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Early Road Surface Testing Machine

A W.D.M. Limited staff member visited the National Motorcycle Museum recently and found an example of how road surface friction was measured and recorded in the UK in the early days of motoring. 

Today, WDM® is the only licensed manufacturer of the Sideway-force Coefficient Routine Investigation Machine (SCRIM®), which measures wet-road skid resistance and helps save thousands of lives worldwide. The first SCRIM rolled off the production line in 1967. 

When the Ministry of Transport wanted a special vehicle for testing road surfaces back in the 1930’s, however, they approached the Osborn Engineering Company. The result was a 1936 OEC motorcycle and sidecar weighing in at half a ton, powered by a 1000cc J A Prestwich (JAP) engine capable of propelling a normal motorcycle at 100 mph.  

The power was necessary because it was no ordinary sidecar outfit. Its main function was to measure the grip of the sidecar tyre on the road surface and to do this the sidecar wheel had to be steered independently of the machine front wheel. 
 
The resistance of the sidecar wheel to being dragged along in the direction it did not want to go - scrubbing the tread off the tyre - was measured on instruments in the sidecar and recorded on tape.  

The equipment, plus the rider and passenger-tester, made the outfit the heaviest sidecar machine to go on the road. With the sidecar wheel pointing in the right direction the outfit was capable of near 50 mph. 

Osborn Engineering manufactured motorcycles in Britain from 1901 to 1954, initially using Minerva and MMC engines. After WWI, production resumed of OEC-Blackburne machines, later shortened to OEC. During the marque's long lifetime models were produced with large capacity V-twin JAP, Blackburne and Matchless engines, and with Villiers two-stroke engines after WWII.                                                                                                                                                                                                                                                                                             

Nowadays WDM® SCRIM measures the wet road skid resistance by lowering a freely rotating wheel on to the road surface at an angle of 20 degrees. A jet of water is sprayed on to the road immediately in front of the measuring wheel.  

SCRIM has now been used for nearly half a century by highway engineers throughout the UK and in 16 countries worldwide to help make roads safer by measuring the surface friction. 

SCRIM is the registered trade mark of W.D.M. Limited

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