Super Efficient Cars [very large pictures]

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Post by NeilBlanchard » Mon Aug 03, 2009 3:37 pm

Hi,

All else being equal, it is far better to be in a light weight car in a one-car crash. It's the size -- not the weight, that matters. In fact greater weight is almost always detrimental.

The only time weight is "helpful" is in a head on crash between two cars -- the heavier one has the advantage, then. But this is a very small percentage of crashes -- something like 1% or 3% at most.

Now if you can combine large size (with well designed crumple zones) and light weight, then you have the best of both worlds.

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Post by NeilBlanchard » Tue Sep 22, 2009 6:42 pm

Hi,

They've made a new version of the VW 1L car, to make it (much?) less expensively, though it now "only" gets 1.38L/100km, or ~170mpg!

Images from: VW Einliter-Auto L1 auf der IAA 2009 - Die Rückkehr des Einliter-VW - autobild.de

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VW has updated its original 1L concept for the 2009 Frankfurt auto show.

  • This one is supposedly good for 1.49 L / 100 km or 157.8 mpg (U.S.), compared to actually achieving about 0.89L /100km (~317mpg) in the original.
  • The diesel's specs: 36 hp two-cylinder diesel, vs. a 1-cylinder 299cc and 6.3 kW / 8.5hp in the original.
  • Weight is about 1,100 pounds / 499 kg vs. 290 kg (639 lb) in the original.
  • No info on changes to Cd or A from this model to the previous one (which had a Cd of 0.159).

Image


Source: VW Einliter-Auto L1 auf der IAA 2009 - Die Rückkehr des Einliter-VW - autobild.de , via ABG

More details are out on the VW:

Volkswagen's 170 mpg car | Frankfurt Auto Show 2009 - CNET Reviews
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In 2002, Volkswagen designed a concept car that could go 100 kilometers on 1 liter of fuel, equivalent to about 235 mpg. This year, Volkswagen shows off the second generation of the 1 liter concept, the L1, with the intention of production by 2013. Using an extremely light and aerodynamic body and a diesel-electric parallel hybrid power train, the new L1 falls short of its fuel efficiency goal, requiring 1.38 liters of diesel to cover 100 kilometers, or 170 mpg. Still, not bad.

Image
The L1's cabin uses virtual rearview mirrors and instruments.
(Credit: CNET)

Volkswagen designers looked at glider design to evolve the L1 concept, resulting in a narrow body with two seats in tandem, the single passenger consigned to a rear seat. Access to the L1 is through a hinged canopy, which should inspire Top Gun fantasies for the driver. Furthering those fantasies are the camera-based rearview OLEDs, offering a 180 degree view behind the car. In keeping with the high-tech cabin, the speedometer and other instruments are all virtual. Although we didn't see a stereo in the cabin, there are volume controls on the steering wheel.

However much the cabin might inspire feelings of piloting a fighter jet, the performance will make the driver envy scooter riders. The L1 takes 14.3 seconds to get to 62 mph. However, the top speed is a reasonable 99 mph. To power the L1, Volkswagen developed a new .8-liter version of its TDI engine with only two cylinders. The driver can select between Eco and Sport modes: in the former, the engine produces 27 horsepower, while in Sport it peaks at 39 horsepower. Being a diesel, its torque is much higher, hitting 74 pound-feet at 1,900rpm.

Where Volkswagen gets really clever is incorporating a hybrid system into its seven-speed Direct Shift Gearbox (DSG). The DSG transmission uses two computer-controlled clutches to provide automated shifting with manual transmission performance. A 13 horsepower electric motor situated between propeller shaft and transmission supplies additional power to the car. The motor is powered by electricity from a lithium ion battery pack in the front of the car. As a hybrid, it has a start-stop system, shutting down the engine when stopped in traffic. With its 10 liter fuel tank, Volkswagen estimates a range of 416 miles.

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Post by NeilBlanchard » Thu Sep 24, 2009 5:36 pm

Hi,

Image
We have a leaked image of the (near) final version of the Aptera 2e (only the side marker lights on the front wheels is to be changed). There are a lot of changes: the door windows roll down, the front wheel track is narrower, the rear quarter windows are revised, the rear wheel housing extends to the rear fascia which now has recessed taillights.

