we also don't feel linear - we feel logarithmic. Our eyes are tuned to very subtle differences in light. You can feel amazingly fine surface disparities with your fingernail. We become numb to the baseline spin - we're doing work but it doesn't feel like. It's the next subtle increment that we feel. So yes, subtle differences in wheel inertia are more significant to us than adding mass to the bike frame.
On Friday, January 3, 2014 9:11:59 AM UTC-6, Ron Mc wrote: > > if riding a bike was the same effort as spinning a wheel on a workstand, > there would be no cars on the road. > > On Friday, January 3, 2014 8:51:19 AM UTC-6, Ron Mc wrote: >> >> Bill, do the same thing on a mag trainer instead of a workstand. >> >> On Thursday, January 2, 2014 9:43:06 PM UTC-6, Bill Lindsay wrote: >>> >>> We're talking about two components of momentum that are orders of >>> magnitude different from one another. Imagine a cyclist starting from a >>> dead stop and spinning up to 30kph. How much effort does it take to do >>> that? Let's call it "a lot". He did two things: >>> >>> 1. He got his whole mass moving to the velocity of 30kph >>> 2. He got his wheels spinning to the right speed >>> >>> Whatever "a lot" is, it is the sum of 1 and 2. With me so far? >>> >>> OK, now here's the thought experiment. Put his bike in the stand. Grab >>> a pedal and spin up to 30kph. How much effort did that take? A small >>> child could do it with one hand. You just did #2 above (to the rear wheel) >>> and reduced #1 above to zero. Whatever force it took, It's not "a lot". >>> It's not even 1/10th of a lot. It's tiny. Put on the brakes. Does the >>> wheel gradually slow down? Or does it stop almost instantly? Why is >>> that? Because it doesn't weigh anything. Comparing 200g of tire weight >>> difference is comparing two miniscule forces. >>> >>> Anybody with a powertap rear hub can do that thought experiment in real >>> life. Measure the power it takes to spin up to 30kph. Then do it again >>> with a tire that's 200g heavier. How much difference is it? I don't even >>> know if powertap hubs can measure forces that small. Does the lighter >>> wheel spin up faster and easier? Of course! Could you feel it? Maybe. >>> But both were ridiculously easy in comparison to getting that 100kg mass >>> moving up to speed. >>> >>> Math can't tell you the whole story, but it can get you into the >>> ballpark. The rotational momentum of bicycle wheels is tiny in comparison >>> to the linear momentum of a cyclist in motion. Orders of magnitude. Tell >>> me you've worked up a sweat pedalling a race bike on the workstand. >>> >>> On Thursday, January 2, 2014 6:38:41 PM UTC-8, Benz, Sunnyvale, CA wrote: >>>> >>>> I don't know. Let's do a thought experiment. Let's assume that the >>>> wheels have a very high rotational inertia. Wouldn't that smooth out the >>>> sine wave you're talking about? The slowing down part is when rotational >>>> potential+kinetic energy gets converted to potential energy against >>>> gravity. Using a high rotational inertia will actually help in maintaining >>>> speed (to whatever extent it does) and thus create lower amplitude sine >>>> waves. >>>> >>>> >>>> -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/groups/opt_out.
