The Electric Car
in [Design]
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From: Richard Henry on 1 Aug 2007 11:56 On Aug 1, 8:26 am, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My-Web- Site.com> wrote: > On Wed, 01 Aug 2007 07:15:06 -0700, John Larkin > > > > > > <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >On Wed, 01 Aug 2007 06:22:36 -0700, MooseFET <kensm...(a)rahul.net> > >wrote: > > >>On Jul 31, 9:12 pm, krw <k...(a)att.bizzzz> wrote: > >>> In article <1185930451.854228.138...(a)x35g2000prf.googlegroups.com>, > >>> kensm...(a)rahul.net says... > > >>> > On Jul 31, 7:21 am, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- > >>> > Web-Site.com> wrote: > >>> > > On Mon, 30 Jul 2007 20:02:28 -0700, Richard Henry > > >>> > > <pomer...(a)hotmail.com> wrote: > >>> > > >On Jul 30, 7:20 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- > >>> > > >Web-Site.com> wrote: > >>> > > >> On Mon, 30 Jul 2007 19:12:03 -0700, Richard Henry > > >>> > > >> <pomer...(a)hotmail.com> wrote: > >>> > > >> >On Jul 30, 5:48 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- > >>> > > >> >Web-Site.com> wrote: > >>> > > >> >> On Mon, 30 Jul 2007 17:30:01 -0700, "J.A. Legris" > > >>> > > >> >> >- I said fuel consumption will never decrease much unless cars are > >>> > > >> >> >much lighter, but even radically lighter vehicles are no long-term > >>> > > >> >> >solution on this overpopulated planet > > >>> > > >> >> Amen! I keep telling people that, and they look at me like I'm some > >>> > > >> >> kind of idiot. > > >>> > > >> >You have also told us how you like to drive your big import illegally > >>> > > >> >fast and tried to rationalize it by claiming that among the vehicle's > >>> > > >> >luxury features is that it runs more efficiently at high speed. > > >>> > > >> I didn't rationalize anything. However I do agree that leftist > >>> > > >> weenies should be taxed more heavily to support my excesses ;-) > > >>> > > >> And I certainly have no problem with YOU driving a tin can, just NOT > >>> > > >> my children and grandchildren ;-) > > >>> > > >OOHH!. Think of the children... > > >>> > > >You sound like a leftist weenie. > > >>> > > >Please explain again the more-efficient-at-higher-speed feature. > > >>> > > I don't ever recall saying "more-efficient-at-higher-speed". > > >>> > > But I guess it WOULD depend on your definition. The engine is > >>> > > optimized right around 3000RPM (85MPH), but external drag is higher. > > >>> > If you shift to a lower gear, 3000 RPM is at a lower speed. If there > >>> > isn't an issue that is well modeled by a fuel leak, the milage would > >>> > improve. > > >>> Ever consider that transmissions aren't equally efficient in all > >>> gears > > >>Yes but he didn't report he was driving with a faulty one. > > >>> and perhaps the over-drive locked-up may be a tad more > >>> efficient than the lower gears? > > >>A tad but not enough to make the difference. The energy per mile > >>increases as the square of the speed. > > >Not in this graph: > > >http://www.fueleconomy.gov/feg/driveHabits.shtml > > >I've seen a few other mpg-vs-speed curves, and they all look similar. > >Looks like aerodynamic drag starts to seriously kick in above 55 MPH. > > >John > > You need to look at engine horsepower and torque versus RPM as well. > > Drag DOES depend on body shape. If you look at new cars offered for sle today, the shapes are all pretty much the same, especially when compared to the wide variations on the market 40-50 years ago. I imagine that is because everybody's wind tunnels give the same answers.
