non metal parts
I was just looking in my local motor store and a cheap cycle that was on display had a plastic crank, I was quite surprised.
Is this ok, or is it just done for cost cutting?
I had seen a lot of plastic cranks on supermarket bikes (very cheap <60$, the whole bike is 60$) and with plastic brake levers, and others. But many of the "plastic cranks" are really from metal coated with a thick plastic housing (of 3-10mm thick).
"Exceptionally" low quality that is
Very cheap bikes have this. I am pretty sure it is just to make it look like a more expensive crank as better ones have much fatter aluminum arms.
Lots of cheap bikes have steel cranks which are quite skinny little things without plastic and I suspect this is what it underneatht he plastic on the bike you saw.
Indeed. There are no plastic cranks per se, just cheap steel cranks covered in plastic to disguise the fact they are pot metal steel.