The Electric Car
in [Design]
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From: Don Lancaster on 7 Aug 2007 13:34 Guy Macon wrote: > Don Lancaster wrote: > >>MooseFET wrote: >> >>>I think compressed air is a better way to go. >> >>Go for what? >> >>The energy density of compressed air is ludicrously low. >>Typically one sixth of lead acid or worse. 15 wh/l is hard to acheive. >> >>The efficiencies of most compressed air motors are much worse than an >>ICE. Typically 29 percent or less. >> >>No means of efficiently compressing air is known. >>Efficient compression requires isothermal operation, which can only be >>approximated by elaborate and costly multi-staging. >> >>The fire service proved all this a century ago after throwing bunches of >>engineering at the proglem. >> >>The ONLY thing compressed air has going for it is shop floor >>convenience. Hydraulics immediately get substituted when serious tail >>twisting or anything remotely approaching efficiency is needed. > > > The ONLY thing? > > There are other advantages. With pneumatics the light-load > cycle rate is higher, the piping for distribution doesn't > need to have a return path, and in some clean-room applications > the system can tolerate traces of ultrapure gas leaking into > the working area, but not any sort of liquid. > > Hydraulics win for strength, efficiency, positional control, > stiffness, and safety if a pipe or cylinder bursts. > > You will never see pneumatics in a bulldozer, and you will > never see hydraulics in a machine that puts CDs into CD > cases. Having worked as a design engineer for both Parker > Hydraulics and SMC Pnuematics, I don't see either of them > cutting into the other's business. > And the number of pneumatic combined CD case stuffers and automobiles currently on the road is....? -- Many thanks, Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss: http://www.tinaja.com/whtnu.xml email: don(a)tinaja.com Please visit my GURU's LAIR web site at http://www.tinaja.com
From: Rich Grise on 7 Aug 2007 14:20 On Tue, 07 Aug 2007 03:48:52 +0000, JosephKK wrote: > Mark makolber(a)yahoo.com posted to sci.electronics.design: >>> >>> It seems to just argued against using any electric motors at all. >> >> Yep, I think the small batteries and electric motor in the Prius >> are there for only 2 reasons.. >> >> 1) efficency gained by regenerative braking >> 2) improve the acceleration so the ICE can be smaller also >> improving the efficency. >> >> If you had the small ICE without the acceleration boost provided >> by >> the electrics, the acceleration would be poor and people would >> not like the "drivablility". >> >> Intersting to note that a flywheel could provide the same >> advantage. >> >> In fact I tend to think of the battery and electric motor in the >> Prius is just an electric implementation of a flywheel. > > Yes, and flywheels bring their own issues with changes yaw, pitch > and roll. There will have to be space for the flywheel to spin not > only during normal driving but the vehicle must not become a hazard > if it rolls over in any direction or spins out. Well, that's simple - just put the flywheel's axis vertical. Of course, you want to make sure that it doesn't lose its structural integrity, and become a spin bomb. ;-) And people are supposed to know better than to roll their cars over. Cheers! Rich
From: Spehro Pefhany on 7 Aug 2007 14:28 On Tue, 07 Aug 2007 16:22:25 +0100, Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > > >MooseFET wrote: > >> JosephKK <joseph_barr...(a)sbcglobal.net> wrote: >> > Mark makol...(a)yahoo.com posted to sci.electronics.design: >> > >> > >> It seems to just argued against using any electric motors at all. >> > >> > > Yep, I think the small batteries and electric motor in the Prius >> > > are there for only 2 reasons.. >> > >> > > 1) efficency gained by regenerative braking >> > > 2) improve the acceleration so the ICE can be smaller also >> > > improving the efficency. >> > >> > > If you had the small ICE without the acceleration boost provided >> > > by >> > > the electrics, the acceleration would be poor and people would >> > > not like the "drivablility". >> > >> > > Intersting to note that a flywheel could provide the same >> > > advantage. >> > >> > > In fact I tend to think of the battery and electric motor in the >> > > Prius is just an electric implementation of a flywheel. >> > >> > Yes, and flywheels bring their own issues with changes yaw, pitch >> > and roll. There will have to be space for the flywheel to spin not >> > only during normal driving but the vehicle must not become a hazard >> > if it rolls over in any direction or spins out. >> >> I think compressed air is a better way to go. > >Compressed air power storage is horribly lossy. > >Graham > Was that proposed compressed air car debunked? It looked pretty iffy to me, though compressed air or a hydraulic accumulator might be fine for a hybrid. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff(a)interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
From: James Arthur on 7 Aug 2007 14:36 On Aug 1, 6:11 am, MooseFET <kensm...(a)rahul.net> wrote: > 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... <snip> > > >> >> > 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. FWIW, I've always gotten about 20% better than EPA-rated fuel economy, by carefully optimizing my driving. I had been driving 55 mph, then even 50 mph in an attempt to improve my Acura's mpg. Careful cross-country measurements show optimum fuel economy to be 41mpg, which applies from 85 down to 65 mph. Going slower reduces mpg. A gearhead pal offered a decent explanation of how providing the engine with optimum load and RPM by going faster makes my particular engine more efficient, making up for the windage loss... up to a point, of course. Cheers, James Arthur
From: Jim Thompson on 7 Aug 2007 15:11
On Tue, 07 Aug 2007 11:36:32 -0700, James Arthur <dagmargoodboat(a)yahoo.com> wrote: >On Aug 1, 6:11 am, MooseFET <kensm...(a)rahul.net> wrote: >> 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... > ><snip> > >> > >> >> > 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. > >FWIW, I've always gotten about 20% better than EPA-rated fuel economy, >by carefully optimizing my driving. > >I had been driving 55 mph, then even 50 mph in an attempt to improve >my Acura's mpg. Careful cross-country measurements show optimum fuel >economy to be 41mpg, which applies from 85 down to 65 mph. Going >slower reduces mpg. > >A gearhead pal offered a decent explanation of how providing the >engine with optimum load and RPM by going faster makes my particular >engine more efficient, making up for the windage loss... up to a >point, of course. > >Cheers, >James Arthur I'm getting 19MPG at 85MPH in my Q45 ;-) ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | America: Land of the Free, Because of the Brave |