Torsion box caster attachment

[rjwaldren]

I have next week off and will finally have some dedicated shop time. It's been tough lately with the holidays and a 3 year old.

I'll be spending my time on tool storage mostly and finishing up the garage-to-woodshop conversion.

I'm sketching out ideas for a mobile base for my 21829. The folding base is nice for storage of the saw, but I don't store it and could make better use of additional cabinet space. I'm very impressed with the designs around here so I'm starting with Rays writeup and picking through other designs for ideas.

I would like to make the torsion box as low profile as possible, without defeating it's purpose. If I build the torsion box to full size and inset the casters will it defeat the purpose of the box? I'm thinking of building the box with doubled up MDF at the top of each corner, then cutting openings in the bottom corners to mount the casters directly to the underside of the top panel as shown in the attachment.

Or would I be better off just laminating the MDF and attaching an apron?

[mschrank]

I can't comment on the structural compromise part of the design, but I'm wondering how you plan on locking the unit in place. If you are using locking casters, you won't be able to reach the locking mechanism if they are tucked up underneath.

May be a moot point if you are planning on using some other method of locking it down. IIRC, Rays design incorporates additional feet that can be lowered to stabilize it.

[rjwaldren]

Yeah, threaded levelers will be used - It won't be moved often, but will require wheels when it is. And due to the slope of the concrete one set of casters will likely remain on the ground rather than lifting it entirely with the levelers at all four corners

[jackellis]

Structurally I think you're fine if you screw or nail *and glue* the vertical pieces immediately adjacent to the wheels to the top and bottom surfaces of the box and screw and glie the doubler plate to the top surface of the box. Glue alone won't carry the load. Screwing and glueing the doubler to the top surface ensures that they will act as a single 3/4" thick member instead of sliding along one another. A similar mechanism is used in flooring systems to distribute loads and to avoid the need for blocking joists.

In place of locking casters, you could make the equivalent of an aircraft wheel chock out of scrap to hold the wheels in place. Something in the shape of a square "C" (or "U") with the insides of the legs beveled at 45 degrees and the inside width of the device just large enough for you to slide it around the caster. Attach a piece of cord and you can pull the chock out without having to bend down. Locking casters would be better if you're moving the base frequently but if it only moves once in a while, an external restraining mechanism isn't too inconvenient. Of course, levelers probably make that unnecessary.

[RayintheUK]

I mounted my castors to a re-inforced corner, prior to enclosing the torsion box, as seen below:






Ray.

[rjwaldren]

Thanks, Ray.

I'm basing everything on your fantastic writeup. I plan on building the torsion box exactly like yours with the exception of the casters. I'll double the MDF in that "compartment", but attached to the toplate. Then mount the caster in a through hole in the bottom plate.

My concern is that partially hanging the torsion box on the caster would not provide the kind of strength that your design has with the box completely on top of the caster. I'll only be using half rails, so my wheel base will be shorter than yours.

Mike made a good point about the levelers. They will relieve the weight from the casters when lowered, which will be it's normal position.

I'm trying to lower the torsion box for several reasons most of which have to do with maximizing the cabinet space available while still lowering the table height to a more comfortable level than the folding stand provides. I plan on enclosing my shopvac within the extension portion of the cabinet, and would like some additional space for storage. I'm in a residential neighborhood, the shopvac is the most continuous and annoying source of noise. Where the T/S normally stays will still allow short reach from the shopvac to other tools. A dedicated DC is not an option right now, so I'm trying to consolidate and make them as multi-purpose as possible, ie the router table is height adjustable to double up as an outfeed when necessary. And everything is enclosed to help mitigate at least the motor noise.

[LCHIEN]

they should be fine that way you plan to do it structurally speaking.
The top plate of the torsion box will be supported, the double layer should be quite stiff. The top plate sort of carries the weight of the unit, the second layer keeps it stiff.

You do have to take into account any operational issues, e.g. clearance for swivelling, access to locks, etc.