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2
SUPERCHARGING FOR
CARS
Opposed Views Of Designers
With no great disregard, for facts, it can be said at the pre- sent tume that the technical minds of the motor world are divided into
of two schools thought; one belleves and con- tends that suprécharging for car "engines will soon be accepted as normal practice, though not ne- cessarily universal or standard on all makes, while the other, scorns the likelihood of suprecharging ever becoming efther desirable or practicable "or. cars intended for ordinary purposes.
Let it be pointed out first that in the normal petrol engine of to-day the fuel mixture-air and petrol vapour-is carried into each cylinder by induction-Le... the "suction effect" arising there- in from the piston descending with the inlet valve open. Now, wher an engine is running at a slow or moderate speed sufficient to charge the mixture
cylinder almost fully is drawn into li never quite tully, for the charge. never attains to atmospheric pres- sure, even when the engine is idling.
But as and when speed in- creases the charges become smal- ier and smaller relative to the capacity of the cylinder; this is due to the meftia of the gaseous mixture causing it to fall to ac-. celerate quickly enough for a full charge to enter the cylinder in
the fraction of a second during (When
" which Induction occurs.
an engine is running at 3000 re- volutions per minute-quite an ordinarily high speed-the inlet valve is open for about one-hund- redth of a second only!),
Power and Speed
Thus it is that above a certain 'speed engine power fälls off. At 2000 r.p.m. an engine may deve- Jup nearly twice as much power as at 1000 r.p.m.; but a. 4000 r.p.m. it may develop, no more power than at 2000 r.b.m., or even jess. 'The peak of its" "power curve" may be somewhere around 3000 p.m. while its "torque' curve" (indicating the actual turning effort of which is is cap- able) may reach its peak at an appreciably lower speed.
Supercharging overcomes the inability of the cylinders to secure a full charge of explosive mixture at high speeds. It implies that in- stead of the mixture being drawn into each cylinder, by the suction effect due to the piston descend- ing. It is forced into the cylinder
by pressure set up by the super- Charger the "blower," as it is familiarly termed.
A supercharger is really a rot- ary air pump. Driven at a high speed by connection with the en- gine crankshaft, It forces air inta and through the carburetter, where petrol is picked up in the correct proportion. In the induc- tion manifold, therefore, while the engine is running there exists continuously a volume of mixture under pressure; the result is that as soon as an inlet valve com- mences to open, and all the time it is open, mixture is forced into the cylinder, fully charging the latter and even supercharging it ----viz., charging it at a pressure abque that of the atmosphere.
Forced Induction
Here it may be said that a des- criptive term sometimes applied to supercharging is "forced in- duction" but this may be held to refer properly to the use of a blower that does not generate more pressure than will just en- sure the filling of the cylinders with mixture at atmospheric pres- sure or slightly above it. Super- charging, did very little more at one time, the maximum pressure in the induction tract seldom if ever, being more than 21b, or 31b. per square inch above atmosphe #ric. But nowadays blowers are in us that give 101b, or even 15lb. aupercharge; and
run at higher speeds, 'could be utilised to make an engine of low tax rating serve the purposes of an unsupercharged engine of high tax rating. Lower gears "would be used, and to gain
a given maximum road speed the engine would run faster. Thus there would be gain in tax economy, the smaller engine would be cheaper manufacture and would ce-
to
cupy less space in the chassis, 80 giving more room for bodywork, or, as an alternative, enabling a car of smaller dimensions and lower weight to carry a body of larger size than at present.
For and Against
But there is another side to the picture. A supercharger must be made with extreme accuracy, and is not at all a cheap, item to pro-. vide and install. It is arguable, In fact, that a small engine with a supercharger may cost as much as a larger engine without one. Then the supercharger is an ad- ditional item subject to wear and to derangement if neglected: and It is sensitive to neglect, parti- cularly in the matter of lubrica- tion. Hitherto is has usually given rise to a whining noise when operating, while it occupies space that counteracts to some extent the gain due to the smaller en- gine.
It is contended, nevertheless. and not without reason, that de-
velopments of late have resulted, or will soon result, in such draw- backs as those mentioned being eliminated, and that cars wit soon be available possessing the advantages outlined
and others.
such as better acceleration and lower petrol consumption.
That may be so, but the op- posed school of thought remains
unconvinced,'
actually if not scornful.
