Designing an FE Car from the ground up.
This is a thread about designing an FE car from the ground up, starting with my thoughts.
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Ok, some initial thoughts:
1) The vehicle must totally embrace the teardrop shape, with smooth fairings the whole way around. Wheel housings must also adhere to this. Worse comes to worse, the end can be truncated at some point, but only slightly. 2) Considering the realities of the situation, total vehicle cost must also be minimized. Few people are going to want to spend an extra $20k up front to save $1000 per year. 3) Considering the teardrop shape and vehicle stability, as it approaches this it approaches a tricycle in terms of appearance (i.e. as the two rear wheels come closer together, eventually it takes on the handling of a three wheeled car with two wheels at the front. This means that most of the weight must be at the front for stability concerns, and very likely, this is where the engine should go. 4) Where to put the luggage? As the rear of the car narrows, it becomes more logical to put the luggage in the center or front of the car, where most of the volume of the teardrop is, and an extra single seat at the back... OR an extendable boattail. Such a boattail would be also useful as a large crumple zone in the event of a rear end collision, remember Force * distance = Work. 5) The car should be full sized. Whether it should be as long as a suburban is debatable, but it should be looked at. The size I am going with for the highway version is 227 inches (same as the Excursion), and 57 inches high (same as the Camry). |
https://i5.tinypic.com/15gur1g.jpg
Here is a very rough sketch of what the car would have to look like. In a front end collision, the driver would be in as good a shape as a collision in a tarago (a van where the driver is up front). Perhaps he could be seated further back if the windscreen wrapped around. Note no rear-view mirrors - this is done via cameras. Also note I forgot to draw the rear wheels in one of the pictures. Also, the highway model needs to be rotated a few degrees clockwise. Miniaturize the highway model, make it a two seater (one in front of the other), and we have something like a single person commuting model. |
Not trying to hijack the thread but are you trying to build the most FE car possible or or you trying to build a more FE car? I don't think that people would be ready to buy anything that is to far out there. I think that if you really wanted to make an impact you would need to do like Henry Ford and bulid a cheap car that gets 50+(like the smart car) that folks with out much money could buy. Something in the 6-10k price range. I think it was you that said most folks buy old cars because they cant afford new ones. So to help the overall situation build something inexpensive that gets good gas mileage so the masses are not driving around in 8-15 year old cars.
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Something like that should get a Cd of 1.0 or less (hopefully less).
Using plastic panels on the outside, it should also be possible to make it quite light weight. Which means that it would be quite possible to power it with a 500cc engine or less, which should be very cheap. Go with whatever fuel saving technology is cheap. Perhaps a large starter motor so that FAS can be easily integrated with the driving, and a tall gearbox. Considering that 0.3 is good for a modern car as far as Cd works out, such a design would use probably less than a third of the power at speed. Market it based on insulating yourself from fuel prices. Advertise it by capitalizing on other people's fear of price rises. Show what would happen if gas went to $10/gallon and interest rates went to 15% (i.e. to general people), and show what would happen to the hypothetical car driver. Start off the advertisement by having a calm voiceover saying something like: "I don't want to have to pick a right time to buy fuel. I work. I have a job I need to go to. I don't need to look good getting there, I just need to be there. If I want to look good, I buy some nice clothes. It doesn't improve my life to spend more money on a car, more money on fuel, more money on maintenance. I like the idea that I can travel across the country for $20. I like the idea that I can spend more money on my family, on a home, on food, on clothes. On whatever I want to. |
Another thing... what would necessarily make such a care expensive, provided that you used cheap trim, seats etc? The motor would be cheap as chips. Rear-view cameras aren't expensive probably less than $200 mass produced. See ebay for examples.
Can the boattail idea perhaps, although it shouldn't be that expensive, all that is required is four panels that slide out, following the contour of the floor, sides and roof. You already have rear-view cameras, so visibility shouldn't be that big of a deal. I think this is one of those things that once there was something out there like it, it would take off, especially in times of high fuel prices and interest rates. With fuel prices taken to their logical endpoint, this is a logically designed car. Of course, all buying decisions are emotional, not logical. So, first you need to create fear by painting a picture of what could happen. Then you need to show how buying this car is like buying insurance, it helps you sleep at night. It's one less thing to worry about. Lose your job and have to commute 100 miles in a day? No problem. Have to tighten your belt because your wife is staying home with the baby? No problem. It's one less thing to worry about. |
https://www.geocities.com/conceptcarc...oit_probe5.jpg
Here is the Ford Probe V, a Cd of 0.137. Very interesting to read about. |
I think going after a normal-looking/performing car, and not a commuter vehicle would be a better idea.
