Worm gearing . teeth surfaces, this formula does not seem to havemuch more than a theoretical value. Moreover, owing to theelasticity of the metals employed, and variations in the qualityof the lubricant, no reasonable figure can be assigned to K inthe equation. All that we can do, therefore, is to establishfrom experience an empirical value for the number of teeth incontact in its relation to actual performance, and deduce somerule from this, The author carried out the following experiment to ascertainthe effect of varying /? in a specific instance. An axle was taken fitted with a standard wo
Worm gearing . teeth surfaces, this formula does not seem to havemuch more than a theoretical value. Moreover, owing to theelasticity of the metals employed, and variations in the qualityof the lubricant, no reasonable figure can be assigned to K inthe equation. All that we can do, therefore, is to establishfrom experience an empirical value for the number of teeth incontact in its relation to actual performance, and deduce somerule from this, The author carried out the following experiment to ascertainthe effect of varying /? in a specific instance. An axle was taken fitted with a standard worm gear similarto many hundreds running in heavy commercial vehicles of theauthors design and giving eminently satisfactory results. Thegear was driven from a 50-H. P. electric motor running at aconstant speed, and an hydrarulic dynamometer was attachedto the other side of the gear, and adjusted to furnish a constantload (Fig. 21 A). The dimensions of the worm gear were asfollows: THE WIDTH OF THE WORM WHEEL 53. 6 54 WORM GEARS Worm: Number of threads 5 Pitch diameter <• in. Pitch circumference in. Length of worm 5 in. Lead 5. 9375 in. Lead angle 30° 11 Thread angle • 60° Length of thread per rev in. Rubbing speed p. s. Worm Wheel: No. of teeth 39 Pitch diameter , in. Pitch in. Subtended angle /3 (see table). The torque at the worm pitch line was kept constant at1990 lb. giving a normal tooth pressure of 4378 lb. The rubbing
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