Creating a hole for rotation and precession

[Anonymous]

I have a part I'm trying to figure out how to model. I want a roller that will sit on a square axle. I then want to angle that roller and turn the axle, and keep the roller angled. The roller rotates in a fixed plane, continuing to point in the same direction. The square axle will sweep out a well-defined area that it needs in order to not interfere with the roller. That is the hole I'm trying to create. The idea is to be able to turn the square axle and force the roller to turn with it, but keep the roller turning in a single plane that is not perpendicular to the axle. (keeping the roller pointed in the correct direction is accomplished with other mechanical means)

Attached is this system for a round axle. The leftmost shaft of rollers continues to turn at that angle. Also attached is a section view. This is easy with a round axle--simple model the axle in at an angle and rotate-cut the area I need out of the roller. I added a flat in the middle (seen in Section C) and I'm done, but a square shaft will not rotate with respect to the roller, and should form a square-star-shaped (hyperbolic?) cut. 

I'm finding this difficult to explain, but hopefully it's understandable.

How do I create this cut in the roller to accommodate the roller spinning in a single plane that is not perpendicular to the square shaft that is driving it?

Mike Slosson

[asiteur]

Hi,

What I understand is that you want to cut holes at an angle.

That is relatively simple if you construct the proper planes.

So you could create a plane, based on a plane, line and angle you specify.

Then, you can place a sketch on that plane and dimension the point that you want to be the center of the cut.

Is this making sense to you?

[Anonymous]

Yes, that part is easy. However, if I were to stick a square shaft through that hole and rotate it, the roller would appear to wobble on the shaft (actually rotating with it, but not in a single plane). I need that hole to allow the roller to be locked to rotate with the shaft, but be able to rotate in its own plane. If you look at the pictures I uploaded, I want the shafts to turn and the rollers to turn, but the rollers should stay pointed in the same direction.

Take a pen, and place one point of it on your desk. Hold pen vertically by the end of the pen that is not on the table it such that the clip of the pen is pointed towards you. Now move your hand in a circle above your desk, keeping the clip pointed towards you. Imagine the pen has a square cross section, and the roller is sitting on the table. That's pretty much the cut I'm looking for.

I about need to get some play-doh and make a video to explain it, because I'm not finding a good way over text. 

[asiteur]

Sorry, I'm not following this...

The 2D drawing seems really easy to create.

I wonder, isn't it just that you want the constraints to allow for certain motion? The pen-table example makes me think of a ball-joint, but I don't think that's what you are trying to do. You can always contraint and allow for a range of angles.

Other than that I won't know.

[Anonymous]

Okay, I modeled it up and took a video of the motion I'm trying to achieve (Motion5.avi)

Roller should be locked to have to rotate with the shaft, but I'm trying to create the hole in the roller that gives the correct clearances for this motion. I have some cutouts shown, but if you watch the upper edge of the rotating shaft, you can see it clipping through the roller at times. 

Hope this is better than my previous attempts at explanation.

[johnsonshiue]

Hi! I am not sure if this is relevant but you may consider creating a cylindrical surface in the square shaft. The cylinder has to be large enough to contain the square shaft (best on the 4 edges). The cylinder represents the virtual volume that the square shaft rotates around. It may help identify areas to remove in the roller.

Many thanks!

[Anonymous]

I guess I'm not sure how the circumscribed cylinder will help me with this cut. Attached is a pack-and-go zip file of the assembly (in 2015). Drive the constraint named "DRIVE ME" and you should see the motion I'm working with. I need to make a cut in the roller that leaves as much material as possible, but matches the path swept out by the shaft. The cut is in some ways a combination of a revolve, a sweep, and an extruded cut with taper.