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Using angles stiffen large "minimal" writing desk?

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Forum topic by thisisurbanmade posted 02-19-2020 11:59 AM 255 views 0 times favorited 6 replies Add to Favorites Watch
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thisisurbanmade

1 post in 41 days


02-19-2020 11:59 AM

Topic tags/keywords: design angles math

Hello! I made a large writing desk for a client a few years back and they have recently contacted me to see if I could stiffen the desk, apparently is has been wobbly since day 1… and.. I must admit… it is.

It’s a minimal design, solid walnut top, 1 1/4” walnut stock for the legs. All dominoed together and with some 3/4” solid brass stretchers also.

First few pictures shows the desk as is. The last rendering shows the angles I am going to suggest to the client.

The flex is primarily in the legs from side to side to be expected.

I am thinking about adding 2 angled sections of brass from the short side stretchers into the underside of the top.

I’m confident on how I’ll attach the brass to brass, and I know this isn’t a metal working forum, but what I’m wondering if how effective the use of angles like this will be?

Trigonometry is not my forte! Any help appreciated


6 replies so far

View John Smith's profile

John Smith

2236 posts in 837 days


#1 posted 02-19-2020 01:27 PM

if you intend to use metal for a support brace, I would suggest 1/2”
copper water pipe from the Box Store. very rigid and less expensive
than brass. flatten the ends, smooth with files, drill holes, paint black.
glue blocks under the top will give more support to hold longer screws.

.

-- I am a painter: that's what I do, I like to paint things. --

View Fred Hargis's profile

Fred Hargis

6042 posts in 3167 days


#2 posted 02-19-2020 02:24 PM

I believe it will work well, but you could temporarily fasten it and see before you do anything permanent. Part of this depends on just how stiff the brass is.

-- Our village hasn't lost it's idiot, he was elected to congress.

View theart's profile

theart

162 posts in 1229 days


#3 posted 02-19-2020 03:12 PM

From an engineering perspective, the closer you can get the braces to horizontal the stiffer they’ll be. Making them into an X, the full width of the desk and pinned where they cross, would be optimal.

From a human perspective, your desk sitter has knees. It’s possible that even the way you’ve drawn the braces they could be a problem. The braces need to be far enough back from the front edge of the desk that no matter where your chair is you’re not going to be hitting them.

So, thinking holistically my approach would probably be to add X bracing to the back and maybe the sides using stock that’s a bit thinner than the stretchers.

View SMP's profile

SMP

1879 posts in 580 days


#4 posted 02-19-2020 04:11 PM

I would want to see underneath and how the legs attach and to what. Having a super solid base that telegraphs movement to potentially weak corner joints won’t be great either.

View bilyo's profile

bilyo

1037 posts in 1777 days


#5 posted 02-19-2020 04:26 PM

The first thing I would do is check the brass to wood joinery at the legs. How did you fasten them? Is there any play in the joints? If everything else is solid then what you propose may provide the best stiffening with the least materials and effort. However, IMO, I think what Theart suggests, putting the “X” in the back and end “panels”, would be more aesthetically pleasing. The only question is whether it will provide the stiffening needed for the front legs. Maybe, with that, you will only need a small angle brace in the corner where the front legs joint the top. You might test it by clamping some temporary pieces in place.

Did you mean that you are “not” comfortable with how to attach brass to brass? If not, I would suggest that you silver braze them together. It is not difficult. You just need some 45 or 55% silver solder, the proper flux, a propane torch and tightly fitting joints. There are Youtube videos on the subject.

Another suggestion: I wonder how a smooth arc would look going from end to end and just touching the underside of the top in the middle where it would be fastened. I don’t know if a brass tube can be bent that way or not. You may have to have a machine shop do it for you.

View olbigun's profile

olbigun

4 posts in 42 days


#6 posted 02-19-2020 04:36 PM

With your addition of 45drg. angles ADD X BRACES from/into the upper area between the legs ON BOTH ENDS and you can PARK A BULLDOZER ON IT.

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