Mechanical drives are used to transmit motion, torque and power from a driver shaft to powered shaft. The driver shaft, in most the cases, is part of primary mover (such as electric engine, hydraulic turbine, steam turbine, etc.); while, the powered shaft is part of the machine unit. There exist four fundamental mechanical drives, namely equipment drive, belt drive, chain drive and rope drive. A equipment drive is a single engagement type rigid drive where movement and power are transmitted through successive engagement and disengagement of teeth of two mating gears. It really is inherently free from slip and this it provides continuous velocity ratio (positive drive). It can be utilized for light duty applications (such as toys, watches, etc.) aswell as for durable applications (such as gear box of machinery, marine drive, etc.).
Driver and driven shafts might have 3 mutual orientations, namely (i) parallel shafts, (ii) intersecting shafts and (iii) non-parallel nonintersecting shafts. There can be found four basic types of gears and a suitable gear ought to be selected based on the mutual orientation of the driver and driven shafts. Spur equipment and helical gear can be applied for parallel shafts. Bevel equipment can be applied for two intersecting shafts, which might not always be perpendicular. Worm gear arrangement is used for the 3rd category (nonparallel nonintersecting shafts). Unlike spur gears that have straight the teeth parallel to the apparatus axis, helical gears possess teeth in helical type that are cut on the pitch cylinder. Although helical gears are commonly used for parallel shafts like spur gears, it can also be utilized for perpendicular but non-intersecting shafts.
Accordingly right now there are two types of helical gears-parallel and crossed. Parallel helical gears, the common one, is used to for power transmission between parallel shafts. Two mating parallel helical gears must have same module, same pressure angle but opposite hands of helix. They offer vibration-free and quiet procedure and will transmit heavy load. On the other hand, crossed helical gears are used for non-intersecting but perpendicular shafts. Two mating crossed helical gears (also known as screw gears) must have same module, same pressure position and either same or opposing hands of helix. This kind of gear has software similar to worm equipment; however, worm gear is favored for steep speed reduction (1:15 to at least one 1:100), whereas crossed helical gears cannot offer swiftness reduction beyond 1:2. Various variations between parallel helical gear and crossed helical equipment are given below in desk format.