How to Animate Gears in a Clock

[kencondal]

Hi All,

I'm building a clock and am having a very difficult time creating motion that respects the gear ratios. I have extracted the hour and minute hand portion of the clock as seen in the photo below. The red items represent the minutes and the arbor poking out behind the frame will be driven such that the minute hand completes a 360 degree rotation every hour (naturally!). The blue parts represent the hour hand and must rotate 360/12 = 30 degrees when the minute hand rotates 360 degrees. The yellow and green gears in the actual clock implement the 12x stepdown for the hour hand (the blue parts are free to rotate on the red parts).

My attached project attempts to do this by creating three motion links.

1. Red gear to red arbor - 360 deg to 360 deg

2. Red gear (20 teeth) to yellow gear (60 teeth) - 360/20 deg to 360/60 deg

3. Green gear (16 teeth) to blue gear (64 teeth) - 360/16 deg to 360/64 deg

If you look at the attached project you'll see that the motion is bizzare and bears no resemblance to what I'm trying to do. Any help would be greatly appreciated.

Oops! The forum is telling me the project is too large to upload. How can I share it with you?

Thanks,

Ken

[TannerReid]

Hi, Ken!

I'm happy to take a look at it!  In fusion, you can right-click the file in the data panel, and choose "Share Public Llink."  That will provide a link to the project so that I can download it.  Just make sure you choose the option that allows others to download, and paste the link here and I'll take a look. 

Thanks!
Tanner

[kencondal]

Thanks Tanner!

Here's the link: http://a360.co/1PGXDtU

Ken

[TannerReid]

Awesome. I'll take a look!

[TannerReid]

Hey Ken,

So, I took a look and it looks like that hour group is somehow connected to the minute group in a way it shouldn't be - almost like rigid group behavior.  I couldn't find out exactly why, but I was able to see that when one of the revolute joints (between the arbor and the hour component) is suppressed, the rest of the assembly worked fine.  So, I just deleted that one, and made a new as-built joint between the hour shaft and the inner wall of the hole that was going through the frame.  I made it revolute, and it now moved freely.  Then, I just added a motion link between this new joint and the joint of the yellow gear.  Here's a screencast of the fix (I think it's about 2mins long): http://autode.sk/1N4I1Tu

And here's a link to the working Fusion File:  http://a360.co/1IzkAtH

Sorry I couldn't pinpoint exactly why that revolute joint was giving us trouble.  It's likley connected somewhere else in the file that we couldn't catch.  But as a general rule, I just try to locate where the issue is happening, and do something (sometimes arbitrarily) to change the conditions.  In this case, it was redefining that joint with another geometry (the frame, rather than the arbor, which I assume is the place that was getting us caught up).

Let me know if it still isn't working for you!

Enjoy,

Tanner

PS - thanks for naming everything so well!  It was very easy to navigate the file.  I treid to keep the naming convention in the fixes.

[kencondal]

Hey Tanner,

Thanks for the quick response! I've implemented your changes in my larger model with the rest of the clock parts and everything looks good. I had a similar problem in the larger model and converting it to an as-built joint fixed that as well. Both problem areas involved a revolute joint attached to a second revolute joint. As someone who has been writing computer programs since the days of paper tape, I'd say there's a bug. My gut says you should have someone in development take a look.

Although the hands are working now, they're not aligned properly. When the minute hand is at 12 o'clock, the hour hand should be pointing at an hour. Is there a way to align both hands at 12 o'clock as an initial starting position?

Thanks again,

Ken

[TannerReid · Accepted solution]

Hey Ken,

No problem!  Glad it worked - and I'll definitely be sure to forward the bug along.

So obviously, to move the component, it'll move both the hour and minute hand b/c they have that motion link.  So what I'd do (screencast below), is move the timeline back right before the motion link was made.  Then, I'd make sure there's some geometry that I can use to align it exactly up and down.  In the screencast, I made a midplane within the component of the hour hand (thinking back, the hand probably already had a plane that would have worked in its origin).  Then selected it and the global corresponding plane to align-component them.  Then, I just moved forward in time to the point after the motion link is made, and it should be set.

Screencast:  http://autode.sk/1KpuBkw

Let me know if that doesn't fix it for you or you encounter any troubles with it.

Thanks!
Tanner

[kencondal]

Hey Tanner,

You're a real magician with this stuff!

I'm new to Fusion and haven't done much with the timeline until now. Changing the past without a Delorean is really powerful and I'm starting to appreciate it now.

Thanks for your help,

Ken

[TannerReid]

No, problem, Ken!  

Any time.

Thanks for reaching out - the timeline is definitely my favorite feature in Fusion!

Enjoy,

Tanner