No aero mods, just drafting

[SlideWRX]

Compared to the regular rush hour traffic I see, 8-10 meters is a 'wide' berth. It may not be safe, but millions drive that way every day quite regularly. The 2 second rule is, well, the rule, but rush hour traffic regularly goes 1 second or less at 70 mph.

[caferacer51]

Ha, does 8-10 metres not become a little more 'unsafe' when your trying to take a picture of your display with a mobile phone...?

[brucepick]

Back when I was in Drivers' Ed. class the rule was one car length per each 10 mph speed. Of course if you're using km/h the math is different. Maybe .7 car length per each 10 km/h??

Anyway, I find it easy to derive and visually estimate 6 car lengths from 60 mph but I know an intelligent adult who once asked how many quarters there are in a dollar... Different strokes, as they say.

[skyl4rk]

You don't need to drive that close to trucks to get drafting benefits. A reasonable distance behind them can help you quite a bit. A lot depends on how windy it is and which direction the wind is coming from.

There is definitely a benefit from drafting, although looking at the back of a truck is pretty boring.

[hamsterpower]

Anyone complaining about how dangerous drafting is- for your own sanity stay away from Massachusetts. On the major routes there, one car length at any speed is all too common and two car lengths is an invitation to merge. I nether practice or endorse this but I see it every day.
On the other hand, if you wait to see brake lights before slowing, you are too late. In close traffic, look two or more cars ahead of the one you follow. If you can't see that far ahead, you are too close.

[euromodder]

Originally Posted by skyl4rk

You don't need to drive that close to trucks to get drafting benefits. A reasonable distance behind them can help you quite a bit.

I've experimented a bit with slowly closing in on trucks, and needed to be rather close for it to really show - too close for comfort to me, so I'd rather not do this for extended periods.

There's also a difference between trucks & trailers.
Big box-shaped trailers are good to draft.
With tanker-trailers the effects are less impressive.
Drafting low trailers (flatbeds without load ; equipment carriers with ramps), the benefits are small.


The best to draft are busses.
They'll do 100kph (62mph) instead of 90kph (56mph) in Europe, are very squarish, and their box shape comes down really low compared to trucks.

But bus drivers especially don't want you to draft them and will often change speed.

[Joenavy85]

Originally Posted by euromodder

The best to draft are busses. They'll do 100kph (62mph) instead of 90kph (56mph) in Europe, are very squarish, and their box shape comes down really low compared to trucks. But bus drivers especially don't want you to draft them and will often change speed.

i look for one of the Semi's with the skirts on the trailer, they tend to have a wake pretty much equal to Buses, and being typical Semi Drivers they tend to maintain a pretty consistent speed on level ground, sometimes have to pass when going uphill, but it really depends on the grade and length of the hill

[aerohead]

For those with Hucho's books you'll already know this,however,for those who don't have his books,he does address drafting( as is done in NASCAR ) and also 'convoy' driving as has been research with OTR long-haul trucking.
Plenty of tables/graphics/data.Good science!
My trailer project employs this science of the 2-car draft to lower the drag of both tow,and towed vehicle for better mpg.

[donee]

Originally Posted by So_SiMpLe_

Ok guy sorry, I was doing it responsibly, at one average car distance maybe.

Just was trying to show the effects of dragting a truck.

Hi SSIM...,

9 meters is 29.5 feet. The average car in Portugul is probably Prius sized, or about half that. And that distance is just too close. Even if your car had radar cruise control, what about the cars behind you?

I saw the remains of a Suzuki Samrai car that got squeezed between a 18 wheel truck and a large SUV. The paint was burned off, and the all the plastic burned away or melted. Needless to say the driver died.

3.2 l/100 km is quite good, about 73.5 mpg US. This is similar to what a 2nd Gen Prius can do in SHM mode on flat terrain above 65 deg F, without allot a wind.