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I was working on the shimmy problem a couple years ago when a bunch of the ES guys were dealing with shimmy. I did some temperature tests on BelRay 30W. I used a Zahn cup to measure viscosity so my measurements were time measurements. I tested it at 60F, 90F, 120F and 180F. From 60F to 90F its viscosity was cut in half. From 90F to 120F it was cut in half again. So from 60F to 120F the time for the oil to flow through the Zahn cup was 1/4.
I'm not sure of the science of damping vs. viscosity measured with a Zahn cup, but the struts are definitely affected temperature.
After running my tests and posting them to the ES group, some of the guys suggested some very high quality multi-viscosity motorcycle racing strut oils like Spectro. They only performed slightly better than the BelRay 30W.
The new style strut uses hydraulic fluid which doesn't change viscosity with temperature. I tested it too.
Some of the ES guys have blocked air flow down the nose strut fairing from the cowl to keep it cooler.
After my shimmy incident that cracked my engine mount, I traded it in to Lancair for the new style strut.
Mike Easley
Colorado Springs
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