Sunday, January 31, 2010

Next wind tunnel session 6 Mar; Pacing Optimisation

Yee ha - back to the tunnel - 6 Mar. Like a drug that thing.

Hot Gatorade race in Melburn today... 37 deg C and with a run time approaching my cycle time I still somehow managed 10th in my age group.

Also been working on a pacing optimisation calculator. Alex Simmons has a ripper one in Excel, but it's pretty slow (well Excel is pretty slow at the best of times) - it takes 20-30 min to optimise a course with 100 segments. The idea is that if the course is hilly (or there is a stinking headwind like today) you can actually be faster by applying more power on the uphill/headwind sections, and less on the downhill/tailwind sections, while still keeping the normalised power at the same level as if you rode the course at the same even power.

Executing such a pacing strategy is pretty simple if the course is hilly - add % grade to the screen of a Garmin 705 alongside power and ride X power for Y gradient.

So I figured I'd have a crack at the same problem, but using a different technique: genetic algorithms. A genetic algorithm is a way of finding solutions to maths problems, but without doing every possible calculation required with brute force. You come up with a way of encoding the problem as a gene (you set the power for each course segment), then determine how well the gene solves the problem (arrive at the end of the course with a specified Normalised Power and fastest time).

By creating a population of genomes, you can then calculate how good each gene is at the problem, and rank the results. Then comes the fun bit, you take the best genes, divide them into Mums and Dads and then start creating children by swapping some of the gene segments of the Mum and the Dad into the babies. You also get to mutate the gene pool randomly to keep things interesting.

Preliminary tests are that I can calculate a population of 1000 genomes on a 6 segment course and do a full generation every half second or so(each 1000 genomes calculate how good they are at the problem, have babies and die off, then a few might get mutated); so in a minute could calculate 120,000 attempts at solving the problem. Because the genes adapt to the problem, picking the better solutions each generation, this might be a lot faster than using Excel... time will tell.

I'm planning on factoring in bearing, wind bearing and wind speed as well as the course (elevation, CdA, Crr) etc. You'll be able to vary things per segment if you need to (like a really rough section of course, or an exposed windy section). If the thing is fast enough, you should be able to run it on the website from your mobile browser on the way to the race site. Under a minute good, longer than that not so flash. And it should be easy to use - upload a TCX/GPX file from a Garmin or exported from WKO and there's the course - tweak the input parameters and solve away!

3 weeks till Nationals - CTL 70.

Monday, January 11, 2010


Raced yesterday after 1 week of full training (instead of just swimming); accidentally won my age group after fastest swim/ride and very slow run. 4th overall fastest ride. All the work in the pool and in aero is paying off. Gotta figure out this running caper... somehow.

Monday, January 4, 2010

Whoa! Cool nerd tool under development

Finally had some time to sit down and fritz around with some new(ish) Microsoft technology that I've been meaning to catch up on for a while (Visual Studio 2008, Microsoft MVC and some other stuff).

And it's good - in fact great. Really streamlines web based development and makes things much faster to develop.

Anyway I won't bore everyone with the tedious technical details, here's a screenshot of the first part of the application:

View of the new power calculator

A brand spanky new power calculator that does, amongst other things, calculate one of Crr/CdA/Slope/Speed/Power from given information, draw a graph of power v speed for current CdA/Crr, and generate split times for a variety of length rides from 20k to Ironman®.

Kind of like analytic cycling, but roided up for the 'teens (we are 2010 now after all). Plus I fixed the stuff that annoyed me over there (sorry Tom Compton) like not having CdA as a single measure, and having to calculate metres/sec all the time from kmh (divide by 3.6). Also now that I programmed in a proper air density calculator, it should be a lot more accurate than guessing at air density values all the time.

Anyway there is a bit more to do on this, but should have something publically available before I have to go back to work towards the end of Jan.

I'm thinking conversion of imperial units for altitude (ft -> metres), temperature (deg F -> deg C), and pressure (inHG -> kPA), plus an override for pressure for people who actually have their own portable weather station (Andy Coggan: Google Wattage for one ;-)), rather than the sea level reported pressure.

CTL up to 50. Big week, including riding with some A graders. Ouch.

Friday, January 1, 2010

Will a Simkins Aero brake be worth it?

Recently saw Matt Simkins new aero brake design - kinda like the old Hooker TT brakes (which incidentally go for a very pretty penny on eBay). The big question is: Are they worth it?

According to Matts real world aero calcs (performed by Tom Anhalt, Google Wattage member), the Simkins brake had a CdA of 0.2125 vs the Cervelo brake mech of 0.2152, or a difference of 0.0027.

That's gotta be a pretty small difference... heading on over to

250w, CdA 0.2152 = 11.62 m/s or 41.83 kmh (25.98 mph)

250w, CdA 0.2124 = 11.66 m/s or 41.97 kmh (26.07 mph)

So a difference of 0.04 m/s... thats 4 cm (about an inch and a half) further per second.

Over 40 km, that's 57:22 compared with 57:11, a scant 11 seconds saved for $335 USD or $30/sec.

Worth it? Might be if the race was a biggie, and the winning margin is less than that! Probably not if 10 seconds can be gained reasonably easily by some other means, like practicing a transition between swim and bike. For TT's only, there would be more merit as the podium is frequently exchanged on the basis of a few seconds here and there.

As an aside I actually sanity checked what a front brake assembly was worth in CdA terms; Cervelo front brake mech on and off the bike the CdA difference was 0.004 - roughly double the difference between the Simkins brake and the Cervelo brake. So the test results do seem to be reasonable.

You can check out Matt's site: