# Ultra efficient EV concept



## Dan Frederiksen (Jul 26, 2007)

a concept I've been working on and would like to build.
it's only a rough concept with no detailing. not done with the nose yet etc.
4 wheels for stability/familiarity, thin disc wheels for aerodynamics yet thin wheel still has good grip vis a vis racing bicycle that only has a few mm of contact yet still able to brake down 100kg vehicle.
sleek spear body for aerodynamics yet able to seat 2 plus cargo (which is the same as Tesla Roadster, Porsche Boxster, Mazda Miata, Aptera etc)
Composite fiber monocoque body for simplicity and strong light weight.
Etek motor in fixed gearing for each of rear wheel.
estimated weight of 150kg including 50kg batteries for 200+km range.

some 10x more energy efficient than Tesla Roadster which makes it virtually free to drive.

if anyone would like to make one for themselves or sale let me know and I can give you the body computer model when it's more finished.


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## Bowser330 (Jun 15, 2008)

http://www.greatchange.org/footnotes-1-liter-car.html

reminds me of the 1 litre car from VW...A very efficient car also..


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## esoneson (Sep 1, 2008)

Dan,

You are bringing back a bunch of memories. Soap Box Derby








I recognize those wheels and even the shape of the 'axle covers'.
Been there, and it was a lot of fun for my boys. They may not have won, but they took home 'Best Construction' trophies.

Keep at it. Can't wait for more mods.









Eric


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## Technologic (Jul 20, 2008)

Few problems I can see mate.

1. your current windshield design is quite nice, however, that molded glass won't come cheap or lightweight... probably be about 100lbs in and of itself if not more. It will have to be thicker than normal glass you encounter as it will be holding up the entire door system. Look into having some lexan heat bent for this, it'll last longer anyway.

2. What seats do you plan to use? those won't weigh under 15 lbs each no matter if they're the lightest racing seats made.

3. any sort of steering column + R&P will weigh about 50 lbs... if you intend to make your own out of aluminum you could drop this to 25-30 lbs, good luck if that's your goal... it'll be some engineering prowess there.

4. the way the nose comes together is rather bad aerodynamically... the CD for this would actually be near 0.17 (you could half that fairly easily) Drop the nose down and make the flow over the front with less sharp points... ie. drop the nose down to level with the bottom and have it taper around the body almost as smoothly as an airplane's nose.... watch your range double. Also if that's a hole into the car in the front (like a radiator) remove it... Your lines on the rear wheels will create pockets of dead air hurting drag.... flow more to the taper without sharp turns.

What in wheel motors are you using?

You could also drop about 30 lbs going to 3 wheels if it's strong enough, you could shed quite a bit of drag here as well. Rear wheels would be doing nasty things to the air coming back from around the front wheels.

If I were you, however, I'd just use 1 aluminum foam panel for the under carriage and the rest out of fiberglass... will be lighter than any attempts at a strong composite without honeycombs.

My rough guess if you were using lithium and did those things... if you were a fairly average healthy male weighing about 170 lbs, this car could have a range at highway speeds around 220 miles. Assuming you used 50kg of LiFePo4 which would get you about 6kwh. If you went to 3 wheels (if possible) probably add another 20-30 miles to that range.


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## piotrsko (Dec 9, 2007)

Technologic said:


> Few problems I can see mate.
> 
> 
> You could also drop about 30 lbs going to 3 wheels if it's strong enough, you could shed quite a bit of drag here as well. Rear wheels would be doing nasty things to the air coming back from around the front wheels.



My $.02: there are aircraft flow studies out there saying that if the protuberances are approx 1.4 to 1.6 times far apart as they are sticking out,(within reason) you get a laminar flow between the wheels and the CD becomes less than .6 of the one wheel alone. I do see intersection drag at the axle/body joints as a major biggie.

There are "freeware" drag calculators available, mostly for aircraft that allow you to really fine tune areodynamics on a wire frame


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## TX_Dj (Jul 25, 2008)

My worry (other than those already expressed) is in regards to suspension.

First, what's absorbing the bumps here, I see nothing but "wings".

Second, what's bracing the axles/ "wings"?

First glance tells me that if someone accidentally drives that thing off a small "drop" like a seam in a freeway slab, the forces will shear the axle "wings" off the body.

Then again, I'm no engineer.


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## Technologic (Jul 20, 2008)

TX_Dj said:


> My worry (other than those already expressed) is in regards to suspension.
> 
> First, what's absorbing the bumps here, I see nothing but "wings".
> 
> ...


