Aerodynamics acording to Myth Busters!

On Jul 28, 7:21 pm, Alan Baker wrote:
In article . com,
Harry K wrote:





On Jul 27, 7:49 pm, Alan Baker wrote:
In article ,
"Bill Daniels" bildan@comcast-dot-net wrote:

You guys haven't mentioned the biggie - roof racks. Removing the cross
bars
from my Grand Cherokee added 2MPG. Glider pilots look at roof racks and
see
open air brakes. I can't believe the number of vehicles I see in Denver
with ski racks in July.

Then, of course, you can park the truck. I understand that trucks have
very
low drag when parked.

If the vehicle has a MPG computer, you can see what speed does to MPG.
At
65, my Jeep gets 19MPG. At 55, it gets 24MPG. At 45, it gets 36MPG. If
you do the numbers, saving two minutes by driving fast costs big time.
Those are REALLY expensive minutes - more than the rental on some
airplanes.

Real world case; let's use your figures for simplicity's sake:

I want to drive from Vancouver to Kelowna. A little check with Google
Maps tells us that that's a distance of...

...393 kilometers, or about 245 miles.

At 65, that takes me about 3 hours, 45 minutes and I use about 13
gallons of gas.

At 55, it takes 4 hours, 30 minutes and I use about 10 gallons of gas.

Even at Canadian gas prices, those 10 litres of fuel cost me only about
$11.50. Is that really too much to pay to save 45 minutes of my precious
time? 25 cents a minute seem pretty cheap to me.

Bill Daniels

"Morgans" wrote in message
...

"Ernest Christley" wrote

I've seen SUV's with what looks like reverse scoops that could have to
catch the air passing over the top of the vehicle and blow it down the
back. Counterintuitive until you realize that attached flow offers
less
drag.

That scoop helps drag, but more importantly, it prevents carbon
monoxide
from entering in the back window when it is open and driving at highway
speeds.

When a chopped off SUV has the window open, that low pressure area in
the
back gathers up the exhaust, and the swirling motion of the vortex
allows
some to enter in though the open window. Not good. The scoop supplies
fresh air flowing down from the top, and keeps the bad air down lower
than
the open window.

They have been doing that since the 60's, on old station wagons, before
they cared about mileage and aerodynamics.
--
Jim in NC

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling four feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect if you
sit in the bottom of that cupboard."- Hide quoted text -

- Show quoted text -

I think it will cost a bit more than that. From my experiences in the
B.C. lakes region and the Coq the cops are a bit anal about the posted
limits. It has been a few years but the Coq was posted 110 (about
62mph). Then there is that stretch from Merritt until you pick up the
Eastern extension of the freeway that is posted 90. Then from
Peachland to Kelowna is again max of 90 with stretches down to 80
(IIRC). You might be parked alongside the road a bit.

I got a ticket in there "Exceeding speed limit while passing".

Harry K

Sorry, Harry, but I can't agree. Stay below about 20 klicks over the
limit and you won't ever get stopped. If you're truly nervous, limit
yourself to 15 over.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling four feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect if you
sit in the bottom of that cupboard."- Hide quoted text -

- Show quoted text -

I keep hearing that on various forums. My experience (1 trip yearly
over the Peachland-Merritt-Kamloops) is that if I punch in a bit under
the posted (don't like to flog my car on those grades), I will be
passed by just about everybody but only very rarely by someone really
cooking. Eyeball says the "flow" is only slightly over the posted
both on and off the Coq.

Harry K