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Old 06-23-2012, 11:06 PM   #21 (permalink)
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Originally Posted by Richard Rowe View Post
As far as traffic spacing goes, I did address that elsewhere in the book when I talked about following distances. My opinion on people cutting in is, and pretty well remains...so what? What's going to happen then?
Exactly my feeling when I read that comment. Last week I found myself in a stop and go situation and decided to try traveling at the average speed instead of bumper to bumper to reduce the number of times I come to a complete stop. Rowing through a close-ratio 6-speed gets tedious in stop and go traffic. Some people got annoyed and changed lanes just to get 1 car length ahead, but generally people just followed behind. Not only did I reduce my use of the brakes, but I effectively forced everyone behind me to follow at a constant rate instead of using their brakes. Everyone that followed got better fuel economy because of this.

The bad traffic added 40min to the trip when compared to light traffic (Portland, Oregon). I estimate that allowing myself to be passed added 30 seconds to this time. The lost time is a drop in the bucket when considering the frustration that is relieved by not caring if someone gets in front of you, not to mention the fuel and brake/clutch wear that is saved. I average the same fuel economy in stop and go traffic as I do at constant 70mph freeway travel.

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As far as the following distances in drafting go: yup. You're right, and no, I didn't get into it. Just going from the Mythbusters test, I believe there was a 26 percent improvement at 100 feet. I was playing with the idea of mentioning it, but I'm kind of avoiding it for a couple of reasons. 1) I wouldn't even have talked about drafting, if it weren't just due process, and 2) since the average person would even react to the truck stopping at 100 feet until 4 feet before they hit it, I thought that might just be setting them up for a harder impact if they are dumb enough to draft. Hit a truck from ten feet away after it brakes, and the speed difference between you and the truck is maybe 5 mph. Hit it from 100 feet (when the truck has had longer to slow down) and the speed differential might be 20 mph or more.

So, if you're going to be close enough to the truck that you'll hit it no matter what, you're better off riding two feet from its bumper than you are 100 feet. So, you can probably see why I didn't get into the distance thing. I'm all for due process and all, but there's no sense in offering any more encouragement than necessary. Know what I mean?
I hadn't even considered that closer following could be safer. Thanks for that perspective!

The tractors in Oregon travel at 60mph. Given the generally accepted 2 second rule, this puts the safe following distance at 176ft. Perhaps there is efficiency to be gained in a relatively safe draft?

I can appreciate your unique perspective having been a driver. You might consider adding the information to the book though, because people will be sure to ask the question "what about drafting further back". They might come to the false conclusion that following 100ft back is safer (I did, and I'm not a dimwit) and adopt that practice. Better to present the full risk/benefit analysis to the audience and let them come to their own conclusions (with the help of a little humorous prodding).

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Old 06-24-2012, 05:32 PM   #22 (permalink)
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Quote:
Originally Posted by Richard Rowe View Post
My opinion on people cutting in is, and pretty well remains...so what? What's going to happen then? You'll need to back off to increase following distance, then another car will cut in. Back off more, and another car cuts in. So, your average speed winds up slightly lower than most other cars...but what else is new lol?
I think you're not thinking it through. If someone cuts in as soon as you open up a 2 car length space, your average distance to a rear bumper is 1.25 car lengths, with some fraction of your time being at 0.5 length. If instead you keep a 1.5 car length spacing, you have a greater following distance all the time, plus you don't have to worry about the other drivers misjudging distance, braking immediately after they cut in, etc.

Of course there's some psychology involved, as you want to keep the max distance you can without tempting a cut-in. But IMHO steady-state conditions are almost always safer than abrupt changes.
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Old 06-25-2012, 12:38 AM   #23 (permalink)
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I enjoy your writing style, & appreciate your technical knowledge, Richard. I don't think you should include a reference to Social Darwinism without acknowledging that it's thoroughly discredited, was never promoted by Darwin, and has no credible or intelligent following.

I used to ride a 90cc motorcycle, with a top speed of 55 mph on the level, and 70 mph on downhills or with strong tailwinds. When big rigs would pass me, I could tuck in behind them and get sucked up to 70 mph & stay there as long as I stayed within about 30' of their rear ends.

