hehe so, after many tests… the problem of the first loop is deleted…
in fact, the important things is… proportions… and gravity!
second loop need to be x % lower than the first one etc…
so, set up gravity to -15…add element by element, and test it…arf
i re used 2 rails for simulation, as in some turn 1 rail is not enought to keep wagon on the way, inertia is too big…
for the preview, i just attach the camera to the wagon, but as you will see, some really big cam shake… so its the wagon who has all these noze…
that work, but dont really know how the wagon has done all this way… 
that certainly need to be more subdivised…
that takes like 4 hours to calculated 900 frames…
anyway, track go on… i start another one, and for now, try to set up mine (…), but will maybe go for a “real” one after have saw some link posted in the forum.
i start with a “downside” loop, who will be a “killer one” i think… dont know if its possible tho… master of rollercoaster will tell me… 
so, i really need to clean the rail to have smooth motion… finish the track, and cross finger to see if wagon go on…
http://perso.wanadoo.fr/yann.goument/perso/rollercoaster/preview_test_06.mov (quicktime 7.5 Mo)

the speed looks like good, but maybe its a little fast… dont really know…
the last loop is hard too, but its already fixed…
and i have very big! problems to attach multiple wagons. for now dont know if its possible to have a “rope” constraint with lw dynamics (some tips??)… all i have test for now doesnt works… we have a spring constraint, but work with the pivot point… so need to attach it to a null… but cant see if i can “fix” the spring to not see the 2nd wagon go over the first one…
so, will see later for more wagons… 
at work!