HONG KONG DAILY PRESS, TUESDAY, APRIL 9, 1935.
MOTOR JOTTINGS
CARS OF TO-DAY
Chevrolet
The Chevrolet is a fast, smooth, and quiet saloon, easy to handle and moderately priced.
The body has four doors, with good entrance all round. The driver can get to his seat from the hearside, and the six side windows give a proper view; the forward and rearmost ones have no-draught ventilating sections worked by winders like the rest of the glasses. The wind-screen 1 fixed, and there is"but one wiper which works by suction, though the speed is variable. The front doors have armrests, and the wheel arches form resta at and the back. The cushions
squabs are comfortable, there is - enough room for five persons, the front seat is movable, and a spare wheel with an extra large hub, and in a metal painted cover, is in a well in each front wing. The upholstery is leather, and the body has improved insulation.
The 6-cylinder engine has over- head valves worked by pushrods, an improved combustion chamber, a better placement of the spark, higher compression, and larger valves, which have the seats cool- ed by water spray.
Invested Colt...
The power unit of engine, sin- gle-plate. dry clutch, and three- speed centrally controlled gear- box is flexibly held at five points with rubber, there being one cen- tral point in front, one either side and well forward of the flywheel, and one either sid. at the rear of the gearbox.. Under the bon- net at the nearside there are the down-draught carburettor with a large air cleaner and senser and exhaust above, the inlet manifolds with thermostatic con- trol of the heat supply for the mixture, the dynamo which shares an adjustable belt drive with a combined fan and impeller the
AMERICAN CARS water gland of which allows easy
or
Manufacturers' Changed Policy
Motor manufacturing compan- ies constituting the membership the American Automobile Manufacturers' Association, have passed a resolution indicating an
of
important change of policy in re- gard to the announcement new season's models, and the date of the first of the annual motor. shows in the U.S.A. The resoin- tion states that "beginning with the year 1935, members of the Association agice to confine their annual announcements of new cars to the month of October, as nearly as possible, and that the Arst car show at which the new models may be shown shall be held not later than November 5 in each year.”
The qualification "as, nearly as possible" is defined as "not more than 60 days before or after Octo- ber 1": this is obviously a gener- vus margla, one that implies new model announcements being made at any time between the early days of August and the end of November.
British Standards
Thus after something like 30 years American manufacturers have changed their policy in such respects and have adopted that continuously maintained by the British mator industry; for hit- herto annual announcements in the U.S.A have been made just before or at the opening of the New York Show in January. The '' 1935 models of American bave, it may be recalled, only just been introduced in this country. nearly six months after the earli
of British
est announcements enable', the
makers. maximum power of a given en- gine to be nearly doubled rela- tive so that obtained without supercharging.
1
It must be noted, however, that the increased power gained from supercharging is pccured in- cipally at the top end of the speed range, Certainly there is more power at even 1000 rpm.; but not much more, the increase be- coming greater in percentage the faster the engine runs. Moreover, the peak of the power curve 18 carried higher at higher speeds.
Supercharging, by enabling an engine to develop more power and
cars
What effect is expected from · this change of announcement and, show dates is not stated, but it is strange to recall that for some years past many British agents have urged our own "manu- facturers, to, fall into line with those of America and hold the Olympia and Scottish Shows in January, or even later, and to defer annual announcements from late summer until the new year. And now we have American Arms adopting the polley that British makers have been urged. lo discard!
regulation or re-packing, the oll filler tube which has a crank case ventilation pipe, and the dip-red. All these parts are to hand. though the filler is rather over- shadowed by the exhaust mani- fold. To run the oil out of the sump a plug underneath must be detached.. All the parts on the offside are handy: they include the inverted coll on the dash, the small sparking plugs set at an angle in the detachable head, the water tap with its extension pipe. the mechanical petrol pump, the nearly vertical distributor and -make-and-break which has auto- matic movement and an octane selector with
a scale, and the starter. Steering is by worm and roller; the starter works by hand. The gearbox has synchromesh and constant-mesh wheels for second and top, the propeller- shaft is enclosed with the univer sat joint automatically oiled from the gearbox, and the half-floating back axle has spiral bevel drive............... There are four mechanical bra- kes, with 12in. drums, worked by rods and cables at the ends and by pedal or central hand lever. At the back the suspension is by long half-elliptical springs with single-acting Hydraulic shock absorbers. The springs Have con- siderable camber. In front there is no axle as a stout cross member is provided and each wheel. is held by a swivel arm which has its own enclosed suspension by two concentric spiral springs and- double-acting
hydraulic shock
absorber, The whole of each suspension and shock-absorbing device is in one neat casing and - forms a single unit which can be detached with reasonable ease. The system provides what is known as kriec action, allowing each front wheel to rise and fall with independence. The steering. arms are devised to suit the su- spension, and they and the track road are well protected. Acces“, sible Jacking platforms are pre- vided.
