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Old 10-03-2020, 04:40 PM   #37 (permalink)
JulianEdgar
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Quote:
Originally Posted by Grant-53 View Post
What Cd is needed to a get 0.40 meter sq. frontal area machine to achieve 50 kph using 100w of power? I will continue to reinforce the nose section and add side panels. Cost down tests to measure the effects.
Looking at the table I posted, and remembering that required power goes up with the cube of the speed (ie your nominated speed of 50 km/h will require 2.7 times the 36 km/h aero power shown in the table), I wouldn't think you'd be able to get the Cd down sufficiently to achieve that outcome.

Using the table, at 36 km/h, a bike with a frontal area of 0.35 square metres and a Cd of 0.13 requires a total (aero + rolling resistance) power of 50W (of that 24W is aero power, so a total of 90W at 50 km/h).

So that would imply that to meet your criteria, you'd need a Cd of something like 0.13 - pretty hard.

Happy to have someone check my maths - never my best area.
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