It's possible to do a floating suspension where the "wings" go up and down. In fact that's probably the best way to do it (on the cheap especially).

My guess is that he will have far more issues finding a bike tire with proper rims to mount to the suspended floating wheels. No bike rim would do... any bump would bend the spokes at the speeds a car travels... I've looked a bit but he really shouldn't be using thin bike tires period.... I like the idea of pressed SiC rims for a bike tire... but god knows no factory in the world could make them either. 

the thinnest car wheel he could use would be about 4 times that wide... which is why I suggested using 3 wheels since he's so weight conscious.



> My $.02: there are aircraft flow studies out there saying that if the protuberances are approx 1.4 to 1.6 times far apart as they are sticking out,(within reason) you get a laminar flow between the wheels and the CD becomes less than .6 of the one wheel alone. I do see intersection drag at the axle/body joints as a major biggie.


Though I haven't modeled this to say for sure... I can make a pretty good guess that the structure of the tire itself won't lend itself to low drag flow so well on the back side of the first wheel... there will be quite a bit of turbulence coming around this... though that's not necessarily avoidable under any circumstances... having other parts directly in the back flow of this turbulence will probably damage the drag by a considerable amt... I can't say how much... and the shape of the underbody worries me more as far as drag is concerned. (it's not a way in which air wants to travel naturally).

Not trying to pick apart the design... I quite like it, just trying to offer some insight so it performs the way he wants


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## saab96 (Mar 19, 2008)

Renders don't impress me. A CG render is the equivalent of a pencil sketch on a napkin. Build something tangible, even if it's clunky, and it means something.

Like This


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## Dan Frederiksen (Jul 26, 2007)

piotrsko, do you know a name of such a freeware aerodynamics software that can take a computer model and give a result with any accuracy? that would be quite helpful.

I forgot to mention that the wheels are intended as solid composites with only a strip of rubber glued to the outside. the idea is to have so low wheel mass that it can do without the suspension of the air.

the illustration doesn't have details about the suspension obviously. the front is intended as a solid wing with perhaps airbag suspension and the rear as double wishbone.

the windshield is not glass but vacuum formed polycarbonate. something you can do on your own if you have a nice mold. a heat gun and a vacuum pump is all you need afaik. I've done some simple tests.

Technologic, the weights you state are way off. think bicycle weights instead of freightrain. a steering column doesn't weigh 50lbs! get rid of that thinking.

the batteries are thought as lithium ion with 177Wh/kg density. I suppose some good LiFePO4 could be used but at substantial range reduction. but LiFePO4 might allow it to go faster than 6 seconds to 100km/h. would be nice to match or beat the Tesla at that too.

esoneson, thanks

bowser330, yes the VW 1L was part of the inspiration as well as the Aptera, Loremo, wrightspeed X1 and formula1. I took all those and made a better combination. it's only drawback is that it looks like a soapbox car but with nice suspension and good design and fast demonstration that association will fade and it will become something on its own.
this tandem or inline2 car type will arrive I believe. VW has recently promised to manufacture the 1L car and Volvo has done some tandem design concepts albeit bad ones. now that oil is cheap again they might be lying but still I think it will arrive unless we get practical nuclear fusion reactors for cars. (which is not as far fetched as you might think)

saab96, some of us know the value of intelligent forethought before building it. the suncar you linked to is mindless. it's an amusement at best. it has no chance of bettering the transport sector. it has the aerodynamics of a parachute. my design is incomparably better for an ocean of reasons.


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## JeffPritchard (Jun 10, 2008)

What program did you draw/render this with?

thanks,
jp


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## Dan Frederiksen (Jul 26, 2007)

AliasStudio made the shape. it's often used by car designers
setup in 3ds max and vray rendered it.

as a side note I'm actually developing my own editor/renderer in part motivated by the obscene price of 3ds max. 3500$ in USA, about double that in europe. Alias costs around 5000$. vray less than 1000$
so I might pay them back for their greed with a 100$ application


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## order99 (Sep 8, 2008)

I like the design, but will the DMV allow it on the road? I suppose there are Kit Car permits...

I the event that I ever get the funding, i'm going to try something similar in a Trike design. I'll need a Motorcycle add-on, but licensing the vehicle itself will be MUCH easier.