“On The Ras4
The saloon submitted by Messra, Pass and Joyce had done Just over 3,000 miles. The engine ran very smoothly and quietty throughout ita range of speed. There is plenty of power, and so- celeration, from a fairly low rate. even under heavy and sudden load, is finely balanced and mo- dernly rapid. There is a pleasing "cleanness about the car's running, and the controls make speed safe.
THE HUMBER SNIPE
With The New Gearbox
The general features of the Humber Snipe "are well known, but it may be noted that the current model has radius rods for the front axle which relieve the springs of braking · stresses and allow them to be designed for their special duty. Then the control of the cooling system is now by radiator shutters opened and closed by all pressure, and by a thermostat and by-pass.. Then the springs are of the "multi-rate" type, in which sup- leaves plementary
come into action as the load or movement increases. Another feature Sk the provision of permanently at- tached jacks.
The principal feature of 'the model placed at our disposal by Messrs Robert Anderson, of New- ton-Mearns, was, however, the new de Norman ville epicyclic gear-box announced recently. This and bax, has many original "practical points
.,"
to
Reference may be made Sorte features
which influence the running and general perfor- mance of the car. For instance, there are no plain, bearings, but ball and roller bearings are used throughout, giving a high effi- ciency. Then pinion speeds are lower than usual in transmissions of this type, which makes for quiet running. The retention of the ordinary clutch relieves the brakes which lock the epicyclic drums of all stafting stesses.
These brakes are metal to me- tal, and a wedge section ensures absence of slipping under any conditions on arst and reverse. On top, too, the cone clutch has the thrust of the spring self-con- tained, and sticking of the cone is obviated by a withdrawal' me- chanism which provides an in- itial impact which knocks
out the cone instead of merely push- ing it out.
Simplicity of Control
The claims for this gear-box would seem to be fully substan- tlated in practice. On all ratios the transmission is really silent, and the lower gears are. of course, quieter than those of any ordinary gear-box. It is, how ever, the gear control which in- tefests the driver most. It is not
possible to pre-select with this box, and the lever above the steering-wheel cannot be moved until the clutch pedal is depress- ed.
Actually the pedal need only be depressed the slightest amount and the control lever moved practically simultaneously. The result is a change which could hardly be quicker, and certainly could not be simpler to effect. The take-up of the drive is al-
For example, the brakes were fully powerful and responsive" by hand or foot either way, yet progressive enough and without side pull; the steering was really light as all times, yet rellably firm and ac- curate. The suspension on the whole is good, and by the inde- pendence of the front-wheel-
much springing
fore-and-aft movement is saved. The only point of criticism I have is that the car, especially the front, is apt to sway down or heel a little with a sharp turn at speed, and thus the steering has to be fully used to bring the car out of the turn, Flatter springs, at the back would probably suit English roads better. The clutch worked pro- peily and it faced the standing start test satisfactorily. The gear-change proved simple and the lever handy. There is no stop for reverse. The pedals are cou- veniently set.
The tests were unusually severe, because there was half a gale of wind...against the car and con siderable speed was absorbed thereby. There were two persons, on board; the road surface was damp. The rates on first, second, and top are about 27, 50, and 80,- and 70 was attained on a co- paratively short distance against the wind and a slightly rising gradient. The rates on the up- graded stretch were 16 and 65, those on the 1-in-22} Dashwood 'Hill" were 30 und 60, and with a standing start on top at the foot of the old hill the crest was pass- ed.st 23 miles an hour...
ways by the main clutch, and there is never any feeling of slip in the gear-box when changing.
The control lever is very light to move, and locates itself almost automatically. The changing system certainly gives confidence.
In neutral the clutch is auto- matically held out, but not when the control is in the coasting
the top position above
gent notch. Between these two post- tions it is not necessary to de- clutch It may be mentioned that the transmission is equaly quiet when coasting.
