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Gearboxes

Since 1978 Hill House Products has been representing and selling gearboxes from the best manufacturers in the world. These manufacturers have built and designed their products to meet or exceed construction criteria from AGMA, NEMA, and ASTM for easy application use as a standalone gearbox or mounted onto a motor.

While many technical books have been written on the benefits of their varying designs, a quick explanation is always useful in understanding the most common designs and the fundamentals of gearing.

A gearbox is a mechanical device utilized to increase the output torque or change the speed (RPM) of a motor. The motor's shaft is attached to one end of the gearbox and through the internal configuration of gears of a gearbox. This provides a given output torque and speed determined by the gear ratio. Typically, a gearbox is rated for input and output torque or horsepower, preferred output speed, backlash, reflected load and overhung loads.  It is worth noting that horsepower is always conserved so, no increase in horsepower is ever achieved using gearboxes; you trade speed for torque minus the losses of the frictional load within the gearbox.

The physical components of gearboxes vary between gearbox types and gearbox manufacturers. Most traditional gearboxes are constructed from materials such as cast iron, steel, aluminum and brass. It is common to have the internal gear sets supported by very large bearings for long life. Additionally, gearboxes require internal lubrication for the gear sets and bearings - most are filled with synthetic oil or, in some cases, grease.  Some common gear and gearbox designs are worm, helical, spiral bevel, cycloidal, planetary and spur, each having its own benefits.

Gearboxes are usually rated in sub fractional and integral horsepower designs, the smaller sub fractions use different types of gear cuts and designs, like spur gears. The spur gears can also be made with plastics such as polycarbonate or nylon which, besides a lower cost, can also offer improvements in noise levels. Other than the raw materials used to reduce noise, the orientation of the gear teeth play a major role in the overall efficiency, torque and speed of the system. Straight gear teeth gearboxes are typically used in low-speed applications. These gearboxes can be noisy, and may have lower overall efficiency. Helical gearboxes are typically used in high-speed applications. These gearboxes are quieter in operation than straight gear teeth gearboxes, which may improve their overall efficiency. In general the use or benefit of a gearbox can be summed up as follows:

  1. Increasing the torque output capacity;
  2. Reducing or increasing the output shaft speed of the motor at a given speed;
  3. Reducing the effective load inertia reflected back to the motor. This is used for optimizing speed and positioning control;
  4. Changing the output shaft vector (Inline, right angle, parallel shaft, etc.);
  5. Increasing an overhung shaft load.

If you need additional information please contact us for help.