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Post by NeilBlanchard » Tue Oct 27, 2009 5:42 am

Hello!

Here's another rendered image of the (near) production Aptera 2e:

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Link to LARGE image

And a lower contrast, lighter version of the same image:

Image

I can now figure out what is going on with the front wheel pods! They are asymmetrical when viewed from above -- the inside face is nearly flat, and the leading "point" is close to the inside; and the outside face is much more convex and it curves inward at the front. From the point of view of this rendering, this curve is foreshortened and it looks squared off -- until you look at the lower part.

It has a hood, and there is a "bumper" now.

The lower part of the side windows appear to be set back from the face of the door, forming a sill surface.

They have abandoned the flexible "boot" that was covering the opening where the suspension struts come out of the body (or at least they are not shown on the rendering).

I think they need to add some marker lights on the front and outside of the front wheel pods -- this was one item that was not settled yet.

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Post by aristide1 » Mon Nov 02, 2009 6:58 pm

I would have been happy with the SMART roadster (but not the repair bills).
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It ended before it even got started. :?

The Mazda Miata is too noisy.

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Post by NeilBlanchard » Mon Nov 02, 2009 9:08 pm

Thanks for reminding me Aris -- the Aptera should be very quiet: virtually no wind noise at all, and electric cars basically have just gear noise.

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Post by Mescalero » Wed Nov 11, 2009 12:18 am

Have you seen the Nissan Land Glider? Concept is similar to the VW L1 but supposedly all-electric and it leans into the corners like a motorcycle. Pretty cool!

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Post by NeilBlanchard » Wed Nov 11, 2009 4:42 am

Hi,

Yes, I've seen it, but I am unsure that it is intended to be efficient. The aerodynamics are unlikely to be anything special, and the complexity and weight of the (hydraulic?) controls that actually lean the thing would also make it less efficient.

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Post by NeilBlanchard » Mon Nov 16, 2009 10:32 am

Hello,

I'm a little sad today because of the major shake up at Aptera Motors. The two founders, Steve Fambro and Chris Anthony have been ousted, and about 2/3 of the employees have been laid off. It maybe that they are just waiting for a $75M DOE loan to start production, but it might be something worse; like suppressing a revolutionary uber-efficient electric vehicle.

http://www.apteraforum.com/showthread.php?t=3529

I wonder if an open source super efficient vehicle would be a better way to go? I've been advocating this sort of thing for a while now, and here's a little blurb from my blog: http://neilblanchard.vox.com/library/po ... ation.html The idea is already out there -- they just mentioned it on the 'On Point' radio show about the renewed energy of inventors and tinkerers.

http://www.onpointradio.org/2009/11/tin ... innovation

The idea is the most important thing, and spreading it around means that you get the input of everyone who uses the information.

[Edit: This whole thing may be much more benign: there is still a shortage of money, and in order to stretch things until they get the DOE loan, Steve Fambro is taking a long vacation, and he'll be back the first of the year, and Chris Anthony has two other concerns (Epic boats and Flux Power battery systems) that he will focus fully on until the production gets going. It would be much more reassuring to see some photos of the production model, and hear lots of details, and hear about work that may be happening on the 2h (serial hybrid) model.]
Last edited by NeilBlanchard on Mon Nov 16, 2009 7:30 pm, edited 2 times in total.

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Post by spookmineer » Mon Nov 16, 2009 4:54 pm

The links to your blog and to the radio site look cut, they don't work...

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Post by bonestonne » Mon Nov 16, 2009 5:02 pm

http://factoryfive.com/whatsnew/showeve ... /ampd.html

How's about that for super efficient?

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Post by NeilBlanchard » Mon Nov 16, 2009 7:24 pm

Thanks -- I've fixed 'em now.
spookmineer wrote:The links to your blog and to the radio site look cut, they don't work...

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Post by NeilBlanchard » Sat Dec 05, 2009 2:40 pm

Hi,

Here's another great looking car from VW: 1530 pounds, seats four, Cd 0.237, 96mpg combined, and 70mpg highway:

http://green.autoblog.com/2009/12/02/vo ... auto-show/

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Post by qviri » Sat Dec 05, 2009 3:29 pm

NeilBlanchard wrote:Hi,

Here's another great looking car from VW: 1530 pounds, seats four, Cd 0.237, 96mpg combined, and 70mpg highway:
Lupo 2.0. Wonder if it'll ever come out of beta :roll:

Am I the only one amused at it being showcased in LA?

