Any reliance you place on such information is therefore strictly at your own risk.The worm is similar to a screw and the worm wheel is similar to a section of a nut.As the worm is rotated the wormwheel is caused to rotate due to the screw like action.If the worm gears are machined basically as crossed helical gears the result is a highly stress.
The ideal combination of gear materials is for a case hardened alloy steel worm (ground finished) with a phosphor bronze gear. Other. This standard is current (2004) and provides information on tooth form, dimensions. If the heat lost to the environment is insufficient then the gears should. Relationship between the output torque M 2 and the input torque M 1. Table x 1,33 Quenched Steel and Aluminum Alloy.Table x 1,33 Steel and Steel.Table x 2 Friction coefficients - For Case Hardened Steel Worm Phos Bros Wheel. It is the moment when gearing cannot be moved using even the highest possible torque acting on the worm gear. The self-locking limit occurs when the worm lead angle ( ) equals atan ( ). It is often considered that the static coefficient of friction is most relevant as the gear cannot be started. However. Metric units. BS721 provides average design values reflecting the experience. The methods have been refined by addition of various application. See Table below l f.2 length of root of Worm Wheel tooth d 2 Reference diameter of worm wheel m axial module Lead angle. Radius of the root R r d 1 2 h ha,1 ( m) c( 0,25.m.cos ) R r d 1 2 m(1 0,25 cos ). The torque on the wormwheel as calculated using the duty requirements (M e ) must be less. For loading other than this then M e should be modified as follows. Z L 1 if correct oil with anti-scoring additive else a lower value should be selected Lubricant (Z M ). Z R 1 if Worm Surface Texture m else use less than 1 Tooth contact factor (K C This relates to the quality and rigidity of gears. Use 1 for first estimate K C 1 For grade A gears with 40 height and 50 width contact 1,3 - 1,4 For grade A gears with 30 height and 35 width contact 1,5-1,7 For grade A gears with 20 height and 20 width contact Starting factor (K S ). Worm Gear Calculation Formula Driver And DrivenK H for 27000 hours life (10 years) with uniform driver and driven loads For other conditions see table below. The table below allows selection of q value which provides a reasonably. The table has been produced by reference to the relevant plot in BS 721 Example If the number of teeth on the gear is selected as 45 and the centre distance is 300 mm. AGMA is all imperial and so I have used conversion values so all calculations can be completed.
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