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Are there theoretical models or are such things pure measurement?
Measurement is best, modelling air flow over wire spoked wheels is not easy. Imagine modelling a helicopter rotor, then turn it on its side right next to the ground and add a rim which messes with the air flow before it gets to the 'blades'. That makes the helicopter simple in comparison with just one side of a wheel, yet AFAIK western helicopter engineers modelled helicopter rotors and decided that an 8-blade single rotor could not work effectively. It took a Ukrainian to prove them wrong :-)
gbj_tester
JWestland
Tx ^=^
So at 56 aero spokes (F+R) the upper bound gain is 2.8W over round. Oh, not bad.
The lower bound is me slowing down at every junction cos stupid drivers which means I barely get to the upper bound :):)
Are there theoretical models or are such things pure measurement? Exp curve, scary Taylor series, how do they do it?