Passing Comments
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To Consult or Not ?
ARE there any good reasons why an engineering concern should engage a consultant instead of expanding their own experimental department? Can some work best be done by consultants and other work by the permanent engineers?
The fact that there are many highly successful independent consultants shows that many concerns believe that they have more "know how than their own men, but one of the difficulties of the "independents" is to reach suitable executives in other concerns and prove to then% the advantages, if any, of making use of their services. There are ethical restrictions on advertising.
There is, of course, one important factor which may help the consultant. This is the experience that he may have had in his particular line of work and which may not be at the command of those whose duties have been connected for long periods with, perhaps, only one company.
Advantages of Blown Engine Confirmed
IN. the article "Operators Turn to Turbochargers," pub' lished in the May 30 issue of The Commercial Motor,mention was made of the Rutland coach operated by Acorn Motors, Ltd., the engine of which had been so equipped. It may be recalled that the power unit was a Meadows 4DC 330 and that this was fitted with a B.S.A. turbocharger to improve the road performanceof the vehicle. Subsequently,laboratory tests were carried out by the engine makers, Henry Meadows, Ltd., to establish the improvement in output obtainable by turbocharging a similar engine, an identical type of blower being used.
In its naturally aspirated form, the engine produced, 96 b.h.p. at 2,400 ,r.p.m., and the output was increased by turbocharging to 115 b.h.p. at 2,400 r.p.m. The maximum torque of the unblown unit was 230 lb.-ft. at 1,400 r.riat., whilst the turbocharged engineproduced 280 lb.-ft. at the same revolutions.
Tests of specific fuel consumption revealed that the consumption of the turbocIrarged engine was around 0.375 lb. b.h.p.-hr. on full load at maximum speed,which compares with 0.39 lb.-b.h.p.-hr. yielded by the normal engine. Consumption did not vary substantially throughout the speed range.
A test detail of special interest is the gain afforded by turbocharging before adjustment to the fuel rack setting to increase the pump output. Use of the blower raised the maximum output from 96 b.h.p. to 100 b.h.p., and this can be entirely credited to an improvement in combustion efficiency. The turbocharger employed is the Type 12 mode), designed to give a maximum compression-ratio of 2 to 1. In the application to the 4DC 330 unit, the intake pressure was increased to 9.9 p.s.i., which is equivalent to a ratio of 1.7 to 1.
Deodorizing Vehicles and Loads
A N interesting method of preventing contamination of r-k susceptible loads, such as foodstuffs, has been developed by an American concern, Airkem, of New York. Problems successfully tackled by them have been contamination of vehicles andtheir contents by oil fuel, smoke, fish, ammonia, blood, decomposed flesh and other causes.
As regards smoke, it has been found that the particle causing odours is a tiny ball containing oils, tars, gums, water and soot, and this may or may not stain, according to the content of soot. When smoke enters a confined space, such particles are deposited on all surfaces and may find their way into every accessible crevice.
To remove and negative the odours it is necessary to introduce counteractants to all places reached by the smoke, employing vaporizing equipment. The Airkem vapours are said to follow the course of the smoke and work in two ways, physically and chemically. It has been found that when two opposing odours are smelled together, it-is possible for one to cancel out the other, whilst the counteractant can carry off the particles. It also attaches itself to the same surfaces as the smoke-odour particles. The 'Airkem molecules are more volatile, and they work down beneath the smoke particles and release them into
he air, where they are blown away by fans or other :.jectors.
Odour-countering detergents may also be used in washing ircas where deep penetration is required, as in the scrubbing of vehicle floors to deodorize fish-oil spillage.
The vapour process is called " dry fogging," the vaporization being so complete that no dampness can be .felt if hand is held before the equipment.
The Last Must be First
LET us hope, says a reader, that when the Minister of Transport has in mind making regulations concerning vehicles halted at road junctions, he will also have a critical• eye on those sometimes left unattended clime to the gates of railway levelcrossings.
It is sometimes impossible to see from behind whether lhe. driver is seated in a box van or high-loaded lorry, consequently, a long line of vehicles may join the queue behind that parked, with resulting delay and inconvenience. Usually few of the drivers behind have left sufficient room La manceuvre in order to pass the stationary offender. sometimes such a queue has to clear slowly from the rear ts,nd when the traffic coming from the opposite direction permits going through.L. • •
Of course, the best procedure of all Would be to eliminate the-level crossings: This is being done in some instances, but there are stilt far too many. obstructing our highways.
The Progress of Refrigeration
MANY . vehicles, particularly those designed for carrying foodstuffs and other perishable commodities where the' climate is often hot, have refrigeration equipment. This is really a development of the refrigerators used in homes, Shops and stores, and it may surprise many to know that if hias taken at least a hundred years of research and aPPlicatiotial study to bring such aids into practical use.
It was in 1685 that Lahire discovered the refrigeration properties of sal-ammoniac, but many years elapsed before Cullon obtained refrigeration by using a pneumatic machine developing a vacuum.
In 1811 Lestre used a method in which sulphuric acid was employed, but the first refrigerator, considered as a machine, was made by Perkins, an Englishman, in 1834. This Operated by the evaporation of ether in a vacuum. A little earlier Faraday had liquefied carbon dioxide. in vacuum, and subsequently he was able to liquefy other gases at lower temperatures.
Liquid air was produced by Luicle in 1895, after Caillete had been successful with nitrogen and oxygen.
• It . was a French chemist-physicist, Gay-Lussac, who claimed absolute zero to be 7-273 degrees C., at which temperature the pressure of gases has a zero value. By boiling liquid helium in vacuum, it has been found possible to attain a temperature of -7272 degrees C.—only one degree from absolute zero.