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Followup to How do I know whether a bookcase will rack/sag/twist if hung using butt hinges as a (non-secret) "door"?

TL;DR:

  1. I have a bookcase, want it to become a door, and load it with heavy stuff. (Not a secret one. Trying to keep it simple, even if ugly, as long as it's functional and strong.)
  2. Didn't initially want wheels because it's above a clay tile floor, therefore not perfectly flat.
  3. Bookcase being sufficiently internally supported depends on its backing plate or attaching the whole thing to an actual door.

Problem with point 3 is, the back isn't where it needs to hinge from, and offset hinges tend to be a lot weaker the more offset the pivot point is (no matter the style of hinge).

So my new question is:

If I use, say, 56 nylon ball casters, each rated to support 3kg static (or 5kg dynamic), will they durably support my bookcase (~135kg fully loaded, worst case scenario) given that heavy-duty butt hinges held by a 7.5"-square post will be there as backup?

Like these but smaller: https://www.amazon.com/Meoly-Transfer-Conveyor-Universal-Transmission%EF%BC%88CY-25B%EF%BC%89/dp/B06XH8T1CF

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    Think a larger wheel would travel over the dips easier, than many small ones. For clay tiles, a single wheel with a soft/rubber coating might be less hard on the tiles.
    – crip659
    Commented Dec 7, 2022 at 22:20
  • do they even work when mounted upside down?
    – Jasen
    Commented Dec 8, 2022 at 2:14
  • it's probably better to find hinges that are strong enough, like used of the door of a vault.
    – Jasen
    Commented Dec 8, 2022 at 2:19
  • I do see one advantage to using a lot of smaller casters: as the bookcase opens, some casters will be over the grout line and not touching the floor (and not supporting any weight) but many more will be on the flat face of the tile. The door wouldn't bump up and down the way it would if just a few (4?) would.
    – RetiredATC
    Commented Dec 8, 2022 at 3:45
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    "Vault door hinges" may be the best bet, @Jasen, but they might somewhat exceed budget...
    – FreeMan
    Commented Dec 8, 2022 at 15:30

2 Answers 2

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don't use casters, use fixed wheels. just point the axles of the wheels towards line of the the hinge pins and the wheels will be at the correct angle.

nylon will tend to collect grit which may damage the tile surface, ruibber may be a better choice.

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  • Swivel wheels, while possibly more expensive than fixed, would make installation much easier. However, they do tend to resist swiveling in place and may make going from "opening" to "closing" more difficult as they need to swivel direction, but there's now "wiggle room" for them to turn. Fixed castors with careful installation would be the way to go.
    – FreeMan
    Commented Dec 8, 2022 at 15:34
  • With fixed wheels and so much weight, won't the fact that the door's path is a curve stress the wheel's attachment points, or does it just wear the wheel's rubber a bit faster, but not enough to worry about? Commented Dec 11, 2022 at 11:47
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    swivel wheels will be metastable kicking from leading to trailing as the shelf is moved, this may cause jerking and and books being ejected. - it's easy to align fixed wheels right. if you don't have a straightedge you should probably not be attempting carpentry. with the wheel aligned correcty (as described) there will be no sideways loads on the wheels.
    – Jasen
    Commented Dec 11, 2022 at 11:49
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56 nylon ball casters, each rated to support 3kg static (or 5kg dynamic), will they durably support my bookcase (~135kg fully loaded)

WOW, that would be quite a job installing 56 casters!

Instead I would use heavy duty casters. For example they are used on toolboxes and they can carry 300 kg each so you only need four of them plus the wheels can be large enough to overcome any floor issues.

casters

They come in different sizes, just pay attention to the load capacity per caster, and you will need swivel type since you are rotating the book case in a half circle.

Additionally I would put the framing around the bottom part of the book shelf just above the floor to hide the casters.

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  • Plus the 56 casters would probably be very noisy. Commented Dec 8, 2022 at 0:33
  • Won't these get stuck awkwardly like they do on shopping carts when reversing directions, especially with such weight? And unlike toolboxes and shopping carts, there's no jiggling around it since they're on a fixed path. Commented Dec 11, 2022 at 11:45

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