Gearmotors: Products, applications, lubrication

Feb. 6, 2009
Gearmotors: Products, applications, lubrication : Gearing up for another road trip : Don't forget your lubes 'n greases : Gearmotors

Gearing up for another road trip

Car trouble. It's the bane of modern life, whether the auto on the roadside is a Yugo or a Rolls Royce. When the vehicle is a 1925 Lanchester 40HP Tourer, replacing an errant part gets even trickier. Such was the discovery of Peter Noble and his wife on a recent summer excursion to Syria. After 15 years of road trips through France, Italy, Greece, and Turkey, the mighty Lanchester took ill just short of Clermont-Ferrand, France. The Nobles recall hearing a “thunderous explosion below the car” during a steady incline along the Autoroute. The rear axle worm and wheel had broken.

The three-ton touring car, which is built like a tank, was a favorite among the Maharajas of India and English royalty alike. Every aspect of the car's engineering is of massive proportion. For example, if a component could be cast in bronze or solid nickel rather than plated, that's how the Lanchester brothers preferred to do it. But even well built parts won't last forever. The Nobles had to abandon their favorite ride and have it sent home. Peter spent the next several months searching the world for a parts manufacturer who could replace the broken worm and wheel. However, most gear cutting companies either didn't want to do a one-off job or did not have the technical know-how or proper tools. Then Peter contacted Renold Gears, based in Milnrow, UK.

Renold was able to not only provide a replacement part, but also a much sturdier design. The company improved the metal by cutting the wheel from nickel bronze where Lanchester had used phosphor bronze. And instead of the hourglass principle favored by Lanchester, Renold employed a Holroyd parallel worm design. Replacement gears have now been fitted into the axle and road tested. The Nobles and their beloved Lanchester are once again ready travel the world in style, with a visit to India planned for next year.

Don't forget your lubes 'n greases

All lubricants minimize friction and result in lower heat generation. However, oil provides the best lubricating properties for gearmotors and is typically used in 1/10 hp and larger gearmotors designed for industrial service. Increasing the service life (over 10,000 hrs) can be accomplished with a circulating fluid lubrication system. The fundamental characteristic of oil is its free flow and constant presence at the tooth surfaces of a gearhead during operation. The oil needs to provide a consistent and continuous lubricating film at the load zone, while withstanding dynamic forces such as centrifugal forces or severe loading that can prevent the lubricant from doing its job.

Lubricants used in parallel shaft gearmotors (which usually employ spur or helical gearing) are relatively less critical than those for right angle worm-gear types. Usually, mineral-based oils with EP additives suffice if the proper level is maintained. Some fractional hp gearmotors use hydraulic-type oils to decrease gearshaft or journal wear. Right-angle gearmotors with worm or other sliding-contact gearing require careful attention because the lubricants reach higher operating temperatures due to lower inherent efficiency. Such lubricants generally have higher viscosity and contain protective additives to prevent oxidation and to enhance “oiliness.”

Despite its advantages, oil is not commonly used in smaller gearmotors because of sealing issues. Smaller gearmotors usually do not have large gasket surfaces and may not have sufficient power to withstand the increased friction of a contact seal on the rotor shaft. Therefore, grease is used as a compromise in most gearmotors under 1/4 hp. Compared with oil, grease provides less consistent lubrication to the gear teeth under load and gear life can be reduced by up to 50%. However, grease provides mounting flexibility, minimizes leakage risk, and eliminates visual oil level inspections.

With regard to operating conditions, lubricant life in gearmotors is directly related to temperature. Generally, within normal operating ranges, lubricant life doubles for every 25° F decrease in temperature. Gearmotors operating in high or low ambient temperature ranges require special lubricants such as synthetic lubricants, or a lubricating system. Gaskets, motor insulation, and lubricant life may be seriously affected by temperature extremes. When other than normal ambient temperatures (32° to 104° F) are expected, consult the motor manufacturer.

Information courtesy of Bodine Electric Co.


Parallel shaft gearmotors

VWDIR14 (Von Weise drop-in replacement) ac parallel shaft gearmotors deliver up to 50 in.-lb output torque from most global ac power sources.

Features & benefits

  • Operates on 115 or 230 V, 60 or 50 Hz; available in six standard models

  • Gear ratios from 10:1 to 494:1, corresponding output speeds from 181 to 4 rpm; 1/20 hp

  • Totally enclosed non-ventilated (TENV) permanent split capacitor ac motors and integral gear reducers are reversible and feature all-position face mounting with a 50 lb overhung load capability

Bison Gear & Engineering Corp.

(800) 282-4766

Actuator-sensor interface for gearmotors

AS-Interface with improved diagnostic capabilities is now standard with MOVIMOT C gearmotors; the interface provides failsafe connectivity under challenging ambient conditions and links easily to higher-level fieldbus and Ethernet networks.

Features & benefits

  • Designed for realtime communications at the sensor or actuator level
  • Easily connects sensors and actuators to distributed control systems using master and slave topologies; up to 31 slaves can be connected to a drive system incorporating multiple gearmotors
  • Maximum communications cycle time is 5 ms for 31 stations and maximum line length is 100 m, or 300 m with a repeater

    SEW Eurodrive Inc.

    (864) 439-8792

    Reversible dc gearmotor

    MMP-TM55-24V GP52-195 is a compact, low speed, high torque unit suitable in applications such as battery-powered electric vehicles, robotics, and factory automation.

    Features & benefits

  • Accepts any 24 Vdc power source, including battery power; motor windings for 12, 36, 48, and 90 V available

  • 2.14 in. diameter × 7.75 in. long; weighs 3 lb

  • Rated for 196 in.-lb continuous torque at 24 rpm

Midwest Motion Products

(952) 955-2626

Precision gearheads

Precision gearheads offer a suitable solution when a motor is powerful enough for motion, but has too much speed and not enough torque.

Features & benefits

  • Standard planetary and spur gearheads in more than 600 varieties ranging from 6 to 81 mm

  • Custom designs available, such as a planetary gearhead with two speeds on the output side

  • Worm gearheads and spindle drives also available

maxon precision motors inc.

(508) 677-0520

Brushless gearmotors

NEMA 23 and 34 integrated brushless permanent magnet (PM) servo gearmotors are suitable for use in industrial machinery, medical equipment, and other applications.

Features & benefits

  • Brushless PM motors are combined with lower noise planetary geartrains

  • Torque values range from 26.5 lb-in. to 224 lb-in.

  • Single, dual, and 3-stage geartrains available in 10 gear ratios from 16:1 to 1,012:1

Dynetic Systems

(800) 899-4372

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