create a triangular shape with bulges on sides

[james.levieux]

Hi All,

I'm trying to create this popular shape for triangular tables but the geometry is challenging for me.  I want to make it parametric because our designers tend to draw these all the time at all different shapes and sizes.

I was hoping that I could create single joined line with the corner arcs locked to the corner reference circles, find the exact tangent points and then all I'd need to do is move the corner circles and all the tangents might work out on their own.  It's not working.

I've had trouble establishing tangencies at all joints and all kinds of other problems.  Does anyone think they can make something like this work?

[ToanDN]

Getting closed.  Maybe you can finish it off.

[james.levieux]

I decided to go with full-on geometry. This horrible looking bio-hazard thing actually works, but it's limited because the arc lengths sometimes get too small when flexed.  If anyone can come up with more robust geometry that would be wonderful.  

The arcs got small because I needed to anchor my bisecting lines using the arc intersection

After I got the monster working, I decided to use the working linework and strip it down per @ToanDN .  All the line ends are tangent but the simple stripped down version doesn't seem to work.  The tangents break, probably because the bulge arc center points aren't moving.