1949-01-13 — Page 8

THE CHINA MAIL, THURSDAY, JANUARY 13, 1949.

RN

·BUSSEIL NEWBERY

Silent DIESEL ENGINES

Anti-knock cumbustion head.

*

Totally enclosed.

Silent and Vibrationless.

• Electric or Air Starting.

MARINE & INDUSTRIAL UNITS

Enquiries to:

7-100 H.P.

SWIRE & MACLAINE LTD.

ENGINEERING DEPARTMENT CONNAUGHT RD.C. TEL. 30331.

A.P.B. 17

THREADS AND REAL

BRITISH MADE G.F. MALLEABLE TUBE FITTINGS

HAVING PERFECT

MALLEABILITY, RELIABLE FOR STEAM, WATER,

GAS, OIL AND AIR:

Every fitting individually tested to 360 lbs.

per square inch.

STOCKS CARRIED

SIBER HEGNER & CO., LTD.

St. George's Bldg.

Telephone 22625

HEATING

ELECTRIC WATER

STEAM

CARTER & SUTTON

234-A, Hong Kong & Shanghai

Bank Bldg. Tel. 28004.

IL W. SUTTON,

Manager.

ENGINEERING PAGE

SEPARATE AIR PUMP ENGINE REPRESENTS GREAT ADVANCE

The type of two cycle petrol engine used in many small motorcycles represents the simplest form of loop scavenge two-cycle engino and is in- variably built as a crankcase compression type. Early examples of two-cycle loop scavenge compres- sion ignition engines were also built on the crankcase compression principle, but their chief virtues were simplicity and low cost of manu- facture.

In performance, however, they were inferior to four-cycle engines which were rightly re- gurded 09 being of higher grade.

1

The crankense compression type of two-cycla diesel engine hay Bow Bargely become obsolete and has been superseded by engines employing a separate Bir

to provide an abundance of air under pressure direct to the inlet, port manifold; these engines re- present a great advance on the early crankcase compression typ

Direct Reversing

The Loop seavenge tive-cycle engine he certa inherent char- acteristics which make it par- ticularly suitable

marine propulsion unit: a marine screw propeller operates best at Blow or nedlum speeds, and the two- cycle engine develops high torque at low speeds of revolution,

Another important point is that

I built

#R

་ ་ ༈

The

and in this direction the loop sea-, engine cylinder at the end venge type of engine scores very scavenging period, and, second, subatan- heavily Indeed.

charges the engine to tally higher pressure than would otherwise be possible.

An inherent feature of the loop type of engine is that the exaust port closing timing is fixed at the same valuo as the

pening timing.

It is not, therefore possible as on certain other types of engine

Loop Scavenge

It has, therefore, overcome an inherent disadvantage of the loop scavenge engine, in that a period of charge loss through the EX- haust ports is now converted in-

Two-Cycle Engine

New two-cycle engine which is particularly suitable as a marine propulsion unit. air pump providea abundance of mir direct to the inlet port manifold.

The

Separate

one of arrangement is

по trent simplicity involving additional mechanical part and utilising what would normally be wasted exhaust gas energy,

the two-cycle engine can readily are usually greater than those of to close the exhaust ports early to a period of useful pressure

direct revers- the two-cycle type. Guite apart on the compression stroke, there- charging of the cylinder, ing engine, operating equally well from such considerations, how by obtaining a Jonger effective In either direction of rutation. Direct reversing can be applied, the loop scavenge two-cycle struke and hence a greater weight to engines having three or more engine has much less mechanism of trapped wir charge.

is Indeed relatively simple. cylinders, whereas the four-cycle There is, therefore, good reason It is, however, possible to off- engine requires a minimum of sia for its established position fort vs disadvantage by a process cylinders, added to which, there marine propulsion,

known as exaust pulse pressure Is the the extra complication of

charging, a method which has Attention is particularly direct- direct reversing mechanlam necen-

teen developed by Messre. Cross-ed to the fact that at port closing sary for the four-cycle type,

y Brothers Ltd., of Openshaw, the cylinder pressure of the trap- Manchester. and is now coming ped air charge is as high as 12 be regardeil as the biggest lbs per square inch, in association single improvement so far made with a scavenging ale pressure

of only 2 lbs per square inch. in these engines.

