"Helical lever"
Posted: Tue Mar 23, 2021 10:43 pm
I have just been reading in a horological publication about the use of this configuration in a series of 19th century clocks. Essentially it describes a wheel / pinion configuration using helical teeth, where the pinion had a veryu low tooth count, usually 1! The advantage claimed is that you can make a pair of gears with a large reduction in one step, with low, essentially rolling friction. The pinion looks like a corkscrew and the wheel thickness must be at least the pitch of the helix. Helix angle was usually 45 degrees.
I had a quick try at designing a pair of gears like this in Gearotic but it didn't let me set the pinion tooth number lower than 4 - is this a programmed limit or can it be made smaller please?
Such gears would be nice because often in a clock you want a 60:1 ratio which is difficult in a single step because lowest practical pinion count of 6 or 8 so the wheel gets rather large, so usually a 2-step reduction is needed. Also, helical gears should contact only at the mutual pitch points, so might use straight flanks at an appropriate angle so be easy to make.
I had a quick try at designing a pair of gears like this in Gearotic but it didn't let me set the pinion tooth number lower than 4 - is this a programmed limit or can it be made smaller please?
Such gears would be nice because often in a clock you want a 60:1 ratio which is difficult in a single step because lowest practical pinion count of 6 or 8 so the wheel gets rather large, so usually a 2-step reduction is needed. Also, helical gears should contact only at the mutual pitch points, so might use straight flanks at an appropriate angle so be easy to make.