# Copy+Array along path+Dynamic

#1

Hi guys,
So I’m working on modelling possible gondola paths. And since I’m probably going to have to change them many times in the future, I’m trying to figure out a way to make them more dynamic and automated.
I currently have the gondola cars dynamically spaced away, and size locked. So I’ve been scaling the overall cables+cars to the desired length and the cars will copy themselves and space out evenly.
I’m looking for a way for the copied cars to also place themselves at the right height to look attached to the cables. Any ideas? I tried Sin(X), but my method didn’t work out.

#2

Hi TJ

the sine function is probably a good approximation, The idea is to use the number of cars as an expression of an angle between 0 and 180 degs.
so for 5 cars, deg= 180 / (5-1) = 45
z= -sin(copydeg)(some sag factor)

the sag factor would be dependent on number of cars, say 50*(copies-1)

you could make it more precise by average weight of car, tension factor of wire…

I have attached example (v8)

cheers
Philip

sine wave.skp (33.0 KB)

#3

Awesome thanks Phil! I could double like, I would.

Since it’s still very much a concept, there’s been no need to do any calculation with the cables and car sag. For now, it’s just finding possible routes and giving an idea on how it’ll look. So I’ve been task with modelling out every new path option someone suggests.

#4

Any ideas on making a rope/cable also dynamic to a sine wave?

#5

yes

one can make a line segment that is based on the copy points of the cars. then get it to copy itself to join the dots…so to speak.,

a line distance is calculated by using pythagoras’ famous formula on x and z, displacements or differences between cars, then arc tan = z/x to get the angle. then plug in to alter the copied lines to suit
example attached (v8)
cable cars.skp (63.6 KB)

a further refinement could be to use a chord with a variable bulge instead of a straight line, but will save that for another rainy day.

The sine is a reasonable approximation to give a visual effect, but as you may have noticed the cars tend to bunch together at the bottom of the curve, they are not evenly spaced…so need some work to figure how to fix that.
Its timely, that Jim uploaded a sine “snake” just after I posted the last reply

worth checking out…animation has got to be another step…

if your project involves the cars going up or down a mountainside then perhaps a polynomial expression maybe required, as the cable would tend to sag more at the bottom, which a sine wave would n’t show when rotated to the slope,

Drawing Sine Curve?
#6

I had thought of either a straight line or many copies in a sine wave. The sine wave copies might be a bad option since I will probably need too many copies over a few kilometers. After looking at your straight line solution, it looks less blocky as I thought. I present the static model in Google Earth, and it doesn’t require all the small details, so maybe the straight line from car to car will work, I’ll give it a shot, thanks!

This is what I have present with the regular curved cable line, you can see at the ends where the cars don’t perfectly meet the cable, not a bad issue unless I had too few or too many cars and then it becomes more noticeable that the cars aren’t following same curve as cable.
Gondola_Cars Tower.skp (666.6 KB)