I've found minimal benefit staying 2-3 seconds behind trucks. I use more fuel keeping up with them than I do going my slower speeds.
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Old 06-25-2012, 05:57 AM   #24 (permalink)
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Originally Posted by redpoint5 View Post
The tractors in Oregon travel at 60mph. Given the generally accepted 2 second rule, this puts the safe following distance at 176ft. Perhaps there is efficiency to be gained in a relatively safe draft?
Our rigs go a tad slower, so I can close in a bit more to around 50m / 164 ft.
It still shows a benefit.

I've done this as much as possible lately, and it has resulted in 2 record tanks in a row.
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Old 06-25-2012, 04:19 PM   #25 (permalink)
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I love the idea of a book. Making the idea of hypermiling more accessible to the public can only be good.

Drafting? A full size pickup with a cap effectively blocks forward vision pretty well, and nobody warns you against being behind them. Following too closely is a bad idea no matter what your goal is or how big the vehicle is, and people are too afraid to recommend drafting because they fear being responsible for mayhem "caused" by their recommendation.

The best benefit of "drafting" is matching your speed to a (hopefully) slower vehicle that tries to move at a constant speed. That gets you moving more steadily and gets you out of the "if I floor it I can get one car length farther ahead" mindset and into an "it's okay for someone to be in front of me" mindset.

But you've read enough arguments about it...
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Old 06-25-2012, 08:28 PM   #26 (permalink)
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The best benefit of "drafting" is matching your speed to a (hopefully) slower vehicle that tries to move at a constant speed.
The buffer function definitely works, but my instant fuel consumption display is a bit higher at the same speed without a rig ahead
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Old 06-26-2012, 12:00 AM   #27 (permalink)
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Hey guys, sorry it's taken me so long to respond. We've got a tropical storm going on down here in FL, and it knocked civilization out for the better part of two days. Just FYI, I'll be sending out copies of the book tomorrow night...so anyone who's in needs to PM me with an outside email address so I can send it.

VMan455: Yeah, I'll check on that. As I recall, the Viper in the MT article did have the three big hood vents, so I'll check it out and make whatever correction is necessary. Can't imagine it would be too much, since those vents primarily reduce pressure under the car to decrease lift...so I don't think there'd be too much of a difference in CD just from that. BUT, that being said, there probably are other factors that would affect it. So, I'll check up...thanks for the catch Like I said, I'll be sending copies out starting tomorrow night, so send me an outside email addy through PM so I can send it.

JamesSQF: Well, man, if you don't think it would work for you, then go with what does. But you might want to try just maintaining a steady, lower speed. I (unfortunately) spent a lot of time on the West coast when I drove for Prime, and I never really had a problem with just maintaining a lower speed in traffic. Even in LA traffic, most of the time I'd just stick the thing in 6th gear and let it idle at about 10 mph. And that was in almost bumper-to-bumper traffic on the freeway.

Obviously, like you said, there is some psychology involved here...people are going to act differently around an 80K lb truck than they are a pickup truck. But, I've still found it to work driving a car in downtown Atlanta...the only major difference is that you do have to sustain a little bit higher speed, just to keep people from doing anything dumb. But Atlanta's just as bad as LA during rush hour, and it worked pretty well there. My last trip up there and back, I average 38 mpg in a 1992 Dodge Dynasty factory-rated at 26 mph. And that was through Atlanta rush hour and through the mountains. Average city mpg through Atlanta (as best I could calculate) came out to about 26, 27 mpg. And I've done the same thing with other cars in other cities, most often getting factory highway mpgs in bumper-to-bumper traffic. So, it's worked every time I've used it. But, you know how it is...results may vary lol.

It does take the patience of frickin Job, though...that's the hardest part. And, yeah, morons are going to jump in your lane and slam on their brakes. That's part of what you have to account for. But average speed is average speed. I never worried about the size of the buffer zone at all...could be two car lengths, could be 50. But half the people who jump into your lane will wind up jumping back into the other at some point, so, it all pretty much balances out eventually. Again, just my experience

Sentra SE-R: lol...yeah, I know. But I'd figure that most people would recognize it as at least as valid as the idea of hairy-palmed Morlocks. By the time the reader gets to that part (about 80 pages in), they're probably used to the metaphor. Here's the paragraph that leads off the braking chapter (about 20 pages in):

"In four words:

THERE IS NO BRAKE.

