In alt.home.repair, on Thu, 26 Sep 2019 02:14:03 +0000, marise
m wrote:

Metal vintage chairs that lean way too far back. Is there some way too
reinforce them?
https://www.homeownershub.com/img/iv

Weld bars across where the legs bend at the front bottom. That's where
they flex the most, too much, when you lean back.

But how to get it right is another story. How long should each bar be.
6", 8", a foot so there almost no bending there? It depends on how much
farther they go back than they should. (Maybe even 4" but that
doesn't seem worth the effort**.)

I assume you feel like the whole chair will fall backwards with you in
it.

If you make it only 6", I wonder if it will bend and fold just above the
weld. Maybe the welded piece should not be centered on the bend but
should start just as the vertical pipe starts to bend backwards. And I
would want the same splint on the left and right legs but insisting on
that might be a bad idea. Do one side, see how much you've accomplished
and decide **how long to make the splint for the other side. Maybe you
don't need anything.

In that case, if you want the second chair to have splints of equal
length, make the first side shorter than on the first chair. Put that
on and sit in the chair. Maybe the second chair isn't the same as the
first.

And, do one chair at a time and hope you learn something for the next
chair.

For the record, I've neve done this.