
003-001 PowerAssist Installation
Page 5 of 24
Rev. 0–27APR07
• Note that some older head blocks feature sheaves in which the pitch diameter of the
operating line is different from that of the lift lines. This type of sheave cannot be used
with the PowerAssist system.
equal pitch diameters
unequal pitch diameters
Figure 3: Sheave pitch diameters
2. Winch mounting conditions
The building structure to which the hoist is anchored must be of sufficient strength to resist
the loads at the appropriate design factors. The PowerAssist exerts 1000 lbs of uplift, plus
dynamic forces, on the structure below. Consult a qualified Structural Engineer to determine
if the building is capable of resisting these loads.