How can I transmogrify a fixed monitor post in to a variable height monitor post?

Question

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:

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:

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?

Answer 1

Start by attaching two rack gears to the post.

Next fabricate a halved trolley.

<sup>Rear Trolley

Front Trolley</sup>

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.

^{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.

^{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.

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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.

Answer 2

This is a bit out there and seemingly off track, but please bear with me.

We have a premium shower system which includes a shower head holder on a vertical bar: Except our showerhead is much more substantial than in this photo and exerts fair bit of torque on the slider assembly. So much so that we barely have to tighten the slider.

As a result, we tend to leave it fairly loose so we can adjust it with one hand and only a little force by providing relief of the showerhead torque. It then slides easily up and down.

Perhaps that adding a single ring to glide closely around your post could use the same principle. It would be about 10.2 cm interior diameter, probably 5 mm thickness, and about 2 cm high. Weld to one side of the ring a vertical bracket to attach bolts to fasten the monitor arm.
I don't expect any artistry awards, but maybe this is clearer?

Answer 3

The solution I finally went with was a combination of DIY and off-the-shelf:

The arm came from SpaceCo. The bottom bracket shown in the picture at the bottom of the post leads to another extensible arm affixed with a 24" keyboard platform, also by SpaceCo.