drcbrath

@groghunter. Actually it is that simple. Widening the center section between the flanges maintains the relative position of the dropouts, flanges, and bearings; so there is no change in leverage on the axle. A shear and bending moment diagram shows the shear across the hub constant and independent of width and the bending moment essentially zero over the length of the center section. The only significant increase is the torsional strain in the longer center section. (The torsional stress is actually unchanged since it is caused by either the torque from the cassette due to chain tension or brake torque, neither of which depend on hub width.) The extra engineering needed to regain the torsional stiffness amounts to a 5 minute back-of-envelope calculation for the required increase in the polar moment of inertia. And whether to get that increase via wall thickness or diameter increase (or some optimized combination). Hub width choice is more a matter of optimization of many factors. But "optimum" means different things depending on what is important to the one doing the optimizing. For a rider/bike owner: strength, stiffness, affordable, "How do I get the best ride for my money?" For a manufacturer, especially a bike company: profit, "How can we make a bike that will collectively make the most profit?"

A new CNC'd hub would cost almost nothing extra over existing standard---only a little more aluminum, same machining steps.

I repaired by carbon swingarm myself. Only about $20 in materials. Stronger than new; I wrapped the carbon more than twice as thick as original. With a layup pattern that adds toughness as well to avoid a repeat failure by another freak hit like the one that cracked it. The skills are simple enough but labor intensive.

Flex joint does add some resistance. More like adding a spring, not like adding friction. That additional spring rate should be accounted for in the suspension and damping design.Limited to short travel (1-2 inches) limits its usefulness to cruiser/comfort bikes in my opinion.

Proper design and application, especially in material selection, can make fatigue life near infinite. But the deflection needs to be small to keep the strain down and avoid fatigue. So no long travel designs. Otherwise, barring abuse, a flex joint will have zero free-play, zero maintenance, and long long life.

Telescoping shaft drive.

59F (15C) and partly cloudy make me think twice. Lucky that doesn't happen often in San Diego.

Some say, the best make it look easy.

Another kind of cost---regret for choosing cheap/affordable rather than what you really want. Two years ago I choose a bike for the great to price; a 2012 GT Force Carbon Sport, 150 mm travel, dropper post, 26 inch wheels complete on clearance for $2300 new! I really wanted a Santa Cruz Nomad Carbon---$2899 frame only. The GT is great when it works. But starting from the second ride, I have been battling a badly creaking suspension pivot; full maintenance then ride, starts creaking again after 2-10 miles! Worse than a nagging wife. There's nothing quite as expensive as buying something you don't really want.