THE MOTOR

Evening Post, Volume XC, Issue 147, 18 December 1915, Page 12

THE MOTOR

ALUMINIUM PISTONS

JFHE OXYGEN PROBLEM.

(By "Autos.")

It was recently stated that, owing to the strong, affinity between aluminium and oxygen, the newly-popular alu-

minium pistons which are coming into vogue in America might suffer severely from the use of the oxygen jet for clear-

ing out carbon, deposits. The oxygen jet is the quickest and easiest carbonremover known. A bit of combustible material is dropped into the cylinder after removing a. valve cap, and ignited, and a jet of the compressed gas turned in. Every particle of carbon is quickly burnt out, leaving the metal clean. It was supposed that the initial heat set up in this way might start oxidation of the aluminium, and some thorough tests of the question would be valuable. A gathering of automobile engineers at Detroit recently discussed aluminium from various points of view, and this matter was among them. One i delegate, Mr. J. E. Vincent, a Packard engineer, said that he had conducted a number of tests with the oxygen flame purposely to determine the point. "I was not personally worried about it," hs said, " because it was my idfea that as soon as the carbon deposit .was burned off the piston, the fire would go out. In other words, it requires carbon to cause combustion, and it seems to work out that way. We ran one motor considerably over 22,000 miles, and we burned out the carbon a number of times when there really was not anything to burn out, just to see i{ any harm would come from putting the flame on to the pistons, or attempting to put it in, when there was no carbon there, but just a little oil. I personally examined- the motor after it was taken down, and I could find no trace whatsoever of the effects of the burning-out process. In fact, the piston head, which had been originally polished, after it was cleaned showed just as high a polish as it did in its original condition." GREEDY STUFF. The statement made by -Mr. Vincent is not final, because he did not describe a case in which there was a heavy deposit, sufficient to provide a large'body of heat. Aluminium is queer" staff in its behaviour with oxygen. Although it seems to tarnish very little, and retains its polish well, it really has an extraordinary greed for oxygen, and will in certain conditions burn up very violently. What happens ordinarily is that the metal becomes coated with a very thin skin of oxide, which perfectly protects the pure metal beneath. No* sooner is this scraped off than a fresh skin forms. Anyone may see the rapidity of oxidation by scraping a bit of aluminium under the surface of some mercury, which will amalgamate with, the bare metal. The amalgam does not form the protecting coat, and a white mossy growth of alumina develops at an astonishing rate. Thermit, a mixture of powdered aluminium and iron oxide, combines with the evolution of a heat far above the melting point of iron, due solely to the affinity of the metal for the oxygen in the iron oxide. The question to be settled is whether any possible carbon deposit I in a motor will raise enough heat to start the aluminium burning. It! seems hardly likely that it would, becauses the aluminium would probably melt before it began to burn. It is the habitual oxide coat which makes it so difficult to solder aluminium.. ..,--. The aluminium piston has already been transferred from the experimental stage and the racing- track to the commercial sphere, and a few cars fit it as standard. Actiglly an alloy is used, the pure metal being too soft, and these alloys can be made as strong as steel, with but one-third 'of the weight. MECHANICAL GEAR SHIFTING. One of the. latest inventions consists of a new type of automatic gear changes for automobiles Generally speaking, the spsed gear comprises * a straight ■through gear box, operated by a central spindle The spindle is connected to a spring controlled sliding member which in its turn is adjusted longitudinally by a centrifugal governor above it. When starting the car, the gear lever is shifted from neutral into ■ either the first forward or veversS positions. After the driven shaft has reached a certain speed, the centrifugal governor automatically brings the next gear into action.; when the speed lias again increased, the highest speed ratio is engaged similarly. Retarding the speed of the_ car causes the reverse, series of operations to take place. Some cars-are fitted with electrical gear changing equipment, the gears being moved by solenoid magnets, which are set in operation by pressing a button. It might be supposed that a large expenditure of current would be necessary, but this does not seem to be the case. Acording to The Motor Age, the current consumed in shifting gears is less than the current used to give a warning blast on ah electric horn. In a factory test, a 12-volt, 80-ampere battery permitted the shifting of gears 134,490 times without becoming exhausted. MOTOR-CYCLES MADE TO ORDER, Practically every motor-cyclist of today has been recruited from the ranks of pedal-cyclists, and many of them remember the time when every cycle dealer offered a machine of his own make. Som« of these local products enjoyed a considerable reputation, especially as, in many cases, they were turned out by a highly skilled mechanic, probably an ex-racing man, who really knew how to build a machine with life in it. Machined parts were supplied by concerns like the B.S.A. Co., and a particular advantage of the assembled machine was that the cyclist could specify the particular features and parts that he wished embodied in his mount. It is not inconceivable in the near future that motor-cycle dealers and repairers may find the assembling of power-driven machines a profitable branch of their business. Even now, if one looks down on the specifications of many machines one finds that each important part is mentioned as the product of a certain firm, and the title that finally appears on the tank is little more than a convenient label by which the collection of parts is known to the public. At present, it is probable that the comparatively small local maker could not compete with the big manufacturer, owing to the fact that he could not buy parts in small quantities at terms that are comparable with the low factory costs of rapid repetition work. Tho popularisation and wide advertising of noted brands of cycle fittings solved this ! problem lor the cycle assembler, and.a similar movement may take place in the motor industry. At present one often | hears riders say that they would like to draw up the specifications of their own I machines. One of these enthusiasts would find immense satisfaction in having his machine built up under his own eyes with parts which experience has taught him to believe in. He would desire a certain engine, a particular type of gear-box, spring forks, etc.. and everything, even to the finish, would be according to his own personal taste. Such machines, of course, would not seriously compete with the highly-de-veloped motor-cycles of famous concerns that, have spent tens of thousands of (wands in their efforts to bring thsm la jierisetion, -