"Bill Tuthill" <ccreekin@yahoo.com> wrote in message news:45b3ab60@news.meer.net...> Ray O <rokigawaATtristarassociatesDOTcom> wrote:>>
I've read that the most aerodynamic shape looks more like a banana, with>> the ends of the banana pointing downwards. A truncated back end will >> create>> a low pressure area immediately behind the vehicle and increase drag.>
Maybe this has to do with whether aerodynamicity refers to a falling > raindrop> or a vehicle moving along the ground?>
The teardrop is the reverse of my expectations: the blunt end is in front,> with the tapered end at the back.>
There are many things that contribute to drag and make the propulsion system work harder. Anything that contributes to turbulence will increase drag. The spoilers and wings on an Indy car are smaller for high speed races than for road races, where the additional downforce to aid cornering is more important than reducing drag.
Having the pointy end at the back of the car reduces the turbulence and drag behind the car. A blunt rear end creates a low pressure area, which sucks the car backwards, but a vehicle following in the low pressure area doesn't have to work as hard to move through the low pressure area, the principle behind drafting in races.
The other area that people often forget about is the undercarriage. A>> shield under the engine compartment will help reduce drag.>
Aha, another use for skid plate!
could be!>
Since the 2007 Trunda is not for sale yet, the Silverado probably is>> "best in class" for cD.>
That explains it, thanks.>
A friend got 23 MPG from his 1999(?) Silverado small V8 on the highway,> with camper shell and nothing on the roof. The EPA for that vehicle> was 21 MPG highway. Pretty good for a pickup truck, eh? His mileage> went down when he replaced the crappy factory tires. (They were crappy> off-road anyway, but obviously had low rolling resistance.)>
The tailgate on a pickup can act as a large wind brake. Shells and tonneau covers keep air away from the tailgate and reduce drag, as does lowering or removing the tailgate or replacing it with a net or mesh. --
"Bill Tuthill" <ccreekin@yahoo.com> wrote in message news:45b3ada6@news.meer.net...> Andrew Stephenson <ames@deltrak.demon.co.uk> wrote:>>> [Edumunds.com] says Prius has a .29 coefficient of drag (cD).>>
Then the article disagrees with commonly available authoritative>> data sheets, that (no doubt while lying through their collective>> teeth) claim 0.26 -- not a big error but whattheheck. <g>>
Aha! So Toyota managed to nearly equal the Insight without specifying> rear-wheel fenders, which make tire changes more difficult.>
The Honda Insight is also very noisy inside at highway speeds.> I'd rather pay more for gasoline than lose my hearing.>
There are lots of tricks to reduce drag and improve fuel mileage besides fender skirts. Reducing interior sound insulation saves weight. I expect to see exterior rearview mirrors go away, replaced by cameras that doesn't stick out into the airstream.
The Prius has some subtle design tricks that maintain decent interior room without major contributions to drag. Look at the roofline from behind, and notice that the centerline of the roof is lower than the left and right side. --
Both the 2007 Tundra and Silverado were compared by MT for the truck of the year award, The Tundra lost out in that comparison. ;)
mike
"Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message news:c18c4$45b2a202$47c2b532$19522@msgid.meganewsservers.com...>
"Bill Tuthill" <ccreekin@yahoo.com> wrote in message > news:45b27851@news.meer.net...>> Recently I've been wondering why truck manufacturers, including Toyota,>> don't do a better job making pickup trucks aerodynamic. Nowadays>> fuel economy at speeds > 55 mph is determined mostly by air resistance,>> not vehicle weight or engine size.>>
This article says my Prius has a .29 coefficient of drag (cD), while>> the Honda Insight has a .25 cD. Would Prius cD improve by installing>> rear-wheel fenders? They're ugly on the Insight but what else could>> explain the huge difference between .25 and .29 cD?>>
I remember .29 is what our 1994 Volvo 850 wagon had, but looking up>> this information now on the web, answers vary from .32 to .33 cD.>> I'm fairly certain the wagon had better cD than the sedan, so maybe>> the wagon was .32 and the sedan was .33.>>
The teardrop is the most aerodynamic shape, so wagons have an advantage>> in that they start out closer to the best shape, although glass in the>> rear windows is heavier than a trunk lid. Teardrop also might be why>> pickup truck owners report improved fuel economy with a camper shell.>
I've read that the most aerodynamic shape looks more like a banana , with > the ends of the banana pointing downwards. A truncated back end will > create a low pressure area immediately behind the vehicle and increase > drag.>
The other area that people often forget about is the undercarriage. A > shield under the engine compartment will help reduce drag.>
The Tundrasolutions.com website (owned by Toyota?) reports the Tundra>> has a cD ranging from .37 - .38 depending on model.>>
The 2007 Chevy Silverado has a cD of .43, reportedly "best in class">> according to Wards Auto, so something is amiss here.>>
Since the 2007 Trunda is not for sale yet, the Silverado probably is "best > in class" for cD.> -- >
"Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message news:1f547$45b3bc56$47c2b532$10307@msgid.meganewsservers.com...> Having the pointy end at the back of the car reduces the turbulence and > drag behind the car. A blunt rear end creates a low pressure area, > which sucks the car backwards, but a vehicle following in the low > pressure area doesn't have to work as hard to move through the low > pressure area, the principle behind drafting in races.
