03-15-2015, 06:04 AM
I'd suggest 2 vertical threaded rods linked by wheel and chain so that they both rotate together and at the same speed, inset from the ends by between 1/4 and 1/3 of the total length Each threaded rod has captive nuts so that they cannot turn and therefore will move up and down depending on the direction in which the rods turn. I'd also suggest that there is some sort of counter-weight system to take some of the weight off the threaded rods - the cassettes/shelves with trains on them are going to be HEAVY! Ball bearing drawer slides, or similar, fitted vertically will help with the guidance, but they MUST be plumb vertical - the slightest deviation will result in jamming.