I trained in Metallurgy then added a Materials Science masters to that followed by a pile of diplomas mostly in various types of diagnostics
So take it from me that 99.999999999% of the clots who post on Face Book , Whats App, You Tube etc are blurting from their backsides when it comes from this stuff.
I have tested plastics that are stronger than mild steel & have superiour wear charasterics to grey cast iron and a diaphragm plastic that was 10 time the price of gold .
In the eyes of Joe Pig Ignorant Public plastic = cheap where as in reality that particular type of plastic is the perfect material for the job.
The drive gears of the Courage cam shafts come to mind , they knock down the engine noise quite a bit and require next to no lubrication.
Then when it comes to design they have less than zero understanding and again I refer to the Courage engine , all but perfect for a ride on mower once they sorted out the counter balance mechanism.
Still the only mower to have a clean hang down oil filter and the ability to strip it down still mounted to the mower which take 2 to 4 hours off the major repair time .
IT should have been the bench mark for all new generations of mower engines but because it was so radically different it got rejected by all of the arm chair experts thus failed in the market place .