2-Dimensional Rack & Pinion

[mloew]

I am trying to help one of the engineering in my office with a mechanism problem in Wildfire 2 (M140). The design calls for a sprocket to roll over a track that is curved in the plane of the sprocket. I thought it should be simulated with a cam and no lift-off to capture the correct rolling (gear ratio) relationship. We tried several iterations of flipping the axis, using an extra point on surface or aligning on planes to get the rolling axis aligned, etc. to get it to work. Nothing. We used a slot (center point on an offset curve) to get the bulk assembly motion, but it will not capture the rolling of the sprocket on the track.

Any clues?

Thanks in advance!

Best regards,

Matthew Ian Loew


Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Guest0527211403]

Matthew

How does the track move (relative to the shaft to which the pinion is fixed)?

If it moves radially, then maybe you can create a gear connection between the pinion's rotation axis and a joint axis which connects the track body to the body that the pinion is attached to. Manually setting the gear ratio should make this work.

Will this be used for dynamic/kinematic analysis or for visual output? If it's the latter, you can make "ghost" motors driven by table values or functions to make gears in an assembly look like they were really moving in sync with everything else. In one case I remember outputting the rotation of an assembly to excel and using a funcion to translate that into the motion of another part, and then finally bringing that table back to define a motor's position vs. time. The end product looked like everything moved perfectly in unison.

 

[mloew]

Mark,

I knew you would be the first to reply!

The curve (two straight sections with a fillet, basically) is fixed to ground and the sprocket rolls over the rack. I am trying to use MDO to get the torque required from a motor (not just the "servo motor" driver) to lift the components attached to the sprocket. I have used the technique of collecting drivers for multiple DOF systems in a spreadsheet and importing them back to Pro/E, but I don't want to do this for this problem. It is a single DOF system and I am trying to solve the dynamics of this problem.




Best regards,

Matthew Ian Loew


Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.