Last week, I scored a base-model Herman Miller Aeron chair on Craigslist for $20.
The base-model version lacks the side paddles and seat-base cabling that permit one to adjust aspects of the chair’s forward and backward tilt. It does have the side knob that is intended to adjust the resistance of the chair’s recline spring.
It is the largest size chair (“C”) and was sold cheaply by the seller because he was leaving the country, had been given the chair, and he thought that the chair was broken due to its apparent inability to recline.
On getting it home, the first thing I did, of course, was find information on disassembly and repair of Aerons. I also noted that the chair now did in fact recline. It reclined so eagerly, in fact, that I feared I had broken a spring. The tensioning knob also appeared to be stripped and therefore did not add any appreciable stiffness to the declinability of the chair.
Once I had disassembled the chair, I was able to glean some useful information.
First, while the tensioning knob’s gear is indeed partially stripped, the reason that the gear was skipping is that the knob drives a right angle gear up and down a center post and the knob had driven the gear to its’ full extent against a heavy-duty metal strap stop.
The inevitable conclusion is that over the chair’s life the recline-tension spring has simply relaxed to the point that the gear mechanism cannot increase the tension available. The chair itself has an original manufacture date of 1998. So I guess it is understandable that the spring has relaxed in its dotage.
After several days of searching it’s clear that while Herman Miller makes a subset of Aeron parts available for direct consumer sale and replacement, the main tensioning spring is not among them. Rather, the base itself is replaced and the base and replacement labor is only available via authorized Herman Miller dealers with a sticker price north of $300.
I did find a couple examples of the base unit on eBay with ship-inclusive prices at about $200.
The forward-and-reverse tile paddles and cables are also in the no-direct-sale category and have individual list prices of about $175.
eBay also has paddles and cables available and they vary widely in price, so while I am unlikely to spring for a $200 base-and-parts assembly I might well lay out up to ten or eleven American dollars for these cables and parts. Until then, however, I wanted to see how far I could get with chewing gum and baling wire.
I am happy to report that a single conventional wire hanger has now been repurposed to provide a strut-based replacement system for the cable-and-paddle mechanisms the chair was designed for. The control cables enter the base via twin access passthroughs to the rear of the base assembly and each cable-and-paddle drives a plastic rocker gear through a short arc of about an inch travel. Pinching the coat hanger wire over the attachment ears of the rocker gears gave complete freedom of movement to the gears actuated by simply sliding the wires forward and back. A bit of fiddling and experimenting with wire-bend detents and right-angle bends to make the wire struts accessible from a seated position and I am good to go.
It is a darn shame that Scott Chaffin did not make it to see the day.