When you increase the size of the axle (spindle) and need to maintain the same outer diameter of the BB, you leave little room for bearings.
Actually, I wasn't planning on changing spindle diameters.
No need to do this over the entire length of the spindle anyway, maybe just at the outer ends where the outboard bearing(s) would be fitted.
Rather the diameter of the ballbearings and their accompanying housings.
Bigger bearings could, in theory, be housing bigger, hence less balls.
Since a ball bearing and it's race make for a point contact when motionless and a line once going into a circular motion the larger the diameter they describe the less revolutions they'll make at the same revolutionary velocity (ouch).
This in turn reduces heat through friction and the bigger bearing assy would in theory be stiffer to begin with and it can theoretically be attached closer to crank and crankarm fixings.
In fact, I see no particular reason why you'd have to stick with the classic cartridge type of ball races.
You could just as well use ball/cup types or it's cousin the cone/cup type I suppose.
Even sleeve type bearings are not unthinkable given modern high-tech materials but, IMHO, might turn out too expensive to manufacture in view of the tolerances required for them to be stiff enough at the right places for this application.
Besides that you need to prevent the sleeve for moving sideways so that may well put the out of the range of options.
It's been worked around already, but it's not cheap.
Still it's fun the explore all possibile options regardless of what the market is willing to cough up for the end product.
It keeps on surprising me that no matter how far fetched the idea, if it works markedly better than what we have currently available, someone always seems to want to foot the bill.
Regardless of Moore's law of diminuishing returns, that is....
And of course this one too:
like Moore's law of transistors: Weight, Cost, Performance, pick two.
P.S. Totally off the wall idea: pressurized airbearings for TT races by 2015 perhaps....
All that running on airless tyres, tyres being made of some space age cellular foam formulated just right for the job....Ah......