I’m always patrolling for potential debunks and rebunks.
Debunk: No, it wasn’t that way!
Rebunk: Yes, it was that way, despite my debunk desires!
Browsing through old radio magazines, noticed an ad for Delco farm radios, powered by 32 volts DC. The ad loudly claimed NO VIBRATOR!
Delco, part of GM, primarily made starters and generators for cars, and secondarily (heh) made ignition systems. For a while they branched into car radios, and even more briefly into home and farm radios.
NO VIBRATOR caught my attention. Car radios used a vibrator to make the necessary AC to drive a step-up transformer for plate voltage. Was this an exception to the high-voltage plate supply that made tube radios unnecessarily large and dangerous?
Rebunk: Delco’s ad was deceptive. The farm radios used the 32V windmill supply for series filaments, but needed the usual B batteries for HV. Delco also made a separate HV inverter that did include a vibrator.
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I hadn’t heard of the 32VDC standard, so started looking through farm equipment journals. It was an unofficial but convenient standard, allowing mass production of generators and batteries for easy replacement.
While browsing through the farm journals, I started noticing LOTS of treaded tractors in 1920. They weren’t the majority, but they were common, made by several manufacturers including Caterpillar.
Treaded tractors are still used around here in the Palouse, where unique soil favors a unique and profitable crop of durum wheat. The unique soil was piled up into steep domes by volcanic eruptions, and the domes require treads. Local legend says that the treaded tractors were uniquely developed here as homemade inventions.
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Graphics sidenote: Those tractor ads are impressive, especially considering that they were aimed at a small audience of farm equipment dealers. Dynamic motion, well-proportioned fonts. Pen-and-ink commercial artists reached a peak of talent in the ’20s. Similar talent levels are seen in anime now, but never in commercial art.