High torque that can be purchased.

[Garret]

I am just throwing this out there, but my team used cable to actuate the arm on our elevator. The idea is based on how cables are used on weight lifting machines to translate rotational motion into linear "lifting", we just do the inverse in our system.

We found it simple and relatively easy to set up with minimal precision work (my team uses a bandsaw and a drill press only). It is nice because you can basically have as much torque as you want by just changing the point where the cable attaches to the arm and/or the position where the cable "pulls the arm from". With cable you can either power the up direction only, down direction only, or power both.

It may not be ideal for the arms of the length you are talking about but it is an easy to implement and reasonably effective solution.

I have included a picture that shows what we did. It was implemented at the last minute so it was not at all refined, but it was quite effective. I don't know if this is useful, I just thought I would throw it out there.