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Problems with Rack & Gear Constraints

Jake_Steidy

Senior Member
Hello Everyone,

Curious if any other users that have been utilizing rack and gear constraints have had any issues? Specifically I am utilizing a rack and gear system to try and verify size and dimensions of parts for a damper and I have to suppress constraints to reset gears to be meshing properly. This happens with both gear to gear and gear to rack constraints.

Then when I unsuppressed the constraints the racks shoot down the gears without any rhyme or reason. I don't know if there's something I am doing incorrectly, but it has happened honestly since these constraints were implemented. I have worked around them by getting lucky and suppressing and unsuppressing 10's of times to get an assembly where I need it to be.

I do really like the addition of the mechanical constraints, I just wish they weren't so wacky in their implementation. I could very well be doing something wrong and please let me know!

Have a great day,
Jake
 

Ken226

Alibre Super User
Can you upload a package file of the assembly thats giving you trouble.

I havn't had any trouble from the gears.

Just remember for rack and pinion, youll usually be selecting the "reverse relative rotation" checkbox.
 
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Ken226

Alibre Super User
Here is an example I whipped up. The Package file is attached so you can open it and look at my constraints to see what I did:

And a link to Alibre's help section on the subject.


Motion:


For the Pitch Diameter, I entered the gears diameter at the point the pinion tooth contacts the rack tooth. I've little doubt that Alibre multiplies this value times Pi to determine theoretical circumference, to control the distance the rack should translate per rotation of the pinion gear.
As shown here:


1654738130861.png


1654738303666.png



1654739803917.png
 

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Jake_Steidy

Senior Member
Hey Ken,

Yeah I am familiar with how the constraints are used, my problem is that I am setting numerous positions and utilizing gears interlocking in a system and when I suppress to set a gears relative position to another or to a rack and the un-suppress the constraint it changes the position of the gear or the rack randomly. I will take a short video to detail what I am experiencing.


Best,
Jake
 

DavidJ

Administrator
Staff member
It isn't clear from your video clip which items the constraints are acting on. With a single rack & pinion, I can suppress the constraint to re-position the rack and nothing jumps when I un-suppress it.

Maybe something specific to your combination of constraints. Can't investigate any further without your model.
 

Ken226

Alibre Super User
Its working fine for me. Nothings jumping at all.

I moved the gears into mesh, then unsuppressed your suppressed gear constraint, and they appear to all be aligned and in mesh.

1654786719177.png
 
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Jake_Steidy

Senior Member
Hey Ken thanks for testing it, I don't know why your unable to generate the random movement. Attached is another video showing me un-suppressing 2 constraints without movement, then doing 2 more and having them shoot the rack arm up twice.

From your video there are 4 more gear constraints that would be unsuppressed in the final version, which were the 4 I unsuppressed in my video, that allow the blades to rotate with those shafts 1:1 ratios.

Don't know if there's much more you can investigate if your able to get it to work successfully, might be something support has to look at.


Best,
Jake
 
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