Bike vs. Roadster - Page 3

doug · 11-16-2009, 05:39 PM

Quote:

Originally Posted by Brent

2) The coefficient of drag for a bicyclist on a UCI-approved (i.e., "normal") bicycle is about 0.9. The Roadster comes in around 0.35. (A fully enclosed bicycle/tricycle (Sinner Mango) presumably has a better coefficient, although I can't seem to locate a number.) However, rolling resistance has to be less on a bicycle.

Just a quick note about drag. You don't really care so much about the coefficient of drag (Cd), but the drag force (Fd) which is proportional to the Cd times the projected frontal area.

Tdave · 11-17-2009, 07:32 AM

Quote:

Originally Posted by doug

Just a quick note about drag. You don't really care so much about the coefficient of drag (Cd), but the drag force (Fd) which is proportional to the Cd times the projected frontal area.

This is why the Roadster has about the same drag as a Prius, even though the Cd for the Roadster is so much worse -- it's pretty bad, I was surprised to learn.

Brent · 11-17-2009, 07:37 AM

Wikipedia puts the efficiency of the human body at 18-26 percent, which seems to be about the efficiency of an ICE. Maybe we need to be electrified, too!

felix the cat · 11-18-2009, 01:11 AM

Thanks for the laugh. This going in direction of Arnies terminator

doug · 11-18-2009, 01:32 AM

Quote:

Originally Posted by felix the cat

Thanks for the laugh. This going in direction of Arnies terminator

elirentz · 11-18-2009, 12:09 PM

If you're talking about carbon footprint wouldn't you want to include the emissions created by building/ shipping the roadster and all of its parts?

waltoninn · 11-18-2009, 01:11 PM

Quote:

Originally Posted by doug

Thanks. I considered mentioning the case of athletes where the energy output can be quite high, but didn't want to convolute things too much. (Talk about Michel Phelps's diet during the last Olympics sticks out in recent memory.) Again, ultimately energy out equals energy in.

I figure the average commuter, who's casually walking or biking, is using energy that would otherwise be stored on his gut or backside.

I suppose at some point someone should calculate the carbon footprint of being a burden on the health care system and add that into the calculation.

.

I would tend to agree with the point that we have to take into account a number of different variables, including the cost and "carbon foot print" of being in poor health and overweight. Although I plan on getting the Model S, and I am really rather supportive of the Tesla electric car, we can probably generally surmise that the more complicated a mechanical, electric or electronic device or machine, the greater the carbon foot print, thus the favor goes to the bicycle. Yet, I have to often think how my health may be suffering by inhaling the small molecular particles produced by non-electric vehicles? That is why I hope for a day when most vehicles on the road are all electric.

bolosky · 11-18-2009, 01:19 PM

Quote:

Originally Posted by elirentz

If you're talking about carbon footprint wouldn't you want to include the emissions created by building/ shipping the roadster and all of its parts?

Yes, of course. I even said that in the initial post. However, you've have to go farther and consider the end-of-life costs and the footprint of building the much larger road that the car takes. It all pretty much favors the bike.

However, I was trying to compute the *marginal* footprint of bike-vs-drive. That is, you've got a Roadster and a bike in the garage, what's the difference between taking one and the other. The fact that it was even close was really the point of the post, not that in the long run you should abandon your bikes and drive electric to save the planet (you shouldn't; you should telecommute and ride the bus).

bolosky · 11-18-2009, 01:26 PM

Quote:

Originally Posted by waltoninn

... we can probably generally surmise that the more complicated a mechanical, electric or electronic device or machine, the greater the carbon foot print, thus the favor goes to the bicycle.

No, we can actually quantify an estimate of the difference. It's way better than surmising, or at least it would be if you started with decent numbers rather than the guesses I pulled from the web.

Anyway, I can provide a counterexample to your point: a big old diesel bus. It's huge, it has tons of complicated moving parts, it belches CO2 and spews particulates, and its carbon footprint per passenger mile is way less than the Roadster (or for that matter the bike). So, big & complicated does not always mean worse.

Squint · 11-18-2009, 04:52 PM

I came across this a few days ago:

Fat Knowledge: Food CO2 and Land Footprints

CO2/cal is much lower than your initial assumptions. Last year I was riding up to 400 mi/week and consuming up to 4500 kcal/day. Most of it was carbs from processed junk foods. I eat beef perhaps 1-2 times a year. Despite riding so much, none of the miles were for utilitarian purposes. I still commuted in my hybrid and was content to separate work from recreation unless gas hits $20/gal.