Two gear-wheels have teeth of 5 D.P., angle of obliquity 20°, the numbers of teeth being 15 and 20. The addendum is the same for each wheel and is as large as possible while avoiding interference.
Find
(a) the length of the addendum ;
(b) the contact ratio ;
(c) the sliding velocity at the first point of contact when the smaller wheel is driving at 3500 r.p.m.