From: Eeyore on 1 Aug 2007 12:10 John Larkin wrote: > Spehro Pefhany wrote: > > >>People don't buy Prius' to save gas, they buy them to be hip and > >>stylish. So instead of smog, we have clouds of smug. > > > > >Yes. _South Park_ dubbed it the "Toyota Pius". My calculations > >indicate the payback to be marginal on hybrids, even with a $4K > >government subsidy, so long as gas remains around $3US/US gallon, and > >the Prius yields significantly better mileage than, say, the hybrid > >Camry. > > Both hybrids would get far better mileage if the batteries, the > electrics, and all the fancy controls were dumped. What's left would > be a small, light, slippery, ugly car with a small engine. All you'd > give up is acceleration and the questionable advantage of regenerative > braking, a small price to pay for dumping the batteries. In city driving it's regenerative braking that can make a huge difference. The complexity of shoving electrical and ICE motive power through some combined transmission seems plain daft though. The series hybrid (in which the ICE simply recharges a battery) seems far more sensible all round. Graham
From: Joerg on 1 Aug 2007 12:13 John Larkin wrote: > On Wed, 01 Aug 2007 07:16:09 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: > > >>On Wed, 1 Aug 2007 00:12:10 -0400, krw <krw(a)att.bizzzz> wrote: >> >> >>>In article <1185930451.854228.138310(a)x35g2000prf.googlegroups.com>, >>>kensmith(a)rahul.net says... >>> >>>>On Jul 31, 7:21 am, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- >>>>Web-Site.com> wrote: >> >>[snip] >> >>>>>I don't ever recall saying "more-efficient-at-higher-speed". >>>>> >>>>>But I guess it WOULD depend on your definition. The engine is >>>>>optimized right around 3000RPM (85MPH), but external drag is higher. >>>> >>>> >>>>If you shift to a lower gear, 3000 RPM is at a lower speed. If there >>>>isn't an issue that is well modeled by a fuel leak, the milage would >>>>improve. >>> >>>Ever consider that transmissions aren't equally efficient in all >>>gears and perhaps the over-drive locked-up may be a tad more >>>efficient than the lower gears? There is also work done just >>>spinning the engine. Me thinks you're wrong. >> >>Don't both Honda and Toyota have models with CVT (continuously >>variable transmission) which keeps engine RPM's in a narrow/optimum >>range? >> >> ...Jim Thompson > > > CVTs are still the holy grail of car design, but none of them seem to > work at serious horespowers. They are the equivalent of a switching > regulator. > It is, in a way, done with switching regulators. A small engine runs at a fairly constant rpm and drives a generator. That goes into a switcher which in turn feeds one or more motors that drive the car. The balance goes into a battery and the engine stops when that's topped off. Pretty much the hybrid concept. AFAIR the closest recent approach to a roadworthy CVT was from Ford but I haven't heard about it in a long time. The first mainstream CVT in a car was actually brought to market in the 50's. My mom had a "DAF 44", a Dutch car. A picture is worth a thousand words, so this is a picture of the CVT in that type of car: http://upload.wikimedia.org/wikipedia/commons/3/3d/DAF_Hinterachsantrieb.jpg I became intimitely familiar with this CVT because as a kid I had the "pleasure" to take the whole heavy CVT out. Only to find out that all that was broken was a small governor weight in one of the "bells". Could have fixed in with the CVT in the car. Arrrgh. This car only had a "forward-reverse" switch and no clutch, plus another smaller switch to increase rpm while muffling the throttle. The only passenger car I ever saw that had a kind of jake brake. The car could go 80mph in reverse and in the Netherlands they actually had "reverse races". Naturally, DAF was the only brand of car that could play. I tried it once but quickly gave up because you can easily roll the car that way. Quite innovative but because of the belt friction the fuel consumption was rather dismal, couldn't yield much better than 25-30mpg and that was not good enough for European standards. IIRC the company sold out to Volvo and then this concept petered out. -- Regards, Joerg http://www.analogconsultants.com
From: Eeyore on 1 Aug 2007 12:21 Spehro Pefhany wrote: > Jim Thompson wrote: > > John Larkin wrote : > > > >>http://www.fueleconomy.gov/feg/driveHabits.shtml > >> > >>I've seen a few other mpg-vs-speed curves, and they all look similar. > >>Looks like aerodynamic drag starts to seriously kick in above 55 MPH. > >> > >>John > > > >You need to look at engine horsepower and torque versus RPM as well. > > > >Drag DOES depend on body shape. > > > > ...Jim Thompson > > For a given shape, at automotive speeds, I think there is a square law > relationship between air speed and drag. You are correct at higher speeds. The relationship isn't simple it seems. http://en.wikipedia.org/wiki/Drag_(physics) Drag coefficient can make collosal differences too. http://en.wikipedia.org/wiki/Drag_coefficient Unfortunately current US styling (the trend for truck like 'slab fronts' ) is producing cars with greater rather than lesser drag. The current hybrids also use skinny tyres to reduce rolling resistance. I hate to think of the adverse effect on road holding. Graham
From: Vladimir Vassilevsky on 1 Aug 2007 12:27
MooseFET wrote: > The power companies can't be counted on to build up the grid. > Spending on new stuff would cut into this months profits. If it > doesn't look like the grid will support it, people won't buy the > cars. When people don't buy the cars no new grid is needed. BTW, at the beginning of the 20th century, one could buy gasoline only in the drugstores... Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com |