Читать книгу The Modern Bicycle and Its Accessories - Julius Wilcox - Страница 29

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This is a Columbia of the very highest grade in every respect; the same wheel, including the well-known Hartford single-tube tires, the same forks and handlebar, the same seat-post and choice of saddle, the same unsurpassed frame of nickel steel, the same pedals and cranks. The difference is entirely confined to the driving mechanism, to three sides of a parallelogram having the rear axle and the crank axle as its ends, and the shaft as one side. On this driving mechanism the very best thought, the very best work, and every resource of the manufacturers have been centred. There was long, costly and careful experimenting before the exact relative proportions of the two members of the front gear could be determined. These proportions, however, are now invariable—one turn of the axle giving 2 ⁴⁄₅ turns to the shaft. The relative size of the rear members is varied to produce the required “gear.” Friction in bevel-gears is dependent upon the harmonic mean of the teeth in both wheels, and in this model theory and experiment have joined hands to make the adopted proportion exactly right. Wherever ball bearings could be introduced to advantage they have been placed. The side shaft is supplied with such bearings near each end, the strength and firmness of the nickel steel tubing permitting the utmost precision in placing them and insuring perfect work under any strain. The wonder is that all this excellence has been attained with such complete absence of complicated devices.

MECHANISM AND FRAME OF COLUMBIA CHAINLESS.

The regulation equipment of the Columbia Chainless is: 24 inch frame, of 5 per cent. nickeled steel tube; nine inch steering head; outside joints, 2½ inch crank-hanger drop; 5¼ inch tread; 66 and 72 inch gear; weight 26½ pounds; Hartford tires.

The model made for ladies’ use is the well-known double loop drop frame pattern; 5¼ tread, 6½ round cranks, 66 or 72 gear, and weighs, without brake and rear guard, 26½ pounds.

An illustration of the great simplicity of the Columbia bevel-gear construction is the fact that when a League wheel was entirely dismembered as to its driving portion only a skilled mechanic was able to reassemble the parts satisfactorily, and that after hours of the most careful work, while a Columbia Chainless can be taken apart and put together by any person of ordinary intelligence in less than twenty minutes. The entire absence of back lash in the Columbia Chainless is very marked. In response to the slightest motion of the pedals the bicycle begins to move; whether forward or backward this is equally true. The marvel of this construction becomes more and more apparent as tests are varied. Lift a bevel-gear bicycle free from the ground, give one of the pedals a sharp push, and the wheel spins with such ease, rapidity and smoothness that the novice is always surprised. There is no swaying and jump; there is no noise. Even neglect can have no influence on the effectiveness of the bevel-gear wheel, but will simply concern its appearance.

It should be said here that the Columbia pattern is distinctive—as the cuts show—in a very novel method of attaching the rear wheel to the frame and providing for its easy removal and replacement.