Background

I am looking to increase the versatility of a desk by allowing the monitor to raise and lower, using a manual mechanical solution (i.e., no electric motors). I am trying to make adjusting the monitor height be as quick and effortless as possible, while eliminating the risk of "dropping" the monitor.

The situation is depicted here:

Monitor Stand

The items involved in this problem include:

a monitor of ~12kg, with dimensions of 449.6mm x 690.2mm x 83mm;
a single post of 10cm in diameter, made from 5mm thick steel; and
an arm of ~3.1kg, with a maximum extent of 37cm.

The extensible arm provides a great deal of motion. The post is notched at the bottom, resting on a type of halved joint, and secured at the back of the desk by thick wood slats.

The monitor needs to have about two feet of motion so that I can stand while working. (Lifting the entire desk would be much [$10k] too costly!)

Problem

As described in this physics answer, the compressive force and the moment conveyed to the post are fairly significant. I'm looking for a solution that would allow the monitor to raise and lower and lock, even if it meant having to retract the monitor close to the post while adjusting the height.

To raise the monitor with the current situation requires unscrewing the post, hoisting it, and reattaching the screws. This is both dangerous (for the monitor) and time-consuming.

Post and Track

The faceplate welded to the post has 10 threaded holes drilled into it (barely visible in the above photograph). I think I need a two-piece sliding track mechanism. One piece attaches to the post and the other attaches to the extensible arm. The logistics resemble:

Sliding Track Mechanism

Question

What type of sliding track mechanism would allow the monitor to raise and lower without much effort, time, or potential for accidentally dropping the monitor onto the desk?

Best Answer

Start by attaching two rack gears to the post.

enter image description here

Next fabricate a halved trolley.

enter image description here
^{Rear Trolley}

^{Front Trolley}

You'll need a couple pinion gears that can mesh with the rack gears.

And a couple pins to allow the gears to spin.

Next assemble the trolley. You can use cotter pins through the gear pins to hold everything together You'll probably want to use 4 cotter pins for each gear pin. One on the front of the front plate, one on the back of the front plate, one on the front of the rear plate, and one on the back of the rear plate.

enter image description here
^{Cotter pins not pictured}

Finally, install a spring loaded release pin (held in place using a C-clip), that will lock the trolley in place.

enter image description here
^{Spring not pictured}

When you want to raise/lower the monitor, pull out the release pin, move the monitor, then let the release pin spring back locking the monitor in place.

For a simpler design. Go take a walk through your local hardware store, and pay close attention to the mechanisms used to raise and lower the table on drill presses.