I think a lot of the old units came from the Romans, so everyone in Europe had them at some point before they went metric.
That is almost as good as the engineers that had trouble with the bird strike testing machine in the 1970's In an issue of Meat & Poultry magazine, editors quoted from “Feathers,” the publication of the California Poultry Industry Federation, telling the following story: The US Federal Aviation Administration has a unique device for testing the strength of windshields on airplanes. The device is a gun that launches a dead chicken at a plane’s windshield at approximately the speed the plane flies. The theory is that if the windshield doesn’t crack from the carcass impact, it’ll survive a real collision with a bird during flight. It seems the British were very interested in this and wanted to test a windshield on a brand new, speedy locomotive they’re developing. They borrowed FAA’s chicken launcher, loaded the chicken and fired. The ballistic chicken shattered the windshield, broke the engineer’s chair and embedded itself in the back wall of the engine’s cab. The British were stunned and asked the FAA to recheck the test to see if everything was done correctly. The FAA reviewed the test thoroughly and had one recommendation: “Use a thawed chicken.”
We sell trees in 30cm height brackets... so 90-120cm, 120-150, 150-180 etc... and get asked frequently why the odd divisions and not in 50cm bands or 10 cm bands? Because it equates to 3-4 foot, 4-5', 5-6' etc etc of course!
But when both systems fail us or when performing field repairs the CH standard is universally understood; whether you are working in a oil field, on a battle ship or repairing a space craft. And there is the RCH standard for increased precision.
I like the way a lot of yanks just have to convert something sensible like 50mm into inches - then argue about how to round off the thou. lol
When buying metals etc we work in £s per kilo, the Americans work in $s per lb. We had to convert for them....because they couldn't.
I like using inches,pounds,feet,etc. But some people... You give then 25.4mm,and they take 1.609344 km...
When I worked for Marconi Avionics at Hemel Hempstead back in the '80's I had to go up to Bae Woodford, near Stockport, a fair bit as we were involved in a joint project. Around the back of where we worked were a couple of hangers and some old Vulcan bombers, one day when we were bored we went exploring round there and found an original "chicken gun". Apparently that was the area that they used to test windscreens by firing chickens at them, there were also huge rings in the concrete where they would chain the aircraft down and run the engines up to max thrust and rapidly fire chickens into them to simulate a bird strike. Imagine going down the pub and when asked "what did you do at work today?" replying with "Oh not much, fired a few dozen chickens into a chained down Vulcan engine at full throttle!"