In mechanical equipment, gears provide a means of conveying power from one rotating shaft to another. Because many common gearbox repairs involve gear tooth damage and other gear-related issues, it’s helpful to have a solid understanding of gear teeth when handling gearbox repairs.
How Gear Teeth Operate
Within a gearbox reducer, a gear operates essentially as a series of levers (the teeth) arranged around the circumference of a wheel and axle. The lever and the wheel-and-axle are two of the six simple machine types, and they function by the principle of ratios – the distance through which the force moves versus the distance through which the load moves.
Gears work similarly in a gearbox reducer. Each pair of teeth on two interacting gears acts as a lever to transmit torque, or rotary force, from one shaft to the other. The relative size of the gears determines the lengths of the lever elements involved and therefore the ratio of force/speed multiplication.
What Gear Teeth Do in a Gearbox Reducer
Gears are used for many purposes, including:
- Synchronization of rotation between two moving elements.
- Reversal of rotation between two moving elements.
- Change of rotational speed and rotational force (torque) from input to output.
- Transference of rotational power from one shaft to another.
Similarly, gear teeth accomplish several important tasks within a gearbox reducer, notably:
Preventing slippage. Gear teeth allow the two wheels to transmit power between them without slippage. The circumference of each gear is machined to have teeth that provide smooth power transfer in a continuous rolling motion, without sliding, providing the lowest friction loss and greatest power transfer.
Creating precise ratios. Gear teeth create precise ratios of power transfer between rotating elements within a gearbox reducer. Gear teeth must be machined as discrete elements, with whole numbers of teeth on each gear. To properly mesh together, the spacing between gear teeth – and hence the “diametral pitch,” or number of teeth per inch of gear diameter – determines the relative size and ratios between the gears.
Overcoming gear imperfections. Finally, gear teeth allow proper functioning of a gearbox reducer despite imperfections in manufacture and slight variations of size of the various dimensions of the gears. As long as the gears can mesh properly, slight differences in dimension will not cause changes in the gear ratio or prevent proper functioning.
Important Gear Tooth Information for Preventing Gearbox Repairs
Gear teeth are machined to allow for manufacturing tolerances, or variations in size. The more precisely made gears are, the more smoothly they run, the longer they last and the quieter they are. Gear teeth are commonly cut in two shapes: cycloidal and involute. Both provide constant velocity operation, but the cycloidal requires more precise manufacture and gear spacing. Most power train gears today are involute.
Gearbox repairs will be minimized when the manufacturer’s instructions are followed for installation, maintenance and repair. Some gear sets are intended to operate only in one direction, so to save costs the “non-power” side of the gears’ teeth is not finished. That side does not have the same precision of manufacture as the “power” side; therefore, installing the gears to move in the wrong direction may cause failures and necessitate costly gearbox repairs. Manufacturers will also provide load and speed limits for each gearbox reducer.
A strict adherence to maintenance procedures must also be followed. Lubricants must be chosen to match the gear type and loads applied and changed at the recommended intervals. As the teeth and bearings wear, the clearances must be adjusted to maintain proper operation.
Posted under Tips and Tricks on Monday, September 26th, 2011