[Amps] CHASSIS

k7fm k7fm at teleport.com
Thu Mar 16 09:22:15 EST 2006


"Amen, Arne, and plywood is stiffer pound for pound than metal.  During
WW-2, the most common beach landing craft were made of mahogany
plywood.   These craft were designed and manufactured by Andrew Higgins
in New Orleans, Louisiana.  Higgins' boats were used in both Europe and
the Pacific theatres."

The main spar in my aircraft is a box made from thin plywood.  The leading 
edge of the wing forms a D spar and is made from thin birch plywood.  I 
trust my life with the stuff.

What wood does not do is shield rf.  But, that can be solved fairly easily. 
Many years ago I built a regen receiver using wood.  But, I found the hand 
capacity, when I got near the front panel, changed the frequency (bad).  I 
solved the problem by covering the inside of the wood panel with household 
aluminum foil, which was connected to the frame of the tuning capacitor. 
Still have that gem.

When using wood, changes need to be made in construction techniques.  Thick 
wood chassis is not conducive to installing tube sockets or other components 
designed to be mounted on thin materials.  Breadboard construction works 
well, and power supplies adapt nicely to wood construction, especially since 
they usually do not need rf shielding.

Often, you can blend the two materials for some gorgeous equipment.  Use the 
wood for exterior cabinets and make the panel and chassis with metal.  If 
the chassis components are self shielding, it can be a pretty package.

And, the British even made wooden automobiles.  There is nothing like seeing 
a Bond, with a burled walnut hardtop.

Colin  K7FM






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