Originally Posted by
achoo
It still takes a lot of power to draft at 25-28 mph or even faster and you still get an aero benefit from more aero wheels - and you get it all the time.
A 500g ideal hoop rolling at 50 km/hr (13.8888 m/sec, 31+ mph) has 96.45 Joules of energy. At 52 km/hr (14.44444 m/sec), it has 104.32 Joules of energy.
To accelerate 500g of real-world rotating wheel weight from 50 to 52 km/hr in one second thus takes under 9W.
I'd say you get a bigger benefit from aero wheels, even when drafting. If you gain 10W from aero wheels, that more than offsets the power needed to accelerate 500g of added wheel weight from 50 to 52 km/hr in one second.
To accelerate that same wheel weight from 30 to 32 km/hr in one second takes under 4W.
I appreciate the work/thought you put into your notes.
I wish I was better with math so I could put some calculations down, thoughts in numbers.
A typical acceleration for me on a Tuesday night takes me from 22-23 mph to 27-29 mph, and the bigger jumps are from 18-19 mph to 30-34 mph. This is happening about once every minute, about once a lap, 45-50 minutes typically, 60 minutes or more for the Tuesday races in 2010-2013. The Tuesday I looked up was
August 12th, which ended in a field sprint. This is the course I race on weekly during the summer so it's a pretty predictable event for me.
In that race I had a number of spikes well into the 700w range with two 1000w spikes before the final 1150w sprint. I was hanging on by my fingernails in that race. If I were using 3 lbs heavier wheels my accelerations may not have been higher peak wattage (since I'd have been limited to whatever I could do) but they'd take longer, maybe a pedal stroke or three, especially the accelerations up to 32-34 mph. The extra power required to accelerate 3 lbs heavier wheels to those speeds realistically would have ended the race for me. I averaged about 200w for that race, my absolute limit if I'm to contest the sprint.
I was on light aero wheels. Light non-aero wheels would have been better, I think, than heavy aero wheels. The field was generally slower so there wasn't the sustained 30 mph stuff. Because of the overall weaker field there were more jumps/accelerations and therefore heavy wheels would have been a handicap.
In the P12 race heavy aero wheels probably wouldn't have hurt as much. Accelerations would start and end at much higher speeds (25->37? mph) so aero becomes really significant, and the sustained single file pace means that you often don't slow for turns like you do in the easier race.