What makes 'good' cranks good?

Yo, what makes good cranks good? Stiffness? Material? Mystery third property?

As an aside: I can’t get my head around the price differences between cranks. Aren’t they essentially a piece of steel with a pedal hole on one end and some chainring holes on the other?

Does the money go into crazy forging techniques? R&D?

an njs stamp

Well for starters, unless we’re talking really cheap cottered cranks, they are made of forged ALUMINIUM ALLOY, not steel.

Blakey would be the best person to ask regarding forging/manufacturing processes of cranks.

But in terms of the differences between track cranks:
-BCD of the cranks? No point having cranks that you can’t buy chainrings for…
-Are the cranks finished well? Sugino 75 cranks for instance have a nice polished anodised finish. Cheap models don’t.
-Square taper, Octolink or External BB interface? Obvious implications for bottom bracket compatibility.
-Are the crank arms offered in difference lengths? Dumb running cranks that don’t fit your body type.

Shimano have developed their ‘Hollowtech’ crank design over the years which are great IMO. The forging is hollow making the crank lighter. This is about as sophisticated as is gets for alloy crank design. To put it in perspective, the Dura Ace 7900 crankset is actually lighter than most of the carbon cranksets on the market.
I use Hollowtech cranks on all my bikes including a single speed. While not track specific, they can easily be adapted for fixed.

An ideal crankset is stiff and light. The less flex in a crank arm, the more power you have going directly into your drivetrain. Things like hollowtech construction and two-piece cranks with external bottom brackets are good because they make the cranks bother lighter and stiffer. If you’ve got shitty cranks, you’ll get a heap of flex and they’ll tend to feel nasty. Lighter also means less rotating weight, which is always a good thing. Same way light pedals and shoes make life easier.

Good quality track cranks are machined or forged to a greater precision which means they centre the chainring better. This translates to less tight or lose spots in the chain tension not so much a problem on a street beater but a issue on a well set up race bike.