In a bunch more words:

Braking is The Great Evil. Take the Necronomicon Ex-Mortis, use it as an assembly guide, and chant backward in Latin to summon the spirit of a little Asian ghost girl who can assemble an hydraulic system, using The Pick of Destiny as a screwdriver. Fill that system with orphan tears, carve a pedal out of sulfur and pads out of orc bones, then use The One Ring in place of vacuum assist – those are your brakes. Savvy?"

So...yeah. I think the whole "Social Darwinism" thing is probably one of the LESS obtrusive forms of BS used to make a point. You think? lol

Far as drafting goes -- Oh yeah, it definitely works. I don't doubt that it did for you. But, it's probably worth mentioning that I once ran over someone's upper torso outside of Reading, Pennsylvania. Not because he was in my way...just because his torso was in the road. I didn't get the whole story, but from what I could tell, the Torso started out as a guy on an Enduro bike riding very close behind another truck about a half-mile ahead of me. There was a second truck between us. The lead truck had to slam on his brakes to avoid a car pulling in from the on-ramp, and the biker went under his rear bumper. He fell off, and went from man to man-minus-legs when the truck ahead of me hit him. I'm pretty sure he was still alive when my left-front steer tire went over his chest. I'm not going to get into the graphic details...especially what happened at the Blue Bell truck wash afterward.

I'm not really sure how far The Torso was behind the truck...driver said he never saw him in his mirrors, so it had to be less than 60 feet or so. But, suffice it to say, I think whatever fuel that guy saved probably leaked out of what was left of the motorcycle's gas tank. Not being preachy or anything, but you seem like a nice guy. Be a shame for the world to lose you

Euromodder: Yep, you might see some benefit from that far out...depends on the leading/trailing vehicles, speed, air density, wind direction ect. And 164 feet is far enough to be plenty safe at interstate speeds. So, I got no argument against that. And I'd even say so in the book, but I can't find any solid evidence to support a quantifiable benefit at more than about 120 feet. Which, at 95 feet per second, is cutting it reaaaaal close for my comfort. If you can find me something that supports a fuel economy gain from a safe distance (more than 150 feet or so), then, hell yes, please send it my way. I'd love to be able to cover the other side of the argument.

Fat charlie: Thankee much That was my thought on it, too...to make it accessible. I'm really looking forward to having you guys read it, and see if it's successful in that way. Right now, I'm going through and smoothing things out before I send it out to whoever wants to take a look. Just send me your email addy, and I'll put you on the list.

I agree that intentionally following someone is probably a good exercise in patience...and, yeah, the fuel benefits are definitely a perk. Even if you're following a car the same size or a little bigger, you're going to see a boost in economy once you get in past the vortices. I've done it with cars, so, yep...it works. BUT, the times I've done it, we had either CBs or those push-to-talk radio phones. And with cars leading, you have to be way closer...for a typical car, you have to get within about 5 to 10 feet or less to get your nose all the way into the drag pocket. With a big pickup, maybe 10-15 feet, depending on the speed and the size of the trailing car.

It is a good training exercise, though. It's hard for most people to get their minds around that "It's OK not to be first" thing. Personally, I think it's little-man syndrome lol.
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Old 06-26-2012, 04:02 AM   #28 (permalink)
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Vman455: You were right...that "2007" Viper was actually an early 2008 released to the press in '07 for reviews. Nice one!
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Old 06-26-2012, 10:11 AM   #29 (permalink)
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One more point I'd add to the "why following closely is generally a bad idea" column of the debate leger: when you follow anything too closely (intending to draft or not), not only do you diminish your forward vision (which is fine, if you like a life full of surprises), you now must brake as soon and at least as hard as the lead vehicle does. (But probably harder, after adding in your reaction time.)

Big deal, you say?

Now consider the usual tailgater behind you, and see how you have lost the opportunity to anticipate & respond to speed changes more gradually and on your own terms. Slowing gradually is a basic defensive technique for reducing the chances of getting rear-ended by your tail-gaiter.
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Old 06-26-2012, 11:23 AM   #30 (permalink)
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I plan to be around past the average actuarial life expectancy for men of my age. I put >100,000 miles on motorcycles without injury, so I developed some street smarts. I haven't drafted like I described earlier, in the past 40 years.

The chapter on drafting is a good read. It covers the topic & gets your/the common sense point across. I'd replace "Social Darwinism" with "thoroughly discredited Social Darwinism," though. I might even consider adding a paragraph about your legless torso experience for more color.

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