Hopper

Internet has been down for a couple of days but I'm back. And I am willing to say that no I haven't been able to find any crankset or remember any that are designed to flex. I am willing to admit I have made a mistake, however I do for some reason remember hearing it somewhere so maybe there are but at the moment I am willing to say I am probably incorrect.

As for lifespan yes some racing components aren't going to have a long lifespan, XT is renowned for being longlasting and still quality. However XTR has quality, it won't last as long as the XT, to make it lighter and higher quality, something has to be sacraficed.

harov3

Tims right, there is nothing thats completely rigid. Rigidity as applied to MB components is a matter of perception, some components feel rigid others dont. I dont see much point in designing flex into components like cranksets but components like frames and wheels may benifit from flex. A wheelset that flexes will absorb more punishment without breaking than a similar wheelset that is more rigid. A MB frame may benifit from the same approach. The trick would be to design just enough flex in that it helped absorb impact without feeling flexy. Frames on race motorcycles (moto-gp) are designed to flex under power to aid cornering speed, do MB frames flex? yeah!....Is it designed in and benificial? dont know...good subject for mech engineering thesis.

TimB

No Mech thesis needed.
All components are designed to flex. Flex hasto happen because to achieve a rigid structure the stress in the material would exceed the Ultimate strenght of the material, the component would not last long is this design method was used.

So engineers decide that the they want a little bit of deflection so they can predict the stresses and thus make the component last a long time.
So all things are designed to flex, some more than others, ie springs must flex continuously for many years before failing whereas I beams used to keep buildings from falling over must have minimal flex or deflection along their length for the life of the building.
The key word is fatigue.

AS for XT out lasting XTR, this is a common myth. Although XTR is much more expensive and lighter, it lats just as long as XT and in most cases longer.
Th reason is that it's designed to handle the rigors of a stronger rider and transmit more power. It's more expensive because it's made in lower volume with higher labour input. For all intents and purposes many mechanisms are shared.

For instance the Dual Control shifters of XT and XTR share a common mechanism but the XTR is removed fromteh assembly line to have an extra bearing fitted. That Extra operation costs money.
Same with the New SRAM X.0 stuff, very expensive due to the large amount of labour that goes into the manufacture.
Just because something is lighter does not mean it's weaker and won;t last.
Materials and design play a large role here.

XTR definately has the longevity to rival XT in a lifecycle cost analysis.

harov3

[QUOTE=TimB]No Mech thesis needed.
All components are designed to flex. Flex hasto happen because to achieve a rigid structure the stress in the material would exceed the Ultimate strenght of the material, the component would not last long is this design method was used.

So engineers decide that the they want a little bit of deflection so they can predict the stresses and thus make the component last a long time.
So all things are designed to flex, some more than others, ie springs must flex continuously for many years before failing whereas I beams used to keep buildings from falling over must have minimal flex or deflection along their length for the life of the building.
The key word is fatigue.QUOTE]


Hmmmmm........................Your not an engineer are you Tim.

sparks_219 

The company may put a little more labour and parts as well as a bit more R&D time into their higher end products. However, the amount of money put into the extras do not add to what they demand (usually 100% more). Companies usually use a skimming pricing strategy to create a perception of much higher quality where in fact the parts may only be marginally better.

Back to the topic, I dont think any company HAVE to scarifice durability for lighter weight. The lighter weight can be achieved by using a better manufacturing process such as cold forging. So in most case scenerios, I would say XTR would be just as rugged and durable as the XT level components.

Raiyn

That's hasn't been my experience and the latter bit is pure garbageJust because something is more expensive doesn't make it better eitherYes they do, however there isn't enough of a weight savings to justify the added expenseBased on what you're saying if XTR lasts just as long as XT how precisely does spending the extra money on something that won't last any longer rival something that's cheaper in the "cost analysis"
Seems to me that the minimal weight savings and added expense would make it LESS attractive. Unless all you care about is the bling factor