Use iron pulleys.

Use iron pulleys.

• A. To Decrease Parasitic Drag
• B. To Increase Parasitic Drag
• C. No effect on parasitic drag
• D. To Increase Parasitic Drag

Answer: (B)

Parasitic drag is energy lost by components that don’t contribute to forward motion, taking power away from propulsion. Iron pulleys are heavier than lighter materials for the same size, so they add more rotational inertia to the belt-driven accessories. That extra inertia means the engine has to supply more torque just to spin the pulleys up to speed and to keep them spinning smoothly, especially during accelerations and throttle changes. The result is greater energy waste in the form of drag within the drivetrain, not useful propulsion. Because of that, using iron pulleys increases the parasitic losses rather than reducing them, and it would not be expected to have no effect or to decrease those losses. Lighter materials or better bearings would reduce the parasitic load by lowering both rotational inertia and frictional losses.

Parasitic drag is energy lost by components that don’t contribute to forward motion, taking power away from propulsion. Iron pulleys are heavier than lighter materials for the same size, so they add more rotational inertia to the belt-driven accessories. That extra inertia means the engine has to supply more torque just to spin the pulleys up to speed and to keep them spinning smoothly, especially during accelerations and throttle changes. The result is greater energy waste in the form of drag within the drivetrain, not useful propulsion.

Because of that, using iron pulleys increases the parasitic losses rather than reducing them, and it would not be expected to have no effect or to decrease those losses. Lighter materials or better bearings would reduce the parasitic load by lowering both rotational inertia and frictional losses.