2
Better Acceleration
The performance of the Hum- ber Snipe is of course good, but this-gear-box provides even bet- ter acceleration though the gears. The actual car tested had cover- ed no great mileage, and the ac- celeration figures on the various gears showed no appreciable im- provement on the test figures ob- tained with a standard Snipe.
Acceleration Agures from rest, however, showed a marked re- duction as a result of the quicker changes possible.
“... · From 40 to 50 mp.h, is an effort- less cruising speed, but much higher speeds can be maintained. with ease, while even at 70 m.p.h. the engine is still unobtrusive. Maximum is about 80 mb.h.. and on third and second about 55 and 35 m.p.h..can be obtained without difficulty.
While the new transmission and control are the interesting features of this model, reference must be made to the effective suspension. excellent steering, and powerful but-smooth trakes
It is a car which combines high efficiency with refinement, and, with the added attraction of this gear-box, it should achieve a still wider popularity.
THE CAR OF 1935 WHY I LIKE THE
HUMBER VOGUE
Have you ever wondered what the car of 1935 would look like had designers at the outset-not attempted to follow the horse carriage of the period? .Suppos- Ing, also, they had given much attention to the vehicle as a whole instead of concentrating on the machinery" and fitting in the seating accommodation after- wards, would not cars of to-day have been entirely different? Our long bonnets show that the engine was, and still is, the first consideration. Wouldn't it be more logical to have a fát engine under the
floorboards amidships and bodies which come out to the level of the wheel hubs, fitted with easy chairs?"
as
The question of car beauty is very illusive. The most beautiful car to-day with a long, imposing bonnet would be regarded absurd if the rear of it went first. It would be a rear-engined job, but in appearance when station- ary exactly as normal car. Instead of the mor beautiful it would become the Lost ugly car.
A
WOMEN DRIVERS IN
ENGLAND
Speaking at Oxford recently, Lord Nuffield paid a tribute to women drivers. He denied that they were a menace, and added that they were as good as male drivers: "If you say there are a number of nervous women drt- vers." he stated, "I will concede, your point, but if you say they are all bad, then I entirely dis- agree."
Continuing, Lord Nuffield' said
that
motorists had much for which to thank the fair sex, the " latter having played a more im- portant part in the evolution of the car of to-day than was some- times realized. Their infiuɛnce was reflected In the colour schemes, upholstery, accommoda- tion, ease of access and body lines,
Lord Nuffield commented upon thegreatly increased activity at the Morris factory, and said the day might not be far distant when they would be making & Car & minute.
Hard Driving In
Britain
A British lady driver writes her upinions regarding the Hnmber, ar follows:-
The visibility is equally good in rear scats as front ones.
The comfort of front and rear seats cause remarks of pleasure- from "all who ride in them.
The wings are ample and wide, and do not allow stone-throwing“ to clip their edges. This is most noticeable.
་་
Although of low build it has a and 15 good ground clearance splendid for cornering.
The acceleration' and top-gear performance are quite exception- jal in a four-cylinder, 11.9 h.p. car of that price, and one can scarce- ly realize there are only four cylinders.
The oil consumption it still as negligible as when new,
It is a delightful car for fast- averages.
It has a short wheel-base, and so is economical when crossing the Channel, and yet one doesn't 'seem to be inconvenienced by it' as the springing is very good and all passengers · sit within the
wheel-base.
It is a smart car with good lines. It is a pleasure to drive, and 15,much admired everywhere,
"It was asked at a Leeds City Council meeting recently whether the Corporation could make a charge for car parking in the streets and whether underground parks might be provided, but the Town Clerk made it known that they had no power to make any · such charges. Underground car parks could be made however, if the council obtained the necessary borrowing power.
TRUST A THOrnycroft WITH YOUR TRANSPORT
DEAL DIRECT
THORNYCROFT
SIX-CYLINDERED
COACHES & OMNIBUSES
MOTOR
Fall
VEHICLES
DIESEL OR PETROL
Ploscer Manufacturers of Commiseratal Motor
Rang
-1
nge of Spares carried in Hong Kong and Shanghah
4 or 6 Wheels
4 or 6 Cylinders
80 Cwt. to 10 Ton Loads
20 to 70 Passengers
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Pioneer Building, Nathan Road, Kowloon,
TEL: 56759.
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