WHAT 300 M.P.H. MEANS.

Horowhenua Chronicle, 4 February 1936, Page 3

WHAT 300 M.P.H. MEANS.

440 Peet Every Second: rive Miles Per Minute. A Land Speed which it is impossible to imagine and which only Sir Malcolm Campbell has reached. None other has approached within 70 m.p.h. on land.

Three hundred miles per hour—a speed that baffles imagination and defies description. A speed never before attained, officially or unofficially, on land by any wheeled thing. A speed which will set another milestone in the history of the automobile.

There are up and down this country a i'ew hundred people who have driven ut 100 ni.p.h. in a motor car. To everyone the first achievement of those magic three figures brings a thrill which is remembered for a life-time. Well do I remember watching a dancing needle creep past the 00 m.p.h. mark and flicker uncertainly upwards towards the "100." How the wind screamed, and tore at my face, plucking at my goggles, blowing ripples in my cheeks, snatching my breath. How the wheel ieapt and juddered in Hollands.

Up soared the engine note. At 0.) m.p.h. the car seemed to he going twice as quickly as at 00 m.p.h. Every single mile an hour, every few extra r.p.ni. of the engine, seemed to equal five ordinary miles per hour. Then —a hundred miles an hour. Colossal speed. Terrific wind and sound and excitement. Perhaps you have done it yourself, and you will remember that moment.

Xow imagine not 1(1 m.p.h. faster, but a whole Jill) m.p.h. on top of that. Then, if you can, try to imagine another whole ]IU) m.p.h. on top of that gigantic speed again. According to the "Motor" that is what. Sir Malcolm has done out there on the reck-hard, salt bed of Salduro Lake, near Utah. You remember how the car felt at its paltry 1UI) ni.p.h. How every bump seemed to swerve it for yardy, how the steering seemed altogether different, that first time? Imagine, then, the feel of the giant "Blue Bird," with its yards and yards of bonnet in front, with rows of exhaust ports spewing flame and gas past the overheated cockpit. That level Jake-bed must seem an unending series of pot holes as the car yaws in the wind and with wheels leaping clear of the ground over bumps which do not exist; at even 1200 m.p.h., navels in slides of hundreds of feet belore the quickest brain can signal a movement to the steeliest wrist. And all the time the haunting thought that something- might break.

Thru, the 12-second blur of the timed mile, and the difficulty of pulling up such a heavy car from such a speed. A hasty move, and disaster; yet there is only limited space left ahead, and the cars is covering that space at 440 ft. every second, five miles every minute — and you can't slow up with safety in less than several miles.

Except'to those who have actually witnesed it, speeds over 250 m.p.h. cannot really be conceived. Those wdio have watched the R.A.F. displays may have seen aircraft plunge at them with throttles wide and wive screaming to pull out of that, breath-taking dive just over their heads. When those machines swing upwards to the sky again, they have just finished a dive in exce.-s of iioo m.p.h. for a few seconds. Now think of sitting behind a steering wheel at that speed, amidst that noise, and trying to keep the car in a- dead straight line.

Campbell's MOD m.p.li. means a quarter of a mile i" throe seconds —flick, like that. A mile in 12 seconds, five miles a minute, 440 ft per second. A lap of Brooklnnds in a fraction over half a minute (theres' a thought for those who have toured round it at l..'!(j m.p.li.), Perth to [■Yemantle in under 2\ minules or Perth to Xortham in L": minutes.

