5EPT&MBER 28 rH , 1907 .

THEAUTOCAR B 3ournal publtsbeb in tbe interests of tbe mecbanicall\? propelleb roab carriag 1;.

EDITED BY H. WALTER STANER.

No. 623. VoL. X IX. SATURDAY, SEPTEMBER 28TH, 1907. [P RICE 3D.

TlfE AUTOCAR.

(Published Weekly.)

Regis•er~d as a nf!w~o:toer for transmission in the United Kin f{d om4

Ent.:r~J as second-class matter in the New Yori( (N.Y. ) .Post Ofuce.

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CONTENTS.

NOTES • • HINTS AND TIPS: ON P ETROL TANKS. Bv A. J. l\'[ cKtNNEY • • THE!30 H.P. SIDDELEY CAR {lLLUSTRATE,D) TWENTY-FOUR HOURS' RACE IN AMERICA COLONEL HOLDEN THE CRITCHLEY IGNITION SYSTEM (ILLUSTRATED) AT 8ROOKLANDS RESULTS OF THE SEVEN PRINCIPAL CONTINENTAL RACES OF I907 MICHELIN DETACHABLE RIMS AND TYRES • • THE A.A. IN THE NORTH-j USTlCE FOR A MOTORIST • • CARRIAGE BUILDERS AND MOTOR BODIES .• SMITH AND PARFREY

0

S SHOCK ABSORB ER (ILLUSTRAT!::D)

BROOKLANDS MOTOR TRACK-THE NEW 25 H.P. \VEIGEL CAR CONTI NENTAL NOTES AN D NEWS (ILLUSTRATED) • . A USEFUL Hoo D . THE PueL1c AND THE M .U .. . ON THE ROAD. B'i OwEN J OHN . • HINTS ON THE USE OF BENZOL SOUTH INDIA N MOTOR UNIO N FLASHES CLUB Dot~Gs ( ILLUSTRATED) A RED LETTER DAY • • THE OLYMPIA SHOW-POLICE REBUFFED • • MOTORING IN NEW SOUTH \VALES . . SO~U~ QUEIUES AND REPLIES

483-484 . . 485 486-488 . . 488

489 490 , , 491 492 -512 · · 493

494 , · 495 · , 496 · , 496 497-498 · · 499

500 . . 506

507 508- 510 511 - 512 513- 514 . . 5 1 4 . . 515 • • 516

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f f Notes. • Tyre Pressure Tests. Last week in briefl y dealing with Mr. Edge's tyre pressure tests at Brooklands we stated that th e results were worthy of far more careful consideration than the time available permitted . Among the many questions which a rise in connection with the results obtained at Brooklands we think p erhaps the most important is th at of the steadying effect of low tyre pressure at high speeds . It will be remembered th at for each fl ying quarter-mile the times were practically the same whether r oo lbs. or 35 lbs. was the pressure of the back tyres, and the question natura lly arises how much of this equality of speed was due to the fact that slip was reduced as th e tyre pressure fell ? We should say with the lower p ressure the car would stick to the track much better. That is to say, the wheels would not bounce from the track, and consequently the loss from slip would be materi a lly reduced. This is another argument in favour of a revolution counter for any further tests of a similar sort which may be undertaken.

The next investigation, t oo. sho ul d deal with the question of starting effort . In all the preliminary t est s made a t Brooklands th e car was sent round the track each time and timed up the straight, so that it had some two mil es in which to get up its speed before coming into the timed quarter. \1/hether it took more or less time to attain its fu ll velocity we do not know. In fact, the question a rises whether (after the races which have been won on bare rims) with two sister cars, one with metal tyres and one with pneumatic tyres, th ere wo ul d be any material diffe rence in the speed.

We abstain from saying anything about the effect of metal tyres upon the car or upon the comfort of it occupants; we are merely looking at the air tyre as something which everyone has hitherto believed in creased the soeed of a car. What is wanted now is a series of tests ·at lower speeds, say, on a car which coul d not exceed forty miles an hour on Brooklands, and let some of the tests be made from a standing start. Then we a lso want a series of hill-climbing tests. The hill within the Brooklands grounds which leads up to the gate nearest to vVeybridge Station would be quite suitable fo r some tes ts of this sort for a comparative ly low powered cars. It is too twisty for speed tests with high powered cars. As Mr. Edge pointed out last week, th e wind resistan ce at high speeds is so enormous that the sum of the work to be done is not greatly a ffec ted by hard blown or soft blown tyres, but there is unquestion ab ly a limit dowmrard in tyre pressures .

We question whether the 50 lbs. suggested by Mr. Ed!!e is not too low a limit. When we say this we have in mind the behaviour of motor bicycl es and low powered cars. Both these- the motor bicycle in particular-a re very sensiti ve to a deflated tyre . Long before any bumping is felt it will be noticed that the machine is sl uggish in hill-climbing, and it will not climb hills properly till its tyres are well inflated. In hill-climbing the questior. of wind resistance is negli gible as compared with the same factor at Brooklands speeds. However, whether the downward limit be 80 lbs . or 50 lbs., we a re not in a position to say, but there is no doubt whatever that furth er t ests to arrive at an answer to this very important question a re badly wanted. They a re tests which might well be taken up by the Royal Automobile Club, as to carry them right through th ey would take an immense tim e : a lmost more than the individua l investigator could give to th em. :\Tot on ly so, they would be very cos tl y. H owever, the end is well ,rnrth striving for if it would bring nea rer the desideratu m of a comparatively Im,· pressure but d urable tyre.

As things are developing at th e moment, the tend ency is to have tyres blown harder and harder and made less and less comfortable, so that the difference between th e pneumatic and the solid is becoming sm aller every