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?
On Monday, August 29, 2016 at 11:36:42 AM UTC-4, Bill Gill wrote:
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.
On Monday, August 29, 2016 at 12:50:26 PM UTC-4, Bill Gill wrote:
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
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:
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 http://diybookscanner.org/forum/viewtopic.php?f=1&t33 .
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.
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.
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