Race Car Drafting


#1

Did anyone confirm they were right on the drafting issue? The leadcar loses suction drag and the drafting car loses pressure drag when they close up so the required power for each at a given speed drops.


#2

Usually both gain. Nothing has changed in years. However each car/truck has different aerodynamics so there can be exceptions. For the effect to really work, you need to be far closer than is safe. If someone was behind me like that, I will be dialing 911 on my cell phone.


#3

It’s just like a boat. The maximum speed of a boat is governed in part by it’s length at the water line compared to it’s girth. The higher the ratio, the less drag and the faster the boat can go. Change the fluid to air and the vehicle to one or more cars (very close together) and you have the situation you ask about.


#4

why does the lead car lose suction drag? Seems to me it would still be there until the drafting car actually became one with the lead, as in smashing until fused together.


#5

Because the high pressure zone in front of the rear car extends several feet in front of the car’s grill. If that car gets close enough, it partially kills the low pressure behind the lead car.


#6

As a former cyclist I can testify to the theory. Anybody who has raced knows that if you have a teammate right behind you (in bicycles we overlapped wheels and we’d swap off positions) you can go faster farther. You can clearly feel the difference. The principle is exactly the same in car racing.

When training cyclists cluster into a lined up group, and every now and then the lead rider drops to the back of the pack. That enables him/her to keep with the pack and get some rest after riding lead for awhile. While having a tail helps the lead rider, it’s still the toughest spot.


#7

+1


#8

What does that mean, “+1”?
Am I getting too old to understand the language of the young?


#9

six stars?


#10

+1 means they are agreeing with the previous post, it means “ditto” or something similar. “x2” means the same thing.


#11

Thanks. This must be text messaging shorthand.
I guess I’m just getting old.


#12

X2, obviously!


#13

I think it started on Slashdot.org many moons ago, one of the first “comment on the news” sites. It means something akin to “add one more to the list of people who agree”.


#14

Basically the idea is that when a car drives by itself it has to move a lot of stuff (air) out of its way in order to move. If you place two cars close enough to each other, they help each other by each moving a portion of the air in their way. So it’s not creating energy as the caller stated, you are simply doing less work. As we all learned (and since forgot…) in high school physics, Work is defined as Force times Distance, and Work is a form of Energy.

In short, you have to move less air per car, meaning less Force is required, therefore less Work, and less Energy.

Edit: Sorry I didn’t post this sooner, was studying for finals and didn’t get around to listening to the podcast until about 5 min ago.


#15

Also, air weighs a lot more than most of us think. A cubic yard weighs about 2 pounds. A 2000 square foot house can contain over 1000 pounds of air. Feel the upward pull of a helium balloon, that’s about how much the air that the balloon displaces weighs.


#16

They proved that it worked on Mythbusters, but only at such short distances that an accident is waiting to happen.

Never have the misguided idea that saving energy is more important than safety. Stay at least 2 seconds back (3 seconds above 45 mph).


#17

A car ‘drafting’ a big truck will decrease the turbelence and drag experienced by the truck. Hence the car drafting increases the milage of the truck and of course, increase it’s own milage. A RV towbaring a small car will not loose as much milage as would be imagined.