In a previous paper (I), the contact forces in a chain bearing during articulation were established. The present note describes the application of these results to the theoretical evaluation of efficiency for a conventional chain transmission using cranked link (or offset) type chain. NOTATION energy loss during narrow articulation energy loss during open articulation total energy loss number of teeth in driver sprocket number of teeth in driven sprocket pitch of chain tight span tension bush internal radius bush external radius articulation angle for narrow end forward articulation angle for open end forward efficiency of chain drive The M S u'as receiued on I8 December 1985 and was acceptedfor publication on I S April 1986. Narrow end forward articulationinstantaneous angle of articulation pin-bush coefficient of friction bush-roller coefficient of friction pressure angle of sprocket tooth angle of repose for pin-bush contact angle of repose for bush-roller contact DESCRIPTION OF CHAIN DRIVEThe scheme of such a chain drive is sketched in Fig. 1.In that diagram the angles a1 and a2 represent under normal loading the periods of articulation during which most of the energy is dissipated and so impairs the efficiency of the drive. The sense of the drive may be that with the open ends of the links leading, or in the opposite sense, and consideration of the rate of wear will influence the preference of these senses. Figure 1 depicts the case of narrow end leading. Open end forward articulation r 118/86 Q IMcchE 1986 Fig. 1 Articulations in a basic chain transmission (a = 360"/N)

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A rigid-body analysis is presented of the forces which occur in a chain bearing during articulation. Coulomb frictional effects due to unlubricated contact are included, as these provide the energy source for deleterious wear processes and affect the force distribution. The analysis differentiates between the two types of chain bearing-open end leading or open end trailing-and the results show that the force characteristics in each are significantly different. Experimental verification of the chain link tension is good. NOTATIONpin-bush normal contact force in articulating bearing link in tight span articulating chain link, precedes link Lo link engaged on sprocket number of teeth in driver sprocket number of teeth in driven sprocket chain link tension from tight span chain link tension immediately preceding articulating bearing bush internal radius bush outside radius bush-roller normal contact force in articulating bearing sprocket tooth force, upon articulating bearing total angle of articulation instantaneous angle of articulation coefficient of Coulomb friction between articulating pin-bush pair coefficient of Coulomb friction between articulating roller-bush pair nominal pressure angle angle of repose for pin-bush normal contact force with respect to corresponding link force angle of repose for bush-roller normal contact force with respect to the engaged tooth force 4 + m -e