Worm Qear Versus
Page 58
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the Hypoid APAPER entitled "Review of Developments in Driving Axles," a precis of which was given in our issue dated February 14, was read by Mr. E. B. Wilson, at the Institution of Mechanical Engineers on March 4.
The discussion which followed centred mainly on the respective merits of spiral-bevel drive and the hypoid gear. Dr. W. A. Tuplin, of David Brown's, was not by any means convinced that the hypoid gear was in any way superior to the worm and wormwheel type.
Mr. Wilson had suggested some form of standardization of differential gears, and it was generally agreed that this would be a good thing. Mr. Wilson said that there were now about 100 different types, and it should be possible to reduce these to about 10.
Regarding Mr. Wilson's remarks relative to two-speed axles, Dr. Tuplin wanted to know what the objection was to the incorporation of these gears behind the gearbox. Dr. Tuplin and Mr. J. G. Rackham, chief engineer of the Associated Equipment Co., Ltd., And others expressed a high opinion of worm drive, particularly from the aspect of its silence in operation. Comparing the respective values of wormgear drive and hypoid gears, Mr. Rackham said that whereas it was possible to arrange final-drive ratios of from 4.5 to 1 to 10.33 to 1 with worm drive in a given size of housing, the use of low ratios with the hypoid gear meant employing a casing which obtruded on the floor space.
• Mr. Rackham referred to trolleybuses which had covered 650,000 miles, and motorbuses 200,000 miles, with one worm and worm-wheel assembly. On the subject of axle-shaft splines, he said that, by providing ample ,radius at the bottom of the splines, the life of a shaft showed a 25 per cent. increase.
Mr. Wilson mentioned that the increased fatigue life of a gear of the hypoid type was claimed to be four to five times that of a spiral-bevel gear.