I started a new workbench a few weeks ago. I wanted to incorporate several Shaker bench designs and make a basic rectangular cube for the base, with the intent to attach a top and put in a cabinet later. I just attached the top, but ran into a real heartstopper. After adding the top, which is 96 x 30 x 3 solid maple, it appears to rack and vibrate the base when under stress. The base is all made of 2 7/8″ by 2 7/8″ hard maple. There are four strechers connecting the two ends, which are also 2 7/8″ squares. I intended to use 3″ stock, but had to adjust for some curvature and joint/plane them down a bit. The general dimensions of the base are about 5′ by 34″ by 30″. All connections use a 1″ tenon and bed bolts that connect to captured nuts. The bed bolts are very tight and have cinched the joinery very well.
The problem: When given a sharp and heavy push, the top appears to move at least 1/8th inch, but then vibrates back like a drum for a few seconds. I mean, you can really feel the energy from the push resonating back and forth between the ends of the bench for a good second and a half.
I think this is telling me two things. First, the base was well built at least in concept, and is functioning like a drum, as it is keeping the vibrations within the unit. Second, I think I undersized the base. Some of the sjoberg benches I have used have similar dimensions, but perhaps 2 7/8″ is undersized for this load?
PLEASE feel free to comment if you have any inputs or ideas. This may be a tough lesson for me to learn the hard way??
Best, Ken
Replies
Nah You Are Doing Good !
Man is this a question up my alley.
Congratulations on building your beautiful bench ! 96 inches, . . . maple . . . 3 inches thick you say . . . very nice. Any chance we can see a photo of it ?
One word for you
Diagonal bracing. Well two words.
There are a ton of ways to do it.
In the mean time jam the bench in the corner of your shop to stop the gymnastics. You can run some temporary lumber to the walls if you need to get around the end or back.
Nowww . . .
How about a skin of plywood over your 2 7/8 frame ? Effectively that braces the rectangular cube diagonally.
Or
All thread and turn buckles here and there diagonally. Works in tension not compression so need to go in both directions in each area; think motorcycle spokes.
Could put in some steel angle braces ( might mean welding on some plates to bolt through so this may be kind of involved.
I am going to go take some picks of some things I have that used to move as you have described that I have braced.
Back in a bit . . .
Photos of various braces
. . . and we're back.
but a skin of steel or ply would have worked as well on two of the three.
Note the workmates have diagonal braces.
I bet a skin of plywood across the back and ends of your bench will do the trick. Leaving the front open for cabinet drawers/ doors what have you.
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