GearHeads Corner

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.

Hi John:

    Your stopped by the program at 4 teeth because at that point the formulas used turn into
singularities. I can picture your gear, it does sound very much like a worm gear rotated
90 degrees to be inline with its pinion.
    I cant help as of yet, but worm gears and cams are on my immediate future list. I never
offered them before as Gearotic was written back in the day before 3d printers were very
popular. Now, with Ticker, I've started the framework for a program to create 3d models
with no concern for how to make them as its output is only triangulated models. This makes
things much easier. I hope to see worm-gears this year as a module, but I cant as yet give
you a timeline.
    Your is an interesting point though and I appreciate your bringing it up, I hadn't really
thought of how one could rotate the action of a worm gear, in your case by 90 degrees.

  Ill keep this in mind for this years developments as well as things such as the sinusoidal
herringbones I saw posted earlier this week.

Art

Thanks Art, that's useful to know - and hopeful!  I can sort of picture how a pinion could be cut, using a 4th axis and a small endmill to gash then shave the teeth.  The article described experimental gears where the pinion was planed on a lathe driven through the leadscrew but the tooth form was highly non-optimal.

John:

  Yes, the toothform places quite a restriction generally.
Im playing with better ways. (Heres a recent test of a worm
configuration..)


Art

What does the flurry of sawdust at the end mean?  A bad parameter destroying the gears?

lol.. its actually a burst of fireworks as a particle test set to go off on a timer.. I was debugging it. :)

Art