Table of Contents
Advertisement
is then brought round to its stop in line with the
pendulum arm. The pendulum arm is released by
pressing button C. The pointer is carried with the
pendulum arm on the forward swing only. Catch the
pendulum arm on its return swing, and note the
pointer reading. Return the arm to the release
position. Correct the zero setting as necessary by
adjustment of the friction rings E.* If the pointer has
swung past the zero position, rings E are screwed up
a little more tightly. If it has not reached zero the rings
should be unscrewed a little.
4.
With the pendulum arm free, and hanging vertically,
place the spacer, which will be found attached to a
chain on the base of the vertical column, under the
lifting-handle setting-screw to raise the slider. Lower
the head of the tester using knobs A and B so that the
slider just touches the road surface, and clamp in
position with knob A. Remove the spacer.
5.
(v) Check the sliding length of the rubber slider over
the surface under test, by gently lowering the
pendulum arm until the slider just touches the surface
first on one side and then on the other side of the
vertical; the sliding length is the distance between the
two points where the sliding edge of the rubber
touches the test surface. (To prevent undue^ wear of
the slider when moving the pendulum arm through the
arc o^ contact, the slider should be raised off the road
surface by means of the lifting handle.) If necessary,
adjust to the correct length by raising or lowering the
head slightly. When the apparatus is set correctly the
sliding length should be between 125 and 127 mm; on
the scale provided, the outer marks are 127 mm apart
and the inner ones each indicate the 2-mm tolerance
allowed.
6.
Place pendulum arm in its release position. The
apparatus is now set ready for operation.
* This adjustment is necessary as the tester is used under different
temperature conditions and in windy conditions: sufficient adjustment has
been allowed to cover all normal ranges of temperature encountered in Great
Britain, but some difficulty may be experienced in correcting to zero in very
high winds—it may be necessary to operate the tester with a positive
error and subtract the error from the mean value.
page 5
Advertisement
Table of Contents
