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 ASTM
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E-1911-98 |
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The D.F. Tester is an easy-to-use portable instrument to measure
dynamic coefficient of friction. The physical principles involved
in the measurement of friction are straightforward, but their
implementation for practical purposes can solve a wide range
of problems. The D.F. Tester is an instrument which can determine
the physical properties needed by different industries as
it can measure coefficient of friction under various conditions.
For example in the case of skid resistance which is closely
related to the performance of automobiles, there was no such
instrument which could directly measure the coefficient of
friction, although there were some measuring instruments that
correlate to it. Many instruments have been introduced which
measure slipperiness but none are as reliable and easy to
use with minimal interference with traffic as the D.F. Tester.
This instrument can be used for all measurements of friction
coefficient, especially for the
measurement of floors, including sports facility floors and
road pavements, which has been the most difficult to measure
in the past with minimal interference with traffic. Today,
the world is looking at the performance and the use is widely
studied.
This device is also contained
in the FHWA's (Federal Highway Administration) Measuring Instrument
Guide.
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Japanese
Patents : |
No.1671471
& No.1641983 & No.1129813 |
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Japnese
Trademark : |
NIPPODFTM |
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U.S.
Patent : |
No.4594878 |
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German
Patent : |
No.DE 3423116
C2 |
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| MAIN BODY |
BACK SIDE |
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Measured values are a continuous
spectrum of dynamic coefficient of friction with good
reproducibility. |
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Measurement can be made
in a very short time. |
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The device is designed to
be compact and easy to carry. (A small van type car is
large enough to carry it.) |
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It reports the friction
as a function of speed from 0 to 80 km/h at a contact
pressure similar to that of typical motor vehicles although
it is small in size. |
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It is powered by 12V DC
(automobile battery) and 100V AC (outlet voltage in Japan). |
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An optional AC/DC Converter
is available. |
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Coefficients of Friction
at each speed (between 0 and 80 km/h) are graphically
recorded in a continuous spectrum for each measurement.
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The standard rubber of the
slider assembly is synthetic rubber as specified in the
ASTM E501 specification. The slider assembly can readily
be replaced at measuring sites. |
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Dynamic coefficient of friction
between any material and surface type can be measured
by changing the test rubber slider. |
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 In
the illustration on the right, the tire rubber is pressed
against the road surface with a force W,
and a horizontal force F is applied
to move the rubber with a speed V.
This force F, which can be measured
by any means, is due to the friction. F
and W being both known, the coefficient
of friction, µ is determined
from this relationship:
µ = F/W -------------------------
(1)
By holding W constant and substituting
K (a constant of proportionality) for 1/W in equation (1),
we obtain:
µ =K * F--------------------------
(2)
Thus, the coefficient µ varies
in direct proportion to F. In the
D.F. Tester, the tire rubber is fitted to three rubber sliders
on the underside of a horizontal rotary disk. The disk bears
on the road surface supported by the three rubber pad on the
sliders under a constant load W
perpendicular to the surface, and rotates at a speed where
the tangential velocity at the location of the sliders is
V. The force F required to overcome
the dynamic friction is measured, and the linear speed V
of the slider is determined from the rotary speed of the disk.
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How to read the measured
data.
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Measurement on pavement surfaces, floors of sports
facilities including gymnasium, etc. |
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D.F. Tester Proper :
540mm (L) x 590mm (W) x 380mm (H)
16.8 kgs. (26.8 kgs. with carrying case)
Controller :
470mm (L) x 630mm (W) x 170mm (H)
11.0Kgs. ( 17.0kgs. with carrying case)
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| 1. |
Rubber Sliders |
10 sets (30 pcs.) |
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Interconnecting cables |
1 set |
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*Replacement recording
pens |
5 pcs. |
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*Recording paper
sheets |
100 sheets |
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Hand tools |
1 set |
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* for the X-Y Plotter only. |
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info@nippou.com