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LlewTube.com "Carpool"

Post by NeilBlanchard » Mon Dec 14, 2009 6:50 am

Hi,

Here a fellow named Robert Llewellyn who does a weekly podcast called "Carpool"; and there are several that are very interesting all about electric cars.

http://www.llewtube.com/

Check out these (in the order from the newest to to oldest/top to bottom on the list on the right side):

* Paul Scott Carpool -- owner of a RAV4 EV and who is involved in http://www.pluginamerica.org/

* Mitsubishi iMiEV Carpool -- Robert Llewellyn will be driving this car on the show for the next year or so; replacing his Prius.

* Chelsea Sexton Carpool -- she was an engineer on the EV1 and appears in "Who Killed the Electric Car?"

* Tesla Carpool -- where Robert Llewellyn interviews a fellow who worked for Colin Powell and knows a fair bit about national security and international energy policy, as well as battery technology.

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Post by qviri » Thu Dec 17, 2009 8:23 pm

Hi,

consider:

1) the use of ICE-powered automobiles resulting in creation of carbon dioxide and particulate matter, with adverse effects on air quality (and consequently human health) as well as environmental factors such as concentration CO2 in the Earth's atmosphere,

2) the overdependence on personal ICE-powered automobiles for human mobility, resulting in a run-away societal psychological and physiological addiction to said automobiles, contributing to obesity epidemics worldwide, the creation of automobile-dominated subdivisions and, in some cases, whole cities, well-intentioned urban planning that under noble goals of child and pedestrian safety has produced neighbourhoods entirely hostile to anyone but automobiles, culminating in necessities such as use of personal automobiles for making any food purchase, and all of the resulting social ills,

3) the development of high-mileage ICE automobiles and non-ICE automobiles.

Which is the disease; which is the symptom; which is the band-aid?

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Post by NeilBlanchard » Fri Dec 18, 2009 3:34 am

Right -- and if most cars used renewable energy, then we would all be better off. And yes, public/group transportation needs to be built/improved. The highway system was a gift to the auto makers, that's for sure; and there have been unintended consequences -- though our obesity has far more direct causes; like factory farming and factory food production, and the food that is made available is at least 2-3X too many calories, and piss poor quality.

But, this thread is about moving in the correct direction in cars -- not solving ALL the world's problems...

So, you've got me thinking: do we need cars like electric bicycles? Where we peddle them with electric assist? I'm sure that if airplanes can be peddled, that we can do this in cars.

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Post by NeilBlanchard » Wed Jan 06, 2010 6:32 am

Greetings,

I'm growing more interested in the FVT eVaro, which is a 3-wheeled plug-in serial hybrid:
Image
The gasoline version got 92mpg, and the eVaro is electric front wheel drive, and has a fuel vaporizing (for efficient combustion) onboard charger that can charge it in 1 hour. Plug-in charging (220v) takes ~2.5 hours, and the all electric range is ~100 miles. This vehicle is very fast (0-60mph in ~5 seconds!) and it is capable of 1.2G turns.

My biggest reservations about it are the canopy entry, and the somewhat cramped (looking) rear seat. It may be a 1+1, in reality. I like the small team built in the garage aspect -- they built 3 or 4 prototypes (or more?) with less than $1M (Canadian?). And I like the quote they have on their web page:

"Never doubt that a small group of thoughtful, committed citizens can change the world.
Indeed, it is the only thing that ever has." Margaret Mead

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Post by alecmg » Thu Jan 07, 2010 2:17 am

Serial hybrid is less complex than parallel, allowing for amazing designs and solutions. I would even cut amount of batteries in half - all-electric range in this case is not a big factor, when generator is so efficient.

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Post by aristide1 » Thu Jan 07, 2010 2:48 am

NeilBlanchard wrote:Hi,

Here's another great looking car from VW: 1530 pounds, seats four, Cd 0.237, 96mpg combined, and 70mpg highway:
This is why design is important for the established goal. Put 2 people on a 150cc scooter you will not get 70 mpg and you won't reach highway speeds either.

