the metal. Possibly this over- size grit is less expensive than
and top back on the right, right, the smaller, and far more
an experienced driver may and himself at fault on a car with" an unusual gate layout, and it is bet ter that all cars should be alike de thi
JOTTINGS
THE AUSTIN HERTFORD
Some Of The Special Features
41
The Austin Sixteen is a popular and well established model with › a reputation for durability. It has no pretensions as a fast car. and no attempt has been made to reduce weight at the expense of reliability. It is a typically. British type of car, soild in con- struction, dignified in appearance, possessing good accommodation and well equipped, at a moderate price,
The current model follows on the ne general lines as before, but its appearance has been smarten- ed by the new radiator and bon- net with hinged louvres, while the spare wheel is enclosed at the rear by a panel which when lowered provides a luggage platform:
Performance has been improved by the use of a down-draught car- burettor, and handling is render- ed simple by the gear-box, which provides synchromesh engage- ment of a very effective type on all gears but first. Zinc inter- leaves are still used in the road- springs, obviating lubrication and ensuring constant spring effect. Mattenance is also simplified by the use of silentbloc bushes,
The familiar ring on the steer- ing-wheel is used for horn opera- tion, self-returning direction in- dicators are operated from the strering-wheel centre, and a foot- switch operates the hip and switch headlamps.
SATISFYING PERFORMANCE
The Austin Hertoford is a five- seated saloon with a wide arid easy entrance and a low floor, Ample head room is a good fea- ture, and the adjustable front and rear seats provide most comfor- table accommodation, while the fittings, which include folding tables, footrests, and a Pytchley sliding roof, are complete and practical.
The driving seat is comfortable and the position sensible, giving a good and unobstructed view. while the brake and gear lever çome nicely to hand. It is, in fact, a car which can be driven in town or country with a minimum of fatigue.
Acceleration may not be re- markable, but it is consistent, and the driver always knows the exact response. to his demands. The car does its work easily, and there is always the feeling that the en- kine is operating without real effort.
It 13, moreover, quiet and
น
34
CARS OF 1936
Rover Models
Standardisation of a car manu¬ often facturing programme justifiable and desirable. With a successful year behind them the Rover Company are making little change of importance in their 1936 models,
The firm nave concerntrated first on refining the many special features introduced into the Rover specifications of recent years, and In which the clutchess. gear- change, freewheel, and automatic chassis lubrication are notable points.
Prices
A number of new features have been added for increased reliabil- eity and performance. have not been changed,
For the
saloon a "Ten"
line has been more rounded adopted for the rear panels, and the spare wheelis now fush-atted and and covered, as with the 12 h.p. and 14 h.p. models. A central folding armarest is now fitted to the rear seat. Glass ventilating louvres are over the doors, and there is a new type of horizon- tal bonnet loure. The sliding roof is flush-fitting.
A ventilated dynamo for large output as required is part of the Lucas special equipment on all models. Special interior spring- ing. with vaumol hide upholstery, is an improvement applied to all "models.
The 12 h.. and 14 h.p. salcons have the tools neatly disposed of in a tray sliding under the in- strument board. The popular. Sports saloon is continued on these chassis. The petrol tank Aller is now carried through the rear wing, leaving clear space in the luggage compartment.
The 14 h.p. programme-is com- pleted by the 4-door streamline coupe and Streamlined saloon brought out last year. The flush- fitted reversing light supplied as standard to these models is now of the automatically operating kind.
Finally there is the Speed 14 chassis fitted with the Streamline coupe referred to above, and cap- able of a fine road fallows:-
Ten h.p. Saloon, £248; 12 hp. Salcon. £278; 12 h.p. Sports Saloon 2298; 12 hp. Open four- seater, 288; 14 h.p. Saloon, £298;. 14 hp. Sports Saloop, £318; 14 h.p. Streamline Saloon. £348; 14 h.p. "Streamline Coupe, £348; Speed 14 h.p. Streamline Coupe. £415.
smooth and if it does not provide DRIVING
a notably power-to-height ratio, It is always ready to do its mile a' minute.
On third from 40 to 45 m.p.n. second may be reached, and on about 28 m.p.h. First is really only for atarting and emergency use; actually it is not really necessary for moving away, on the level.
The synchromesh change func tions smoothly without delay, and The indirect gears are quiet. The clutch is light, but the effective travel is comparatively short, needing a little, care in engage- ment until this characteristic be- comes familiar. Steering is good being light and not transmitting road shocks, while the brakes are adequate and tree from effect on the steering.
From 45 to 50 m.p.h. is a very pleasant, effortless cruising speed which can be maintained ind?- finitely, and acceleration over the most useful range of speeds is Bood
From a standing start 20 m.p.h. was reached in 5.8sec, 30 m.p.h. In 11.8sec., 40 mph. in 17.8sec., and 50 m.p.h, in 29.58ec.
COMMERCIAL MOTOR EXHIBITION
In addition to the internation al Motor Exhibition. (better known as the Motor Show) the Commercial. Motor Transport Ex- hibition, organised by the Society of Motor Manufacturers and Traders, will be held in 1837 and onwards at the new £1.250.000 exhibition building which is about to be erected at Earia Court
A substantial portion of the suitable variety, but it is to be
British Industries Fair will also hoped that the Roads Depart- ment of the Ministry of Trans-be held at Earls Court from 1937, "port will use its influence to dis- courage an economy which may well cost motorists dear,
but which section will be moved to the new building has not yet been dec
::
VISION
Food For Thought
It is never wise to argue from the particular to the general, but It 18
the wise to consider former in its possible relation to been a the latter. There has good deal written of late as to the poor visibility afforded cat drivers by some types of modern suggestions to bodywork, and remedy 'the trouble have" not lacking Note, however, been that the matter has been raised almost exclusively in connection with private cars. That they are not the only offenders is proved by the following amazing inci- dent, reported by a reader.
an Driving very slowly in Austin Seven on the. extreme edge of a London street, he gave a hand signal and pulled out to pass a fruit barrow. A huge petrol tank lorry which was ran 'into following the Austin the back of it, alewed it round s that it was standing across the front of the tanker, and pro- ceeded to push it in this positioni for 52 feet. The driver of the tanter, then pulled up-because "his steering felf queer" "He had never seen the small-car; nor could he do so from his driving seat owing to the im- mense, high bonnet of the lorry." Fortunately, the Austin" remained upright. Had it fallen over, our correspondent says,⠀⠀ "nothing "could have saved me.”
vehicle While most heavy drivers have an excellent view of the road ahead it is obvious that this is not always the case; for the safety of all concerned It Would appear that some regula tion ay uld be framed to deal with exceptional as that here:
THE TAIKOO DOCKYARD & ENGINEERING COMPANY OF HONGKONG, LIMITED.
"
BUILDERS OF ALL CLASSES OF SHIPS.
BUILDERS OFL RECIPROCATING STEAM ENGINES. BUILDERSHOFI MARINET AND LAND BOILERS.
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Under License From Messrs Parsons.
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