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## Dan Frederiksen (Jul 26, 2007)

I live in Denmark, Europe so the DMV doesn't apply but despite the law clearly being written only with typical cars in mind it seems that all that's needed for a one off to be allowed on the road is to pass normal biannual car inspection which entails steering wheel play, brakes, emission and noise levels.
but as I said the law is written assuming cars never change so all you need is an obtuse inspector and you have a no you can't do much about and an expensive car that can't drive. but I'm guessing it can be done.

I have applied for about 40k$ from a state EV promotion fund (because of lower prices in USA that should maybe be translated to 25 or 30k$ in buying power). I don't know if I can build it if I get the money but I'll find out  
it should reasonably be possible, after all it is a glorified soapbox car and it doesn't have to be so perfect that it could be sold with all the liabilities that entails.
with all the custom cars being made in USA I have a hard time believing that it's that hard to get a 4 wheeler on the road. I found out that at least in Denmark it was much easier to get approval than the myth said. it was basically common knowledge that a custom car had to be crash tested etc to be allowed but that was not the case. look into the actual wording of the law and practice. it might be much easier than you think.


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## Voltswagen (Nov 13, 2008)

Dan
I encourage you to continue. Though there may be some difficulties with your design, further modifications could overcome these.
You must keep an open mind. Here in the USA it *is* and *was* the narrow-minded thinking of the Detroit Auto Manufacturers which prevented the
continued production of a short range EV. 
Nearly every family here owns 2 or more cars. Why isn't one of them a short range EV? The answer is *not* that all Americans would reject a vehicle with a 40 mile range. In the short time that I have owned my EV dozens of people have expressed an interest in owning one. Not everyone has a 50 mile commute to work.
So why didn't Detroit begin mass production of one after the first Gas Crisis? We now all know why...*MONEY. *For example: Due to the low maintenance on the EV1 all the dealers who leased them complained that after the lease was signed....they never saw the car again. Dealers make very little money on the sale of the average car compared to the money to be made during the years of repair and maintenance which follow.
So it was Money which stunted their thinking. Again, keep an open mind Dan. First build the car....then think about the economics.


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## Technologic (Jul 20, 2008)

Dan Frederiksen said:


> the windshield is not glass but vacuum formed polycarbonate. something you can do on your own if you have a nice mold. a heat gun and a vacuum pump is all you need afaik. I've done some simple tests.
> 
> Technologic, the weights you state are way off. think bicycle weights instead of freightrain. a steering column doesn't weigh 50lbs! get rid of that thinking.
> 
> the batteries are thought as lithium ion with 177Wh/kg density. I suppose some good LiFePO4 could be used but at substantial range reduction. but LiFePO4 might allow it to go faster than 6 seconds to 100km/h. would be nice to match or beat the Tesla at that too.


Polycarbonate is what I was suggesting... it's just goes under the name Lexan here 

LiFePo4 would be range reduction? What batteries do you intend to use then? Considering there's no batteries with a better energy density nor life cycle currently I'm not sure what you intend to use to get 200km ranges.

FLA = 1 battery is 50 lbs.
you said the battery would weigh 50kg... I suggested using LiFePo4 for just that reason. You'd be sitting on about 7kwhr with that weight (ie. a crap ton of power for such a light/low aero car). 

Again what rims do you intend to use for the tires? bike rims won't due at all.


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## dtbaker (Jan 5, 2008)

Dan Frederiksen said:


> I forgot to mention that the wheels are intended as solid composites with only a strip of rubber glued to the outside. the idea is to have so low wheel mass that it can do without the suspension of the air.


...not gonna happen. First pothole you hit the wheel will collapse. Also, unlikely to get enough traction out of super-narrow tires for reasonable accel or brakings, and with super narrow profile (like a motor cycle wheel) are not intended for side load and would collapse under cornering. bikes and motorcycles are intended to take load axially. Solid tires went out with the horse and buggy for a reason as speeds went up.... unless you have a perfect road.



Dan Frederiksen said:


> the windshield is not glass but vacuum formed polycarbonate. something you can do on your own if you have a nice mold. a heat gun and a vacuum pump is all you need afaik. I've done some simple tests.


may be adequete, but will scratch pretty fast, and probably not legal as a front windsheild in most states UNLESS you go three wheels and slide in under motorcycle rules which are much more leinient.


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## Technologic (Jul 20, 2008)

dtbaker said:


> may be adequete, but will scratch pretty fast, and probably not legal as a front windsheild in most states UNLESS you go three wheels and slide in under motorcycle rules which are much more leinient.


depends how thick it is... 1/2" thick lexan would be significantly more safe than regular windshields... with about 1/4th the specific gravity. Not sure about scratching... with such a low 3.2 GPA YM it won't exactly stand up to much handling even with fingernails. Might be best to use something else for heat forming.

