19" Rack History

Just checked a 1939 Radio handbook--construction there is for 17" chassis fitting on a "standard" relay rack panel, so I'm assuming that 19" was a "standard" even back then. Looking at some of the old transmitter power supply designs reminds one how much weight one of those panels could support. There are ads for both Bud and Par Metal, but no specifics. When I worked in steel-mill process control before "computers", none of the installations used relay rack construction. Usually a large 1/4" steel panel was simply welded into place with L- or U-channel backing it. Holes were then cut and drilled to mount everything. Of course, this was mostly electro-pneumatic or electro-hydraulic control, so relay rack panels probably made no sense. Cheers, Chuck