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Supercapacitor Battery Electric Vehicle

Post by NeilBlanchard » Thu Jan 07, 2010 3:03 am

Hi,

I just watched this very informative video:

http://www.youtube.com/watch?v=tCArK17Hu1M

The professor talks convincingly about using a small supercapacitor to cache power for quick charging during regenerative braking, and to then use that energy first, instead of the battery. In city driving they found that this can stop using the battery 40% of the time -- which has excellent implication in stabilizing the battery temperatures, and greatly improving the longevity of the batteries. It also would relieve some of the most stressful requirements on the battery, so possibly making it possible to use less expensive batteries.

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Post by NeilBlanchard » Sun Jan 24, 2010 9:51 am

I have never seen this "Antro Duo" before:

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Antro

The Solo (which has 3 seats) weighs just 270kg / 596 pounds!

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Here's the 'Duo' (which has 6 seats):
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Updated list of Vehicle Efficiencies

Post by NeilBlanchard » Wed Jan 27, 2010 6:50 am

Here is the full updated list of vehicle efficiencies:

I want to try to list steps that car makers, and drivers could/should take to improve the fuel efficiency, in approximate order of cost:

* EcoDriving involves moderation: top speed should be reduced, use only as much throttle as needed (try to not need to use the brakes!), thinking ahead so you can take full advantage of downhills, minimize the use of air conditioning, trip planning to reduce cold startups – and walking to everything that is a mile or less. (See my blog link for more on this!)

* The most obvious improvement to cars, would be to mold the plastic on the front of the vehicle to be smooth and round, with grill openings that are sized (and placed) only as required to cool the engine. Some new plastic bumper covers and grill pieces could be snapped onto cars. Flush covers should be used on all lights. Fairing pieces could be added to side mirrors. Hood gap gaskets, and streamlined wheel covers are easy, too.

All these improvements (above) can add at least 10% and as much as 25% to the fuel economy. Here's more:

* Sealing all the seams and joints (with gaskets or backing flanges) in the high pressure areas of the vehicle.

* Smooth floor pans with no sharp protrusions -- this is part of the drag just as much as the parts of the car that can be easily seen. Smoothing the underside with covers (like the EV-1).

* Transmission ratios should be optimized for efficiency at normal driving speeds. Higher gearing with 6-7 speeds would be optimal (smaller engines need more gears to work efficiently); or CVT transmissions.

* Narrower and lighter, LRR (low rolling resistance) tires should be used.

* Average & "instant" MPG displays, that are on all the time. The new Honda Insight, the 3rd gen Prius, and some Ford models, have excellent displays that help the driver be more efficient.

* Throttle control (rather than cruise/speed control!) that maintains even throttle in a user-set speed range, with minimal throttle increases to maintain the speed in that range.

* Tire pressure monitor, that warns the driver when the tires get below the recommended pressure (which could be adjusted upwards if the driver wants to run a pressure up to the tire sidewall maximum). Or better yet:fill tires with foam,so they would never deflate, and minimize rolling resistance.

* Efficient and effective fresh air flow through the vehicle, with intakes on a high pressure area, and exhaust vent(s) out the back of the vehicle into the low pressure wake zone, to reduce drag as much as possible.

* Coat all the window glass to exclude as much heat as possible. With effective fresh air flow (see above) this may completely avoid the need for A/C (see below).

* On defrost mode, the A/C should only come on automatically at maximum defrost (if at all), and it should be on a timer of ~1 minute, and it should always be toggled on/off by the driver. I would prefer to make A/C on the defrost setting optional.

* Efficient lights such as LED's and HID, that use a little power as possible while functioning as well (or better) than incandescent lights.

* Lower consumption electronics, such as A/C, fans and audio systems. Some/all of these could be powered by solar PV panels with a robust battery system; even in conventional internal combustion engine (aka ICE) powered cars.

* Active grill, that opens when more cooling air is needed, but remains closed – and is more aerodynamic most of the time. This can also be done passively with the right airfoil shapes that effectively closes off air flow when the velocity goes up.

* Wheel alignment and brake drag needs to be minimized, easy to adjust, and robust – to maximize rolling efficiency.

* Fully ducted engine cooling system, with the intake down low on the front, and the exhaust flows into a low pressure zone; minimizing the size of the radiator and the reducing the "internal" drag as much as possible. The Britten V1100 (racing) motorcycle is an good example of how this could work. NASCAR has shown that for a fully ducted cooling system, you only need 16 sq in for every 100HP.

