Drive and Gears

Most mixers are driven by electric motors, or in some cases by mechanical turbines, with gears ratioed to give the proper performance speed of the impeller. A variable or 2-speed driver or gear system often proves worth the extra cost, since it is difficult to predict the exact speed requirements for some new installations. This is particu- 

Usual practice, particularly for good estimating is to assume that the gear drive requires 5% of the impeller horsepower and that system surging or variations require a minimum of 10% of this impeller horsepower. Thus 

When the actual maximum gear box horsepower is known from the manufacturer, it should be used as long as it is equal to or greater than the 5% allowance noted above. The impeller/fluid horsepower allowable variation should still be 10% or greater. For example, if the calculated required motor drive (or turbine drive) hp = 23, (i.e., 19.55/0.85), the next standard motor is 25 hp, so use this, never less than the 23 indicated above because 23 hp is non-standard, and no such motor hp exists. 

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Speed changers, industrial high speed drives, and gears... 

Draft tubes, 309, 313 Drive and gears, 306, 308 Impeller, location, 322 Impeller types, 290, 291-295 Materials of construction, 307 Motor horsepower, actual, 307, 318 Shaft, 306... 

Fig. 6.5 Schematic view of an SSE. Its main components are a rotating screw within a stationary barrel. Polymer is fed through an inlet port and leaves the machine through a closure equipped with a die at the discharge end. Not shown in the figure are the electric motor drive and gear reducer for adjusting the rotational speed.

Figure 9-6. Preparative ultracentrifuge (a) with the cover panels in place, and (b) from the front and (c) from the rear with the cover panels removed. A, armor plate surrounding the rotor chamber B, drive and gear assembly C, electronics bank housing the speed, temperature, and vacuum control and monitoring systems D, vacuum pump E, vacuum pump motor F, refrigeration unit G, diffusion pump and H, drive oil reservoir. (Courtesy of Beckman Instruments, Palo Alto, Calif.)...

The differential can introduce a problem when driving on a slippeiy road because the torques on the two differential pinions are always equal, thus delivering equal torques to the drive wheels. In the extreme, if the tire of one drive wheel rests on ice and therefore lacks traction, the differential allows it to spin freely while the opposite drive wheel, and the vehicle itself, remain at rest. Special differential designs have been devised to overcome this problem. Traction is also improved in some vehicles through the application of four-wheel drive, whereby additional shafts and gears are employed to distribute engine power to all four wheels of the vehicle. 

This relation includes a 50% static efficiency of the fan and gear losses, assuming a gear drive [19]. If belt driven the difference will not be great. 

Figure 10-175 illustrates the assembly of a typical forced draft unit with electric motor and gear drive. Note that walkways and access ladders are necessary to reach the exchanger connections where valves are usually installed. If... 

Figure 14-25. Standard datasheet for steam turbines (and gears). (Used by permission API Standard 615, Mechanical Drive Steam Turiiines for General Refinery Service, 1= Ed., Appendix 1, 1958. American Petroleum Institute.)...

An internal spur gear, in combination with a standard spur-gear pinion, provides a compact drive mechanism for transmitting motion between parallel shafts that rotate in the same direction. The internal gear is a wheel that has teeth cut on the inside of its rim and the pinion is housed inside the wheel. The driving and driven members rotate in the same direction at relative speeds inversely proportional to the number of teeth. 

Despite its demand for special lubrication, this gear type is in widespread use in industrial and automotive applications. It is used extensively in rear axles of automobiles having rear-wheel drives and is increasingly being used in industrial machinery. 

Source Adapted by Integrated Systems, Inc. from Gears and Gear Drives, 1996 Power. Transmission Design, Penton Publishing Inc., Ohio, pp. A199-A211. 

Unlike gear sets, there can be two distinctive tooth-mesh frequencies for a chain-drive system. Since the drive and driven sprockets do not directly mesh, the meshing frequency generated by each sprocket is visible in the vibration profile. 

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