To better illustrate how these changes apply to the lifter, a graph of the torque (
F
R
x perpendicular
distance to the fulcrum) during lifting a 500 pound evenly loaded TS-03, TS-04 and 50 inch diam
-
eter tire is shown in Figure 24. The solid vertical line marks the torques on all three implements
at 18 inches off the ground or approximately the beginning of the second pull phase of the lift.
The dashed line, at approximately 45.5 inches off the ground, shows the torques at the beginning
of the push phase.
Using the same 500 pounds on three different size implements, the torque required to rotate the
50 inch diameter tire at a hand height of 18 inches is less than 800 ft-lbs. The TS-03 requires 1020
ft-lbs and the TS-04 requires 1155 ft-lbs. Therefore at second pull, the TS-04 requires 46% more
torque to lift the same total weight of each implement at a constant velocity.
An even more dramatic difference is seen during the push phase. At hand height of 45.5 inches
off the ground, the center of gravity of the 50 inch diameter tire is directly over the fulcrum, as
illustrated in Figure 25. This means the torque required to rotate the tire is zero. If the tire is
rotating at a constant angular velocity, there is no effort required by the lifter to perform the push
phase of this lift. Therefore, a critical component of the lift, the push phase, is nonexistent for this
lifter with this size 500 pound tire.
22
Using the Flipper - Size Matters
Fig 24