Snapped crank.

[tinywheels]

Good for you. And what exactly do you think does that prove? Does this change the laws of physics? Singular evidence is random and is not usable as general prove for anything. There are 100.000s of Bromptons out there on the road for decades where the cranks did not snap over the last 35 years since their invention. And a handful where they did.

It was not a frame that snapped here but a crank, so I do not see what you want to express.

I wish to express that cannondale seemed to build a near bombproof mtb.
Therefore I posed "are modern bikes built to a price "
I do realise there are numerous reasons why a crank may snap. Am I being unreasonable in thinking price may be a factor? In view of the shimano debacle, many others may be concerned.
Personally I looked at my brompton cranks and decided my weight and riding style etc may cause an issue. Hence my move to hope.
I would imagine the vast majority of brompton owners do a minimal mileage on paved roads so don't suffer.

 

[FishFright]

I wish to express that cannondale seemed to build a near bombproof mtb.
Therefore I posed "are modern bikes built to a price "
I do realise there are numerous reasons why a crank may snap. Am I being unreasonable in thinking price may be a factor? In view of the shimano debacle, many others may be concerned.
Personally I looked at my brompton cranks and decided my weight and riding style etc may cause an issue. Hence my move to hope.
I would imagine the vast majority of brompton owners do a minimal mileage on paved roads so don't suffer.

Cannondale used to be called Crack'n'Fail for the number of frame failures, but they would honour the warranty.

 

[tinywheels]

OK here's a pic òr two with serial numbers it appears sugino made the cranks. ]

 

[berlinonaut]

Still no idea how this may even loosely connect to the thread topic.

 

[presta]

Dead gaps in the reaction to force direction changes grow. Also in the case of tapered...

If you had a square axle with parallel sides and no taper, there would always be some clearance between them due to both manufacturing tolerances and compression of the metal under pedalling forces. This allows movement which causes fretting and wear, which then allows more movement causing even faster wear.

On the other hand, when you have a tapered socket, the crank slides on until the clearance all closes up and the surfaces mate without any gap, then when you tighten it the axle is pressed into the socket by force. With the bolt tightened to the correct torque, the force now pressing the mating surfaces together exceeds the force caused by pedalling, and this ensures that the stay pressed together and don't move, preventing wear.

if play is experienced, just tension further the cranks bolt until the play is gone

If a crank isn't tightened enough when fitted new it will move, cause wear, and come loose, and then keep coming loose. No amount of retightening will fix the problem once the taper's worn because the wear will allow movement even when tightened to the correct torque.

a combination of two brands (left crank Sugino XD, rest Stronglight Track 2000)

Some cranks from those brands use different tapers, they might not both be compatible with the BB.
https://www.sheldonbrown.com/bbtaper.html