A nubie needs HELP with gearing

#1

I believe this is something fairly simple, but I am just a novice & are having trouble figuring this out. Hers is my problem. I have 2 plates horizontal and parallel to each other, approximately 6" apart. They share a common pivot point equal distant from the top & bottom as well as left to right. What I’m trying to attempt is to have is to top plate rotate the same degree as the bottom except opposite. In other words. Using the right side as an example, If the lower right plate angles down 10 deg. the top right plate will rotate 10 deg. up. If anyone could help me using gears to have these plates pivot in equal amounts in opposite positive directions. ANY and all help and comments will greatly be appreciated. Thank You. Jerome.

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#2

Gears. You can use gears. Look up double-reverse 4-bar in this forum. They do what you are looking for.

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#3

Different rotation about a common axle, is what I’m taking away? Fasten one to a gear with green inserts, and the other to a sprocket with green inserts (so the gear and sprocket are free to spin on the shaft). Put another axle nearby with an identical gear and sprocket, but this time with the axle gripping inserts. Mesh the gears together, chain the sprockets together, and bam, 1:1 reversal with a common pivot. There’s probably better ways to do it, but that’s the quick and dirty way.

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#4

Just saw the reply and trying to understand the concept that you described. Confused about the green inserts?
Thank you for the response.

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#5

Will do.
Appreciate you taking the time to help.
Thank you again.

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#6

John, sorry to bother you BUT i’m not into robotics & don’t understand about using the double reverse 4 bar in my application. I have studying the concept since i got your message, It doesn’t seem to accomplish what i’m looking for. Could PLEASE give more details on the original reply of “Different rotation about a common axle, is what I’m taking away? Fasten one to a gear with green inserts, and the other to a sprocket with green inserts (so the gear and sprocket are free to spin on the shaft). Put another axle nearby with an identical gear and sprocket, but this time with the axle gripping inserts. Mesh the gears together, chain the sprockets together, and bam, 1:1 reversal with a common pivot. There’s probably better ways to do it, but that’s the quick and dirty way.”
I don’t understand on how to accomplish this.
SORRY, i’m just frustrated. EXTREMELY!
I have trying to accomplish this for a month or so, day and night. Glad i’m retired & have the time.
Thank You
Jerome

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#7

If you notice, I’m not actually the one that suggested a DR4B. @Rick_TYler probably suggested it because it uses a similar concept at its elbow joint, with the difference of not sharing a common pivot.

The leading question on my post was asking you for more information on what you were trying to accomplish. Are both of these pieces meant to rotate in different directions (one clockwise, one counterclockwise) on the same axle? Or can they be on different axles? If they can be on different axles, you can ignore the bits about inserts. If they can be on pivots even half an inch apart, you can ignore the bit about a chain. Can you clarify the design constraints for me?

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#8

Sorry about the identity error. YES i’m trying to rotate the bottom in the exact same amount about a commor rotation point. Example - If the bottom right point goes down 20 degrees the top right goes up 20 degrees and vs. vs. PLEASE refer to my original sketch. If you need more info I would be glad to get it for you. The part about the same or different axles are irrelevant to me just so they pivot equidistant, opposite from each other.
Thanks again
Jerome

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#9

Awesome, exactly what I was looking for.

The thing about inserts was a thing that can be done with Vex gears: some gears in the kit have big holes through the center, larger than the standard 1/8" axle. For those gears, they come with inserts that fit the big hole and adapt to the 1/8" axle. There are two varieties, the green ones that don’t grip the axle, and so let the gear spin independently from it, and the gray metal ones that engage the axle and make the gear turn with it. If you want two things spinning in different directions on the same axle, at least one of them needs green inserts or another way to avoid engaging the axle.

To reverse the direction of rotation, you need a 1:1 gear mesh. That doesn’t end up on the same axle, though, so to transmit it back to the other thing to rotate you’d need something that transmits power but doesn’t reverse rotation: a chain and sprockets.

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#10

Thanks for the rapid response. I’m going to try to understand the concept.
I really appreciate your patience with me, although I have using drafting software forever, I never got involved in gearing, let alone an impossible one.
Is there anyway possible to send me a link that has Vex gears. I will research it as soon as i understand what you are trying to explain.
SORRY for being a pain!

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#11


These are the chain gears (and you can see the green inserts)


And here we have the high-strength gears and more inserts.

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#12

Wow. You want a common pivot point , not axis? And mirrored movement around that point? Sort of a reverse helicopter control rod and swash plate assembly? Crossing (“reversed”) linkages gets complex. Perhaps you need to invent and 3D print 3" hemispherical gears, the “teeth” concentric circles around the common normal pivot… With elastic connection through normal pivot point, like tendons in the middle of our knees… Would need a way to prevent twisting.

What causes one plate to tilt? External force, or does it need to be a motor/servo?

How big are the plates? What material?

Nice drawing.

Later edit: Oh. Axial constraint.

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#13

i think you could do something similar to this:
Test
The 1 By’s have joints on them, with one joint on the gear and the other on an arm. The two 1 By’s length will be the exact same so the arms both turn the same amount.

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#14

THANK YOU for the info!
Jerome

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#15

Interesting. I believe i will study this.

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#16

A more detailed sketches of my dilemma. Maybe this additional drawings would help.

image

image

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#17

Are these drawings your given exercise? Or a partial solution? Questions,

  1. The plates do not seem equidistant from common axis.
  2. Is the lower gear is fixed to the red bracket and the upper gear fixed to the green bracket, or are they free to turn? It seems the intention is all fixed, except green bracket pivots on lower axle.
  3. Movement of both plates would need to be in reference to an external stationary mount point, otherwise the problem is moot.

Is there more info available?

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#18

Hey, @ProStreet how many degrees do the plates have to rotate?

What are the forces that you expect on those plates?

If you tell us what you are trying to build at the end it will save a lot of time for everyone.

If you already have something that you need to work, why do you think vex parts are you best choice?

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#19

Interesting idea for several uses, but wouldn’t the mechanics be more like this:
Untitled-2-Recovered
?
Or a linear slide.
I think your sketch will keep the plates parallel as they move.

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#20

They need to rotate approximately 13 deg. from the horizontal plane.
That being said, this means if the top rotates CW 13 deg,
the bottom needs to rotate CCW 13 deg.
Of course that means between the top and the bottom it will be a 26 deg. total.
The only reason i was considering using the vex gears as to build a working model before i build the actual project.
I can modify my materials as depending on the forces.
FYI this is just a challenge i gave myself quite a while ago.

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