[ODE] Spring organism not moving forward

[Marcel Krcah]

Hi!

I'm trying to simulate a spring organism similar to those at
<a href="http://old.sodarace.net">old.sodarace.net</a>

I needed to make a kind of muscle between two bodies. The length of a
 muscle lineary depends on sine (sine changing according to time).
Because I haven't found anything that forces two bodies to be at the
distance I want them to be, I ended up using a slider joint and
correspoding joint motor that manages the slider's velocity. I had
success and muscles expand and contract periodically.


A problem appeared when I made 'legs' with these muscles and let the
organism move. Eventhough it makes correct movements the whole
organism remains at the same place. For better understanding I placed
a video of the organism on the web. You can find it here:

<a href="http://prgs.xf.cz/video/small.avi">prgs.xf.cz/video/small.avi</a> (1MB)
or <a href="http://prgs.xf.cz/video/big.avi">prgs.xf.cz/video/big.avi</a>
(15MB) - if the previous one doesn't work<br/>

I tried to play with the gravity, bodies' mass, friction in contact points
but nothing worked. Maybe the problem is in the slider-joint motors
because it brings a piece of unnatural movement to the simulation. I
really don't know.

Does anybody have an idea how to solve this? Should I change a
'muscle' system from joint-motors to something else?

Thank you!


Marcel