This project came about after I picked up a few Eames fiberglass chairs that needed new mounts. The shock mounts on these chairs are often cracked and squished after 30+ years of use, or the glue has failed and they've fallen off.
If you already have shock mounts, skip to the last step of this Instructable for Installation tips. The remaining steps will show you how to make your own mounts.
Since I had 4 chairs that needed new mounts, making them myself was a lot cheaper than buying reproductions. There's no waiting for shipping, I can have the mounts the next day, and I can control the quality myself. Aside from the mold rubber, the only cost is the weld nuts ($1.63 each for Stainless Steel or $.74 each for Zinc Plated). Stainless weld nuts are an improvement over reproduction or even the original mounts, because they won't rust if the chairs are being used outdoors.
Eames related links with nice photos and some history:
Almost everything you need to know about shock mounts is detailed in the FURNITURE SHOCK MOUNT CONSTRUCTION Patent (US2649136), submitted in 1947. Although the drawings in the patent are for a prototype DCM chair, the concept is very similar for the later chairs. The patent goes into detail about the construction, type of rubber, and adhesives used to make shock mounts.
There are different types of rubber shock mounts on the Eames chairs. The very early fiberglass chairs have a larger shock mount than the later, more common fiberglass chairs. The bent plywood chairs, like the LCW and DCW have wider and more rectangular mounts. The DCM and LCM with bent metal tube frames have similar mounts to what we're making here, but they are thicker. This process can be adapted for any of those mounts, but it is focused on making shock mounts for the fiberglass armshell and side shell chairs.
The cutaway view of the mount shows how the piece of hardware is cast into the rubber (this is what the bolt threads into, attaching the shell to the base). The closest off-the-shelf hardware available is called a weld-nut, and the ones used here are made by Rotaloc.
Eames Fiberglass Shock Mount Specifications:
In the patent, there is this paragraph (emphasis added in italics):
"In this specification and the accompanying drawings, I have shown and described a preferred embodiment of my invention and various modifications thereof; but it is to be understood that these are not intended to be exhaustive nor limiting of the invention, but on the contrary are given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify and adapt it in various forms, each as may be best suited to the conditions of a particular use."
I was surprised and delighted to read anything like this in a patent, because it's a philosophy that a lot of us here share, and it's one of the reasons this site exists in the first place. Open source design... in 1947!
Now, let's make shock mounts.