Low-profile horizontal sliding mechanism

[Bert Coules]

Following my earlier thread, I want to mount two computer monitors side by side on a base which can slide across the surface of a desk to bring either monitor into a central position.

I'd like the base (which I'm thinking of as a sort of shiftable shelf) to be as low profile as possible, so I'm wondering about something other than a basic panel-on-wheels arrangement.

The base will need to be approximately 30" long by 9" deep and the length of travel must be 20". It occurred to me today that drawer runners used flat might be a possibility if the load wasn't too much for them though they might well need a bit of fettling. But is there any dedicated product for just this sort of application? I've no problem with fixing something down to the surface of the desk.

My various Google explorations haven't turned anything up but I've probably not yet hit on the right search term, so I'd be grateful for any thoughts.

Many thanks, Bert

[jon]

You could adapt drawer runners.

[Bert Coules]

I've suddenly thought of a possibility (funny hoe posting a question can have that effect): what about a floor-mounted sliding door mechanism? Perhaps even the most basic nylon-runner type might do, if sufficiently lubricated:

[Bert Coules]

Thanks for the confirmation. My only thoughts are first that they might not be able to take the weight when lying flat, and second, isn't 20" an unusually long travel for a drawer?

Bert

[Theo]

You can get under-mount drawer slides, which tend to mount at the bottom corners of drawers, or centre-mount ones which go in the middle:

Theo

[Colin Bignell]

Could you make the base in the form of an inverted roller conveyor, with the rollers running on the desk top? Roller conveyors can take quite heavy weights and there will be no limits of the length of movement, other than any end stops you might want to fit.

[Bert Coules]

That's an interesting idea; thanks. I wonder just how small the rollers could be and remain practical? The bearings would be a bit of a challenge, maybe.

Bert

[Bert Coules]

for that, and for the link; I'll investigate.

Bert

[Bert Coules]

[Colin Bignell]

If you buy conveyor replacement rollers, they usually have the bearings built into the roller end and only need a hole in the metal sides. The pins on the ends are spring loaded to clip into the holes, not unlike watch strap pins, but much easier to put in. They may come smaller, but

1.5 inch diameter (in various lengths) seems to be standard for all but the heaviest use.

[John Rumm]

Drawer slides will indeed work laid flat, and can take significant weight. They are also available in length up to a meter.

If you use 19mm material, then you can route a channel into it, to fully flush the drawer slide.

The AV drawer I built into my media centre carries a high load, and uses both upright and flat placement of the slides - with one on the underside of the draw at mid span to stop the drawer sagging.

[John Rumm]

You can also get linear rails and bearings to run on them - popular in CNC routers, 3D printers etc:

[Bert Coules]

That was one of the terms that escaped my memory when I was Google checking. Thanks, John.

Bert

[Bert Coules]

Thanks John, that looks excellent. Drawer runners used flat is certainly the lowest-profile possibility, and has the most appeal for that reason. I haven't tried sketching it out yet but I can foresee one possible problem: screwing the fixed runners to the desktop will be perfectly straightforward, but attaching the the sliding sections to the shelf might be tricky: there won't be the same access as there is with a drawer.

If the runners are the type that allow the drawer to be completely removed then with careful positioning I could fit the shelf runners with them unattached, but I suspect that since there will be two of them, separated by some seven or eight inches, the usual method of inserting the slider at angle won't be possible.

I have a couple of old runners too short for this job but probably suitable for experimenting with. I'll have a play tomorrow.

Bert

[RJH]

Yes - I've used some from screwfix for the bench/bed in my camper conversion. Each set supports 50kg.

[John Rumm]

The two sections come apart - so you can fix to both "sides" separately, and then engage them later.

One thing to keep in mind with a slider is that if fully extended, it won't be able to support much load where there is no overlap (there is not the same amount of stiffness when in the flat orientation).

So for this example a very long par of runners, where you are only using part of the available travel might be better. or use shorter ones in opposing directions so that moving the shelf opens one, but closes the other - however that makes assembly more difficult since you can't insert from both directions at once. (however if you fix the surface mounted part, and then just rely on the rebate for the rebated side to restrain the other half, it won't need screwing on that side)

Yup sounds like a plan.

[Bert Coules]

With drawers I've always had to engage the two sides with the drawer angled up, then lower it to the horizontal to slide it into place. If the units I use for my shelf are like that, the angled approach won't work: it's fine if there's just the single assembly as on a drawer, but with two in parallel a few inches apart it's not possible (unless perhaps the already fixed runners are staggered). The planned experimentation might help throw up a solution.

That's a good point about the diminished support when fully extended. Thanks.

Bert

[John Rumm]

I am familiar with the type you mention - these are often the undermount type or those that "pull in" the drawer the last little bit using a slope in the runner.

The full ball race type don't lift or drop in - they have to be slid straight into the open end. There is normally a retaining clip that latches it into place once the runner is pushed far enough into its mating part.

So in this sequence I have installed the runner halves using a template to set the position on the drawer box, and a spacer to set the position for the next runner in the cabinet. You can see the opening at the end of the lower runnier nicely:

It may not matter if the shelf is fairly light. Monitors are not that heavy these days.

[Bert Coules]

Which makes them ideal for my purposes. Excellent.

Thanks for that link. It's a superb job and both instructive and reassuring to read of the mishaps along the way.

With both of mine the base units are considerably weightier than than the screens. Actually, I have had another thought: one drawback of the sliding horizontal shelf idea is that it will occupy a considerable area of the desktop, where nothing can be permanently or even semi-permanently sited. What about a vertical panel (a la a splashback) with the sliding unit (also vertical) moving across that? It would mean using wall- (or rather panel-) mounted VESA mounts and the splashbackish part would need considerable bracing, but the extra desktop area freed might make it worthwhile.

[John Rumm]

The shelf does not need to be at desk level - it could be at shelf level well above the desk with the monitors mounted on the underside of it...

Or even a fixed shelf, with a pair of these:

hanging under it - they allow easy side to side movement if you don't tighten the linkages too much.

If you had a slide or rail at the top and the bottom, then it would not need any bracing - it would be puled by the top runner, and pushed by the bottom one in cantilever.