THE MOTOR

Evening Post, Volume CII, Issue 41, 17 August 1921, Page 14

THE MOTOR

FOUR-WHEEL BRAKING RESULTS OF A TEST (By "Autos.") • An interesting and instructive test of the comparative effectiveness of the four-wheel and two-wheel systems of J motor-oar braking was recently carried I out in. France. The car used was a powerful 8-cylindea- machine, the total weight being 43ewt, of which 22041b was carried by the front axle, and 25231b on the back. The machine was equipped with brakes on all four wheels, the bands being two inches wide, applied simultaneously by, means of the brake pedal. A wet day was intentionally chosen for the first, trial on a deserted stretch of macadam highwax- At' 30 miles per hour the car was pulled up in 65g feet; at 40 miles per hour, in 98ft 4in; at 50 miles per hour, in 147 ft; and at 60 mjflas por hour, it took 239gft before the . car came to a dead stop. ' A few days later the test was repeated over the same road in a perfectly dry condition, the results were :—' At 30 miles per hour the car stopped ,in 54|ft; at 50 miles per hour, in 137-^ft: and at-GO miles per hour,, in~229ift-^ surprisingly little difference considering the different road conditions. With the front brakes slackened off so as to be ineffective, it took the car 123 ft to stop when travelling 30 miles per hour, or 83ft more than' when aD. four brakes were operating. At 40 miles per hour, it took 242-ift, 144 ft more; at 50 miles per hour, 319£ ft, at difference of 182jft; whilst at 60 miles per hour, the car came to rest at 430 ft, as against 246 ft with four brakes. The figures obtained were conclusive proot of the superiority- of the four-wheel braking system. A feature that is not revealed by the 'figures is the feeling of greater security with brakes on aJI wheels, which lias to be experienced to be realised. All the contestants in 4>he recent French Grand Prix Race ■used care braked onfall four wheels. ' THE GRAND "PRIX WINNER.. For the first time in the' history of automobile, road racing, America has scored a success in a European classic, when J. Murphy, on "a Duesenberg, carried off the French Grand Prix. The time for the 321 miles—4hr 7min lOsec— was a record, and waa particularly fast , (averaging 78 miles an hour), considering that the contest was decided on a ■short circuit' of only 10J miles, which had to be negotiated thirty times. Path; iracing practice . undoubtedly won this event for America. For some years past car racing'has been thoroughly developed in the United States on the many fine speedways upon which the leading American firms have had every opportunity of perfecting their racing models. The Dueeenberg has been particularly isuccessful; im fact, this car holds 36 official world records, from one to 300 oniles, included in which is the straight- : away flying mile on Daytona Beach, in ' ,tbe remarkable time of 23sec, equal to ; 156 mdl«s an hour. The weight _of the ■ Ipower unit with transmission., in ; this war, is only 6001b. Novel features are : the water-jacketed sparking plugs and ,: oil-operated brakes on all four wheels. '■ FORD TYPE CYCIiE WANTED. , The cheap utility motor-cycle, which for the sake of clarity.of expression is often referred to as the " Ford of motorcycles," is a long time making its appearance. ' What is wanted is a motorcycle which will be to the cycle what a \ Ford'car is to the horse and trap. First, i the price should be iii the region of; £SOj ■■■; and the weight about 1001b. A simple single cylinder developing about 3 h.p., fitted with two speeds, is all that is wanted by the average man who desires a machine for utility purposes and weekend runs; In the early days of motorcycling, a first class machine was ob: „ tamable from between £50 and £60, and wonderfully, efficient outfits they were. The craze for big-powered twins has to ah extent pushed the single-cylindered machine into the background, but there's little doubt that in time the pendulum will swing' in the other direction, and the efficient light-weight "single" again come into its own. OVERLOADING AND ROAD DAMAGE. Overloading of trucks is disastrous to both the vehicle and the highway, says the Scientific American. If its results were confined to the" truck, it might be well to let each individual learn for himself that it does not pay. But, tinfortunately, overloading is one of the principal causes of road wear. A motortruck designed to carry a certain tonnage is. constructed throughout, including width of tires and safety factors, to handle just its rated load. Any consider* able overload gives more than the standard 800 pounds per inch of tira width and concentrates the load on this small point'of contact. Furthermore, the overload is not distributed on all four wheels, but rests entirely on the rear axle/ which further concentrates the load. Overloading ' does not materially cut down the speed, and the result is that a higher rate of speed is maintained than should be given to the load, even though properly supported by adequate tire width. It has been extremely noticeable in sections where the use of large capacity trucks is discouraged that there is a strong tendency to overload small trucks. This is only natural, since the demand for motor hauling service remains the same, and practically none can be diverted to other channels. ' When the smaller vehicle is overloaded, its effect on the road is tremendously magnified, because its springs fail to operate properly and the narrow bearing surfaces of its tiros concentrate the impact forces so that they are greater than the road is capable of withstanding. There is economy both, as to road wear and as-to truck operating 1 costs in big unit loads, but not when they are carried on vehicles too small to handle them. REPAIRING SCORED CYLINDERS If the automobile engine has been run at any time without adequate lubrication, one or more of the cylinders may , be found to have vertical scratches running up and down the cylinder walls. The depth of these will vary according to the amount of time the cylinder was without lubrication, and if the grooves are very deep the only remedy is to purchase a new member. Of course, if sufficient thickness is available in the cylinder walls, the cylinders may be rebored and new pistons may be fitted. Where the scratches are not deep, they may be' ground out • with a high-speed emery wheel or lapped out if that type machine is not available. Wrist pins have "Been known to come loose, especially when these are retained by set screws that are not properly locked, and as wrist pins are usually of hardened steel they may make a pronounced groove in the cylinder. Cylinders that have been damaged in this manner have sometimes been repaired by the _ autogenous welding process, the oxy-acetylene' flame being used to. fuse new cast iron into the grooves, then grinding out the ridge of excess material in order to obtain a smooth bore. 'Another patented process, says the Scientific American, is to deposit some hard metal, such as nickel, in the grooves by the electroplating process or use iron deposited by the same means. Only the grooves are filled by this process, as the remainder of the cylinder bore may be protected by some form of varnish or lacquer so the metal will not deposit except ■■ in the grooves prepared, for its reception., ,