* Video cameras and screens in place of side mirrors. This would help a lot with aerodynamics. An example of this starts in post #167: http://ecomodder.com/forum/showthread.p ... 69-17.html

* Automatic engine shut off and start up; at least with CVT (or automatic) transmissions -- and possibly with standard shifts, based on having both the clutch and the brake applied?

* Lean burn in low vacuum conditions. Use variable valve timing to gain efficiencies.

* Store hot coolant in a vacuum insulated tank, to speed up warm-up time; a-la what the 2nd generation Prius does. Or, do what the 3rd generation Prius does: heat the coolant quickly using the exhaust heat. Preheating intake air would also help fully vaporize the fuel; making it higher efficiency.

* Tighten up wheel openings, and always use aerodynamically designed wheels/covers, with rear wheel skirts (at least optional).

* Make roof racks removable. Years ago, I saw a "papoose" add-on storage system that locked onto the back of the car, with a single caster wheel to support the weight -- it tucked completely into the air flow behind the car; and it would be a great way to add storage space when needed; that did not affect how you drove very much. It could actually greatly improve the overall aerodynamic drag of the vehicle.

* An item that has indirect benefits: instead of thick foam and spring seats, they should be mesh or fabric stretched onto frames that provide the right ergonomic shape and provide good support without weighing so much, and taking up a lot of space. This allows a smaller and lighter vehicle because the size of car can be smaller and/or just have more room. Mesh seats would be much cooler in hot weather, and reduce/eliminate the need for A/C.

* Regenerative shock absorbers: MIT has a method of using hydraulics to drive a generator, eliminating the need for a mechanically driven alternator; or, to charge the electric drive batteries. These can also be used to lift and level the vehicle, to improve aerodynamics under different loads.

* Use a composite wheel/tire that has low weight, very low rolling resistance (by being strong enough to stay round), and low aerodynamic drag, no worries about inflation -- and re-tune the suspension to work with said wheel/tire. (see item above) This could gain even more energy, since very little would be damped by the tires.

* Multiple car door latches could be used to increase strength & safety of the chassis -- helps to further reduce weight, increase strength & rigidity, without requiring an unusual entry method (such as the VW 1 Liter car or the Loremo).

* For new 4-cylinder engine designs, the crankshaft could be split with a hydraulic coupling that can automatically disengage two cylinders completely; saving all the pumping and friction losses, for situations when 2 cylinders are enough to provide the required torque to move the vehicle. There are also cam-driven designs that about double the efficiency of the ICE.

* Nissan is (supposedly) going to reduce their cars weight by ~15%. I think all cars could be reduced by 20-30% with smarter steel fabrications, smarter use of materials. Here's a site that shows a steel chassis that is 25% lighter and nearly twice as stiff/strong as a conventional steel chassis:

http://www.bluescopesteel.com.au/go/...ulsab-project/

* Use an EV drive train, combining batteries and a supercapacitor, and a "smart" controller, that makes use of GPS and elevation data, to use the supercap for the high current regenerative charging and short(er) duration acceleration, and/or to then charge the battery at a rate that does not stress them. In other words, using the supercap as an I/O energy cache, to reduce the requirements on the battery. This can either reduce the cost of the battery, and/or increase the battery lifespan and probably increase range; especially in high traffic urban driving or in hilly conditions. Driving on flat terrain at (more or less) constant speed probably will be more dependent on the battery, and less on the supercapacitor.

* Make every vehicle with a plug-in electric w/ serial hybrid ICE drive train, with regenerative braking. Use a cam driven engine that spins the armature and the stator in both (counter-rotating) directions, to charge traction batteries. The engine could have rotary valves to reduce parasitic losses. It would run at it's ideal RPM to drive the torque load of the alternator.

* Serial hybrids should use some of the energy near the end of the battery charge to run a block heater to warm up the ICE.

* Use the ICE coolant system to cool the electric motor, the electric controller, and/or the battery pack — it would preheat the engine for start up & help to heat the cab reducing the need for electric heating.

