• Right Angle Gearbox Basics
  • What is a Right Angle Gearbox?
  • Right Angle Gearbox Cost
  • How does a Right Angle Gearbox work?
  • Right Angle Gearbox Advantages
  • Right Angle Gearbox Selection

A Right Angle Gearbox is defined as a set of gears, shafts and bearings that are enclosed in a housing unit. The way the gears, shafts, and bearings are arranged resemble solar system because one or more of the plant gears orbit around a sun gear.

A Right Angle Gearbox is a set of gears, shafts, and bearings that are enclosed in a housing and are arranged in a way that resemble a solar system, (thus the name Right Angle) with one or more planet gears orbiting around a sun gear. They convert input speed (typically provided by an electric motor) into a lower output speed while correspondingly creating higher torque. In other words, gear-boxes reduce RPM, turning it into power for use in low-RPM high-torque applications. Gearboxes come in different arrangements including Right Angle, bevel, cycloid, helical, harmonic, spur, and worm. Our focus here is on the Right Angle type of gear system.

The Right Angle gearbox comes in many sizes and torque capacities, with varying speed ratios depending upon configuration. These Right Angle gearbox products that are pictured above are approximately 60 mm to 2.4 inches in size, and produce output torque ranging roughly from 2,000 to 25,000 ounce-inch.

A much larger Right Angle gearbox exists for industrial processes, providing output torque in excess of 500,000 ounce-inch. The focus of this website, however, is on these smaller Right Angle gearbox types.

The input power to these small Right Angle gearbox products comes from small electric motors (either a stepper motor, DC motor, or servo motor). Small motors are found in many household devices such as fans, clocks, timers, cassette players, printers, computer disc drives, etc.

The price of planetary gearboxes varies based on many factors. For backlash in the 30 arc-minute range, the cost for a gearbox might be as low as $100. For low backlash gearboxes under 5 arc-minutes they will cost quite a bit more. Below is a listing of right angle gearbox products offered by Anaheim Automation - they list comprehensive specs and prices on their website with web discounts.

Model Cost Size Backlash  Ratio Range
gear motor $30.00 under 40 mm varies 3 to 512
GBPH-060 $195.00 60 mm square (Fits NEMA 23) 10 arc-min 3 to 512
GBPH-090 $295.00 90 mm square (Fits NEMA 34) 8 arc-min 3 to 1000
GBPN-120 $457.00 120 mm square (Fits NEMA 42) 9 arc-min 3 to 512

The Right Angle gearbox system has 3 main components: a central sun gear, a planet carrier (carrying one or more planet gears),and an annulus (an outer ring). The central sun gear is orbited by planet gears (of the same size) that are mounted to the planet carrier. The planet gears are meshed with the sun gear. An outer ring (the annulus) has teeth facing inward that also mesh with the planet gears.

There are several configurations for Right Angle gearbox systems. Typical configurations require that out of the 3 components: one is the input, one is the output, and one is stationary.

For example, one configuration is where the sun gear is the input , the annulus is the output, and the planet carrier is stationary. In this configuration, the input shaft rotates the sun gear. The planet gears rotate on their own axes, simultaneously applying a torque to the rotating planet carrier, that in turn applies torque to the output shaft (which in this case is the annulus).

The rate at which the gears rotate (gear ratio) is determined by the number of teeth in each gear. The torque (power output) is determined by both the number of teeth and by which component in the Right Angle system is stationary.

The Right Angle gearbox arrangement is an ingenious engineering design that offers many advantages over traditional gearbox arrangements. One advantage is its unique combination of both compactness and outstanding power transmission efficiencies. Typical efficiency loss in a Right Angle gearbox arrangement is only 3% per stage. This type of efficiency ensures that a high proportion of the energy being input into the Right Angle gearbox is multiplied and transmitted into torque, rather than being wasted on mechanical losses inside the Right Angle gearbox.

Another advantage of the Right Angle gearbox arrangement is load distribution. Because the load being transmitted is shared between multiple planets, torque capability is greatly increased. The more planets in the system, the greater load ability and the higher the torque density.

The Right Angle gearbox arrangement also creates greater stability (it's a balanced system) and increased rotational stiffness. Disadvantages of the Right Angle gearbox arrangement include design complexity and accessibility issues.

In the drawing above, the Fixed Axis Gear System is the traditional arrangement where a pinion is driving one large gear on a parallel shaft. In the Right Angle Gearbox System arrangement, one or more gears (planet gears) surround the pinion (sun gear). The two systems above have approximately the same ration and same volume. However, the Right Angle gearbox system has 3 times higher torque density and 3 times higher stiffness due to the increased number of gear contacts.

Fixed Axis Gear System:
•Volume = 1, Torque = 1, Stiffness = 1
Right Angle Gear System:
•Volume =1, Torque = 3, Stiffness = 3
Other gearbox arrangements (as mentioned previously) include bevel, cycloid, helical, harmonic, spur, and worm.

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It's important to know certain performance specifications when selecting a Right Angle Gearbox, such as: input speed (this determines the gear ratio), output speed, and output torque required.