My idea is this: 1) The vehicle must be a midsize car capable of seating five 200 pound, 6'5" adults 2) Must be able to run on renewable energy 3) Must obtain at least 50 mpg 4) Must obtain 0-60 mph acceleration of under 8 seconds 5) Must not appear radically different from the cars of today 6) Must cost under $30,000 A midsize car with the above seating capacity is easy and outlined above. This would basically be a vehicle at least the size of a Toyota Prius. Trimming out much dead weight from the interior could yield such a car with a weight around 2,900 pounds. Due to the car's size, frontal area will be about 23 square feet. 0-60 mph of 8 seconds or less? Must run on renewables? This calls for a diesel with at least 200 horsepower. Take a turbodiesel from a VW Jetta, add a performance chip and additional turbo boost. 50 mpg? The frontal area is set in stone, so the drag coefficient must be worked on. A .18 Cd sounds pretty reasonable given past accomplishments in the auto industry in regards to their concept vehicles or in the case of small companies, actual production cars. Google search the GM Precept(.16 Cd), Dodge Intrepid ESX-2(.20 Cd), Ford Probe V(.137 Cd), Alfa Romeo BAT7(.19 Cd), Tatra T77a(.21 Cd), among others. Basically, a Cd of .18 and 23 square foot frontal area yields a Cd*A of 4.14, about half that of a normal car. But aerodynamics only affects fuel economy at higher speeds. We already set the weight in stone at 2,900 pounds. So to get this efficiency? We're going to need LRR tires, synthetic transmission oil, low friction wheel bearings, and brakes that don't drag. Appearance? Something along the lines of those cars I told you to google search. GM Precept: https://www.gmcanada.com/static/engli...pt_main_bg.jpg Dodge Intrepid ESX-2: https://carstyling.ru/resources/conce...pid_esx2_4.jpg Those look like something people will buy. They look rather normal, if not sporty. Cost? Well, we haven't used exotic composite materials, or exotic engine components. We haven't used a hybrid drive. Aerodynamics add little, if any additional cost to the manufacturing price of the car because it's simply a matter of how the car is shaped. Realistically, this could be a $20,000-25,000 car. So overall, could these goals be met? 1) Midsize car? yes. 2) Capability to use renewable energy? Yes. It's a diesel and can be fit to run on B100. 3) At least 50 mpg? Yes. Diesel midsize cars in Europe without significant efficiency modifications like Mercedes' V8 diesels are already doing over 25 mpg combined. This car would probably get around 60-70 mpg with the outlined efficiency modifications and a more efficient diesel powerplant. 4) 0-60 mph acceleration under 8 seconds? Probably. 200 HP in a 2,900 pound car would theoretically allow 0-60 in the low 7-second region. As an added bonus, with the low drag design, top speed would be roughly 170 mph with the right gearing. 5) Normal appearance? Certainly achievable. 6) Under $30,000? Yes. No hybrid drive and no exotic components would make this a car that is certainly cheaper to produce than today's hybrids. It could probably sell for about the same as most entry level midsize cars, around $20,000-25,000. |
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https://www.usmotors.cz/old/akce/akce..._precept_3.jpg
https://mclellansautomotive.com/photos/B17430.jpg I like the precept. It also does a good job of providing plenty of room in front for crumple zones in an accident. Not to mention the phenomenal drag coefficient. The thing I love about these pictures is that they give so much in the way of ideas for our own vehicles. There isn't that much we can do about the exterior shape without incurring a lot of cost, but wheel covers, front skirts (Ford Probe V has a flexible membrane, I think I'd prefer something mechanical that would last longer), undertray, shaved door handles, rear view cameras, deflectors. |
Toecutter, I like your way of thinking.
