Hello all You're going to hate me as I'm about to ask a very silly question here. As it says in my profile, I'm a student, but in software engineering and not mechanical engineering. But I need to come up with a proof of concept model for the mechanical part of my design. The problem is, I think I've chosen an imposssible design now, and it's getting very late in the day to suddenly scrap everything and start again with an idea which actually works. I also worry that you're going to call the XY problem on this, but here goes. I'm designing a project which requires objects to hang from the ceiling, and be mobile around the ceiling. Imagine if you will, an large airport scene with lots of "flying" model planes which have the ability to cross over each other's flight paths. This is what I am trying to achieve, only on a bigger scale. The other problem is that the design, although currently only modelled on a small scale, must have the ability to be scaled up to full size, which would be exactly 15 objects suspended from a false ceiling, a bit like 15 gantry cranes which have the ability to cross over each other's paths. Each must be able to carry a load of up to 90kg. And I'm actually tearing myself apart right now. I can't think how to make it possibly work. I've thought about various different types of rails/track, electromagnets, cars on top of the false ceiling which hold electromagnets....but 90kg is a lot for an electromagnet, in practical terms. I'm guessing this is going to have to a rail type design. But please, does anybody have any ideas? I've been a complete idiot and attempted the solve the impossible, haven't I? It's all about showing off the code behind modelling various heavy objects on the end of a variable length rope which swings around, so ensuring that they don't hit each other, just get very close. Does anybody have any ideas how to solve this? Thank you so much.