Cycling UK Forum

snibgo wrote:Anyone is looking for a very comprehensive model of the energy (or power) requirements of cycling could do worse than use Modeling road-cycling performance, Olds et al, 1995, http://jap.physiology.org/content/78/4/ ... f_ipsecsha

It includes allowances for drafting, tyre pressure, kinetic energy of moving legs and feet, and the effect on drag of different helmets, long hair, short hair or baldness, and whether legs are shaved.

I can't find software that incorporates this model. If someone has an hour or two to spare, perhaps they could knock one up?

The model doesn't mention sex or age. But someone might simplify it by assuming that women have long hair but shaved legs, old men are bald, and so on.

This has twinged my memory.
I have a copy of another paper...

Catalogue Data
Hintzy, F.; Mourot, L.; Perrey, S.; and Tordi, N. (2005). Effect of endurance training on
different mechanical efficiency indices during submaximal cycling in subjects unaccustomed
to cycling. Can. J. Appl. Physiol. 30(5): 520-528. © 2005 Canadian Society for
Exercise Physiology.

which describes this as "VO2 unload", where the rider rotates the cranks without applying pressure to the pedals; or 'air spinning'....

This report also does not mention any differences between the sexes, as per ingested CHO vs power output.

Ayesha wrote:

snibgo wrote:Anyone is looking for a very comprehensive model of the energy (or power) requirements of cycling could do worse than use Modeling road-cycling performance, Olds et al, 1995, http://jap.physiology.org/content/78/4/ ... f_ipsecsha

It includes allowances for drafting, tyre pressure, kinetic energy of moving legs and feet, and the effect on drag of different helmets, long hair, short hair or baldness, and whether legs are shaved.

I can't find software that incorporates this model. If someone has an hour or two to spare, perhaps they could knock one up?

The model doesn't mention sex or age. But someone might simplify it by assuming that women have long hair but shaved legs, old men are bald, and so on.

This has twinged my memory.
I have a copy of another paper...

Catalogue Data
Hintzy, F.; Mourot, L.; Perrey, S.; and Tordi, N. (2005). Effect of endurance training on
different mechanical efficiency indices during submaximal cycling in subjects unaccustomed
to cycling. Can. J. Appl. Physiol. 30(5): 520-528. © 2005 Canadian Society for
Exercise Physiology.

which describes this as "VO2 unload", where the rider rotates the cranks without applying pressure to the pedals; or 'air spinning'....
This report also does not mention any differences between the sexes, as per ingested CHO vs power output.

I can only see the abstract (without paying!) but maybe its because all the subjects of this paper were women!

Furthermore, lots of male road cyclists and triathletes shave their legs.

Does atmospheric pressure deserve a mention here regarding opposing forces during cycling??

Example; cycling in a period of anticyclonic high pressure of say 1040mb; the following week doing the same in a low pressure trough of say 960mb.

From a previous post, allow for skin surface area of 2 sq. mtrs, let's say 1 sq. mtr being presented for 'pushing' through the atmosphere, then the theoretical thrust required for both scenarios would be:

High pressure 100cm x 100cm x 1.060505 (kg/cm2 equivalent of 1040mb) = 10,605 kg

Low pressure 100cm x 100cm x 0.9789276 (kg/cm2 equivalent of 960mb) = 9,789 kg

Therefore, in my esteemed wisdom it would seem that you would require an extra 816 kg (ie nearly a ton of thrust) to propel yourself on those balmy sunny days!!!

I quite often used to get told: 'Ward, you are a fool, go stand in the bin' during school science lessons thus I may have missed something here. I can't imagine what having a kid stand in a bin for upto 30 minutes would do to a teachers career nowadays!! Although I don't think it has psychologically damaged me too much.......

Anyhow, I know the above is probably a little simplistic but atmospheric pressure, & the daily relative differences, must have some bearing. Any thoughts??

Um, wot is "a very cool free bik[sic]?"

snibgo wrote:Anyone is looking for a very comprehensive model of the energy (or power) requirements of cycling could do worse than use Modeling road-cycling performance, Olds et al, 1995, http://jap.physiology.org/content/78/4/ ... f_ipsecsha

It includes allowances for drafting, tyre pressure, kinetic energy of moving legs and feet, and the effect on drag of different helmets, long hair, short hair or baldness, and whether legs are shaved.

Does it include allowances for what Bicycling Science calls "bump losses", i.e. the energy exttracted from forward motion on a bumpy road in shaking the visco-elastic tissues of the human body?

The assumption of a smooth road, on which bump losses may be negligible, seems to me the single greatest inadequacy of all models of cycling energy use, including mine.

Chuck Glider wrote:Um, wot is "a very cool free bik[sic]?"

My guess is the OP hit the character limit, which clipped:

ing for slimmers website

off the end of his post. Any more suggestions, humourous it you can, for the missing text?

SimonCelsa wrote:Does atmospheric pressure deserve a mention here regarding opposing forces during cycling??

Yes, Olds's model accounts for that. (But the effect is far less than you suggest. Your calculations of "theoretical thrust" are, umm, somewhat creative.)

CJ wrote:Does it include allowances for what Bicycling Science calls "bump losses" ...

The model can accomodate different surface types for rolling resistance, but gives numbers only for asphalt and concrete. It notes that "The lack of an obvious way of quantifying surface smoothness and the lack of data relating surface characteristics to rolling resistance mean that a more sophisticated analysis of the effect of surface characteristics on rolling resistance is not yet available."

It seems to me that bump losses matter more than the hairyness of legs or head. As the mechanism of bumps is more complex than smooth roads of different types, I suspect that a bumps resistance should be of a different nature to that of rolling resistance.

(In Olds's model, increasing tyre pressure reduces rolling resistance. But I suspect that on a bumpy road, reducing tyre pressure, within limits, will reduce bump losses.)

As an aside: Olds's model for rolling resistance accounts for wheel diameter and tyre pressure, but not tyre width. But width does make a difference: increasing width will decrease rolling resistance but increase air resistance.

Cyclenut wrote:

snibgo wrote:Yes, and slope of course. And air resistance varies with rider position, and rolling resistance varies with tyres and road surface, and bike transmisson efficiency is another factor.

Some other power calculators:
http://bikecalculator.com/wattsMetric.html
http://www.kreuzotter.de/english/espeed.htm

My spreadsheet does all of that. You really should take a look at it.

Of course I would love it if someone who does javascript would help me to put that calculation directly into a webpage, but unfortunately nobody has yet, and CTC doesn't seem to want to pay for such enhancements.

Be fairly easy to put in a web page. You just need a simple form, then the submit button calls the JavaScript to do the calculation to produce the result and write back to thge page. Be easier to convert if your formula used named fields rather than cell names.