The gun system of the M1 series tank rides on a pair of self-aligning spherical bearings that allows the elevation and depression
of the cannon. Because these bearings are encapsulated within the rotor housing, periodic lubrication or maintenance is impossible.
To overcome this problem self-lubricating bearings were incorporated into the system. There are two basic liner designs, molded
and fabric. Molded liners are produced by applying a formulation of teflon and typically asbestos into a phenolic resin, which
is applied to the bearing surface, then cured. Fabric liners utilize a woven fabric bonded to the bearing surface, then teflon
which is mixed into phenolic resin is applied to the bearing surface and cured.
Initial studies of the existing bearing liner were completed to determine the liner composition and establish a baseline or
standard to compare thermal and mechanical properties with potential vendors. DSC revealed an average teflon content of 39.53%,
which varied significantly throughout the liner. TG analysis showed an asbestos concentration of 12.22%. The remainder of
the liner was phenolic resin. Physical testing of the bearing from −20 to 120‡C under normal loading conditions demonstrated
excellent thermal stability with little wear.
Bearings from each vendor were tested and compared to the standard properties of the baseline bearing. Some properties were
difficult to compare or insignificant due to the design differences between molded and fabric liners. The testing program
resulted in the qualification of two bearings, which met or exceeded the established standards. Both of these bearings were
designed with fabric liners.