tag:blogger.com,1999:blog-35788819.post3789959904206148123..comments2023-10-12T00:18:31.629+11:00Comments on Alex's Cycle Blog: Resistance is futile, even for MTBAlex Simmonshttp://www.blogger.com/profile/00698332397074026424noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-35788819.post-25012475116722930192016-09-18T15:46:02.971+10:002016-09-18T15:46:02.971+10:00I'm not really sure what additional value exte...I'm not really sure what additional value extending the charts adds. The gravity portion of the energy demand will just gradually increase from the 85% mark closer to 90+% of total energy demand. IOW at steep gradients the energy is almost wholly due to overcoming gravity, all that happens is the speed slows the steeper it gets.<br /><br />For riders of different weights, the chart looks exactly the same shape, just the gravity portion of energy demand is a bit more at each gradient for heavier riders, and a bit less for lighter riders. Or if you like, it'd be like shifting the gradient values for each column to the left or right.<br /><br />Knowing the precise values wasn't really the point of the exercise, rather it is simply to show the relative importance of each of the energy demand factors when riding on terrain of different gradients.<br /><br />As for downhills, yes of course you get a return of gravitational potential energy, which is why you can coast at speed for zero power input. Pedalling at a given power on a descent simply increases speed attainable, or the rate at which you accelerate.Alex Simmonshttps://www.blogger.com/profile/00698332397074026424noreply@blogger.comtag:blogger.com,1999:blog-35788819.post-20835163594318453382016-09-15T12:06:06.134+10:002016-09-15T12:06:06.134+10:00Actually it would be cool to generate this chart b...Actually it would be cool to generate this chart based on values input by the viewer. I'm 95 kg and my bike is another 12 on top of that so your twiggy little rider is quite a long way different.<br /><br />Would be even better if the negative gradients could be selected too...<br />does the model say that weight helps on a downhill?<br /><br /><br /><br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-35788819.post-65649542513850363952016-09-15T11:51:13.454+10:002016-09-15T11:51:13.454+10:00I'd really like to see the numbers for steeper... I'd really like to see the numbers for steeper climbs too - there are a couple of 18-20% roads near me.<br /><br />Can you please extend the graphs with breakdowns for 12/14/16/18/20%, and 25% and 30% ?Criggiehttp://criggie.org.nz/noreply@blogger.comtag:blogger.com,1999:blog-35788819.post-43328956851449662082013-08-27T13:55:44.518+10:002013-08-27T13:55:44.518+10:00@djconnel
Yes, the context for the MTB magazine wa...@djconnel<br />Yes, the context for the MTB magazine was for fairly hard pack trails. Clearly loose and/or rough terrain brings with it all sorts of other variables, and presumably a loss of drivetrain efficiency as well.<br /><br />Really it was just to illustrate how the relative forces vary in different situations (and for me to simply publish a chart I'd done a whie back).<br /><br />I've no real idea how one would or could reconfigure the Crr model for such terrain. Maybe it's more a drivetrain efficiency thing, with losses between tyre and surface.Alex Simmonshttps://www.blogger.com/profile/00698332397074026424noreply@blogger.comtag:blogger.com,1999:blog-35788819.post-71758746699755837132013-08-26T23:20:49.785+10:002013-08-26T23:20:49.785+10:00Great chart. Extremely simple and illuminating.
...Great chart. Extremely simple and illuminating. <br /><br />I should also make a script for myself, where power in use is not as ambitious as 300 W ;)travelboozehttp://travelbooze.comnoreply@blogger.comtag:blogger.com,1999:blog-35788819.post-26202723160665114252013-08-26T22:48:43.360+10:002013-08-26T22:48:43.360+10:00Nice! I wonder how good the Crr model of rolling ...Nice! I wonder how good the Crr model of rolling resistance is on a mountain bike The principal assumptions are (1) resistance is proportional to weight (2) resistance is proportional to speed. With a bike rattling over rough trails it's easy to imagine that neither of these assumptions is good, although averaged over a large population of trails, perhaps the model does as well as any other.<br /><br />"Rolling resistance" in a road bike is typically modeled as primarily due to deformation of the tire. On a mountain bike it is likely more related to vibrations. This, perhaps, complicates matters.djconnelhttps://www.blogger.com/profile/01484858820878605035noreply@blogger.com