Perma-Tork® Selection Rewind tension control Quick selection charts (Web Tensioning) Continuous slip applications Perma-Tork clutches provide constant tension or controlled taper tension on rewinds. If you need assistance selecting an eddy current or hysteresis clutch for your rewind application, call the factory. First find slip RPM on the vertical axis, then locate torque on the horizontal axis. Find the intersection of two lines. If you fall below the line and in the dark area, the brake is thermally sufficient to handle the heat generated. If it lands on the line or in the white area, a larger unit is required. Overload protection/Torque limiting/Soft start (Torque Limiting) The dotted curve represents the thermally safe area for intermittent duty, such as 3 minutes on, 3 minutes off. Model HB1/2 Model HC4 Motor horsepower method Information required: Motor HP =1/2 HP Motor RPM = 1750 RPM How to size: Torque (lb in) = HP x 63000 RPM 1/2 x 63000 = = 18 lb-in 1750 Select a HC-5 from the specification chart Model HC2 Model HC5 String and Pulley Method Affix a pulley to the shaft of a machine to be measured. Secure a string or cord to the outer surface of the pulley and wrap the cord around a few times. Tie the other end of the cord to a spring scale. Pull on the scale until the shaft turns. The force (in pounds) indicated on the scale, multiplied by the radius of the pulley (in inches) gives the torque in pound-inches. Permanent Magnet Clutches & Brakes Cycling (Bottle Capping) Information required: Slip RPM = 500 RPM Torque - 8 lb-in % slip time of total cycle time = 25% How to size: Watts* = .0118 x Torque (lb-in) x Slip RPM x % slip time = .0118 x 8 x 500 x .25 = 11.8 watts Select an HC-4 from the specification chart *Note: Consult factory if peak slip watts are extremely high or if duration of slip period is in excess of 1 minute. 152 Permanent Magnet Clutches & Brakes Model PB6 Model HC6, HB6