I've always been a performance nut too, long before I started caring about fuel economy. And I think something shaped like the Precept and done the way you are talking about according to the criteria you set out would sell. But since I started getting in on the FE kick, the engineer in me sees the shape of current cars with the Cd of 0.33 or so, and then a dolphin with Cd of 0.004, and sees an improvement to be made of approximately 80 times! Of course, if that figure is to be believed. This link makes me think otherwise. Even just the streamlined body is 0.04, which is about 8 times better than what most cars are currently. And seeing as cars like the following sold once: https://www.thesource4ym.com/images/Tommy-the-Tarago.jpg It should be possible to have the driver in a more forward position, which gives more room for the boattail, and hence, lower Cd. It also means more usable space, since there is no penalty to starting out with the largest cross sectional area fairly early. The Mercedes Benz Bionic Car is a step in the right direction, but even that is a little compromised IMO. https://specieslist.com/images/external/Mini3L.jpg https://specieslist.com/images/external/thMini1L.jpg Both articles are well worth reading btw. Of course, if you want to really optimize for low Cd, something like the Sailfish, Tuna or Mackerel are good to observe. Sailfish (note that the sail is down at top speed, it folds back into a groove): https://photos1.blogger.com/blogger/3.../sailfish1.jpg Yellowfin Tuna: https://cars.er.usgs.gov/Fishes_of_Is..._2000/tuna.jpg Mackerel: https://www.freedive.net/ibsrc/Ful_si...n_mackerel.jpg Mako shark: https://www.starfish.govt.nz/shared-g...-shark-sml.jpghttps://www.firstlighttravel.com/Assets/dive_shark1.jpg Marlin: https://www.pier.org/images/Jumping%20black%20marlin.jpg All are essentially streamlined bodies in three dimensions, somewhat elongated I suspect to make changing direction/propulsion easier. I guess I just like the idea of reducing my vehicle costs to practically zero, especially over long distances at highway speeds. Equipping a car to get FE equivalent to such low drag means of course reducing engine size OR pulse and glide driving. Both have their downsides - P&G means that cruise control is not practical, you need a larger starter motor and a good way to control the engine properly, to turn it on and off safely etc. A reduced engine size lawnmower style motor means that getting up a steep hill will mean slowing down significantly. A couple last pictures: the Orca or Killer Whale: https://www.seaworld.org/infobooks/Ki...lerwhale99.JPG https://www.whale-images.com/orca_ima...ale_breach.jpg Note that the widest point is about a third the way back. Adding some wheels, removing the sharp edges (I probably should have elongated the back JUST a fraction)... https://i5.tinypic.com/15mjqzs.jpg |
I'm surprised that nobody posted drivetrain designs. Efficiency starts with the engine, transmission and its accessories. Here's my candidate for an ultra-efficient drivetrain:
ENGINE Two cylinder gas engine, a "boxer" layout for good balance and even firing. About 1.5 liters Undersquare bore and stroke Cast iron block Aluminum heads DOHC 4 valves per cylinder Atkinson cycle cam timing primarily, but high valve overlap at high speed Direct fuel injection Lean burn, open loop at idle, closed loop at load. ACCESSORIES NO belt drives Ebullient (boiling water) cooling or thermosiphon Electric radiator fan High capacity (NIB?) alternator (mounted on crankshaft, like a Harley Davidson) generating electricity only on decelleration or low battery voltage Deep cycle battery Electric power steering (or none) Water-based based adsorption system A/C using either ammonia, lithium bromide or silica gel. (A/C would be powered by exhaust heat.) TRANSMISSION Magnetic eddy current CV automatic transmission. This would not require fluids, clutches, bands or torque converter. These are already commercially available from Magnadrive. https://www.magnadrive.com/ This drivetrain should power a Corolla-sized vehicle from 0-60 mph in 10-12 seconds, and could get upwards of 50 mpg highway WITHOUT weird shapes or aero mods. In a Prius body, it'd get 60 mpg. In a streamliner, it'd get 100 mpg. The logical company to develop an drivetrain like this would be Subaru, since they already make boxer engines. Subaru doesn't seem to be focussed on economy these days, though. |
