Page:EB1922 - Volume 32.djvu/754

728 Motorcycles were fitted with clincher tires both in America and Europe, and aeroplanes with either clinchers (fig. 3) or wired-on according to the demand. Passenger cars were fitted with Euro- pean Standard clincher tires for European productions. Amer-

FIG. 3.

ican small cars took 3i-5n. American Standard clincher tires, while cars using larger than 3^-in. took American Standard straight-side tires. All American " motor trucks " using pneu- matics operated on straight-side tires, and for solid tire equip- ment took pressed-on, channel base tires (fig. 4).

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FIG. 4.

European " lorries " were fitted with the typical English band tire (fig. 5). Progress in details of design, materials, and methods

of manufacture was very gradual, the general idea being always to build a " balanced " tire, that is, one in which all parts were. equally durable. There are practically no formulae or theories on tire design (except the rubber compound formulae) of value to

T -

FIG. 5.

the tire manufacturer; whatever good qualities any particular make of tire embodies are the result of persistent and constant experimentation, combined with the policy of the individual company controlling the standard of quality which it desires to offer to the public. The square woven tires of 1920 averaged 5,000 to 6,000 m. of service. There was one outstanding develop- ment during the period 1910-20, namely, the "cord construc- tion." The cord idea was old, having been used in bicycle tires in the 'nineties, but the " square woven tire duck " appeared to be more practical for motor vehicle tires.

About .1912 electric automobiles in America created a demand for " power saver " tires to which the tire makers responded by offering special casings of cord fabric structure for which excep- tional resiliency and lack of internal friction were claimed. Not at all durable at first, as they were gradually perfected the leaders of the industry became convinced that this was to be the quality tire of the future (fig. 6).

FIG. 6.

Ply separation and fabric breaks in cord tires are effectively prevented because the cords, being completely insulated from each other, provide a flexibility of the " carcass " without chafing,