Motion constraints

[Mr_iso]

The attachment shows a wobble plate assembly that utilizes a gear set for timing during rotation. The rear gear with the key is fixed to a housing. During rotation of the front shaft the angled rotor and wobble plate revolve around the fixed gear with a ball bearing in the center providing a bearing surface via slight spring pressure. This action turns rotary motion into linear motion thus driving push rods and pistons that are not shown. I attempted to attached a working model of this for better illustration and clarity but discovered the system has limits. One motion constraint is all I'm lacking from having a complete working model. I've tried all the constraints, motion constraints and even contact sets but can't find any combination that will keep the gears meshed when roating the shaft. Not sure if I setup contact sets properly or not. It would not allow me to do so in the main assembly. The wobble plate with gear & other items are a sub-assembly and I was forced to open it to apply. This attempt still didn't work. Any suggestions or ideas would be appreciated.

Thanks in advance!

[JDMather]

Do you have Dynamic Simulation (Inventor Professional)?

Roll up the EOPs.

Save and zip the files.

Attach the assembly here.

[Mr_iso]

I don't have Inventor PRO. What is the largest size file that I can send? Will a shrinkwrap version suffice if I can get it downsized enough or will that blow out all constraints?

[Curtis_Waguespack]

Hi Mr_iso,

As JDMather mentioned, you can use the End Of Part (EOP)  marker to shrink the file size. Just drag it up to the very top of the tree and then save the file in that state. Do this for each file. Then add all of the files to a zip file and upload the zip file.

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[Mr_iso]

Hi Curtis:

Attached is the zip file with the part files reduced as requested.

[JDMather]

Do you know the pitch cones between the two gears?

I suspect the solution would be a Motion constraint between the pich cones.

I usually create these as surface bodies in beveled gear sets.

I don't have time to derive them as they are not in the files already.

[Mr_iso]

I modeled the gears from ACAD drawings provided by our sister company that just happens to be offshore and incidentally all text is in a foriegn language. I see what might be the pitch cone you are asking about on the drawings. I will experiment with this and attempt the constraint you mention. Thanks for your help.

P.S. Pursuant to the subject of language translation, last year I posted on this board inquiring about the ACAD Mech. langauge translator feature for the purpose of reverse translating a drawing so that I can read our sister companies drawings. I'm not sure my question was fully understood because the replies I got were instructing me on how to translate text as I would be placing it on the drawing. That's not what I need. I want to take the drawings with the foreign language, translate it so I can read it. Is this possible in ACAD Mech?

[JDMather]

If you use the Gear Generator Design Accelerator you will see the pitch cone surfaces and Motion constraint that is automatically created by Inventor when you use the gear generator.

[Mr_iso · Accepted solution]

After much diligence I was finally able to make this work. I think it worked the 1st time I tried contact sets but I got no movement when I grabbed the rotor for rotation and gave up on it. After suppressing many features on the parts, moving my files to an isolated drive to eliminate network issues, the contact set feature will keep the teeth in time. Apparently all the tangency contact points between the teeth really tax the computer processor while in motion (And mine is brand new). The aforementioned suppression really helps but it still rotates at a very slow rate. The files are attached for anyone who wants to see it in action. Make sure you activate contact solver and you can suppress the ball bearing to witness the teeth mesh.

Thanks for your help and all the suggestions.

[JDMather]

Contact sets are calculation intensive.

A Motion constraint between conic surfaces would be much more efficient.

- a key in any case an Drive Constraint on an angle constraint to drive the shaft would be the best way to impart motion rather than dragging by mouse.

[SBix26]

Regarding translation: I simply copy and paste the text to Google Translator.  Not perfect translations, but pretty good, at least for the few languages that I have some knowledge of.  For technical stuff you can usually figure out what's intended.

Sam B
Inventor 2012 Certified Professional

Please click "Accept as Solution" if this response answers your question.
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[Mr_iso]

Hello JDMather:

I can't keep the teeth engaged attempting what you describe. No doubt I am missing something here but I have included the cone angles and plugged in a starting angle for driving the constraint angle. The motion works but the teeth do not stay engaged. Efficiency as you mention is definitely what I'm after for future animation of my complete model. Have you or anyone else on the forum seen this constraint scenario before where gear teeth are used exclusively for timing and the gears are not really rotating but one follows a path around the other gear that is fixed?

[JDMather]

I don't have time to go through this to find the problem, but a couple of observations -

I would not use Contact Set - turn the Solver off.

The cones for pitch should be tangent (but I'm not really sure this matters since your ratio is 1:1).

I always rename my angle constraint for driving as Drive This so that it is clear which constraint to drive.

I always use Directed Angle to create the constraint.

I have used this technique with planetary gear sets (one gear locked).

Do the initial alignment of teeth by eye (suppress constraint, drag with mouse and then unsupress constraint).

[JDMather]

I took a bit longer look at this - and I suspect the wobble plate angle isn't correct.

[JDMather]

Look at what Extrusion5 does to your hole in the wobble plate?

I don't think this has a real bearing on the problem, but when I start to reverse engineer things like this - any mistakes in basic stuff start to worry me about the overall design.

I think I would sart with just the two gears and get that motion correct before proceeding to the rest of the mechanism.