Motorcycle News (UK) - - This Week -

Dynos, or dy­namome­ters, are fairly sim­ply pieces of equip­ment – the clever part is in­ter­pret­ing the data they gen­er­ate. While you do get en­gine dynos that mea­sure the power of a static mo­tor, most of us will only ever en­counter a rolling-road dyno, which is used to test the power of a com­plete mo­tor­cy­cle. A dyno con­sists of a static plat­form, which is used to sup­port the mo­tor­cy­cle and stop it break­ing free, and a large drum un­der the rear wheel. This drum weighs in the re­gion of 200kg and is very ac­cu­rately ma­chined to en­sure it is per­fectly bal­anced, as any im­bal­ance would cause data er­rors. The sur­face of the drum is knurled so that the bike’s tyre can grip, not slip. Gen­er­ally a dyno will mea­sure what is known as trac­tive force, which is the force the bike’s tyre uses to turn the drum. As the in­er­tia of the dyno’s drum and also the re­sis­tance of the bear­ings are known pa­ram­e­ters, the com­puter can cal­cu­late how much force the bike is ex­ert­ing dur­ing an ac­cel­er­a­tion run, thus en­abling this force to be ex­pressed as horse­power and torque, which are then plot­ted against the bike’s revs. These charts can have var­i­ous cor­rec­tion fac­tors ap­plied them to stan­dard­ise the re­sults, tak­ing into ac­count vari­a­tions in tem­per­a­ture, air pres­sure and hu­mid­ity.

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