Owners' Stories

[Tdave]

I plan on getting good highway range by drafting a big rig about half the time on a long trip. I expect to be able to go 65 mph at the same energy usage of going 50 mph without drafting. Maybe even better.

There's a lot that goes into actual mileage.

 

[efusco]

And anyone that is pushing the distance envelope will probably be doing it on the highway.

Good point, add to that that there are probably fewer opportunities for opportunity charging during a hwy trip as well.

 

[Kevin Harney]

Dave I think that is a good idea however I think that PLANNING on doing that for a trip might leave you stranded. Not my idea of fun ..... I need a cushion to make sure I will get there. :smile:

 

[Tdave]

Kevin, if range will be tight, you can always slow to 50 mph when there's no big rig to draft. The Roadster gets 30% more range at 50 mph compared with 65 mph. 30%! It's all in JB's blog entry from December.

And if that's not enough, you can get 50% more range by going 42 mph. Or 100% more range by going 20 mph. Of course that would be unsafe on the highway. But you get the idea.

 

[TEG]

My current EV has only 60 mile range, and so I have done some drives where I had to draft a big rig to make it. Let me tell you, it is not fun to have to do that on a regular basis. The truck you find may pull off, or decide they don't want you on their tail so it becomes a game of "find the next truck" which wears thin quickly.

 

[NEWDL]

not to mention the risks.....

anyone not comfortable drafting a semi in a roadster?

 

[Tdave]

You don't need to be very close to get the benefits. Check out the Mythbusters test on this. You'd be suprised. I know I was.

Based on their results I'm expecting 15% better range at 100 ft following distance, and 20%-25% better range at 50 ft following distance. I'll be interested to do real world testing once I get my Roadster.

 

[Palpatine]

That Mythbusters was excellent. It made it obvious that it helps even at 100 feet, which is still a fairly safe distance.

 

[Kevin Harney]

yes but the average stopping distance from 55 to 0 is about 135 feet so that leaves little reaction time even if the Roadster is better than average....

 

[Tdave]

The Roadster can stop tons faster than a semi can. If the semi hits something, he'll clear the way for you to have space and time to stop. As long as you're not asleep, you're safer there than not behind the semi.

 

[vfx]

yes but the average stopping distance from 55 to 0 is about 135 feet so that leaves little reaction time even if the Roadster is better than average....

What is the Tesla stopping distance at 55MPH?


C and D just got 170ft from 70 MPH.

 

[TEG]

...unless it jackknifes, throws some retread, drops something off the back, or runs into some immovable object that you couldn't see ahead of it.

Efficient but not too safe.

 

[donauker]

Under riding
One of the most deadly type of accident results when trucks lack adequate safeguards on the rear of the truck to prevent vehicles from "underriding." A car underrides a truck when the truck brakes quickly and the car fails to stop before plowing into, and under, the semi - typically shearing off the top of the car. Underrides kill approximately 1,000 persons each year, and all of them are car occupants - only about 2% of those occupants survive the accident. These accidents occur because trucks stop or slow suddenly and the driver of the car is unable to avoid rear-ending the truck.

 

[Kevin Harney]

looks like the Roadster will stop in 119 feet from 60 mph. Probably not worth the risk of following at 100 feet ..... 19 feet under the truck does not sound too appealing to me !!!

http://www.roadandtrack.com/assets/download/0209_tesla_datapanel.pdf

 

[vfx]

looks like the Roadster will stop in 119 feet from 60 mph. Probably not worth the risk of following at 100 feet ..... 19 feet under the truck does not sound too appealing to me !!!

Well that is assuming the truck pushed the laws of physics and came to an instant stop..

 

[Kevin Harney]

Well trucks do have that special ability !!!! There are amazing ..... Sometimes things meet immovable objects and sometime something behind you can push you forward.

 

[efusco]

I'm gonna vote very strongly against drafting.

At 65mph you're traveling at 95 ft. per second. Average human total reaction time (perception plus reaction) at that speed is 0.7 seconds. Thus, even if the semi is just slowing quickly you'll close the distance from 100ft. to 29ft before you even begin to slow and the slowing progress of the semi will be accelerating (IOW, greater deceleration).

Add to that any distraction, inattentiveness, higher speed, whatever and your brand new Tesla is a crumpled aluminum can.

Many hypermilers used to promote tailgaiting/drafting as a technique to improve FE, but it's now universally accepted as an unsafe practice. Most recommendations are to follow no closer than 3 seconds behind the vehicle ahead of you. There are also better ways to maximize FE, even in an EV.

 

[Kevin Harney]

There is Preception time + reaction time .....

Human perception time: The time required for a driver to recognise a potential hazard. This time is assumed to be approximately 0.75 seconds in normal situations
Human reaction time: Once the hazard has been perceived, the driver must respond by applying the brakes. The average reaction time is about 0.75 seconds

so at 1.5 seconds you will have traveled 190 feet and when following at 100 feet that is a slight problem even if you are better than twice the average.

 

[vfx]

I too am against drafting (off the racetrack).

 

[Tdave]

Oh c'mon. When the semi slams on his brakes, he'll be going no more 10 mph slower after 1.5 seconds. You'll be at most 14 feet closer to him at that point, and already slowing faster than him. It's really not a problem.

Driving at the race track 20 feet behind the car in front of me, there was never a problem with that car going to maximum braking right in front of me. In that case I'm anticipating it, so it's a little different, but so is 20 feet different from 50 or 100 feet. And that's with a car in front of me with brakes every good as mine.