Sunday, April 25, 2010

Golden Cheetah - Aerolab - figure out your CRR and CdA

Got around to looking at the new Aerolab extension to Golden Cheetah.

Golden Cheetah is an open source ride managment / power analysis tool that runs on Windows, Mac and Linux.

Aerolab is an extension that allows you to use the Chung Virtual Elevation method to derive CdA and CRR from a power file.

Currently this emulates the Chung spreadsheet quite well, but does not auto-solve. You have to play around a bit to look for the best solution. Also you have to jump through a few hoops to get the Rho constant (air density, for which you'll need altitude, temperature, dew point temp and know how to calculate, I can provide a small spreadsheet if anyone is interested.)

I'm still a bit confused as to how to discern the effects of CRR and CdA. But within some reasonable degrees of accuracy you can get some good ideas.

The above shows a VVV TT, the 10k Iona course, out and back. With reasonable results, I think this was my PB for the year. Assuming about 0.0033 for CRR my CdA would be about 0.229.

Just a sanity check, plugging those numbers into analytic cycling gets me a speed for just about exactly 40km/h for 284 watts average. On the day it was about 43.7 (exclusive of start and turn-around.) So getting close...

4 comments:

Robert said...

I'll have to write some documentation and hints for usage. That'll probably happen after next month since I've got a big project due in the meantime.

Stuart Lynne said...

But at least as usable as is as the various Chung spreadsheets...

The problem is that the math challenged like myself don't quite get the relationships...

I actually like math, just was never that good at it, never got past 3rd year calculus, and simply haven't needed to exercise any of it in 35 years of working for a living... so mostly atrophied.

Mark said...

Opensource, C++, Math, TT... I think I need to contribute. Probably a good summer project.

Robert said...

Mark:

Please do. Download Golden Cheetah and play with it for a while.