This gets me to thinking about drafting behind trucks on the highway to save fuel. Just how close does one need to be to make this effective (notwithstanding safety issues of being that close). How about for behind a pickup or a 'regular' car? Tomes
"Mike Hunter" <mikehunt2@mailcity.com> wrote in message news:2LOdndSGxpWeTy7YUSdV9g@ptd.net...> Both the 2007 Tundra and Silverado were compared by MT for the truck of > the year award, The Tundra lost out in that comparison. ;)>
mike>
From what I have seen and read of the 2007 Tundra, it is a much better truck than the previous generation Tundra and getting closer to the F series Ford and Silverado in utility but have not passed them yet. I predict that a few more people will purchase it as a work truck than the previous Tundra but it will still appeal primarily to urban cowboys. --
"Tomes" <askme@here.net> wrote in message news:k9Rsh.13809$yx6.11883@newsread2.news.pas.earthlink.net...> "Ray O" <rokigawaATtristarassociatesDOTcom> wrote in message > news:1f547$45b3bc56$47c2b532$10307@msgid.meganewsservers.com...>> Having the pointy end at the back of the car reduces the turbulence and >> drag behind the car. A blunt rear end creates a low pressure area, which >> sucks the car backwards, but a vehicle following in the low pressure area >> doesn't have to work as hard to move through the low pressure area, the >> principle behind drafting in races.>
This gets me to thinking about drafting behind trucks on the highway to > save fuel. Just how close does one need to be to make this effective > (notwithstanding safety issues of being that close). How about for behind > a pickup or a 'regular' car?> Tomes
Notwithstanding safety issues, depending on speed and the shape of the leading vehicle, you probably need to be within 1 to 3 feet. --
Larry Moe 'N Curly 22 January 2007 01:06:27 [ permanent link ]
Ray O wrote:
I've read that the most aerodynamic shape looks more like a banana , with> the ends of the banana pointing downwards.
Is that why the Oscar Meyer wienermobile, with the ends of the hot dog pointing upward, has never broken any speed records at the Bonneville Salt Flats?
"larry moe 'n curly" <larrymoencurly@my-deja.com> wrote in message news:1169426453.651362.45820@s34g2000cwa.googlegroups.com...>
Ray O wrote:>
I've read that the most aerodynamic shape looks more like a banana , with>> the ends of the banana pointing downwards.>
Is that why the Oscar Meyer wienermobile, with the ends of the hot dog> pointing upward, has never broken any speed records at the Bonneville> Salt Flats?>
Andrew Stephenson 22 January 2007 15:01:57 [ permanent link ]
In article <57886$45b43ff5$47c2b532$13171@msgid.meganewsservers.com> rokigawaATtristarassociatesDOTcom "Ray O" writes:
On the damaged ship, the story I recall hearing is that the bow> was damaged, patched, and towed stern-first to reduce the> strain on the patches, and that towing it backwards worked> well.
Backwards. Aha. Rather different. (And, ever since, though we don't know it, "performance" ships have been _built_ backwards.) Puzzlingly, the context of the version I heard was it apparently revealed a new way of shaping ship sterns. Oh well, I shall see what explanations come my way in future. -- Andrew Stephenson
Andrew Stephenson 22 January 2007 15:06:38 [ permanent link ]
In article <hqWdnTEX-a2GEinYRVnygw@bt.com> coyoteboyspuduk@hotmail.com "Coyoteboy" writes:
[...] The teardrop is a trade-off of water weight, surface> tension and air resistance all of which are very important at> the scale of a drop but not in the same orders when on the> scale of a car.> [...]
On top of that, (according to someone in the meteorology NG) real raindrops are not shaped like picture-raindrops. Pressure on the leading surface flattens it while any tail collapses and the drop becomes a ragged disc. -- Andrew Stephenson
In article <hqWdnTEX-a2GEinYRVnygw@bt.com>> coyoteboyspuduk@hotmail.com "Coyoteboy" writes:>
[...] The teardrop is a trade-off of water weight, surface>> tension and air resistance all of which are very important at>> the scale of a drop but not in the same orders when on the>> scale of a car.>> [...]>
On top of that, (according to someone in the meteorology NG) real> raindrops are not shaped like picture-raindrops. Pressure on the> leading surface flattens it while any tail collapses and the drop> becomes a ragged disc.
Yup, thats correct good point, initially the drop forms normal drop shape but then rapidly turns into a ragged disc as you mention - presumably as the apparent wind speed increases the different forces contribute differently to shape.
Bill Tuthill 23 January 2007 06:57:18 [ permanent link ]
Ray O <rokigawaATtristarassociatesDOTcom> wrote:>
I expect to see exterior rearview mirrors go away, replaced by cameras> that don't stick out into the airstream.
Good idea!
The Prius has some subtle design tricks that maintain decent interior room> without major contributions to drag. Look at the roofline from behind,> and notice that the centerline of the roof is lower than the left and> right side.
Is that entirely to increase headroom for driver and passenger, and outside positions in the rear seat, or does it have aerodynamic purpose?
Coyoteboy <coyoteboyspuduk@hotmail.com> wrote:>
How, exactly, does a pickup with a camper shell look anything like a> teardrop?
Well, more like a teardrop than a pickup without camper shell, which has a dead area behind the cab, a wind baffle at the far back, and another dead area behind the tailgate. Anecdotal evidence says driving with the gate down increase fuel economy about 10%.
c) the drag co-eff of a car is determined by a lot more than just the> overall body shape, as you mention the wheel arch areas create vast losses> and the underbody is by far the worst and most messy area aerodynamically.
Couldn't 4WD and high-clearance vehicles have a retractable front shield that the driver could remotely extend down below the grille at high speeds? Obviously this stuff needs to be computer-modelled, but if the underside is such a huge aerodynamic problem, it seems that cost-effective solutions could be provided.
"Bill Tuthill" <ccreekin@yahoo.com> wrote in message news:45b5879e@news.meer.net...> Ray O <rokigawaATtristarassociatesDOTcom> wrote:>>
I expect to see exterior rearview mirrors go away, replaced by cameras>> that don't stick out into the airstream.>
Good idea!>
The Prius has some subtle design tricks that maintain decent interior >> room>> without major contributions to drag. Look at the roofline from behind,>> and notice that the centerline of the roof is lower than the left and>> right side.>
Is that entirely to increase headroom for driver and passenger, and > outside> positions in the rear seat, or does it have aerodynamic purpose?
Aerodynamic.
Cathy
Coyoteboy <coyoteboyspuduk@hotmail.com> wrote:>>
How, exactly, does a pickup with a camper shell look anything like a>> teardrop?>
Well, more like a teardrop than a pickup without camper shell, which has> a dead area behind the cab, a wind baffle at the far back, and another> dead area behind the tailgate. Anecdotal evidence says driving with> the gate down increase fuel economy about 10%.>
c) the drag co-eff of a car is determined by a lot more than just the>> overall body shape, as you mention the wheel arch areas create vast >> losses>> and the underbody is by far the worst and most messy area >> aerodynamically.>
Couldn't 4WD and high-clearance vehicles have a retractable front shield> that the driver could remotely extend down below the grille at high > speeds?> Obviously this stuff needs to be computer-modelled, but if the underside> is such a huge aerodynamic problem, it seems that cost-effective solutions> could be provided.>
"Bill Tuthill" ...>> Ray O <rokigawaATtristarassociatesDOTcom> wrote:>>>
I expect to see exterior rearview mirrors go away, replaced by cameras>>> that don't stick out into the airstream.>>
Good idea!>>
The Prius has some subtle design tricks that maintain decent interior >>> room>>> without major contributions to drag. Look at the roofline from behind,>>> and notice that the centerline of the roof is lower than the left and>>> right side.>>
Is that entirely to increase headroom for driver and passenger, and >> outside>> positions in the rear seat, or does it have aerodynamic purpose?>
Aerodynamic.>
Cathy>
OK did I miss something? Looks like that's what he said?
