[paul cotter (OP)]

As we well know science is bedevilled with cranks. To me, a crank is a mechanism for converting reciprocating motion to rotary motion. I am just curious how it came to be used for describing some of the nutjobs that inhabit the fringes of science.

[Petrochemicals]

Probably a wind up Paul, which typing it shows what a peculiar language English is, it's very blowy. 

[alancalverd]

I think the connection is either via perpendicularity or offset, or less probably from the Germanic krank meaning sick.

The essence of crank behavior is either that it is completely orthogonal to the norm (like anti-monarchists) or that it runs parallel but distinct. One of the best London restaurants was a pioneering vegetarian establishment called Cranks that flourished into a successful chain for about 50 years - perfectly normal facilities but with the menu just offset a bit.   

[Bored chemist]

I always assumed it mean they were "not quite thinking straight".

[Petrochemicals]

Perhaps it similar to "hack" ?

[alancalverd]

As we well know science is bedevilled with cranks.

The life cycle of a scientific idea: denial, ridicule, contempt, acceptance, arrogation by those who dismissed it in the first place.
A prophet is not without honor, save in his own time and among his own people.

[paul cotter (OP)]

There's Alan, quoting the bible, yet again!

[alancalverd]

First rule of atheism - know your enemy!

[Petrochemicals]

An  agitator? Whom agitates to gain attention and hold sway.

[alancalverd]

Good point - you can't stir much with a straight stick!

[Petrochemicals]

Good point - you can't stir much with a straight stick!

Very good.