ropes, chains & equations

hello all..
the recent post re: 'cosmetic roller chain' has found me
experimenting.

a few things i can't seem to get right... perhaps its
a fundamental misunderstanding on my part..

say i model a simple pulley.. a solid fixed disk and
two weights. i can develop the model just fine and sweep
in a nice 'rope' from top/center of the weights over
the pulley.

if i set the sum of the two rope lengths as equal to a constant,
then raising one weight should lower the other.

but, will i be able to see this in am assembly file?
can i "drag" one weight and see the other move?
or will mates prevent me from moving the weight at all?

no way to get physical dynamics to simulate one weight falling
and one rising?

-tony

 

It will not dynamically move but upon rebuild it will update to the new
location. Simulation might crap out or not update like you want. Using
animator you should be able to make a flowing AVI though.

 

:> no way to get physical dynamics to simulate one weight
falling

SolidWorks' "physical dynamics" is actually "rigid body dynamics".
Since the rope has a changing shape, it is not a "rigid body".
You could model it as a chain of connected segments, which would more or
less result in a "finite elements" approximation of the rope.
The problem will then be to model the contact between then rope/chain and
the pulley...

 

Tony,

I tried to model a trebuchet and had to utilize Cosmos\Motion. With
some help from the Cosmos folks, they were able to get close. But
when the rope looses its shape and is no longer rigid, things fall
apart. Like any complex engineering dynamics problem, the only way to
approximate is in steps.

So in SolidWorks, I used configurations to represent key steps in the
motion. Perhaps you can do the same with your weights.

Regards, Marie