Mythbusters : Drafting video
 

[IMG]ttp://www.youtube.com/watch?v=Cu0uNPFCf68[/IMG]

I missed this one. Amazing reduction in drag from drafting !
I'd like to see the full episode to see how they built that wind tunnel.

Watch it fast before it gets taken down !

EDIT : I'm seeing some 'wierdness' in the site lately. I'm not seeing what I wrote ( here it is again )


I missed this one. Amazing reduction in drag from drafting !
I'd like to see the full episode to see how they built that wind tunnel.

Watch it fast before it gets taken down !

http://www.youtube.com/watch?v=lttgT1XZVvE

Part one

http://www.youtube.com/watch?v=y18mewmFNOQ

Drafting with a motorcycle.

EDIT : Scratch that - he on a bicycle .

I hesitate to even comment but here goes:

I think Mythbusters is right and their numbers are probably valid. Once upon a time on motorcycle I got behind a horsetrailer with horses in it- the ultimate draft vehicle because horse trailers are close to the ground (unlike that semi and trailer), have a large rear x-section, and because when horses are in them the driver is going to be extra careful and avoid sudden speed and lane changes unless it's really an emergency (unlike semi drivers who might swerve or lock up their trailer brakes to shake off a tailgater).

There was very little traffic but I got in "the bubble" undetected by the driver (I'm pretty sure) and hung out in there for a looooong time (150 miles at 75 mph!). I noticed that when I pulled in real close- maybe not 2 feet but... let's just say not far from that- I had to back off the throttle some and the temp gauge suddenly shot up. Bike had no windshield and I had my visor up- amazingly calm back there, not even the expected turbulence and buffeting. I didn't stay that close for long because the temp gauge climbed up against the red, I clearly heard the fan kick on, and I was sweating bricks too, so backed off enough to feel airflow again and see temp gauge go down. Still, at that point (I dunno- 25'?) much much less air to punch through than non-drafting although it was buffety and turbulent and unpleasant besides. Got way better mpg that tank even though cruise speed for that 150m was 20 mph faster than I usually go and also that segment was only part of a tank. Sorry, even though I calculated fe at most every fill, I didn't keep fe logs on the bike back then so I won't quote an exact value but yes it seemed to be a better than 40% improvement. Yup, it definitely works.

That was years ago and that was also the last time I took chances drafting even though there was no incident whatsoever. The chance of an incident is extremely high and I'm not suicidal these days... but sometimes we do stupid things in the name of science right??? Also it seems potential draft vehicles are never going the speed I want to go anyway. Seems like they are always kicking up rocks and gravel too. I don't draft (unless following using the 2 second rule counts as drafting) and don't recommend it.

Frank, I remember we had a conversation on another post related to drafting. I asked about tailgaters, and whether or not they hurt your FE.
I forget what the verdict was on that.
I remember the point that the vehicle behind you supplies it's own power, and this offsets any parasitic 'drag' - as in drag on your own vehicle.
Still, it would seem to me that eventhough they supply their own power, they add to your overall frontal area and wake size ( if there is a large SUV tailgating you.)
Besides, their vehicle now provides less power to the vehicle in front, since it has less drag to overcome.

I still slightly confused still about that.

Frank - about the horse trailer incident...the first thing that comes to mind is horse manure...flying horse manure.

Yeah if they farted I knew it.

Well if NASCAR is any indication, tailgating helps BOTH vehicles out.

There is almost no danger driving 2' behind another vehicle, except for the cosmetics on the bumpers. Even if the lead vehicle slams on their brakes, the relative speed at impact is under 8 MPH. Pilots flying in really close formation know this. At 200 mph, a NASCAR driver can't ease over to the wall and touch it because of air pressure, but he can swerve into it from farther away.

I can sympathize with the mythbusters for overdramatizing the danger, because a long train of close tailgaters would need progressively better reflexes if the lead vehicle slowed slightly, and they are in the entertainment biz anyway, but they promoted another myth. Perhaps we will get electronically controlled brakes to allow close following.

This was tested about 5 years ago... There was a "Smart Highway" test road build and the test mules were 5 or 7 Ford Taurus cars. They all had sensors front and rear and sensors in the roadway that would let the vehicles communicate with each other while driving. The drivers basically didn't have to do a thing, the vehicles steered themselves as well as maintained speed and also, a very close following distance. This allowed the vehicles to get better than average FE and were much safer as they could react faster and smoother than the human counterpart.

I'll try to see if there is any more info on that project.

I believe that is how the "Smart" cruise controllers and lane stability systems came about in some of the higher end cars.

EDIT:
Ah! found the name of the program: Intelligent Vehicle-Highway Systems (IVHS) initiative.

ARTICLE HERE
I guess I was off a bit, this program was started in 1994 and Demo'd in 1997.