305 / | HD | WHEEL SUBSTITUTES FOR LAND VEHICLES |
185 | DF | TRACKS OR TREADS {14} |
193 | DF | .~ With guide means for interfitting with sprocket wheel or roller {3} |
195 | .~.~ Sprocket and track engagement {2} | |
196 | DF | .~.~.~> Track formed of rigid links {2} |
199 | DF | .~.~.~> Sprocket wheel structure, per se |