Gears and Gear Drives

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

The major uses of gears and gear drives are to transmit power, with reduction or increase of speed and multiplication of torque. In addition, gears are used to transmit rotary motion from one shaft to another in a uniform manner, and for positioning. Gear drives are usually classified as reducers, increasers, high-speed drives, or drives for the accurate positioning of loads. 

Right-angle gear drive is preferred for fans over 3 m (10 ft) in diameter, for electric motors over 22.4 kW (30 hp), and with steam-turbine drives. 

Disk Filters A disk filter is a vacuum filter consisting of a number of vertical disks attached at intervals on a continuously rotating horizontal hollow central shaft (Fig. 18-127). Rotation is by a gear drive. Each disk consists of 10 to 30 sectors of metal, plastic, or wood, ribbed on both sides to support a filter cloth and provide drainage via an outlet nipple into the central shaft. Each sector may be replaced individually. The filter medium is usually a cloth bag slipped over the sectors and sealed to the discharge nipple. For some heavy-duty applications on ores, stainless-steel screens may be used. 

Girth-gear drives can cause the concrete foundations to fail if not designed to resist harmonic vibrations (Saxer and Van der Heuvel, 31st IEEE Cement Industiy Conference, 1989). 

Phinney, J.M., Selection and Application of High-Speed Gear Drives, Proceedings of the 1st Turbomachinery Symposium, Texas A M University, October 1972, pp. 62-66. 

Portable or fixed mixers up to 5hp normally use propellers and run at either direct drive speeds of 1,150 or l,750rpm or at single reduction gear drive speeds between 300 and 420 rpm. They may either be clamped on the rim of open tanks or mounted with a fixed assembly for open or closed tank operation. These mixers are the most economical and are usually used in tanks without baffles. They are rugged and long-lasting. 

Industrial equipment is a continuing area of development for plastics. Pipes, pumps, valves and sight glasses, made from such materials as PVC, PTFE and poly-4-methylpent-l-ene, have become well established on account of their corrosion resistance. The nylons are used for such diverse applications as mine conveyor belts and main drive gears for knitting machines and paper-making equipment. These and other materials are widely used where such features as toughness, abrasion resistance, corrosion resistance, non-stick properties, electrical insulation capability and transparency are of importance. 

Amongst the products made by polymerisation casting are propellers for small marine craft, conveyor buckets used in the mining industry, liners for coal washing equipment and main drive gears for use in the textile and papermaking industries. 

Gear boxes are used on just about all large field erected cooling towers and many factory assembled towers- all of the propeller ty e fan, draw-through type. Almost all are right angle gear drives with the input shaft horizontal and the output... 

Normal electric motor speeds run from the standard induction speeds for direct connection of 3600, 1800 and 1200 rpm to the lower speed standards of the synchronous motors, and then to the somewhat arbitrary speeds established by V-belt or gear drives. For some cases, the pump speed is set by the type of drivers available, such as a gasoline engine. 

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... 

Figure 5-20 illustrates a vertical propeller mixer assembly, with vertical mounting with gear box and motor. Figure 5-21 is a typical right angle, vertical impeller shaft with horizontal gear and motor drive. 

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... 

The cost of these drives is significantly greater than that of a comparable geared drive, but the quality of ride and maximum speed of car travel are much improved. Gearless drives usually have applications in prestige offices and hotels where the elevator travel is in excess of 35 m. 

Table 52.5 Lubrication of industrial enclosed gear drives. AGMA Lubricant Number recommendations for helical, herringbone, straight bevel, spiral bevel and spur ...

Table 52.6 Enclosed cylindrical and double enveloping worm-gear drives...

---