"Bill Tuthill" <ccreekin@yahoo.com> wrote in message news:45b5879e@news.meer.net...> Ray O <rokigawaATtristarassociatesDOTcom> wrote:>>
I expect to see exterior rearview mirrors go away, replaced by cameras>> that don't stick out into the airstream.>
Good idea!
That idea was on some concept cars at the auto show last year, they will proably start to appear in luxury production cars soon.
The Prius has some subtle design tricks that maintain decent interior >> room>> without major contributions to drag. Look at the roofline from behind,>> and notice that the centerline of the roof is lower than the left and>> right side.>
Is that entirely to increase headroom for driver and passenger, and > outside> positions in the rear seat, or does it have aerodynamic purpose?
My guess is that the depression in the centerline is a way to reduce drag while maintaining headroom for the occupants.>
Coyoteboy <coyoteboyspuduk@hotmail.com> wrote:>>
How, exactly, does a pickup with a camper shell look anything like a>> teardrop?>
Well, more like a teardrop than a pickup without camper shell, which has> a dead area behind the cab, a wind baffle at the far back, and another> dead area behind the tailgate. Anecdotal evidence says driving with> the gate down increase fuel economy about 10%.>
c) the drag co-eff of a car is determined by a lot more than just the>> overall body shape, as you mention the wheel arch areas create vast >> losses>> and the underbody is by far the worst and most messy area >> aerodynamically.>
Couldn't 4WD and high-clearance vehicles have a retractable front shield> that the driver could remotely extend down below the grille at high > speeds?> Obviously this stuff needs to be computer-modelled, but if the underside> is such a huge aerodynamic problem, it seems that cost-effective solutions> could be provided.>
Front spoilers and air dams are generally designed to prevent air from building up under the undercarriage and creating lift, which is bad for traction and cornering.
A simpler solution is to design the undercarriage to reduce drag so the air flows smoothly under the car. --
"Wickeddoll " <wickeddoll1958diespammersdie@yahoo.com> wrote in message news:ep3giq.dc.1@news.evilcabal.org...>
"Cathy F." <...>>
"Bill Tuthill" ...>>> Ray O <rokigawaATtristarassociatesDOTcom> wrote:>>>>
I expect to see exterior rearview mirrors go away, replaced by cameras>>>> that don't stick out into the airstream.>>>
Good idea!>>>
The Prius has some subtle design tricks that maintain decent interior >>>> room>>>> without major contributions to drag. Look at the roofline from behind,>>>> and notice that the centerline of the roof is lower than the left and>>>> right side.>>>
Is that entirely to increase headroom for driver and passenger, and >>> outside>>> positions in the rear seat, or does it have aerodynamic purpose?>>
Aerodynamic.>>
Cathy>>
OK did I miss something? Looks like that's what he said?
"Wickeddoll " <wickeddoll1958diespammersdie@yahoo.com> wrote in message news:ep3giq.dc.1@news.evilcabal.org...> "Cathy F." <...>> "Bill Tuthill" ...>>> Ray O <rokigawaATtristarassociatesDOTcom> wrote:>>>>
I expect to see exterior rearview mirrors go away, replaced by >>>> cameras>>>> that don't stick out into the airstream.>>>
Good idea!>>>
The Prius has some subtle design tricks that maintain decent interior >>>> room>>>> without major contributions to drag. Look at the roofline from >>>> behind,>>>> and notice that the centerline of the roof is lower than the left and>>>> right side.>>>
Is that entirely to increase headroom for driver and passenger, and >>> outside>>> positions in the rear seat, or does it have aerodynamic purpose?>>
Aerodynamic.>>
Cathy>>
OK did I miss something? Looks like that's what he said?>
Natalie, cornfuzzled.
