Aero testing in Surrey ...

liversedge

Hi,

I'm trying to find a good location to do some aerotesting using Virtual Elevation (aka Chung Method) in the Surrey / Guildford kind of area. Mostly around my way (Cranleigh) there are lots of quiet tree-lined lanes, but they are hilly with no easy loop back.

I'm guessing there must be someone out there that's found a neat place to do it ?

TIA

Mark

xavierdisley

Surrey Research Park ~1.1km

liversedge

That is a great call. It will be empty on a weekend too.

Thanks!

xavierdisley

No probs

RChung

It's also possible to do this on out-and-backs (works especially well if the out-and-back is sort of half-pipe shaped) -- or even up a hill without a loop or return -- but in that case Aerolab would have to be modified to handle one-way tests.

To do a one-way test up a hill, you just have to vary your speed and power over a pretty wide range for each repeat. The height of the hill is the same, and your weight is the same, and your rolling resistance is the same, so if you have the right values of Crr and CdA the VE for each repeat ought to be the same (and the total elevation gain from VE should match the true height of the hill). I do this with a special "one-way" routine that lets me cut-and-paste sections of a file and then overlay the VE profiles.

For out-and-backs, I "reflect" or "mirror-image" the profiles and then overlay them. But Aerolab can mostly handle this anyway since an out-and-back looks to the algorithm ike a loop.

liversedge

Autumn such a good time to do this !
Minimum wind speeds 10mph.

Oops !

RChung

Steady wind or gusty?

If it's gusty then you'll have to wait. If it's mostly steady the precision can be poor but the overall estimate will be unbiased (in a statistical sense) if you do loops at various speeds. In one-ways, steady wind will bias the estimate but there are still some things you can do if you're desperate.

I try not to be so desperate that I can't wait until a time when it's less windy.

liversedge

I'll cycle out there tomorrow and see how it is.

Its more out of curiosity as I have been working on a lower position, spending more time on the drops, lowering my stem etc and its made a big difference to my speed. I want to get the skinny on the sorts of CdA changes I've made, kinda aero testing in reverse !