drawing cables between pulleys

[2ms1]

What's the best way to draw a cable running through a network of pulleys? Is there some straight-forward way?


Below you see a shaft with3 pulleys on it where3 cables are terminated. I would like to draw the 3 cables that run out from itto over the other pulleys and on off to other pulleys I haven't created yet. I figure this involves doing a sweep protrusionwith a circle cross section and a datum curve that represents the center of the cable.


The problem is I don't know how to draw the curve so it wraps around the pulleys correctly. For the two cables where I only have one pulley so far, it's clearthat it was easy to draw a straight line. However, I do not know how to draw things beyond that first line segment. An example of how not to draw it is simply putting datum point on the pulleys and connecting them with a spline curve as shown below in the case where there are two pulleysrather than just one. If you select the single radius option for creating datum curves, it would theoretically be possible to get at least the correct radius for each bend in the curve, however it seems to me that in practice it doesn't work because it is impossible to tell where to place the datum pointsforthe curvein the first place(it would be if each bend was 90 degrees or something, however they're not).


Anyone have experience with doing this?

 

[spidernate]

I assume your pulleys are pointing towards the next pulley in line, right? (If not, you will have issues with the cable wanting to run off the pulleys...)

Here's what you can do:

It appears you have sketched circles around the pulleys representing the center of the cable:

1. Create a curve from center of one pulley to center of another.
2. Create a datum plane through the end of the curve and normal to the curve.
3. repeat for the other side.
4. create datum point at the intersection of the sketched circle and the datum plane.
5. repeat for the other end.
6. repeat 1-5 for each pair of pulleys.

The datum points are your tangencies. Now you can create datum curves from point to point.

 

[design-engine]

there is some sag in your pulley system. Whats up Nate? how is contracting going?

 

[spidernate]

The other day I showed my boss a skeleton model I created using techniques I learned in your class. Then I changed it right in front of him in a matter of seconds... I think I heard crickets.


(how's that for a plug? Still waiting for the linkedin recommendation, buddy!)