Coast down calculations

[kitcar]

The story:

It started out looking for graphics of laminar air flow over pickup trucks for my Aero episode, went into looking at Formula One cars, from there I started looking at pickup truck aero mods, found some vortex generators (that I ordered) and then I found (in a web archive of all things) a coast down calculation page (Cd, rolling resistance) which had the lamest 1980's colors I've ever seen so I gussied it up a bit and put it active on the web. I wish I could take credit for the Javascript but alas I can't. I might mess around with the calculations at some point. We'll see.

Here it is.

[Bill in Houston]

Wow, cool.

Can someone who used a different method see if this gives similar results?

[Bill in Houston]

removing inadvertent double post.

[lca13]

I've been trying to get this ready for others to use. If anyone wants it, drop me a personal message with an email address and I'll send it to you. After I get some feedback, I'll post it for all.

[kitcar]

Originally Posted by lca13

I've been trying to get this ready for others to use. If anyone wants it, drop me a personal message with an email address and I'll send it to you. After I get some feedback, I'll post it for all.

I don't care who you are, that looks a lot better than that crap I have!

[oneinchsidehop]

like wind, temp, altitude, humidity, and most of all, elevation change.

I guess the first 3 have to just be consistent to get a ballpark, and the elevation? I guessing it needs to be dead flat.

Can anyone use google earth (my old mac can't run it) to help me find a flat test road in Northeastern Vermont? Any idea how long a stretch I might need?

[GasSavers_maximilian]

I was looking at the coast down calculator and was wondering how much the estimate of my vehicle's mass will effect things. I'm trying to think of a way to actually weigh it, but the only idea I have (going to my local dump and using their scale) is of unknown accuracy.

A perfectly level road is a toughie. I guess with enough data points you could calculate the grade. Maybe if you did the test on the exact same stretch in both directions? I should research the math.

[GasSavers_maximilian]

I called the dump and apparently their scale is tested once a month for accuracy. Now I just need enough trash that they're willing to weigh me (normally for bags they just count 'em). They're pretty nice, so maybe I can just persuade them to do it for me.

Also, the link at the beginning of this thread is similar to this one, but minus most of the notes and directions, so here it is.

http://web.archive.org/web/200408030...DownCalcs.html