The Electric Car
in [Design]
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From: Phil Allison on 2 Aug 2007 01:56 "Nobody" > > The part of the curve where economy increases with speed is primarily due > to increasing engine efficiency. There isn't any source of opposing force > which decreases as speed increases. > ** There is one - the " rolling resistance " of the tyres decreases with speed. At 100 kph, a car tyre experiences about 200Gs of centrifugal force making it larger and rounder - this reduces flattening at the point of road contact and so there is less resistance. >> 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. > > It kicks in way before that. Even at cycling speeds, you get a very > noticable reduction in effort when riding in the slipstream of a truck. ** False comparison - a bicycle plus rider ain't very aerodynamic compared to a modern sedan car, so air resistance is far more significant at lower speeds. ...... Phil
From: JosephKK on 2 Aug 2007 02:01 Richard Henry pomerado(a)hotmail.com posted to sci.electronics.design: > On Jul 31, 9:38 pm, JosephKK <joseph_barr...(a)sbcglobal.net> wrote: >> MooseFET kensm...(a)rahul.net posted to sci.electronics.design: >> >> >> >> >> >> > On Jul 31, 6:48 am, John Larkin >> > <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> On Mon, 30 Jul 2007 23:31:20 -0700, Richard Henry >> >> >> <pomer...(a)hotmail.com> wrote: >> >> >On Jul 30, 8:25 pm, krw <k...(a)att.bizzzz> wrote: >> >> >> In article >> >> >> <1185850948.051175.139...(a)d30g2000prg.googlegroups.com>, >> >> >> pomer...(a)hotmail.com says... >> >> >> >> > 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. >> >> >> >> Not at all. Not "the" children. *HIS* children. There is >> >> >> a difference. >> >> >> >> > Please explain again the more-efficient-at-higher-speed >> >> >> > feature. >> >> >> >> It's entirely possible as was explained at the time. >> >> >> >It was bs then and it's bs now. All fancy gearing and >> >> >ignition tricks will be overcome by the inevitability of the >> >> >non-linearity of increase of air resistance with speed. >> >> >> The air resistance is highly nonlinear, cubic power:speed >> >> roughly, whereas other losses are essentially independent of >> >> speed. Every car will have an optimum speed for miles/gallon, >> >> and it won't be zero. >> >> > It also won't be much over about 50MPH. It takes about 15 HP >> > to push >> > a modest sized car at 50MPH. The windage losses per mile run >> > as just about the square of the speed. >> >> Not necessarily. My first new car got about 22 mpg at 55 mph and >> about 26 mpg at 70 mph. Back then i had plenty of documentation >> to >> back it up. Kinda funny, 70 mph occurred right the rmp torque >> peak. It couldn't be a coincidence could it? > > Documentation? > > The first question would be: How did you measure it? Quite simply, miles traveled divided by fuel to top up again. With trip the odometer it was very easy.
From: JosephKK on 2 Aug 2007 02:07 MooseFET kensmith(a)rahul.net posted to sci.electronics.design: > On Jul 31, 9:38 pm, JosephKK <joseph_barr...(a)sbcglobal.net> wrote: >> MooseFET kensm...(a)rahul.net posted to sci.electronics.design: >> >> >> >> > On Jul 31, 6:48 am, John Larkin >> > <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> >> On Mon, 30 Jul 2007 23:31:20 -0700, Richard Henry >> >> >> <pomer...(a)hotmail.com> wrote: >> >> >On Jul 30, 8:25 pm, krw <k...(a)att.bizzzz> wrote: >> >> >> In article >> >> >> <1185850948.051175.139...(a)d30g2000prg.googlegroups.com>, >> >> >> pomer...(a)hotmail.com says... >> >> >> >> > 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. >> >> >> >> Not at all. Not "the" children. *HIS* children. There is >> >> >> a difference. >> >> >> >> > Please explain again the more-efficient-at-higher-speed >> >> >> > feature. >> >> >> >> It's entirely possible as was explained at the time. >> >> >> >It was bs then and it's bs now. All fancy gearing and >> >> >ignition tricks will be overcome by the inevitability of the >> >> >non-linearity of increase of air resistance with speed. >> >> >> The air resistance is highly nonlinear, cubic power:speed >> >> roughly, whereas other losses are essentially independent of >> >> speed. Every car will have an optimum speed for miles/gallon, >> >> and it won't be zero. >> >> > It also won't be much over about 50MPH. It takes about 15 HP >> > to push >> > a modest sized car at 50MPH. The windage losses per mile run >> > as just about the square of the speed. >> >> Not necessarily. My first new car got about 22 mpg at 55 mph and >> about 26 mpg at 70 mph. Back then i had plenty of documentation >> to >> back it up. Kinda funny, 70 mph occurred right the rmp torque >> peak. It couldn't be a coincidence could it? > > > It was likely a combination of coincidence and something very > wrong > with the car. 22MPG at 55MPH is a horrid milage. This is very > like the leaky fuel line case. It was not that bad in the early 1970's. Please consider the noun phrase "My first new car" more carefully. Besides, the point being made was that better fuel milage can occur at mean (and nearly constant as well) speeds above 55 mph.
From: JosephKK on 2 Aug 2007 02:17 MooseFET kensmith(a)rahul.net posted to sci.electronics.design: > On Aug 1, 9:10 am, Eeyore <rabbitsfriendsandrelati...(a)hotmail.com> > wrote: >> 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. > > > No, I disagree. The dual electrical machine design beats the > series > system hands down. Having the engine go straight to the wheels > when it makes sense to do so makes the demand on the electrical > system way less. The highest demands are during maximum acceleration / deceleration. Since it would complicate the controls hugely to no gain, there is less than no point in trying to parallel the mechanical paths. During cruise the electric drive train is loafing just like a direct ICE would.
From: JosephKK on 2 Aug 2007 02:24
Nobody nobody(a)nowhere.com posted to sci.electronics.design: > On Thu, 02 Aug 2007 03:53:28 +0100, Eeyore wrote: > >>> > 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. >>> >>> No, I disagree. The dual electrical machine design beats the >>> series >>> system hands down. Having the engine go straight to the wheels >>> when it makes sense to do so makes the demand on the electrical >>> system way less. >> >> Why's that an advantage ? It also means you can't have >> 'meaningful' true electric only operation of it, plus it >> requiresa gearbox which otherwise may not be needed at all. > > The disadvantage of an all-electric or series hybrid vehicle is > that the maximum total power is constrained by both the ICE and > the electrical system, while a parallel hybrid can potentially > combine the two, or at least provide a more powerful ICE for > motorway cruising without having to size the electrical components > to match. > > A secondary consideration is that the generator losses subtract > from any efficiency advantages of the electrical drivetrain. > > But mostly it's a case of having to size the electrical system to > the power requirements for motorway cruising even though it has > fewer advantages over a mechanical drivetrain in that context > (i.e. regenerative braking is of no benefit). NO! The electric drive train has to be sized to the maximum (majority electrical contribution) acceleration in all cases. It must be sized (possibly much) larger than the ICE. |