No, Cathy answered Bill's question: whether it was for headroom or for aerodynamic purposes. It is for aerodynamic purposes or at least not for headroom. I just went out to look at mine and noticed 2 things. First, the lowest points of the roofline are exactly over one's head whist one sits in there. Second, on the inside, the interior roof goes in a uniform arc across the top - does not bulge up (or bulge at all) for added headroom where heads go. Tomes
Bill Tuthill 23 January 2007 08:22:35 [ permanent link ]
"Wickeddoll " <wickeddoll1958diespammersdie@yahoo.com> wrote:>>>> The Prius has subtle design tricks that maintain decent interior room>>>> without major contributions to drag. Look at the roofline from behind,>>>> and notice that the centerline of the roof is lower than the left and>>>> right side.>>>
Is that entirely to increase headroom for driver and passenger, and >>> outside rear seats, or does it have aerodynamic purpose?>>
Aerodynamic. --Cathy>>
OK did I miss something? Looks like that's what he said?> Natalie, cornfuzzled.
Note the words "maintain decent interior room" without increasing drag. I can't see how those Prius side humps would help, except to maintain forward momentum in a crosswind.
"Bill Tuthill" <ccreekin@yahoo.com> wrote in message news:45b59b9b@news.meer.net... "Wickeddoll " <wickeddoll1958diespammersdie@yahoo.com> wrote:>>>> The Prius has subtle design tricks that maintain decent interior room>>>> without major contributions to drag. Look at the roofline from behind,>>>> and notice that the centerline of the roof is lower than the left and>>>> right side.>>>
Is that entirely to increase headroom for driver and passenger, and>>> outside rear seats, or does it have aerodynamic purpose?>>
Aerodynamic. --Cathy>>
OK did I miss something? Looks like that's what he said?> Natalie, cornfuzzled.
Note the words "maintain decent interior room" without increasing drag. I can't see how those Prius side humps would help, except to maintain forward momentum in a crosswind.
****** Tomes blew my headroom theory out the window, at least the aerodynamic part should still be valid . The humps will not maintain forward momentum in a crosswind. --
Andrew Stephenson 23 January 2007 14:38:56 [ permanent link ]
In article <95299$45b59408$47c2b532$29198@msgid.meganewsservers.com> rokigawaATtristarassociatesDOTcom "Ray O" writes:
A simpler solution is to design the undercarriage to reduce> drag so the air flows smoothly under the car.
Makes sense. At the same time, one probably gains a splash guard (which my Volvo 440s had and benefited from, on meeting puddles). -- Andrew Stephenson
Andrew Stephenson 23 January 2007 14:41:02 [ permanent link ]
In article <45b59b9b@news.meer.net> ccreekin@yahoo.com "Bill Tuthill" writes:
Note the words "maintain decent interior room" without increasing drag.> I can't see how those Prius side humps would help, except to maintain> forward momentum in a crosswind.
Stiffening the body as whole? Bracing for door frames? Provide conduits for cabling and such? A place to attach a roof rack if you must? It's likely to be a mixture of reasons: common in the Prius design. -- Andrew Stephenson
Maybe the humps are there to make the Prius even uglier than it already is (speaking of things common in the Prius design).
Andrew Stephenson wrote:> In article <45b59b9b@news.meer.net> ccreekin@yahoo.com "Bill> Tuthill" writes:>
Note the words "maintain decent interior room" without increasing drag.> > I can't see how those Prius side humps would help, except to maintain> > forward momentum in a crosswind.>
Stiffening the body as whole? Bracing for door frames? Provide> conduits for cabling and such? A place to attach a roof rack if> you must? It's likely to be a mixture of reasons: common in the> Prius design.> -- > Andrew Stephenson
Andrew Stephenson 23 January 2007 18:16:40 [ permanent link ]
In article <1169561053.636933.212030@k78g2000cwa.googlegroups.com> bogusmailmark@yahoo.com "Mark" writes:
Andrew Stephenson wrote:> > In article <45b59b9b@news.meer.net> ccreekin@yahoo.com "Bill> > Tuthill" writes:> >
Note the words "maintain decent interior room" without increasing drag.> > > I can't see how those Prius side humps would help, except to maintain> > > forward momentum in a crosswind.> >
Stiffening the body as whole? Bracing for door frames? Provide> > conduits for cabling and such? A place to attach a roof rack if> > you must? It's likely to be a mixture of reasons: common in the> > Prius design.>
Maybe the humps are there to make the Prius even uglier than it> already is (speaking of things common in the Prius design).
I thought it was only we aesthete Prius owners who cared about such details. So nice to know others are also getting it. -- Andrew Stephenson
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