I'm designing a hand operated lifting mechanism using a crossed axis helical gearset with a 40:1 ratio. As this gives a point contact, the compressive stress on the tooth surface is in the neighborhood of 200 ksi, and I'm having difficulty reducing this. Some things I've tried:
(a) increased the O.D. of the driven gear to the maximum allowed, 4.5 inches, by increasing diametral pitch.
(b) made sure the contact ratio is over 2.
Typically we've used a steel (not heat treated) worm with a gray iron gear, but I'm afraid this will wear very prematurely. The gearbox is open with the possibility of running dry.
Is there any way to get this stress down, or will the gear wear to a point and then stop? Does this merit a change to a true worm gear? Any material suggestions are appreciated as well.
(a) increased the O.D. of the driven gear to the maximum allowed, 4.5 inches, by increasing diametral pitch.
(b) made sure the contact ratio is over 2.
Typically we've used a steel (not heat treated) worm with a gray iron gear, but I'm afraid this will wear very prematurely. The gearbox is open with the possibility of running dry.
Is there any way to get this stress down, or will the gear wear to a point and then stop? Does this merit a change to a true worm gear? Any material suggestions are appreciated as well.