I made this
- Copy move the circle's wheel
- UnwrapeCurve by the Michael's Plugin http://moi3d.com/forum/messages.php?webtag=MOI&msg=5136.1
- Extrude the Line obtained
- Copy the module (Array Line)

then Flow
Any problem :)

How many time take your Flow function ?

With above the Flow has taken one half minute
(middle module + little line is your file)