Also as a suggestion I'd still put an "under body sheel" on the front nose that bolts directly to the aluminum foam (I hope this is what you choose) underbody. make it with ridges out of fiberglass woven cloth (not the mat) this will absorb enough crash energy so the worst thing that happens at say 40mph (a common crash speed) is a broken foot. It would only add about 25 lbs... well worth it IMO considering the compactness and death trap this car might honestly prove to be otherwise.


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## Guest (Dec 13, 2008)

Dan _O,

Your reputation precedes you. Lets not slam someone for making a statment or linking to a real tangible item. He was only referring to the fact that renders are not tangible but a prototype is. He only showed that someone made a render and a working prototype then announced the intentions. I do agree that the linked item is rather boxy but it does show promise and it really does work. No speculation here. So I say KUDOS to showing a working model/prototype before making an announcement. The box did take loads of forethought and action. Simple as it is it really works and is only intended to be used as an inner neighbor hood vehicle and not a super fast sleek looking commuter. It's the ideas that work that make things happen. 

I like your idea but would love to see a working model too. Remember we see way to much of this could be or that could be rather than this really is and here is my working model. Now it is time to improve it.

Pete : )








Dan Frederiksen said:


> saab96, some of us know the value of intelligent forethought before building it. the suncar you linked to is mindless. it's an amusement at best. it has no chance of bettering the transport sector. it has the aerodynamics of a parachute. my design is incomparably better for an ocean of reasons.


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## Bowser330 (Jun 15, 2008)

I think its a great idea...and the more prototypes that are developed the faster the industry witll grow...

Making cars lighter (while still safer) and more aerodynamic (better than the cd of .26 (prius)) is the solution for the current infantile stage of battery and electric motor technology...

The auto industry spends billions on R&D to make ICE engines 5% more efficient and 5% more powerful...imagine if 1/10th of that was invested into electric motor technology...

The loremo is another good car to mention, Im glad you are using that as an inspiration..with such a low cd...it can operate with very little power and still quick with good range....


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## TX_Dj (Jul 25, 2008)

Pneumatic tires can be light and can have very low rolling resistances (compared to other pneumatics) while still being pliable enough to absorb wheel shocks like the mentioned potholes.

There are lots of very lightweight composite motorcycle wheels available. :shrug:


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## Technologic (Jul 20, 2008)

TX_Dj said:


> Pneumatic tires can be light and can have very low rolling resistances (compared to other pneumatics) while still being pliable enough to absorb wheel shocks like the mentioned potholes.
> 
> There are lots of very lightweight composite motorcycle wheels available. :shrug:


 
motorcycle tires seem like a good alternative here... but they usually weigh about 20 lbs/each wheels included (assuming aluminum rims).

I wish there was a way to have these very thin tires (rolling resistance afterall is proportional to tire width), I'm sure there is a way (with elastomers) but not any right now unless you want to make injection molds for Akulon 



> The auto industry spends billions on R&D to make ICE engines 5% more efficient and 5% more powerful...imagine if 1/10th of that was invested into electric motor technology...
> 
> The loremo is another good car to mention, Im glad you are using that as an inspiration..with such a low cd...it can operate with very little power and still quick with good range....


You'd probably be surprised mate how little money they spend on efficiency... ICE motors once the power hits the wheels are on average only about 25% efficient. 

the advantage to this design is the the low frontal area and low CD possibilities... I can't tell from the photos, but area is actually the best thing to lower (with logrithmic increases in efficiency).

if your average car is say 8 ft x 5 ft tall (seems about right to me), and you made that car 3 ft x 4ft (about what this car looks like), you'd actually have reduced the area by 75% (increasing efficiency by such an amt). Obviously cars are more ellipses than boxes like SUVs, so the difference between a Chevy Tahoe and this car in base area would be substantial. Say a Tahoe has a front area of around 40 sqft (which sounds about right to me), this car actually only has a frontal area of around 9 sqft (rough guess, but probably close), almost 5 times less.

You're still roughly 1200%-1400% more efficient than the tahoe using electricity, just from the body design (this should have a Cd about half or 1/3rd that of a tahoe). My power around here comes from a Nuclear plant, which usually run at about 85-90% efficiency, you do the math on the other portions of the car....

