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Assembly vs. Motion Study Gear Motion + Interference

Question asked by Lauren Smith on May 10, 2014
Latest reply on May 10, 2014 by Jared Conway

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Hi all,

I am currently dealing with a gear train design that has a central gear and then three trains composed of three additional gears (per train) that stem from that (almost resembling a Y shape). In my assembly, when I drag the central gear, all the gears rotate. In the motion study, the last two gears furthest from the center do not rotate for two of the three trains.

Is there any simple explanation for why this might occur? I have checked my mates and don't know what the problem could be.

Additionally, my gear teeth all intersect in the animation. Is there any way I can keep my gear mates but prevent this from happening?

There are a number of componenets in the assembly, so I don't know if it would be approrpiate to upload the assembly + all the part files here, though I will gladly do so if someone is willing to take a look.

Thanks in advance!

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Jim Boland May 10, 2014 3:29 PM

First issue, final gears not rotating. The first thing to check is the stroboscopic speed of the gears that you think are not rotating. In most problems like this the gears are in fact turning, but as they are turning such that the teath are in the same position at each frame, it looks like they are not rotating. Change your framerate slightly and see if they rotate or change the rotational speed of the driving gear slightly and see if the gears are in fact turning.

See: Creating Animations using SolidWorks, starting page 473

Second issue, teeth interference. You have to manually move all the gears at time zero to the correct relative positions and update the keys. Move the time bar to zero. In the Motion study, start with the central gear and work outward toward the end of the trains. Suppress the first mate and drag the follow gear so that the teeth do not intersect and then unspress the mate. Select the position key for the follow gear and click Update Key. Repeat through all the gear mates.

Reference: Creating Animations using SolidWorks, starting page 497

If those do not solve your problem, then you should upload your assembly and parts.

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Jim Boland @ Jim Boland on May 10, 2014 3:33 PM

One other way to check the rotation of gears is to make one tooth a different color so even if the gear looks like it is in the same postion, seeing the colored tooth in different postions will tell you it is moving. Another way is to put a feature on the gear hub, like a logo. This may show the rotation even if the teeth are in the same positions.

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Lauren Smith @ Jim Boland on May 10, 2014 3:55 PM

So I think the frame rate is the problem, but it seems like the frame rate doesn't fix this for all of the gears. Would you mind taking a look if I upload the files? How should I go about uploading all of the components since this forum only allows five files?

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Jim Boland @ Lauren Smith on May 10, 2014 6:38 PM

In SW, use Pack and Go and save the assembly and files as a single zip file.

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Jared Conway May 10, 2014 10:08 PM

high level question here, do you want to animate or simulate? i can't tell and this would affect the way to troubleshoot your questions/issues.

from a troubleshooting perspective you've done the first step which is to make sure things drag properly

the next would be to make sure if you create a motion motor that it rotates properly in an animation

then you can try moving to soliworks motion for a simulation but remember that the gears are only connected with mates, they don't actually interact like gears

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5 Replies

Jim Boland May 10, 2014 3:29 PM
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First issue, final gears not rotating. The first thing to check is the stroboscopic speed of the gears that you think are not rotating. In most problems like this the gears are in fact turning, but as they are turning such that the teath are in the same position at each frame, it looks like they are not rotating. Change your framerate slightly and see if they rotate or change the rotational speed of the driving gear slightly and see if the gears are in fact turning.

See: Creating Animations using SolidWorks, starting page 473

Second issue, teeth interference. You have to manually move all the gears at time zero to the correct relative positions and update the keys. Move the time bar to zero. In the Motion study, start with the central gear and work outward toward the end of the trains. Suppress the first mate and drag the follow gear so that the teeth do not intersect and then unspress the mate. Select the position key for the follow gear and click Update Key. Repeat through all the gear mates.

Reference: Creating Animations using SolidWorks, starting page 497

If those do not solve your problem, then you should upload your assembly and parts.
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- Jim Boland @ Jim Boland on May 10, 2014 3:33 PM
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  One other way to check the rotation of gears is to make one tooth a different color so even if the gear looks like it is in the same postion, seeing the colored tooth in different postions will tell you it is moving. Another way is to put a feature on the gear hub, like a logo. This may show the rotation even if the teeth are in the same positions.
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  - Lauren Smith @ Jim Boland on May 10, 2014 3:55 PM
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    So I think the frame rate is the problem, but it seems like the frame rate doesn't fix this for all of the gears. Would you mind taking a look if I upload the files? How should I go about uploading all of the components since this forum only allows five files?
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    - Jim Boland @ Lauren Smith on May 10, 2014 6:38 PM
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      In SW, use Pack and Go and save the assembly and files as a single zip file.
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Jared Conway May 10, 2014 10:08 PM
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high level question here, do you want to animate or simulate? i can't tell and this would affect the way to troubleshoot your questions/issues.

from a troubleshooting perspective you've done the first step which is to make sure things drag properly
the next would be to make sure if you create a motion motor that it rotates properly in an animation
then you can try moving to soliworks motion for a simulation but remember that the gears are only connected with mates, they don't actually interact like gears
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Assembly vs. Motion Study Gear Motion + Interference

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