Four cycle engines Are. therefore, usually built as unl directional engines employing a mechanical reversing gear to provide reversal of the propel ler through gearing. The Hour-cycle

also engine usually operates at a higher speed

Stationary Work

to

On the other hand there has been a reason for the popularity of the four-cycle type for station ary work. Engines for this pur- pose are usually coupled to clec- trle generators which are толе It consists of the use of a plug conpret the higher Lu speed. of gas instead of mechanical This corresponds very well with means to prevent escape of the

Exhaust Pulse Pressure Charging

Loft;

Piston ascending, scavenging complete. Air advances into the exhaust branch and manifold. Fight: Platon ascending. Exhaust pulse pressure wave, due to another cyclinder exhausting, in foroing clean air back into the cylinder.

sanie

power.

Prossure Pulso As each cylinder in

turn ex-

15

d

This represents a cubstantial degree of pressure charging when it is remembered that in four-cycle engines it la often worthwhile thought

to add charging equipment, pressure comprising

exhaust turbine -driven centrifugat blowar, with д!! itu com. plication, in order to Hit the cylinder to a pressure of 3 to 4 lbs per square inch,

מת

The result of these recent de- velopments is that the loop sca- venge type of engine is now com- parable in quality and perform- ance with the best types of four- cycle engines, whilst still retain- ing its inherent advantages of simplicity compact- dimansions and high torque at low speeds of revolution.

These engines are now rated at brake mean pressures of 75 ibs per square inch and higher, in association with specifie 'fuel con- sumptions of 3.30 to 0.37 lbs

Per b.h.p.-hour, a performance equal to, if not better than, the best types

of four-cycle engines. Given

equal performance, therefore, the engine which 1s the simplest should be judged the best, and

Phonevision

"Phonevision," a technique by which telephone facilities are used to enable television programmes to be received on special receivers, is being In- vestigated by the Austration Postmaster-General's Depart-

and incorporates reduction gear- fone of the outstanding charac-cylinder charge down the exaust, from this point of view there is ing as well as reverse gearing. teristics of the four-cycle type, ports early in the compression a great deal to be said in favour mumety Its high specific brake stroke, thus, In effect, producing of the modern loop scavenge The basle four--cycle engine horse-power at high speed. the same result as the early elos- two-cycle engine incorporallog operating at twice the speed of

ing of the exhaust valves possible exhaust pulse pressure charging. the two-cycle type and at the With loop scavengo engines it on other types of engines. sanie“ brake „mean pressure, would I would appear at first sight not develop the

In unreasonable to assume that con- practice, however, the brake siderable mixing of the Incoming mean pressure of the two-cycle air charge and the spent exhaust ergine may be a little less and gases should take place, and, in hausts, a pressure rise is produc- the distance between cylinder fact it did take place in early ed in the exhaust manifold. These centres a little greater.

types.

But too much has been pressure rises have been.control. assumed regarding the supposed led and empified into pressure inefficiency of scavenging by the pulses of some magnitude, from loop system.

which considerable energy e available. This energy can be harnessed by suitable phasing of this pulse and by controlling is amplitude and spread so as to

combined effect provide a pressure charging the engine.

As is usual with loop scavenge In four-cycle engines, for ex- ample. mechanical means are engines, surplus scavenging air provided for separating the pro in respect of the cylinder volume cesses of exhausting, scavenging is provided during the scaveng- and charging: for exhausting, a ing period. As previously mosi- poppet valve is provided and a tioned, it is not possible to close whole stroke of the platon la do- the exhaust ports early on the voted solely to pushing out the compression stroke, with the re

Bult that the end of the sca-

at

gear,

To the four-cycle engine, how ever, must be fadded the marine reversing and reducing with the result that the loverall length and weight of the

four- cycle version for a given power

SHERWOODS PAINTS LTD.

BARKING ESSEX, ENGLAND

"ASTRIUM" BRAND

HIGH GLOSS PAINT

"ASTRAFLAT" BRAND

UNDERCOAT

"STARBRIGHT” BRAND

COPAL VARNISH

Established 1777

“SUNRAY” DISTEMPER

A MODERN WASHABLE

OIL BOUND DISTEMPER

OF HIGH QUALITY.

AMELENE

DRY DISTEMPER

Stocks Available in a Wide Variety of Shades and Packings.

