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Model 'B'

BS 812 : Part 114 : 1989 prEN 1097/8

This outstanding contribution to road safety is the result of over 10 years' intensive development by the Transport Road Research Laboratory (TRRL) of the Department of Scientific and Industrial Research - a British Government organization concerned with studying problems that arise in designing, building, maintaining and using public highways.

The New Model 'B' version of the instrument has been specially strengthened to meet the demands of countries like Germany, who prefer a more rugged design. Model 'B' also includes an additional scale for use in the laboratory at no extra cost.

The instrument which is direct reading, gives a measure of the friction between a skidding tyre and wet road surface. It provides the Highway Engineer with a practical means of obtaining reliable scientific evidence on which to take the appropriate measures to reduce skidding.

Satisfies the following standards:EN 13036-4 EN 1097-8, ASTM E303, BS812:114, NLT 174, CNR No 105, 140 & Australian Standard (AS3661.1:1993)

Also can be used for testing slip resistance of floors and sports surfaces.

We also offer a model which meets the requirements of the latest FIFA Report for testing the slip resistance of artificial playing surfaces.

To ensure consistency and maintenance of standard all instruments are submitted to the British Standards Institute for calibration and approval before supply to customers.



Portable Skid Resistance Tester Outfit comprising Tester, 3 rubber sliders,, 2 spanners, water bottle, tools, complete with transport case. Cat No S885













Cu: metres




Aluminium Case




Studies of accident sites have revealed that the polishing of roadstone is a major factor in skidding. An important application of the Skid Tester is in the laboratory determination of the resistance of roadstone to polishing.

Scale for roadstone polishing is built into the machine. 6 special small rubber sliders can be supplied for this test: S886/5

Base Plate for laboratory use of skid tester with specimen mounting block S885/9


As the nature of the rubber used for sliders has a critical bearing on the performance for the Tester, and as no rubber properties can be guaranteed for longer than two years, the date of issue is marked on each slider.

Spare mounted rubber sliders for use with Main Tester: S886/6

Spare mounted rubber sliders for Stone Polishing Tests S886/5

Skid Resistance TestThe resistance of wet road surfaces to skidding can be checked by means of a Portable Skid-resistance Tester (Portable Pendulum Tester). This apparatus is used to measure the frictional resistance between a rubber slider (mounted on the end of a pendulum arm) and the road surface. This method provide a measure of frictional property, microtexture of surfaces, either in the field or in the laboratory.

Skid Resistance TestThe quantity measured with the portable tester has been termed "Skid-resistance" and this correlates with the performance of a vehicle with patterned tyres braking with locked wheels on a wet road at 50 km/h.

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Skid Tester Calibration S885

Introductory Note

The calibration procedure which follows is based on BS 812 Partl 114:1989. However it will be replaced shortly by the European Standard EN 1097-8.

This procedure is intended to be used, together. with the Skid Tester Calibration Rig S892. This system has been designed to allow laboratories outside the UK to calibrate their Skid Testers without the major expense and inconvenience of sending Skid Testers back to the UK for this purpose.

The Skid Tester is a precision instrument and needs to be calibrated by a competent technician.

Calibration Procedure

  1. Calibration must be carried out in a temperature controlled environment of 20°C.
  2. The out of balance moment of the rotating head of the pendulum must be less than 12g.cms. If more, calibration moments and calculations must be adjusted.
  3. Mass of pendulum pointer to be less than 85g, excluding felt pads.
  4. Pointer to balance on a knife edge about the centre of oscillation.
  5. Weigh the complete pendulum arm. 1.5kg ±30g.
  6. With the adapter nut in its extreme position and the slider lifting handle down, balance the pendulum horizontally on a knife edge and mark the centre of gravity.
  7. With the arm horizontally balanced oil the knife-edge and with the slider lifting handle down, adjust the counterweight until the foot is horizontal.
  8. With the arm mounted oil the Pendulum measure the distance of the centre of gravity mark from the centre of oscillation.
  9. The arm must fall freely from the catch.
  10. Set the pointer to reach tile zero position on the scale by swinging the arm in free air and adjusting the pressure oil the felt pads.
  11. If without pressure from the felt pads the arm fails to reach the zero position on the scale, mechanical problems exist, N.B. bearings, which must be corrected.

  12. Check the alignment of the pendulum foot swinging parallel with the base by measuring the difference at the toe of tile foot, of the swing across the front face of the base. ±1mm. This measurement can be corrected by setting cotters oil the pendulum column.
  13. Check that the foot is square to the base by measuring the difference between the toe & heel of the foot, related to the front face of the base, in the static vertical position. ±0.5min. Adjustment can be made by setting the clamp oil the adjuster nut.

  15. Calibration Weights
  16. The following are used in calibration:

    CW1 -Applied Weight 2244 g.

    CW2 Small Calibration Weight 60 g.

    CW3 - Large Calibration Weight 120g.

    The calibrating weights should be attached to the lifting arm, after removing the cover plate.

  17. With the arm inverted on the calibration rig mounting block and the mean load (CW1 and CW2) applied, raise the slider by turning the screw adjuster anticlockwise until the slider arm just touches the retaining bar. Measure this high point with the micrometer. Turn the screw adjuster clockwise until the slider arm just touches the low stop, measure this low point, set the mean point of these two measurements on the micrometer and turn the screw adjuster anticlockwise until the slider touches the micrometer. This is the mean setting of the slider.
  18. Note:

    The adjusting screw on ‘Type B’ units requires a screwdriver applied through the access hole in the adapter nut.

    ‘Type A’ units require removal of the adapter nut assembly to access a thumb screw.

  19. Remove the small calibrating load (CW2) from the mean load, check that the slider arm is still free of the internal rest and measure this setting. Add the large calibrating weight KW3) to the load and measure the deflection.
  20. Set the alignment of the pointer vertically parallel to the arm.
  21. Adjust the pointer stop until the cc-titre line of the pointer is parallel with the pendulum arni in a vertical position, with the friction tester assembled and levelled.
  22. Adjust the spring tension until the lifting handle is brought to its median position. The complete movement of the slider (parallel to the pendulum arm) when using the lifting handle shall be at least 6.5 mm.
  23. The Complete movement of the slider (deflection) shall be at least 11 mm.
  24. Force of Swinging Arm (In Newtons)
  25. W=Wx9.806

  26. Slider Force (in Newtons)
  27. .037xWx411

  28. Change in Slider Force (In Nmm)

SF=.69/Vertical Displacement (mm)




Calibration Certificate

Calibration Laboratory:


Certificate Number:

Serial Number of Machine:


Mass of Swinging Arm (W1)



1.5 ±0.03


Force of Swinging Arm (W)



14.6 ±0.03


Centre of Gravity from Centre of Oscillation



410 ±5


‘F’ Scale Vertical Distance


Mm (Nominal)

85 ±0.5


Slider Force (P)



22.2 ±0.05


Change in Slider Force (SF)





Sliding Distance



76 ±0.5


Length of Pointer





Mass of Pointer





Distance from Sliding edge to axis of suspension


Mm (Nominal)