* Rework the overall shape of the vehicle to reduce drag. Cd of 0.16-0.25 are achievable! The 1937 Schlör “Pillbugâ€

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Nissan Leaf @ Boston Science Museum

Post by NeilBlanchard » Tue Feb 09, 2010 1:31 pm

Okay, I've seen the Nissan Leaf in person -- it is one of only two actual cars they've made, so far. It cost them ~$2.5 million to build it. It looks larger than I expected, and it has a typical-for-today look: thick doors and thick seats, a quite tasteful dash with large screen GPS navigation system (more later) and the dash is all electronic. The backseat looks pretty decent, and the hatch/boot looks pretty darn large and deep. It will have ~100 mile range.

The battery is 24kWh, lithium manganese polymer (IIRC) designed and built by Nissan. There are 48 ~inch thick cells that are about the size of a piece of paper; and each of these has 4 prismatic "sub-cells". They are in a sealed enclosure, and it has a 10 year warranty -- it will have 70-80% of its capacity at that time. There is no active cooling in the battery pack.

There are three types of charging:

Level 1 is 120v AC and will take up to 16 hours to go from no charge to full charge.
Level 2 is 240v AC and will take up to 8 hours to go from no charge to full charge.
Level 3 is 440v DC and will be able to charge 0-80% in ~27 minutes.

Charging starts after you plug it in, and after the car and the charger have "talked" to each other, and everything is hunky dory. It will be nearly impossible to get shocked, even in a rain storm, as the cord is not energized until after this happens. I believe I heard someone talking about being able to program the car/charger to work during specific times, to take advantage of (possibly) lower rates.

The cost of the car will include the battery. You will be able to buy the car with the battery -- or you can lease the car with the battery. It's not "official" at this time, but they will *not* be leasing the battery separately from the car.

You will be eligible for the $7500 federal tax credit for buying the car. If you have a charger installed (this may be for a Level 1/2 charger?), you can get up to an additional $2,000 tax credit, as well. Level 3 chargers are eligible for more, IIANM.

They will announce the actual pricing in April (at which point I believe they will start taking pre-orders). For the moment, they say the price will be "the same as a similarly sized and equipped [conventional] car." Remember the nav system I mentioned? This is part of the battery monitoring system, and my understanding is that it is standard equipment:

There are 4 ways to monitor the battery charge:

A "miles left" estimate display.
A percent of charge left display.
A circle of approximate range highlighted on the nav screen display
An "idiot" light that warns you when you get close to 10% (IIRC) charge left, and it soon thereafter goes into a "limp home" mode that limits your speed to 55mph, (and probably turns off things like the A/C?).

I forgot to ask about how regenerative braking works. Darn. Oh, they will start shipping at the end of this year, to the pre-orders, and then after that, they will be at the dealerships. They had a dealer conference/training happening concurrent with this public "tour". Tomorrow/next they will be in New York city.

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Post by NeilBlanchard » Thu Feb 18, 2010 7:01 am

Okay,

Here are two amazing high resolution versions of the Schlörwagen "Pillbug" (from here) that I had not seen until today!

Image
Image

If these don't float your boat, then Jack you dead!

This drawing of the lofting lines is from the Hucho book, which has the various drag numbers they got by varying the height of the wheels. It is different that the actual car (the drawing shows a center pillar in the windshield) and the height dimension is probably for the body only and should not include the wheels. (I found this by scaling the image in DataCAD.)
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More beautiful shots with a gentleman that may be Karl Schlör himself?
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I even found a picture of the interior:
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With articulated front wheel skirts, the width and stability could be addressed.

A modernized (read: safer and lighter weight structure) an EV version of this design would be a stunner. It could be made narrower and the front track could be widened. You would probably want to keep the proportions close, and the trailing edge behind the rear wheels, also probably some wheel strakes -- could make this design close to perfect.

For the aero geeks among us, check out the high resolution pictures of the wind tunnel(s) from the 1930's in Germany -- the link is http://www.dlr.de/100Jahre/en/desktopde ... 16_read-7/

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Post by NeilBlanchard » Thu Mar 25, 2010 4:45 am

I am designing an uber-efficient electric car, that I'm calling CarBEN:

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I've got a blog post all about the design criteria I'm trying to use, and with pictures of a wooden model, as well -- see the link in my signature!

