SW2013 - Circular reference workaround - Power Chain.

[AReed]

Hello,

I am building a power chain (ex. Igus) as a sub assembly for work and I am able to get the links of the chain to fit to a curve in a static form. I can draw from this various configs to get my machine stroke limits in several different positions. What I'd like to be able to do is make the assembly flexible, length of one of the linear sides driven by user input (drag with mouse) while the other linear portion takes up the slack all with a constant bend radius at the fold point.

I have two problems:

1.) I have a circular relationship in the lengths of the linear legs. Currently I know the overall length of the entire power chain and the arc length consumed by the half circle portion of the path. I subtract these to numbers to acquire the "linear length" that is left over. I then dimension the top leg with the formula: Linear - Bottom and dimension the bottom leg: Linear - Top. So I clearly have 2 unknowns and one hell of a circular reference. Basically I am trying to get the two linear portions of the path to consume/use the linear amount the other gives up/receives.

2.) Even if I could get this to work I don't know how to link it to the different levels of the assembly structure this item is going to get tucked into to allow it to be flexible and still driven by the curve.

I know what I want this assembly to do, I just lack the skills/knowledge/clarity to execute it.

Any Ideas on how to execute this type of control, or am I out of my mind?

 

[Updraft]

AReed,

Here are a few ideas, one of which may work for you:
1. Use a simple equation to compute the lengths of the dependent sections.
2. Use a belt mate without creating a physical belt part. Just utilize its sketch for a sketch-driven pattern of the links.
3. Get on SWX2014 (I expect my disk to arrive any day now). In 2014 there are several things that should directly benefit you. One is that we can now control the length of a spline which you could use for the fixed length but flexible path of the chain. Another thing I saw in the rollout demo had to deal directly with chain elements, but I don't recall the exact details. Perhaps you can see that if you research the rollout info.

I hope this helps.

- - Updraft

 

[EEnd]

thread559-332990 includes a description of my most successful attempts at modeling Igus chains. As I mention there, any time I have attempted to model it with links, it invariably blows up. I have settled on a couple of ways of representing the volume occupied by the chain. They all share the same technique for placing the arc relative to the ends of the chain. There is a part with only reference geometry which links the two ends of the chain. The midpoint of this part moves at 1/2 the rate of the free end and serves as a reference point for the arc. The referenced thread has links to a couple of examples based on this technique.

Eric