During the early part of the last century, it was an accepted practice to put grooves in the piston and to let the piston skirt emerge quite a way out of the bottom of the barrel. I was interested to see this quoted again in a 1914 book by Dr A M Low “A manual of the coming form of internal combustion engine” (price one shilling and sixpence) It was previously owned by T B Ward of Ward Motors, 32 Hustler Street, Bradford. and loaned to me by Titch Allen. I would suspect you are correct, Dave, to point out that the lubricants, like the fuel, was significantly inferior to that we have today. We have also learned that we should pay much more attention to the texture of the walls of the barrel, as if it is too smooth, the rings just squeegee off the oil and leave insufficient lubrication. There was a fashion at one time to consider that a good bore should be honed to a mirror finish. Very unwise. I prefer a fairly fine bored finish then to finish with a flex hone to give a cross hatched oil retaining finish and to radius the corners of the ports.
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Like many other design features on the Scott, they were just continued through the years rather than re evaluate as conditions changed.
The most interesting pistons I remember seeing came out of a Fiat 1500 and these had a series of circular grooves turned in of very big radius but shallow. The engineers amongst us can liken it to the “Broadnose” tool finish used on planers when making marking out tables. Roger