Primitive Dynamometer

The Classic Motorcycle January 1991

Its 1915 and the Headingsley Motor Company of Leeds has set up a competition to compare the efficiency of engines and clutches. The device consisted of a plank attached to a spring balance to which the more or less stationary motorcycle was attached.. 
According to the article, motorcycles with multi-plate clutches came out best, a 500 Sunbeam managed a steady pull of 204 lbs. and of the metal expanding ring type clutches a 500 cc P&M managed 115 lbs before the  engine stalled. I'm not familiar with that type of clutch unless they are describing a centrifugal type arrangement? I expect the winning Sunbeam may have ruined its clutch during the abuse too.