Fric′tion-wheel.
A wheel the motion of which is caused by the friction of a moving body, or, conversely, which communicates motion to a body by frictional contact.
In the annexed illustration
a b, one wheel being driven becomes a motor to the other, their perimeters being in contact.
The surface is usually clothed with leather, rubber, or some sufficiently elastic material which does not polish too readily, and thus induce slipping.
By grooving the perimeters of the wheels, the contact may be made more intimate, as the surface engaged is increased, and the elastic material of the respective faces caused to bind.
The term
friction-wheel is often, but erroneously, applied to wheels which diminish friction; these are properly called anti-friction wheels (which see.)
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Friction-gearing. |
Howlett's friction gearing
c has an upper indiarubber wheel with a Vedge, clamped between two metallic plates.
By screwing up the nut which holds the parts together, the disk is made to expand radially, and thus increase the tractive power on the lower driving-wheel.
d shows another form.
A collar fastened to the central shaft has four pivoted arms.
When the rim turns in one direction, the arms turn on their pivots, leaving the rim and failing to transfer the motion to the shaft.
When the rim turns in the contrary direction, the arms catch against it and are rotated by the contact, turning the shaft also.
The friction-wheel feed, by which logs are fed to the gang-saws in the large lumber-mills of
Ottawa, Canada, consists of a horizontal wheel 40 inches in diameter, and an upright one driven by band from the engine-shaft, and 24 inches diameter.
(See
Fig. 1601.)
The horizontal wheel is vertically adjustable by a hand-wheel and shaft on the working floor of the mill, the friction-wheel slipping on a spline.
As the said wheel approaches towards the center of the driving-wheel, the speed of the feed is lessened, and conversely; if it cross the center, the motion is in the other direction, and the feed is reversed.
