TM-55-2350-215-10-15 M60 Series Transportability Guidance Download
Page 29 of 66
TM 55-2350-215-10-15 practical. Civil highway permit officials should be consulted to determine specific permit requirements for the state or country in which the movement is planned. b. Bridge Limitations. The high tandem axleloads and suspension characteristics may overstress typical bridge structures in the United States. Most States will permit tandem axleloads of up to 50,000 pounds under special conditions. Accordingly, all highway movements of the M60-series tank on the HET system may be refused or required to have a "certification of essentiality to national defense." The certification is issued to the appropriate State highway department by the major command making the move and is required prior to movement. c. Loaded Characteristics. Characteristics of the loaded system are shown in individual axle weights in figure 5-1. The HET transport system's tandem axles, that is, the two adjacent axles pivoting at a single suspension point, are over the 50,000-pound tandem- axleload limit recommended by AASHTO. When the M60-series tank is positioned on the M747 semitrailer so that the load is equally distributed to all axles, the tandem axleload limit is exceeded. The rear two axles of the M746 semitrailer are retractable pusher axles. When extended, they can be adjusted to push against the surface to distribute the load to all four axles of the semitrailer. The M746 truck tractor has two sets of tandem axles. The M911 truck tractor has one set of driving tandem axles, a single steering axle, and a single pusher axle just forward of the tandem axles. The pusher axle may be extended to distribute the load when the fifth-wheel load increases the tandem axleload to greater than acceptable limits. Placement of the M60A3 tank's center of balance 243 inches from the kingpin of the M747 semitrailer, with the semitrailer pusher axles properly extended (when towed by the M746 truck tractor), will achieve the individual axleloads shown in figure 5-1. Placement of the M60A3 tank's center of balance 237 inches from the kingpin of the M747 semitrailer, with the tractor pusher axle and the semitrailer pusher axles properly extended (when towed by the M911 truck tractor), will achieve individual axleloads shown in figure 5-1. 5-2