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Post by flapane » Fri Mar 26, 2010 2:08 pm

Hi,
are you doing those concepts as a hobby, for work (I don't think so, the drawings should be kept secrets) and/or keeping in mind a real production of the models?
Do you design the model trying to find the best looking shape only, or with aerodynamic (I'd choose this, looking at the CarBEN concept EV draw which resembles a water drop) in mind? You put your in-scale wood model in a wind gallery, I suppose.

Do you know that Renault publicized the ugly looking 1985 Espace as the car with the best C_d in its range? It should be an epic FAIL considered its truncated tail, bu I didn't really indagate further. If I remember well there was one trick Renault used to consider a bigger superfice than the correct one in order to lower the coefficient (on the paper).
Donnow if it was ever sold in US, by the way.
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Hey, that Pillbug photos are great... germans have always been the fathers of aerodynamic.

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Post by NeilBlanchard » Fri Mar 26, 2010 6:08 pm

Hi,

Thanks for your comments -- I am doing the CarBEN design as a hobby, and I hope to actually build it. I am doing it as an open source project -- so no secrets!

I am definitely going for low drag aerodynamics; trying to learn the lessons of the Mercedes Bionic car and the Schlörwagen "Pillbug" and the GM EV-1, etc. The problem with doing the scale model in a aerodynamic drag test, is that the Reynolds number requires that the air speed go up proportionally (at 24X faster than 55mph that would be supersonic!) or you have to use a more viscous fluid like water. That is why I would like to try it in a CFD computer model.

I have seen the Espace, but only on TV -- the Top GEar show used one once. They do not sell any Renault vehicles in the USA currently; not since the 90's, I think?

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Post by NeilBlanchard » Sat Mar 27, 2010 6:50 pm

I actually found a shareware program that says it can convert about 400+ different 3D formats! So, I *might* be able to do the CFD testing after all? I had no idea that there are that many different file types! Holy sheewow... But, naturally, you have to pay for it to actually convert them, so I have not tried yet.

Here's some more images of the revised model -- the "shoulders" are lowered, all the windows are revised (and the lights) and the purple figure is about my size (6'-4") and is positioned about where the driver would be.

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Post by NeilBlanchard » Tue Mar 30, 2010 2:02 am

I've started to design what I hope will be an uber-efficient electric car, I'm calling the CarBEN EV. I made a 1/24th scale (aka 1/2" = 1'-0") wooden model first, and then traced photos of it in DataCAD. Then I did orthographic projection from 5 views to make 15 section profiles; separated by 1 foot in Z-height. Then I used the ruled surface tool to connect as much as possible, and then I exported this to SketchUp, using a DWG file. Then, in SketchUp, I built the rest of the surface.

I then revised it several times and simplified the number of polygons, and ended up with a decent looking model, if I say so myself. I've written an entry in my blog, describing the design, and I've included photos of the model, the DataCAD drawing I did, and image captures -- and an animation from SketchUp. Here's my blog entry (updated periodically):

http://neilblanchard.vox.com/library/po ... oject.html

And here's the YouTube URL where the animation video is:

http://www.youtube.com/watch?v=C7jbqgCvx8U

My main idea is to have it be as low aerodynamic drag as possible. So, the wheels are fully enclosed, and in order to keep the width of the front as narrow as possible, this will require having the front wheel skirts be articulated -- i.e. when steering sharply, they will move with the steering. At highway speeds though, there will be enough space around the wheels to allow the wheels to move without having to move the skirts. The skirts will not move with the suspension, as this would be too much unsprung weight, and it would create more problems then it solves.

My hope is to do some CFD testing on a computer, but so far, I have not found a way to get the SketchUp model into a CFD program. They require a "solid" type model; as opposed to a surface model that SketchUp creates. My blog entry goes into how I hope to build it (similar to a monocoque airplane,); though composite construction would lend itself well, too, I think.

I'm hoping to eventually use a supercapacitor for regenerative braking (like the Carnegie Mellon "Charge Car" project). And I'm hoping to use regenerative shock absorbers, like the ones that were just announced from a company called Levant Power: http://green.autoblog.com/2010/03/27/sh ... /#comments

If and when I get the rolling chassis built, I'm sure I'll be looking for lots of input on the battery pack and the drive system. I'd appreciate any and all comments you may have on the overall concept, as well.

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