Makerspace challenge: How do we fix this chair?

MSU Surplus has lots of these very nice Hayworth rolling chairs for $35.00 each. They have a fold-up seat so they can be nested. Most have arms, but some don’t. We have these in my office, and I can confirm they are very nice comfy chairs until they break. And they all break in the same way, leaving them in a state of permanent recline. Clearly it’s a design flaw.

There is a pair of black torsion springs, and the end is bent at 90deg. and fits into the frame at the end of the long slot. The end of the spring is in a plastic bushing. On a working chair (1st photo), there is a vertical black cover over the springs that I think is the key. Reclining twists the spring arms that are under the cover, and the end slides in the slot just a bit.

The second photo is a broken one. At the bottom you can see the same socket head screw, but the cover is broken. The cover keeps the spring close to the frame, so it’s forced to twist. The springs are completely intact on all the chairs I saw, but the covers are all broken or missing. Without the cover, it’s free to flop around, and it offers no resistance to reclining.

I think the fix is some kind of retaining clip around the spring in the corner to hold it close, but let it twist. There is a heavy screw right there for just this purpose.

In any case, I bought one to experiment with, and I welcome collaborators and opinions. If we can crack this nut, our chair problems are solved.

And yes, it is my last day in the office before two weeks of vacation, and there is no one else in my hallway. Why do you ask?

This might be a solution. A couple big of cable ties. They say they’re 180 pound tensile strength. It’s working well at the moment, but we’ll see if they stretch.

This could open up a whole new world of comparatively inexpensive sitting.

I sell some 3D printed replacement parts for Steelcase and Herman Miller chairs on eBay so I’m interested in this problem.

It looks like a small printed part could bolt on with the fastener from the broken cover and retain the torsion bar? I think a 100% infill part in PLA Pro or polycarbonate might be durable enough.

Or maybe one of these in the right size would work even better:

Apparently Haworth recognized this issue. Here is a bulletin for replacing the broken cover with a metal reinforced one and larger bolts.

x99_seminar_torsion_cov_083117 (1).pdf (258.4 KB)

Are they supplying that replacement kit for free? So far two large zip ties are working fine, at a cost of about $0.40 per chair, or a pair of metal clamps for $4.00. And you don’t have to drill and tap new holes.

I’m going to propose a targeted donation fund for buying more chairs from MSU Surplus. Six to 12 of these would be great to have.

I didn’t see anything about where to get the kit. I’m assuming that would be under warranty only.