Hi, love your Popular mechanics plans builds. I HAD Popular mechanics from 1914 to 1963, by Grandfathers collection. (destroyed in the 2011 Floods).
BUT writing here to point out, you mention Imperial Measure. But America has never had Imperial measurements. That only is found in England and english Commonwealth countries.
America kept the “then” english feet and inches and volume measure that it had when it was an English colony. And when it separated from England in 1776. (these were later ratified by your early Congress)
Then the french worked on the Metric System which was brought into being in France in 1818. Napoleon found out when he crossed through the “German Federation” (pre Germany), to attack Prussia, that each “german” state and many cities had different lengths and weights. 18 known differences.
and Metric was finally brought into being 1818. while they were working on it, England got word of it and how simple it was, and sent a spy to get a copy of it. but as they were still working on it, it was not yet finally agreed on as to the exact weights and measure, and he may have copied rejected plans. the English Weights and measure dept was at that time based in Winchester. (the old english weights and volumes were Called Troy Weights, and the old English Gallon was sometimes called the “Winchester Gallon”.
England then though about bringing into being a new set of weights and measures that they though would be devisable into the metric system. and named it the “Imperial weights and measure”, finally approved by Parliament in 1824 (but it never was devisable into metric). And then based their Weights & Measure department at Greenwich, where the Zero Meridian is.
the difference between the Imperial Inch and the American inch goes down the about 6 decimal points. the American Mile is only an inch or so, shorter than the Imperial Mile. the biggest difference is the the liquid volumes, where the American Gallon is approx. 20% shorter than the Imperial Gallon. (The english Imperial Gallon is defined as 101 Cubic inches (Imperial) of Barley. (The english based many of their measurements on Barley and Peppercorns, because they did not shrink or swell in heat or cold.
(Trivia. when the Metric system was introduced the litre was to be of Sea water, but is now of distilled water. and Australia (where I am ) the introduction caused more that a few problems, and also lead to a Small Revolt called the ‘Eureka Stockade’. The gold miners had many grievances, but one was a belief that they were being ‘ripped off’ by the official gold buyers, who were using faux ‘Imperial’ weights to price the gold. (But confusingly in the 1824 Weights and measure act, bringing in Imperial Weights and measure, precious metals, were to be weighed in the old “Troy Weights system”, so is Gunpowder., the miners were right that they were being ripped off, but could not prove it)
This was better detailed in a 4 page Popular Mechanics article in the 1950’s. and dam sad I lost them. i read them all from cover to cover. took years. I am trying to collect a library of them again, but will never be able to afford the WW1 issues.
Regards, Sandy Barrie.