Description

When I was a senior at Berkeley in the early 80s I did a physics lab in which the goal was to understand and take a hologram. The optical setup sitting on the third floor of LeConte Hall required an incredibly stable platform, which was composed of a huge sand filled platform sitting on inner tubes. It worked amazingly well. Other companies have made isolation platforms with this basic concept in years past. I told Matt I always wanted to do one and we set about working up one that was simple, elegant and effective. Matt made a prototype using a couple pieces of plywood with silicone caulk between to create a constrained layer. He then machined a nice little set of curved “fences” attached to the bottom in order to center a small inner tube under the platform. I also asked for a sand filled version. Being a competent engineer, Matt took measurements with an accelerometer (iPhone with app) on the platform and dropping a ball from a fixed height onto the surface the platform sat on. This was done with and without sand, with and without innertube, etc., until he had a reasonable amount of data to interpret. Turns out the sand didn’t do much, but the inner tube and constrained layer worked really well.

Construction is Sapele plywood for the main platform, with an alder skirt to hide the inner tube. Dimensions are 17″ wide x 15″ deep x about 2.5″ tall (432mm x 381mm x approx. 63mm). Tests done by dropping a lead weight on the equipment rack shelf upon which the iso platform sat, with my Analog Engineering modified Empire 208 turntable sitting on it, showed about a sevenfold reduction in the peak energy transferred to the iPhone accelerometer placed on the turntable platter vs. the turntable sitting directly on the shelf without the isolation platform. Significant.