worm gear and worm wheel

The arrangement of gears seen above is named a worm and worm wheel. The worm, which in this example is certainly brown in colour, just has one tooth but it is similar to a screw thread. The worm wheel, coloured yellow, is like a normal worm gear and worm wheel equipment wheel or spur equipment. The worm often drives the worm wheel round, it is never the opposite way round as the system tends to lock and jam