As far as FF volume goes i generally find 10ml has been the magic number for me with a wider 45/50mm stator and haven't experienced any appreciable real-world drag or increase in freewheel current.
Exciting update on the Hubsinks, they're currently in transit to aus ready to send out to beta testers!
Final CnC drilling mounting holes is complete
Ready for Anodising
Anodising complete, matte black to improve emissivity from 0.09 to around 0.88-0.89 (9.1w to 274w static radiation @ 95c )
Calculated Thermal Impedance*1 - 0.07 - 0.08 °C/W ~1100W @ 95°c 18kph
Heat transfer emissivity*2 - 0.88 - 0.89 ε ~ 274w @ 95°c static
Approximate total heat dissipation: 1375w @ 18kph on a 20ºC day
*1 The thermal impedance of a heat sink is measured in ºC/W, which is the temperature rise of the heat source for each Watt of power dissipated. (these should increase 0.8°C per Watt of heat dissipated at 18kph ~ 1100W )
*2 Emissivity represents a conversion of thermal energy into electromagnetic energy on a scale of 0(no emissivity) to 1(perfect emissivity)
(These have a value of 0.88 - 0.89 due to the matte black anodising allowing them to shed an additional ~274W at 95c)
Back of the napkin workings, in theory if a hub like the MXUS is overheating after a 15 min ride because its being hammered on and off at 13Kw peaks and producing 2600W of heat under throttle, on paper it looks like we can dissipate more than half of that excess to potentially let it be ridden in the exact same manner indefinitely with ff and hubsinks.
But its hard to say how much more power the hubs will be able to handle due to the drop in efficiency and rise in thermal output as input power levels increase, ill leave that up to the beta testers.
In practice we've done that with the prototypes in the TT1500 race and the D'aguilar hill climbs at 18Kw on a QS205, but i'm super excited to get it out to beta testers who are interested in posting some real world results.
