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Table 20-9   Recommended Lubricants for Worm Gears by AGMA

Types of Worm Center Distance mm Rotating Speed of Worm rpm Ambient Temperature, ºC Rotating Speed of Worm rpm Ambient Temperature, ºC -10 ... 6 10 ... 52 -10 ... 16 10 ... 52 Cylindrical Type £150 150 ... 300 300 ... 460 460 ... 600 600< £700 £450 £300 £250 £200 7 Comp 8 Comp 700< 450< 300< 250< 200< 8 Comp 7 Comp Throated Type £150 150 ... 300 300 ... 460 460 ... 600 600< £700 £450 £300 £250 £200 8 Comp 8A Comp 700< 450< 300< 250< 200< 8 Comp

Table 20-10   Reference Values of Viscosity               Unit: cSt/37.8ºC

Operating Temperature Sliding Speed m/s Maximum Running Starting Temperature Less than 2.5 2.5 ... 5 More than 5 0ºC ...  10ºC -10ºC ... 0ºC 110 ... 130 110 ... 130 110 ... 130 0ºC ...  10ºC More than 0ºC 110 ... 150 110 ... 150 110 ... 150 10ºC ...  30ºC More than 0ºC 200 ... 245 150 ... 200 150 ... 200 30ºC ...  55ºC More than 0ºC 350 ... 510 245 ... 350 200 ... 245 55ºC ...  80ºC More than 0ºC 510 ... 780 350 ... 510 245 ... 350 80ºC ...  100ºC More than 0ºC 900 ... 1100 510 ... 780 350 ... 510

SECTION 21 GEAR NOISE    There are several causes of noise. The noise and vibration in rotating gears, especially at high loads and high speeds, need to be addressed. Following are ways to reduce the noise. These points should be considered in the design stage of gear systems.   1. Use High-Precision Gears - Reduce the pitch error, tooth profile error, runout error and lead error. -Grind teeth to improve the accuracy as well as the surface finish.   2. Use Better Surface Finish on Gears - Grinding, lapping and honing the tooth surface, or running in gears in oil for a period of time can also improve the smoothness of tooth surface and reduce the noise.   3. Ensure a Correct Tooth Contact - Crowning and relieving can prevent end contact. - Proper tooth profile modification is also effective. - Eliminate impact on tooth surface.   4. Have A Proper Amount of Backlash -A smaller backlash will help reduce pulsating transmission. - A bigger backlash, in general, causes less problems.

5. Increase the Contact Ratio - Bigger contact ratio lowers the noise. Decreasing pressure angle and/or increasing tooth depth can produce a larger contact ratio. - Enlarging overlap ratio will reduce the noise. Because of this relationship, a helical gear is quieter than the spur gear and a spiral bevel gear is quieter than the straight bevel gear.   6. Use Small Gears - Adopt smaller module gears and smaller outside diameter gears.   7. Use High-Rigidity Gears - Increasing face width can give a higher rigidity that will help in reducing noise. - Reinforce housing and shafts to increase rigidity.   8. Use High-Vibration-Damping Material - Plastic gears will be quiet in light load, low speed operation. - Cast iron gears have lower noise than steel gears.   9. Apply Suitable Lubrication - Lubricate gears sufficiently. - High-viscosity lubricant will have the tendency to reduce the noise.   10. Lower Load and Speed - Lowering rpm and load as far as possible will reduce gear noise.

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