This car could effectively get 50-70wh/mile (if not lower if he's using a fixed transmission)... vs the roughly 2117wh/mile (generous) a Chevy Tahoe gets off of gasoline (gasoline has a potential energy of about 36 kwh per gallon). 

Once you factor in the value of no emissions, no maintenence for 200k-300k miles, no repairs, no energy that goes into actually producing the gasoline, and uniqueness.... well... there's a reason a lot of us are in love with EVs.

All of this assumes that he's driving at a fixed speed... expect even larger differences with the EV leading in the city (where weight becomes more of a factor for efficiency).


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## Bowser330 (Jun 15, 2008)

when i said efficiency i meant specifically... fuel economy...they spend billions to improve power and fuel economy by 5-10% and consumers eat it up...meanwhile we could have something so much better with EVs or hybrids...


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## Dan Frederiksen (Jul 26, 2007)

Technologic, LiFePO4 has become popular because of its power, safety and decent density but it's not the highest energy density. LiFePO4 is around 90-125Wh/kg where as the more conventional lithium ion (lithium cobalt) is as high as 180Wh/kg. this is what laptop batteries are.

the Tesla Roadster also uses laptop batteries. 
for my use however it is a tradeoff as the LiCo batteries are usually less powerful than the high power LiFePO4 so a lithium iron based car could be made quicker in accel but only go 60% of the range.

it might all boil down to what batteries are easiest to work with. the laptop cells are very small so you have to combine a lot of them.

lithium polymer batteries also have higher energy density than LiFePO4 but have very short lifespan unfortunately. only really good for things like model aircraft where price and lifespan is unimportant.

Someone said that traction would be poor in thin wheels but that's not the case. the science actually says that traction is independent on tire size in the simple case. that is quite counter intuitive but seems to be the case anyway. you can convince yourself of this fact by thinking of a racing motorcycle that with a very narrow wheel manages extreme acceleration. it comes from the fact that as the tire gets thinner the pressure per area grows at the same rate because it has to carry the same weight.
one minor drawback, which I can live with, is that the tire does wear faster the thinner it is, given the same material.


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## Technologic (Jul 20, 2008)

Dan Frederiksen said:


> Technologic, LiFePO4 has become popular because of its power, safety and decent density but it's not the highest energy density. LiFePO4 is around 90-125Wh/kg where as the more conventional lithium ion (lithium cobalt) is as high as 180Wh/kg. this is what laptop batteries are.
> 
> the Tesla Roadster also uses laptop batteries.
> for my use however it is a tradeoff as the LiCo batteries are usually less powerful than the high power LiFePO4 so a lithium iron based car could be made quicker in accel but only go 60% of the range.


Cobalt is significantly more expensive also, that's why I suggested the more stable, cheap, easier to get, easier to BMS, LiFePO4


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## dtbaker (Jan 5, 2008)

Dan Frederiksen said:


> Someone said that traction would be poor in thin wheels but that's not the case. the science actually says that traction is independent on tire size in the simple case.


Absolutely not true... The amount of force that can be applied before slippage is dependent on weight, friction coefficient of the rubber (and road surface), and the size of the contact patch. As horsepower goes up, so must the 'downforce', or contact patch size, or coefficient of friction. F=MA.... The faster you want to start or stop, the trickier it is to make sure the F does not exceed available friction between rubber and road.

racing motorcycles (and cars) use rubber that is very soft and aerodynamics to generate as much downforce as possible at speed without adding weight to preserve acceleration. Dragsters use enormous soft tires to create as much friction as possible at the start. Super-wide tires on 'muscle cars' are not purely for looks.

Hence, jamming big torque thru narrow tires would be a mistake. Similarly, for a given weight vehicle with given rubber compound and road surface, there will be some tire width that yields the most friction for braking OR acceleration.....

The other issue with narrow rims is limited strength for side forces from cornering. Bike and motorcycle rims are NOT made to take much side force, and if used on a three or four wheel vehicle, you'd have to be VERY careful not to corner hard or risk wheel collapse.


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## Technologic (Jul 20, 2008)

dtbaker said:


> The other issue with narrow rims is limited strength for side forces from cornering. Bike and motorcycle rims are NOT made to take much side force, and if used on a three or four wheel vehicle, you'd have to be VERY careful not to corner hard or risk wheel collapse.


 
I personally hope he just uses a solid rim of 1/2"+ thick aluminum 
Or uses standard (thin) compact car tires.

motorcycle tires probably would work for this with a decent selection, if the car really only weighs 500lbs it should be ok.


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