How to brace the base

[Bill Gill]

I built a gadget with a 2X4 base. The usual sort of thing

4 each 2X4 pieces on edge. The joints are made with 3 1/2 inch screws. This weekend I moved it and managed to wrack the joints. So I need to tighten it up. The first thing of course will be to tighten the screws. But to keep it from doing this again I need to add some bracing. I figure if I screw plywood triangles to the top and bottom of each corner it will provide plenty of strength. Now I am trying to figure out whether 1/4" plywood would be strong enough. Should I go for 5/8" instead?

Thanks Bill

[bob_villa]

You say, top and bottom, so 1/4 should work fine.

[Scott Lurndal]

You should be able to find sheet metal gussett plates at your local lumberyard. Or you can simply use a square bit of scrap sheetmetal. It doesn't need to be a triangle.

[TimR]

Can't tell from your description.

Suppose your gadget is basically an open cube - the bottom has 4 sides, and then 4 uprights at each corner.

Classically each joint should get 3 braces: leg to leg, leg to upright, other leg to upright. You could do those braces with plywood triangles easily. 1/4 should be plenty depending on the load.

[Bill Gill]

Ok, so far the consensus seems to be that 1/4 would do. So that is what I will go with.

Thanks for all the help.

Bill

[DerbyDad03]

What is the base for? The reason I ask is this:

You are planning to add 1/4" of material on the bottom. Other than raising the entire "gadget" 1/4" since the base will now rest on the plywood, I don't see that as a problem. However...

You are also planning on adding 1/4" of material on the top and essentially removing access to the inside of the corners of the base. Once again, we'll disregard the extra 1/4" (now 1/2" total) in height, but I gotta ask:

What is sitting on top of this base and will the fact that it will now sit on top of the corner gussets and not fully on the 2 x 4's be an issue?

If so, I would just eliminate the top gussets. With enough screws in the bottom gussets, it'll take a lot of force to rack the base. If you are concerned, glue two 1/4" gussets together.

Another option, if you need access to the corners for uprights and you don't want to raise the height at all, would be to use diagonal 2 x 4's, cut at a 45° angle and placed *inside* the base, something like this:

[clare]

Does it need to be either or? What's wrong with 3/8"?

[Bill Gill]

None of that is a problem. The 'operating' stuff sits inside the base with plenty of clearance so the gussets won't interfere. So I will do both top and bottom just to make sure.

Bill

[Bill Gill]

Basically I have some scrap 1/4 and some scrap 5/8. So those are my choice. It doesn't take much. Just 8 pieces

6" on a side. That way I don't have to spend extra money to fix the problem.

Bill

[DerbyDad03]

Now I'm really curious.

What the purpose of a "base" such that the object it is the base of apparen tly doesn't even touch it?

[Bill Gill]

What the gadget is is a DIY book scanner. It holds a book in a cradle. The cradle has to move from side to side, so it is mounted on drawer slides mounted in the base. A general idea of how it looks can be seen at

Mine isn't quite like that one, since I built it kind of ad hoc with what I could lay my hands on easily. In the picture the back column supports the platen that holds the pages down flat. The uprights at the sides support cameras to take pictures of the pages. Anyway I can easily put the braces on without interfering with the operation.

Bill

[DerbyDad03]

arently doesn't even

Thanks for letting is know what the gadget is. Have fun with it.

[TimR]

arently doesn't even

1/4 plywood for that shape is massive overkill. It should be fine.

Next time at least half lap the joints - if you want bragging rights do a d ovetail. (get some help with that one though)

[Bill Gill]

Unfortunately I am not a craftsman. My father and brother were carpenters and craftsmen, but I didn't get the gene. I can knock stuff together and make it work, but I will never become famous for the beauty of my workmanship.

Bill