740 



BELL SYSTEM TECHNICAL JOURNAL 



by assembling the spring on the clutch arbor and to the 0.05-in.-lb. 

 testing torque. The backlash of the other three samples remained 

 constant to slightly above 0.5 in. -lb. and then began to rise. At low 

 loads the phosphor bronze was better while at higher loads the heat- 

 treated stainless steel had the advantage; the breaking load for the 

 latter was also about 30 per cent higher. 



0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 



MAXIMUM PREVIOUSLY APPLIED TORQUE IN INCH POUNDS 



Fig. 10 — Effect of overload on clutch backlash. Arbor diameter, 0.190 in. 



(a) Phosphor-bronze-ribbon spring, 0.0085 X 0.022 in., heat-treated 4 hr. at 230° C, 

 0.1835 in. ID. 



ib) 18-8 stainless-steel ribbon, 0.0068 X 0.021 in., wound on 0.127-in. mandrel 

 and released, 0.183 in. ID. 



(c) 18-8 stainless-steel ribbon, 0.0068 X 0.021 in., wound on 0.120-in. mandrel 

 and released, 0.170 in. ID, mechanically expanded to 0.183 in. ID. 



(d) 18-8 stainless-steel ribbon, 0.0068 X 0.021 in., wound on 0.157-in. mandrel, 

 heated 4 hr. at 470° C, cooled, and released, 0.182 in. ID. 