Think of it this way. Imagine standing a few yards up the mouth of a 20ff. tunnel, with ".Blue Bird" about to cross the entrance at right angles. You womd liear the roar of the car's approach, then .something would shoot

across the brightly lit. mouth . . . but you would not even see it, for it would take about one-twentieth of a second, which is too quick for the eye to focus on it and to re-cord an image. S->a:" a. ti:ov:rkt vow for the J)unlop tyres which shoe this cur. I'aper-thin treads to minimise the tremendous disruptive effect of the centrifugal force of the whirling wheels. Those tyres actualiy sv. e!! an inch under the stress —a f'v.-t d. h'rili'dy allowed for in designi::';' the ground clearance of the ear and ia determining the gear ratio. The life of those t/res, the highest, achievement, in lyre manufacture, is measured in a I'vw minutes. The fi.il force of that (ngir/o, the five-ton weight of the car, is transmitted to the ground through those thin treads levering the car along. For a fraction of time, in each revolution, any point of those tread.-* is stationary, yet reaches 600

m.p.h. during the rotation. That is to way, the tread is accelerating and slowing down between rest and (500 m.p.li. on every turn of the wheel. Power to Overcome Air Resistance. The force of the wind at these ultrahigh speeds is something that can only be visualised by those who have foolishly stuck their heads over the side of a high-speed aeroplane. The slightest side wind becomes a dominant factor, and combined with the resistance of the air due to the speed of the car, absorbs about nine-tenths of the entire power output of the engine. Thus the vital importance of stream-lining. A reduction in front area of a square inches means a great deal more horse power devoted to increasing speed.

At Daytoua on Sir Malcolm's last, visit, the force of the wind was sufficient to seize a projecting piece oi metal sheeting and twist it like so much paper. On that occasion Campbell came within four-fifths of a second of 300 m.p.li. —a split second which is not distinguishable in the ordinary way, but all the difference between 2St m.p.h. and :500 m.p.h. Such is really high speed. Hitherto, wheel-spin has been the villain of the piece. Time after time "Blue Bird's" instruments have registered suliicient r.p.m. for this speed, but she wheels were spinning in the air as the car shot, from bump to bump. At Utah this bogy was exorcised —but with the accompanying ganger that, the much harder rock-salt surface wore the tyres faster than the comparatively soft sand surface of Daytona Bcadi. Hence one of his tyres burst.

As an example of how the speed exaggerates the smallest bumps on the

course, it may be recalled that a bump which was quite invisible and quite innocuous at 2(H) m.p.h. sent the five tons of "Blue Bird" rocketing through the air clear of the ground for over MOl't at Daytona. The terrific impact as the car hit the sand again tore the tyres to shreds.

One instance of streamlining: On the modified "Blue Bird" a shutter was provided to close the radiator to lln.' onrush of tile »ii', operated by a lever from the cockpit, when the car reached the pea!-: of its speed. Tests demonstrated that this action alone added 1U m.p.h. to the speed of the car. Here are some details of the magnificent car, designed by Reid A. Hailton, of Thomson and Taylor's. It is an almost entirely rebuilt edition of that used in VXV-) when Campbell recorded 270.4.°>2 m.p.h. at Daytona. The body is better streamlined and incorporates many new ideas —the air brakes, a front axle controlled by radius arms and stabilisers, and twin rear wheels to minimise wheelspin. The engine is a. supercharged Roils-j Royce 12-cylinder area unit (the supercharging was increased to overcome j the drop in barometric pressure due to the -llliiDfl altitude of Snlduro Lake. As against this, the air resistance is appreciably less than at sea level on 'Daytona Beach.) Lead ballast is used to keep the tail down ami weight the rear drivingwheels. Including this, the car scales just under five tons. The wlieelba.se is Rift Sins, with a track of oft. The overall length, from nose to tail, is a

more 28i't .".ins--about the sumo as a London b,us. For the first time, an effort has been made to accumulate data as to the behaviour of the car at 300 m.p.h. It is obviously impossible to read more than the essential instruments at speed, and oven Unit is possible only in swift glances. Sir Malcolm used a complete photorecording apparatus in "Blue Bird" whereby a cinema camera recorded the movements of the needles on a .special set of instruments, so that after the run it was possible to read the revolutions attained and the increase in temperature, and so forth. Thus for the first time really scientific data of the historic run was obtained.