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However, I'm asking a few questions that seem to be going unasked... Why does an FE car have to have the vestigial aerodynamic ugliness of 3 box design? Why does an economy car have to be shaped like an inefficient box? Why should an economy car have less room for passengers? Why can't it use the same parking spaces available to full-size cars or even SUVs? If we are going to have a boattail, why not halve the length by sloping up from the floor as well as down from the roof? Most of all, I'm asking if there is a market for a car that costs less than $10k and can virtually completely insulate the buyer from fuel price rises? Why can't we have the practicality of an econobox (speed, storage, protection from weather) with the cost to run near that of a bike, if the compromise is looking a little weird at first? I think a case can be made for starting off with the most efficient shape and then only throwing away components of that shape once every avenue of both retaining that shape and satisfying other constraints has been tried, rather than working the other way and trying to make the three-box design as aerodynamic as possible. With higher fuel prices changing the underlying economic assumptions of the automobile and a whole new array of technology and knowledge at our disposal since the last energy crisis (1970s), it would befit us to spend a little time questioning all our assumptions. |
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My point with starting off with the aero stuff is that it once you determine (minimize) the maximum and steady state load conditions, then you are in the best position to select an appropriate engine size and even the basic type of engine (electric, gas, almost rubber bands etc). Although potentially it will do a bit of chugging on acceleration and hill climbs. With all that you'd be able to get away with a smaller engine and thus the load on it would be higher and more efficient. With a 1.5l engine it'd be a sportscar. Very interesting about all the belt driven accessories. |
I think such a car should be designed with the possibility of there being a choice multiple drive systems one could buy for their vehicle.
For instance, the above diesel concept I mentioned. It should also be designed so that it could accomodate an electric drive and lots of batteries. Imagine, for instance, if there was this huge space under the floor to fit 2,000 pounds of lead acid batteries. In a car that aerodynamic, it could have 150-200 miles highway range on cheap lead acid batteries, no NiMH or Li Ion needed. Sure, the car might end up weighing 4,500 pounds in such a case, but with a dual 8" motor setup and Zilla 2k controller with a series/parallel shift in place, it would still do 0-60 mph in 6 seconds. It would probably cost the same as its diesel counterpart, sacrificing some range and incurring a long refeulling time for the benefit of more performance and dramatically lower operating cost. Or for increased performance and range but with higher cost, give the option for advanced batteries, say a Li Ion option to cut the weight down to 2,900 pounds(same as diesel counterpart), extend range to 300 miles, and drop 0-60 time to 4 seconds, but it might cost $20k extra. The same platform should also be designed around a CNG engine and tanks as well. Imagine the buyer being able to walk into a dealership and choose which kind of fuel they want the car to run on. With 150 miles range, many would be able to use the pure EV on cheap lead acid batteries for all of their driving needs, while some would rather have the diesel and run it on B100. The whole idea is to keep costs down though. Going to a plug-in hybrid would mean paying for two drive systems, which would bring the ciost up quite high. |
AeroCarbon car
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They don't give it but from what I remember it was very low which is why it took so much money to develop its shape. 660cc HOnda motor and 100mpg. |
It is a custom called the AeroCarbon built onto a Lotus Elise chassis with a Honda engine.
It has a drag coefficient of .22. Nothing spectacular. I think it's quite ugly, especially for having a Cd as high as .22, when other cars that look much better have attained .16-.18. Definately needs some work on the overall finish. https://64.233.167.104/search?q=cache...ient=firefox-a And if you're going to build the car on such an expensive chassis, at least keep the horsepower high to justify the expense! If the original Lotus Elise engine were maintained, it would still get ~80 mpg, only it would accelerate from 0-60 mph in ~4-5 seconds and top out near 180. Fuel economy and performance can coexist nicely. If fuel efficiency is to be marketed to the public, it has to be fast. The truth is, a more efficient engine with lower horsepower numbers is not going to affect fuel economy more than ~20-25%. Compare the EPA mileage data on cars of a certain model with their different choices of powerplants. The V8 Mustang, for instance, gets near the same fuel economy as the V6. The V6 Corolla gets about the same fuel economy as the L4. The real truth is, it's mostly drag that effect's fuel economy. The only way a powerplant swap by itself will give amazingly good fuel economy is if you're keeping it at peak load for normal highway cruising, and that just won't provide adequate acceleration to even keep up with traffic. Even