Something wrong with my gear assembly - can't create gear relation

will_parker589

Hi community,

I am very new to this but so far I've managed to create some spur gears with sprockets attached and create an assembly where they are all correctly depthed and revolve around their axles.

I can't seem to create a gear relation however.  I managed to do this with a youtube tutorial where I just placed simple pair of gears together and define the ratio and get a good articulation and animation (including how to align the teeth).

In this case despite the different gears being able to be revolute manipulated individually I can't seem to add anything to a gear relation dialogue.

When I create the gear relation and I need to add the two gear mates I cannot click on anything at all that selects.  I can't select the gears from the left assembly parts or by clicking on them in the assembly drawing.

It just always wants me to add "Mate(s)"

billy2

holy smoke!

I might not be the guy to answer this question for you, I'm very picky about assembly structure and how they're put together. 

My goals are to open an assembly and understand easily what's going on. 

You have 4 moving parts and 16 mates. A lot of your mates are just for static positioning.


You can group items with your fixed part and omit most of your mates. The problem with grouping is their position won't update with changes. To fix this, I start moving things into sub-assemblies which do update as changes occur. Since OS inherits mates from sub-assemblies, my structures are fairly deep. What I'm going for is a structure that'll allow me to open an assembly and quickly understand it's motion. Building up simple assemblies I'm finding allows me to create large projects with motion in a meaningful way.

I'd expect to see something like below for this assembly.


I ask myself what moves in this assembly? That's what I expect to see in an assembly.

Assembly structures are hard to follow in most CAD systems and many times I end up deleting the structure and starting over especially on stuff I get from other people. Onshape is unique in that the assemblies can be broken up allowing us to build structures that are easily understood.

If you're just starting out, which I think you are, you're probably just trying to the thing to work and my discussion might be too much.

The anchor, I don't know that it'll ever move correctly because it needs be to a contact. Tangent mates & contact mates are different. Onshape doesn't have contact mates which I think you'll need to make this tic-tock.

Like I noted previously, I'd probably change the grouped "fix" to a sub-assy because I can get a sub-assy to update properly when changes come along. But starting out, just group the static stuff with a fixed part.



 

John_P_Desilets

Hello @will_parker589. Welcome to the forum. Please share your document as public and post the link here. This will give us all a better understanding of the issue you are having. Here is a link to the forum post checklist. 

https://forum.onshape.com/discussion/9107/forum-post-checklist-read-this-first#latest

billy2

@will_parker589

Debugging an assembly isn't fun. I suppress one mate at a time until I get movement. When I find the offending mate,  choose another mate that's less restrictive. It's usually a constraint in a different direction that's creating the error, it's always a constraint I didn't think of and OS has always been right. ie.. many times I'll have a revolve when I should have a cylindrical. The cylindrical removes a translation constraint from the stack allowing the kinematics to solve.

And, like @John_P_Desilets says, it's easier to help if you share.

will_parker589

I was trying to share the public link but it’s not publishing my replies or edits for some reason. Trying this on the mobile browser. 

https://cad.onshape.com/documents/3b52677f546a824ab450d8e7/w/aec6629973b7f76b479b2827/e/762f54dc4567d6b43fd45b19

billy2

holy smoke!

I might not be the guy to answer this question for you, I'm very picky about assembly structure and how they're put together. 

My goals are to open an assembly and understand easily what's going on. 

You have 4 moving parts and 16 mates. A lot of your mates are just for static positioning.


You can group items with your fixed part and omit most of your mates. The problem with grouping is their position won't update with changes. To fix this, I start moving things into sub-assemblies which do update as changes occur. Since OS inherits mates from sub-assemblies, my structures are fairly deep. What I'm going for is a structure that'll allow me to open an assembly and quickly understand it's motion. Building up simple assemblies I'm finding allows me to create large projects with motion in a meaningful way.

I'd expect to see something like below for this assembly.


I ask myself what moves in this assembly? That's what I expect to see in an assembly.

Assembly structures are hard to follow in most CAD systems and many times I end up deleting the structure and starting over especially on stuff I get from other people. Onshape is unique in that the assemblies can be broken up allowing us to build structures that are easily understood.

If you're just starting out, which I think you are, you're probably just trying to the thing to work and my discussion might be too much.

The anchor, I don't know that it'll ever move correctly because it needs be to a contact. Tangent mates & contact mates are different. Onshape doesn't have contact mates which I think you'll need to make this tic-tock.

Like I noted previously, I'd probably change the grouped "fix" to a sub-assy because I can get a sub-assy to update properly when changes come along. But starting out, just group the static stuff with a fixed part.



 

billy2

Richard Doyle is holding a users group meeting that might be beneficial, I can't make it but I'm sure there will be discussions on how to get started.

https://forum.onshape.com/discussion/16549/making-things-move-onshape-user-group-meeting-august-17th#latest

 

billy2

As far as lining the teeth up, suppress the gear relation, move to the desired position, then un-suppress the gear relation. 

You could also use a layout sketch from a partstudio and align the gears to the layout. If you do this approach, I'd probably insert mate connectors at certain point to highlight the gear attachment points. Using a sketch in a part studio to drive your design/assembly is good practice especially if you want to control changes to your design.

There's dozens of "timing" techniques, probably referring back to a part studio layout sketch is the best.

will_parker589

Thank you so much Billy2. Yea I am completely new to OnShape and modelling in general. I got far enough with SolidWorks to be able to make the clock going-train work but that was with it’s surface simulation or contact detecting or what ever - so the anchor and escape wheels worked as I’d hoped and i get that OS only does a calculated simulation based on relations between gears and other constraints. 

I appreciate your methods and am far away from being able to do that. 

Actually I’ll try some alternative methods to ensure my parts are likely to work and 3DPrint them to test in the real life. 

I can see that the journey is necessarily long and rushing to a relatively complex assembly like this in my first few weeks of OS is unrealistic. 

Thanks again for the support and insight. I’ll try to absorb as much of your approach as I can and continue to learn!