Bradstuff, in the interest of liveliness I'll respond.
Just because carbon fiber bikes cost thousands doesn't mean carbon fiber cost for a bike is anywhere near that. I know someone with enough CF for dozens of bikes that he paid low hundreds for, so if I wanted to go that route I could do it economically. If I was serious about the racing and would spends thousands on a trip to do it, then I'd obviously have no problem spending plenty on my vehicle anyway. I just don't believe in spending high prices on batteries, because the prices are declining so fast, especially the high power Lipo that will be needed for this racing, since A123's don't have good enough gravimetric energy density to be a real contender with a 70lb weight limit.
I have confidence that Arlo will budget his energy accordingly, though his numbers and DocBass's numbers (10kw to run at 100kph), tell me there's some big energy waste going on with those X5's at extreme power...stator saturation maybe. If he runs out of juice before the end, then he just didn't pay attention to his CA, which I believe is unlikely.
My measly 3kw continuous would be more like bursts of 6-7kw under acceleration and then slowing down and getting some back through regen on the short curvy track. It's not stop and go, so the motor should stay at or close to it's prime efficiency band of operation, though there will be some efficiency hit, but a lot of my 64% increase to get to 100wh/mi will go directly to performance...maybe even more since less will be given up to the wind. For mine 100wh/mi should definitely include 10kw bursts. That 3kw average continuous was just with my fairly tame controller on my cargo/schoolbus bike, not a race bike controller.
I've shown that I can fit a high power hub motor and almost 10kg of batteries on a bike that comes in within the 70lb limit. 10kg of Lipo gets you 1.4-1.5kwh of capacity for 50-60cents/wh from Hobby City. At 100wh/mile a 12.4 mile race only requires 1.24kwh, leaving a nice cushion. Have you ever ridden a 70lb ebike at 100wh/mile other than maybe bogged down going up a steep hill? I can assure you that 100wh/mi will be up way high in the fun department.
We can even break it down a different way, and call the average speed 35mph, which of course will depend on the track, but probably isn't too far off from what's possible on the Spooky Tooth track...20-25 in the curves and 45-50 on the straights. At 35 avg the 12.4 mile race will take 21.5 minutes. That's works out to an average continuous power of 3.5kw to use 1.24kwh, but once you consider that you'll really be under hard acceleration maybe 25-30% of the time, then it's easy to see how a 10kw max power bike can run in this race, and finish. That's before considering significant portions of that energy required for acceleration can be recovered during braking.
One thing I can guarantee is that little commuter type ebike that Tiberius pedal assisted to victory in the UK isn't going to cut it in 2011.
I wish there was some way to get the gas consumption of some of the top competitors in the 2010 races at Spooky Tooth, so we could try to back into the energy requirements they used for comparative purposes.
John
Even a bike with a 30 mph top speed was pretty dang fun on a kart track last spring.
