On Mon, 18 Dec 2017 03:24:03 +0100, Emanuel Berg
wrote:

John B. wrote:

That's sort of asking "how long is a piece of
string" :-)

Actually, that was to be my very next
question

Bike chain, how many speeds, runs inside
a chain case, how fast, how much power
transferred, new cogs or old, lubricated, how
frequently, etc., etc.

OK, then let's assume a single speed bike,
either Torpedo or Shimano. It does have a chain
guard. Speed doesn't exceed 25 km/h. The person
cycling weights in at 80 kg. The chainwheel and
sprocket are 10-15 years old. The chain is
lubricated one a month.

One of the "etc's" has to be "and how far do you ride in a normal
year, Sir?"
--
Cheers,

John B.