Re: [TCML] primary tubing

[G Hunter <dogbrain_39560@xxxxxxxxx>]

> The only discrepancy I have is that I thought Al simply
> oxidized in air, maybe you could also call it anodization
> but I thought that was adding pigment to the outside oxide
> layer.
> 
> Drake
> 

That's what I keep coming back to.  What about the Aluminum Oxide layer?  Aluminum Oxide is an electrical insulator, and it is so hard it is used as an abrasive for sandpaper and the like.  A rock-hard layer of insulation would seem to make good electrical contact problematic.  Shining the Al with steel wool won't help, as the oxide layer instantly forms again.  Also, the usual hardware store-grade primary terminations and taps (alligator clips, fuse clips, ground lugs, etc.) are typically made of copper, brass, or copper-plated steel.  Not only are they too soft to cut the oxide layer, but contact between dissimilar metals only aggravates the formation of a high resistance connection.

Seriously though, I wonder how much these theoretical concerns really affect actual coil performance.  I've used solid aluminum wire as the primary for a very small coil, and it worked fine.  I suspect Al is probably OK for the small stuff, but becomes a bigger issue as the coil gets bigger and the kva goes up.

As far as the compactness issue of fat Al tube -vs- skinny Cu tube, that could sidestepped by using flat aluminum strap. 

Greg


      
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