Is there a motor that can travel linearly up and down a threaded rod. I already know that you can attach a motor to the end of a threaded rod and make a nut travel along the threaded rod but this is not what I'm trying to do. For example, if the magnets inside a stepper motor were threaded like a nut, then when the motor spins it will travel along the rod. Is there anything like this already made?
There are "hollow shaft motors" similar to these. The inside of the shaft can be threaded (or a nut can be fitted inside) to make the motor itself travel along a matching threaded rod.
I believe that many years ago I saw a motor spec sheet that featured a hollow, threaded shaft, and here is a modern one.
The problem is that you need some way to prevent the motor housing from spinning in the opposite direction, in the worst case causing the motor to remain stationary on the threaded rod. Given the mechanical demands of doing this, it's a technique that isn't used much.