It's Tapley...
"The Mechanical Tapley Meter
is a small pendulum-based decelerometer that consists of
a dynamically calibrated oil-damped pendulum in a sealed housing. The pendulum is
magnetically linked to a lightweight gear mechanism to which is attached a
circumferential scale that shows values as percentage of g, 1 g = 32.2 ft/sec2. A
lightweight ratchet retains the maximum scale deflection reached upon completion of a
test. The mechanism is enclosed in an aluminum case and the scale is covered with a
glass face. The whole assemble is mounted in a cast-base plate by means of a fork
assembly, Each meter is statically tested and dynamically calibrated before being issued a
calibration certificate. When the meter is used in a fiction survey, it is placed on the floor
of the vehicle. The data have to be visually read and recorded by the operator.
The Electronic Tapley Airfield Friction Meter
provides a recording of the data taken
during a fiction survey, including averages for each segment (one third) of the runway.
The meter is a pendulum-activated, semi-automatic, recording decelerometer, and it
operates on the same principles as the original Tapley Mechanical decelerometer. When
preparing to conduct a friction survey, the operator places the meter on the floor of the
test vehicle. The actuating pad is fitted to the brake pedal, and the command module is
attached to the vehicle window by a suction pad in front of the driver’s side or at another
suitable location that is readily visible to the operator. The power leads are connected
either to the vehicle battery or to a separate battery. The equipment is now ready for
testing the runway. These devices should only be used on runway surfaces covered with
4
ice and/or compacted snow, because, under dry and most wet-runway conditions, RCR
vehicle wheel lockup becomes inconsistent and vehicle stability is degraded.