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# Rotate diffrent gears size teeth in each other

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 Rotate diffrent gears size teeth in each other on Mar 31, 2013 at 10:26:24 am

Hi There,

First of all, happy easter.

Like the subject mentioned i am having BIG trouble to get diffrent gears rotate in each other. Yes, i have read all te prevous topics, and they where very old, but i just dindt got the trick, maybe also because i am dutch and my reading and understanding in english isn't that good, to understand the technical things.

Yess, al my gears i designed are having the same size and space of teeth and gaps. I am working wit Ae Cs4, expressions isnt my thing, so i try to do it by hand and keyframes, but it just looks good.

Does anyone knows how it can be done in a easy way or explain it or have some where a video tutorial?

i am in a very short deadline, but the gears are killing me

Thank you...

 Re: Rotate diffrent gears size teeth in each otheron Mar 31, 2013 at 1:39:07 pm

So, without expressions:
If the diameters of the gears differ, you need to do some math to figure out how each gear rotates in reference to the one before. Select the initial gear and calculate based on the number of teeth how many full rotations you get on the next gear for one full 360 rotation on the first gear. For the exact number of teeth and diameter it should be 1 to 1. A smaller gear will rotate faster, thus you get 1.x times and a larger one slower, thus 0.x times. Then using this method you determine the ratio for the second and third gears and so on. Using the above you can start figuring out the values for the final keyframes on rotation for each wheel. If lets say you want the initial gera to rotate 3 times for the length of your comp, then based on the info you got previously you can calculate the amount of rotations for the second wheel:
3 x 1.X= Y rotations.
Then you can use this number and the initial calculation for the difference between the second and third gear ( let's say for 1 rotation of the second gear you determined that the third one rotates 2.Z times)
The data you have:
gear 2, 1 rotation - gear 3, 2.Z rotations
and
gear 2 rotates Y times (as per your calculation relating to the first gear rotating 3 times)
gear 3 final rotation = 2.Z x Y

And so on... it sounds pretty complex although it's not really, but I strongly suggest digging in expressions, it will make your life easier.

Tudor "Ted" Jelescu
Senior VFX Artist

 Re: Rotate diffrent gears size teeth in each otheron Mar 31, 2013 at 2:49:26 pm

Have you seen this tutorial - http://library.creativecow.net/articles/zwar_chris/cogs1.php

RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects ACE/ACI (version 7)

 Re: Rotate diffrent gears size teeth in each otheron Mar 31, 2013 at 2:51:19 pm

Chris Zwar updated his gears tutorials recently. Here's a link to the fresh version:
http://provideocoalition.com/pvcexclusive/story/create_and_animate_3d_cogs_...

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 Re: Rotate diffrent gears size teeth in each otheron Mar 31, 2013 at 7:33:22 pm

First off all,, thank you to every one who recponced.

Todd, i did watch the video's but he doenst explain how to rotate the gears together, i have made all my gears, because of his video's i founded. So thank you.

///

Tedd, thanks for the help. but i just dont gett the math..i all ready found on the Internet some way like you mentioned.. but i think i am just to stupid to understand.

////

For the rest of you all, also my thanks.. i will await the turorial
when it is done.. i hope you can sent me a link.. for now i'll try to make other way's the design.. but i know the gears need to be in the video, that is a MUST for the client.

Thank you for al your help, any other help is preciated.. if you think you can explain it in a simple way.

 Re: Rotate diffrent gears size teeth in each otheron Mar 31, 2013 at 4:59:50 pm

I am in the process of putting together a tutorial for expression driven gears that I have used on a recent project with a gear design element also. You create a cog by simply selecting how many teeth, and what the source is for rotating it.

If you want to change the shape of the teeth, the cog design element allows you to do this. Subsequent gears can be linked to the main gear and they will automatically orient and mesh to the parent gear and rotate accordingly., and placed anywhere around the parent cog. Very simple to use ad very flexible, BUT, I have not done the tutorial as yet, I won't have time until after Tuesday.

If this will be of use, and within your timescales, then let me know and I will knock up a quick guide mid week and post a sample project.

Declan Smith
After Effects CS6/ FCS3 / Canon 7D / Canon XL2 / Reason / Cubase

"it's either binary or it's not"

 Re: Rotate diffrent gears size teeth in each otheron Apr 1, 2013 at 10:33:13 am

Thank you all, once again.

I did find it like you al mentioned, i just didn't read wel.

Cheers and God bless you all!!

 Re: Rotate diffrent gears size teeth in each otheron Apr 2, 2013 at 8:07:38 am

I recently made some gears using the technique of a load of Vs along a circular path, similar to one of those old tutorials mentioned in this thread. Getting the speed of the gears correct is very simple. Don't worry about the diameter of the gears - it's actually irrelevant. All you need is the number of teeth per gear.

The rotation of "small gear" meshing with "big gear" will always be:
thisComp.layer("big gear").transform.rotation*-(20/15)

...where "big gear" has 20 teeth and "small gear" has 15 teeth. Put that expression in the rotation of the "small gear", change the "20" and "15" to the number of teeth of each gear, and you're done. If you want to drive a big gear with the rotation of a small gear, just swap the teeth numbers:
thisComp.layer("small gear").transform.rotation*-(15/20)

- Paul

 Re: Rotate diffrent gears size teeth in each otheron Apr 2, 2013 at 8:33:12 am

Thank you a lot.

It indeeds just works like you said, amazing things expression.

But i have another question.

Why does it only rotate for almost 3 sec, and than it stops??

What if i want to make it rotate for al longer or shorter period?

And maybe you can help me with this also:

Say i have on my screen from left to right a solid or rectangle and i put the letter V's in it so it wil have theet like a gear, but not round, but a straight line.

And say i have my roundgear coming out of the screen from left to right, and i want only my gear to rotate on the still image gear?
So it looks like my gear is rotating and rolling on the other.

How can i make the rotation work with the position from left to right so the theet will fit in eachother even as the gear rotate from left to right?

I hope you understand want.

Thank you again!!

 Re: Rotate diffrent gears size teeth in each otheron Apr 2, 2013 at 10:05:02 am

You'll have to link the rotation of the gear with its x-position:
1. Remove any expression from the gear's rotation, it there's one in it.
2. Alt-click the rotation and add this expression:
transform.position[0]

3. Move the gear left & right; it will rotate.
4. You'll probably have to modify the speed of the rotation; you can do this with a bit of guesswork; if it's going too slowly, add a multiplier on the end, for example to double the speed:
transform.position[0]*2

...or to make it rotate at 25% speed:
transform.position[0]*.25

You could alternatively add an expression slider and use that instead of the ".25" or "2" to give you a speed control slider.

- Paul

 Re: Rotate diffrent gears size teeth in each otheron Apr 5, 2013 at 8:34:08 am

Thank you once again.

it also works.

Just like you said it will need some adjustment, how ever.. i just cant get the theet fit in the wholes of the other gear... it rotates and moves good.. but what ever i try it just rotates and the theeth are falling instead of IN the other theet holes ON the other theethh..

grrr but thanks again.. your help was verrryyy usefull.