"Helical lever"

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JohnHaine
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"Helical lever"

Post by JohnHaine »

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.
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ArtF
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Re: "Helical lever"

Post by ArtF »

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



JohnHaine
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Re: "Helical lever"

Post by JohnHaine »

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.
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ArtF
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Re: "Helical lever"

Post by ArtF »

John:

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


Art
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Mooselake
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Re: "Helical lever"

Post by Mooselake »

What does the flurry of sawdust at the end mean?  A bad parameter destroying the gears?
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ArtF
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Re: "Helical lever"

Post by ArtF »

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

Art
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