RChung wrote:
Ale Martinez wrote:
CptanPanic wrote:
Can you post a spreadsheet that calculates this?I wrote this little one, you can load up to 10 coast down tests (in Run1, Run2, ... columns and n=number of tests), Mass (M), Air density (rho) and descent (h in m) and it gives you estimates of CdA and Crr via linear regression and a graph with virtual elevation for each run:
You used regression? What was the model you were estimating.
Robert, the model I used for regresion is based on end-to-end conservation of energy (deltaPE+deltaKE = workAeroDrag + workRRdrag), so:
[M*g*h + 1/2*M*(Vi^2-Vf^2)] = [1/2*rho*sum(Vi^3)] * CdA + [M*g*sum(Vi)] * Crr
where Vi=initial velocity, Vf=final velocitiy, Vi=velocity at i second from start, h=descent from start to finish.
In the spreadsheet al terms are divided by [M*g*sum(Vi)] to use standard linear regresion formulas in excel.
Ale Martinez
www.amtriathlon.com
Last edited by:
Ale Martinez: Oct 25, 11 5:40