It looks like what they’re suggesting is that you put a ball above each rail and a ball along the inside of each rail and then weld or somehow connect those balls to the train. The two balls on top act as wheels that ride along the tracks and the two inner balls act as guides to keep the train centered over the tracks.
Also, just to clarify. Welding your train to the rails themselves doesn’t sound like a good idea because it would prevent the train from actually moving.
Yes, if you weld two and two together, they will either not move or move together, depending on if they are both designed to move. Also, in your image, I think they were trying to tell you to weld the balls to the carriage itself.
My suggestion is to make an InvisiblePart and weld the train to it. Lift the train up from the track, pixel by pixel and script something to get the InvisiblePart to follow the tracks. In simple, you could also do that for just the carriage itself, but you do what you want.
If you are using physics like in the real world then you need 2 spheres to roll on top of the track and 2 spheres to run inside the track. The 2 inside shouldn’t touch the wood… they bump against the track and keep the car from tipping over. They should all be welded to a single part under the car. The track is welded by itself.
I meant physics of the game vs. using a different method to move the train. In other words something simple like activating a drive seat and then letting the track physically collide with the spheres. I know real trains don’t use multiple spheres …
The ball method his friend drew him is correct for this case.
Btw… the real world example and 4 ball example are doing the same function. The inside part helps keep the car on the track.
There is a ton of posts that are somewhat similar to this one. I think you could find these helpful, because “welding” a train to a “rail” would most probably cause more issues than solutions if found.
Using different methods for these issues honestly would be your best bet.
I suggest that you CFrame trains. Use nodes to make the train follow where its going. This youtube video should help solve the problem: https://www.youtube.com/watch?v=OQtiCt7jma4
This may work if you’re using only a few short trains with no controls, but this will quickly become unscalable if you want to have users controlling their own trains.