YU TUNG TAI LTD.

Engineering Department · ·

213, Queen's Buildings. Ico House St.

Tol. 33145

Sole, Agents Hong Kong & Chlon.

Development of two-cycle lasp scavenge engines to mini- miss this effect is certainly most dimeuit, Involving a great many Interlocking variables.

In

mont.

Little is known locally of the technique, which is E In its experimental stage' in the United States of America, and reports are being, studied by goverment experta in Aus- tralia.

BRITISH PLANE

Britain's

new airliner, the

spent exhaust gases from the en-engig period, surplus scaveng. Vickors Viscount, first four-en- | Alne cylinder; whilst charging. again is positively controlled by ing air escapes through the ex-gined civil transport in the world means of a poppel valve and an- haust ports (before port closing) to be powered exclusively by air- other complete piston stroke.

to the exhaust crow-turbines, is designed -32 branches in the region of the ex-carry passengers at high haust ports.

In an air-conditioned,

In the loop scavenge two-cycle engine, however, the separation of these three processes is not car- rled out by mechanical compou- ents of the engine and much more subtle means are employed.

Difficult Design

There arisen the paradox that the engine which is by far the simplest mechanically has been the most complicated to design and develop. Years of patient

and fills" with uir

allituend cabin over ranges of

However, when exhaust pulsa 1,800 nautical miles. All under- pressure charging is employed carriage units are retractable and the exhaust pulss produced by when retracted. they are fully en- the aucceeding cylinder ox closed by automatically operated hausting Is Do controlled that doors.

the steep front of the pulse

rama, this air back under prasi

The flight deck and saloons are

sure into the engine sylinder fully air-conditioned and pres- through the rapidly closing surised, the pressure system per- mitting cruising at a maximum exhaust porta.

of 30,000 ft. with internal condi- qulsida tions equivalent to an

Pressures as high as 12 iba, per work have. however, resulted in square inch have been recorded the attainment of a scavengo em- in the cylinder at ports closing clency of the order of over 90 per by means of Cathode Ray Oscil cent in this type of engine.

lograph indicator.

of 8,000 ft. From the safety point of view the Viscount is one of the world's most advanced air. liners. There is full thermal do icing. Double-slottod, flaps per- Exhaust puise charging, there-mill safe landings in smaller ale the engine which is the simplest fore, first prevents valuable air fields than those normally used by should be assessed as the best charge from escuping";from thol aiellhors,,'*

-Given equal scavengo efficiency,

:

You Never Need

a

SHEEN

Till You Need It In A Hurry!

Don't wait till the fire's naging get Sheen Fire Extinguishers NOW! Car- bon Tetrachloride and the A Double-Acting pump system make Shoon your finest safety-factor!

Sheen C T C

EXTINGUISHER Approved by F.O.C.

Sheen Fire Extinguishers

Sole Agents:

GILMAN & COMPANY LTD.

ENGINEERING DEPARTMENT,

4A Des Voeux Rd., C.

BRC

FABRIC

Tel. 31148.

ELECTRICALLY CROSS-WELDED

STEEL WIRE MESH

IN ROLLS OR SHEETS

FOR CONCRETE REINFORCEMENT

Block Available

DAVIE, BOAG & CO., LTD.

Chartered Bank Bldg.

Tel. 98117

Agents for:

BRITISH - REINFORCED-CONCRETE-ENG.-CO.,LTD.-

Sportsmen will be delighted to hear that a first shipment of HIGH PRECISION

HELJER

STOPWATCHES

WRIST

and

CHRONOGRAPHS

has just arrived and is now on sale at all leading watch dealers.

Specialities: Timers for HORSE Racing

TRACK BACING FOOTBAIL

BASKET BALL НОСКЕХ YACHTING

etc.

Sole Agents:

DE SCHULTHESS & CO.

LEVELS

Shell House, 4th floor.

K+E

KEUFFEL & ESSER CO.

AVAILABLE STOCKS

FORESTRY COMPASS'

TRANSITS

STEEL TAPES -

DRAWING SETS TRACING PAPER

SLIDE, RULES AGENTS DISTRIBUTORS

ANDERSEN, MEYER & COMPANY, LTD.

„DAVİD HOUSE

TEL: 28091.