This is not my area of expertise, but to get things started, I went to a site[0] and looked up some formulas and specs, and came up with:
outside circumference of wheel ~2200mm (700c wheel w/ tire)
30 mph == 0.5 mpm (Miles per minute).
0.5 mile == 804500mm
a 2200mm circumference will need to roll ~365.68 times to cover that distance. If that distance is covered in 1 minute, that means 365.68 rotations per minute.
This: Ef = 1/2 I ω2
wants I and ω.
I = m r squared.
m == 700g (this isn't properly distributed here, but it's a start)
1J/s == 1watt. So with this fudgey math above (assuming it's even correct) we're working w/ ~60 watts(max, for an instance, then decreasing). I don't even know if that's enough to spin a bicycle around like was shown. I hope somebody that actually understands this field can chime in and fix my bad assumptions (which I think err to supporting this was strictly the spinning wheel (not a motor)) and what this means. I'll do practical tests later when I have my bike.
I saw that earlier too, and forgot about it. So the question is less about whether its even possible, but whether or not it was likely in Ryder Hesjedal's circumstance. And the stakes, circumstances, etc aren't exceptional enough to warrant a commission.
60 watts is definitely sufficient to power a bike like that. I know I produce 50-80 pedaling at a "rest" pace, maybe 10-12 mph. Assuming your math is correct, it seems sensible that a wheel at 30 mph could move the bike. It seems like the biggest assumption here is that the wheel wasn't stopped in the crash and that it hovered above the ground, or sustained sufficient RPMs it was slowed.
outside circumference of wheel ~2200mm (700c wheel w/ tire) 30 mph == 0.5 mpm (Miles per minute). 0.5 mile == 804500mm a 2200mm circumference will need to roll ~365.68 times to cover that distance. If that distance is covered in 1 minute, that means 365.68 rotations per minute.
This: Ef = 1/2 I ω2
wants I and ω.
I = m r squared.
m == 700g (this isn't properly distributed here, but it's a start)
r (at 2200mm circumference) == 350.14
0.7kg * ((350.14mm)(0.001m/mm))^2 == 0.7 * .122598019 == 0.085818613 kg/m2
1 rad/s = 9.55 r/min (rpm) 365rpm == 38.29 rad/s
so if this is at all correct:
Ef = 0.5 * 0.085818613 * 38.29^2 == 0.5 * 0.085818613 * 1466.1241 == 62.910368373 Joules
1J/s == 1watt. So with this fudgey math above (assuming it's even correct) we're working w/ ~60 watts(max, for an instance, then decreasing). I don't even know if that's enough to spin a bicycle around like was shown. I hope somebody that actually understands this field can chime in and fix my bad assumptions (which I think err to supporting this was strictly the spinning wheel (not a motor)) and what this means. I'll do practical tests later when I have my bike.
[0] http://www.engineeringtoolbox.com/flywheel-energy-d_945.html