trail wrote:
AlexS wrote:
The banking angle at the black line is the same as it is at the top of the track.
That clarifies it thanks - agree with the rest...there are some possible issues I have with your blog math, but I'll sort it out myself before I make myself look stupid(er) by posting here.
But, back to the question being asked...
Quote:
but that's not what was asked, which was about the relative difference experienced while riding on the track. In other words, two riders going at 40mph on the track will experience the same g-force in the turns irrespective of their mass
So we've established that g-force will be the same, but force will vary with mass. I'm not - yet- totally convinced there's no "relative difference."
Let's say I do an hour all-out from a rolling start (to remove the effect of mass on initial forward acceleration). Then a strap on an aerodynamically invisible 20 kg. weight at my existing center-of-mass. And do another hour. Will I get the exact same time? My intuition says no - that it will take at least some marginal level of effort to counter the additional lateral force (with the same g-force) that results from the additional 20kg.
Which brings up the tire inflation calculation for the track. It seems if you had a precise inflation vs. weight chart you'd want to inflate your tires not to your static rider+equipment weight, but the something like the average between the static weight and the calculate pressing-into-the-track force at peak turn radius.
Adding such a hypothetical 20kg to a 64kg rider and 8kg bike will reduce distance achieved due to the additional time taken to get up to speed initially (very minor) and then extra rolling resistance due to the additional mass. It'd cost about 450-500 metres at a W/m^2 required to ride at women WR hour speeds on a concrete track. Less distance would be lost on a high quality timber track due to the lower overall proportion of energy demand from rolling resistance (e.g. such a mass would add ~350m).
The lateral forces don't really come into play because the track pushes back as much as you are pushing into the track (else you would sink into or float above the track - hence there is no work done in that direction). It's the additional rolling resistance that matters and that's proportional to "weight" felt at the track, which of course varies depending on where you are on the track and COM velocity but can be considered to be an average value per lap. Add 20kg and all you do is up the average rolling resistance by whatever proportion 20kg is of your original mass.
In the case above, rolling resistance increases from ~10% of the total energy demand to ~13% of the total energy demand.
http://www.cyclecoach.com http://www.aerocoach.com.au