What is this gearset called?

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Circlotron
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What is this gearset called?

Post by Circlotron » Sat Apr 18, 2015 11:51 pm

Not an automotive question but gear-related so I thought I'd throw it out there so some of you that understand the finer points of gear stuff might enlighten me.

Suppose you had two gear wheels joined side by side on a common shaft with the left one having 40 teeth and the right one 39 teeth. Same size teeth so the rhs one is smaller diameter. Then you have two gear racks with identical tooth pitch sitting side by side on the bench and our two gear wheels sit on them. The left one for 40 tooth wheel is nailed to the bench; the right one can slide free and is slightly higher to match smaller diameter of 39 tooth wheel.

Now suppose you roll the two joined wheels along the racks; every time they complete one revolution the free rack will slide along the distance of one tooth. Now say we wrap the racks into two side by side circles with the teeth on the inside edge so it looks sorta kinda like a planetary setup. Again, if we roll our gear wheels around the inside of the "carrier" gears, one fixed and the other free, we have a very great single stage reduction ratio between the rolling gears and one of the carriers.

I dreamed up this setup all by myself but someone *must* have though of it before. Does it have a proper name?

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Re: What is this gearset called?

Post by pdq67 » Sun Apr 19, 2015 10:48 am

A "hunting" gear set comes to mind IF I am using the term right??

Gears are done this way to let any tooth wear be divided between all teeth if not mistaken...

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Re: What is this gearset called?

Post by pdq67 » Mon Apr 20, 2015 4:48 pm

Well, am I right or not???

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Re: What is this gearset called?

Post by autogear » Tue Apr 21, 2015 11:25 am

Hunting gears are gear sets (pairs) that add up to essentially prime numbers; so that tooth A only contacts tooth B very infrequently. This lessens the chances of high NVH (noise vibration and harmonics). What the OP is describing may include that feature; but not necessarily.
As far as what the OP is describing; I passed it along to my boss George; I'll report back.

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Re: What is this gearset called?

Post by pdq67 » Thu Apr 23, 2015 8:58 pm

Thanks AG, will be looking for your comeback.

I miss this crap. I wasn't fortunate enough to have went to GMI instead of UMC here in town, (Columbia, MO), because my grades weren't all that good and once out of school I was too busy supporting my family..

I have been blessed because GOD created me to figure out how to make widgets, but alas, all that crap has been pretty-much out sourced.. Don't matter now anyway because I'm an ol' man and retired!!

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Re: What is this gearset called?

Post by Circlotron » Fri Apr 24, 2015 8:37 am

In this article -> http://en.wikipedia.org/wiki/Epicyclic_gearing I found the following statement:

"During World War II, a special variation of epicyclic gearing was developed for portable radar gear, where a very high reduction ratio in a small package was needed. This had two outer annular gears, each half the thickness of the other gears. One of these two annular gears was held fixed and had one tooth fewer than did the other. Therefore, several turns of the "sun" gear made the "planet" gears complete a single revolution, which in turn made the rotating annular gear rotate by a single tooth."

Similar basic principle to what I was saying except that one of the annular gears has one less tooth and uses a single wide planetary gear spanning both annulars.

Edit -> https://youtu.be/P-Obt-9tZVo

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Re: What is this gearset called?

Post by autogear » Wed May 06, 2015 9:08 am

I nagged George about this for awhile; and he said its a good idea, but it may not have a lot of reduction (which could be a bad thing or a good thing depending). Its not the most compact design either; but thats neither good nor bad...it just is.

As to what it "IS"; it seems to be more or less yours so you get the fun of naming it (The link above for the radar geartrain is very interesting).

Thanks for this, it was fun.

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Re: What is this gearset called?

Post by oldjohnno » Fri Jul 03, 2015 3:50 am

It's a stepped-planet compound planetary gearset. http://au.mathworks.com/help/physmod/sd ... ygear.html
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