Sell start-up spring

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The torque-deflection characteristic of a power spring is non-linear. This condition is caused by the constantly changing amount of active material, the normal hysteresis effect throughout the working deflection, and inter-coil friction.
Most spring motors operate through a maximum of about fifteen useful revolutions. It is possible to prestress the strip by forming, and then backwinding it into the retainer. This causes higher stresses; however, it also increases the number of useful turns to as high as thirty-five. A more constant torque load through the entire spring deflection will result. John Evans' capabilities range from very thin (.002) to heavy (.080) material, and widths from fractions of an inch to multiple