[petek]

Cybersonics has been making telescoping structures out of extrusions for years, mostly 8020 1010, though we used Bosch 2020 last year. Instead of using linear bearings, they just interlock parallel extrusions and apply a little lithium grease.

The engineer in me cringes every time I look at how we do it, but it's simple, it works and is very light weight. I think the key to this working is the hard anodized coating on the aluminum keeps it from galling. Needless to say, I wouldn't expect this to work for a real long time, but the only problem we've had (besides cringing engineers) is when the strut gets bent, but that would be a problem with linear guide bearings, too.