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Involute gears are great. They are designed so that the
force from the drive gear is always pushing the driven gear
in the same direction.
The surface of the drive gear slides/rolls across the
surface of the driven gear.
My idea is to stick a roller bearing in between the gear
teeth to
reduce friction.
The bearing would be actually be a trolley of three
bearings connected together as shown in the linked
Veritasium video.
The trolley would be attached to a spring. The trolley
starts at the bottom of the gear tooth. As the gears move
the trolley moves up the tooth, tensioning the spring.
When the trolley gets to the top of the tooth it is no longer
held between the teeth of the two gears, and the spring
pulls it back to the bottom of the tooth.
Instead of a trolley attached to a spring on each tooth, it
might be possible to have just a pair of trolleys somehow
connected such that they travel from one tooth to the next
such that one trolley was always at the touching point
between the two gears.
This might be useful in big gears, where friction and wear
are significant problems.
Animation of involute gears
https://i.redd.it/0aathzyjbwt71.gif
[xaviergisz, Oct 17 2021]
Veritasium video
https://youtu.be/yCsgoLc_fzI?t=13m40s
[xaviergisz, Oct 17 2021]
https://en.wikipedi.../Recirculating_ball
[pocmloc, Oct 17 2021]
https://en.wikipedia.org/wiki/Ball_screw
[pocmloc, Oct 17 2021]
[link]
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As far as I can remember (been a while since I studied...), the
point of the involute is that the surfaces DON'T slide; they roll
together smoothly (in a perfect world, of course). Not sure
about HELICAL gears. Maybe 3D print a couple of large scale
gears to experiment with.
There are similar weird transmissions like the cyclo-drive,
that sort-of do this in a different way (all contacts are rollers,
IIRC). |
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With proper lubrication, there is always a thin layer of oil or
grease so metal-on-metal contact never occurs between the
moving surfaces. |
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I like the idea, but I think there is a detail that will make
this not work. When contact first happens (dot on blue
double arrow in the first animated .gif link is at the highest
position), the surface of the upper gear is moving to the
right relative to the lower gear. So presumably a trolley
similar to the one in the second link (and the same
orientation) could be constructed that would move at the
right rate and stay at the point of contact. But wait, as
the point of contact moves toward the center, the relative
speed of the two surfaces decrease, even though the
point of contact continues to move. When the contact
point is half way between the gears, there is no sliding,
just rolling. As the contact point moves farther right (and
down), the relative motion is actually reversed: the surface
of the top tooth is moving left relative to the surface of
the bottom tooth, so our trolley in the original orientation
would want to move left, even though the contact point is
still moving right. |
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I'm afraid you need a trolley with independent rollers top
and bottom and some mechanism to move it to keep it
lined up with the contact point. This is not impossible
since the contact point does move along a straight line as
shown in the animation, but it will be a bit more
complicated than your idea. |
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That is some fine analysis [scad mientist]. This already overly
complicated idea has now been shown to be quite
impractical! |
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It might be possible to salvage this idea by using gears with
straight/flat triangular teeth. The trolley acts as an
intermediary to keep the force smooth from the driving to
driven gears. |
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