Stepped motion between joints

[dorianfleury]

Hi there! 

I'm new to this forum so I hope I've posted in the right place.

I'm new to Fusion 360 (coming from Blender) so there's a lot I'm trying to understand and translate into that new word.

I'm currently trying to design a very simple watch movement to learn how it all works and I'm struggling to create "realistic" motions between my components. The basic gear trains are fine as it's just math and 360° revolutions but my problem is on the ticking part of the watch.

For those not familiar with the principle, there's a balance wheel that rocks back and forth with a pin that moves a pallet which creates the tick-tack. The are on separate axles and have movement limits. On my example, the pallet fork can rotate only by +5°/-5°. The balance wheel can rotate by approximately 300°.

My problem is that for it to represent the reality, the pin should push the pallet fork by 5°, the pallet fork is blocked in that position, the pin is released and continue its course for 150°, then swing back, pushes the pallet fork down by -5°, continue its course, etc...

I'm not sure if it's entirely clear what I'm trying to achieve but basically, the pallet fork should be in motion when the pin is "in contact" and then stay still for the rest of the balance movement.

I tried contact sets but they seem very unreliable as they keep jumping outside of the fork...

Is there a way to introduce those more "complex" motion links between the joints please?

Thanks a lot for your help!

[jhackney1972]

Please attach your model.  If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it. If needed, ZIP a F3Z file.

[dorianfleury]

Thanks @jhackney1972 , I have now attached the model.

To give more details, if you "Animate with joint relationships" the "pallet_beat", it should be pretty clear (You might want to use the Bottom view to see the pin that is supposed to move the pallet fork in action).

The pallet fork should be stopped by each banking pins, stay locked in place until the roller pin comes back.

Thanks a lot for your time!

[davebYYPCU · Accepted solution]

Motion Studies do that.

Pin rotates about 35 degrees, and the Fork goes 5 degrees, and then the fork position flat lines.

I would start the Motion study with pin at 150 degrees, fork in the correct position, and adjust from there.

Should be obvious that the pin strikes the corner point inside the fork, and I would not use splines for the clearance cut.

You should not need Move or Press Pull, when building in place.

You need to study up on Rule #1.

Might help.....

[dorianfleury]

Thank you @davebYYPCU !

I did see Motion study before but didn't understand how it worked and what it is used for. I did manage to create something that look somewhat realistic.

As you pointed at, nothing is exact yet, I'm just trying to get a good grasp of the mechanics behind the watch movement before diving more in details in the math and any exact values. I also use it as an opportunity to understand Fusion360 better so thanks for all the advice (I'll try to understand and remember that rule#1)!