the deplorable Hummer is using only about 30 horsepower to maintain 60 mph. That wouldn't do much to accelerate it! Likewise, a lightweight aerodynamic car will be able to cruise that same speed with only around 6-7 horsepower, and likewise, having an engine that small just isn't practical on anything roadworthy. Anything other than that peak load, and efficiency rapidly drops off. It upsets me when designers try to tackle increasing fuel economy through mostly engine downsizing, when that is where there are some of the least significant gains to be made. The real gains to be made are the low hanging fruit that is aerodynamics: you expend far less effort, sacrifice far less quality, for much greater fuel economy. That Ford Probe V? If someone somehow managed to shoehorn a 350+ horsepower V8 into it, I bet it would still get ~45 mpg if driven conservatively! If you've ever seen the movie "The Wraith", that concept Dodge M4S turbo interceptor that made its appearance in that movie had roughly 440 horsepower. Guess what fuel economy it got? THIRTY-ONE mpg. Why? Its drag coefficient was around .20. Here we are, with our car fleet not even approaching that, still struggling with inline four cylinders and V6s of around 170 horses. Imagine making an ultra aerodynamic car. Could have performance out the *** and high horsepower, yet still get double the combined fuel economy of cars available today. All this, with no magical new technology needed. But when consumers demand fuel economy, Detroit punishes them with anemic powerplants they don't want and dramatically downsized cars that they don't want. Aerodynamics are everything. Literally. Powerplant? Not so much, unless you go 100% electric or B100! |
[quote=The Toecutter] Aerodynamics are everything. Literally.
Not in my world: Vehicle mass and propulsion plant efficiency are more important FE factors in stop and go driving, which is how most Americans drive most of the time. Sure, I love to get big numbers in highway driving, but my 10 mile commute has over 20 stop lights, none of which are synchronized. As a matter of fact, political pressure from residents along Wollaston beach has caused MDC traffic engineers to time the lights to stop at every one, regardless of pedestrian or side street traffic. I never get over 45 mph in my commute. Aerodynamics won't help me much.:cool: |
Sludgy - Sounds like you need a pure electric vehicle with really good regen braking. I built a scooter from a 6000 watt eCycle electric MG13 motor and mounted it on a Bladez Transport with 3 Hawker Genesis 26ah batteries and very seldom did I need to use the brakes in stop and go traffic or down steep hills.
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Thanks for the excellent post, toecutter!
It seems like you have been as obsessed about this as I have been the last few years. Long have I looked at the eco-speedster and thought "Why don't they produce something, anything like it for the public?" https://www.hydro.com/library/images/...edster_335.jpg BTW Here are pictures of the Wraith interceptor (Cd around 0.20 according to toecutter): https://www.us-car-history.de/filmaut...nterceptor.jpg https://www.us-car-history.de/filmaut...nterceptor.jpg Note: sideskirts, front air dam (which I'm not a big fan of, I think undertrays are way better and more practical, if not from a maintenance POV, at least from a speed hump POV), barely vestigial 3-box design (note no difference in angle between windscreen and hood, as in 99% of cars), and my favorite, the boattail that both slopes up from the floor and slopes down from the roof. Booyah! Also note that it reaches its largest frontal area approximately 1/3 back, like a fast swimming animal such as a mackerel, shark or killer whale. No rear wheel fairing either, which goes to show how great a shape it is already! Quote:
https://www.drivingfuture.com/auto/da...00000039sb.jpg Again, note the aerodynamic cues taken from marine animals, such as the complete lack of a nod towards conventional 3-box design. https://autoblog.it/uploads/6.jpg Note the way the rear sweeps up from the bottom as well. Not surprisingly, the Cd is 0.16. Quote:
Yes, that's obvious if we look at the above graph, taken from this page. Let's have a look at some equations and sample figures just to get a feel for it. Take a toyota camry like car. Cd = 0.3 (camry actually has 0.28 as of 2007, but we are making it more similar to an average family car), frontal area = 26 square feet, or 2.41 square metres. Kerb Weight 3200lbs, or 1454kg. Max Power = 121kW (158hp). Acceleration is shown roughly by 0.0832kW/kg. If the car is cruising at 70mph, then what is the load on the engine? We know that at cruising speed, drag dominates. So if we can compute the drag, we can basically compute the load on the engine. Again, if we use this site, we find that the equation for power loss due to drag is: https://downloads.openchannelsoftware...on/eq_drag.gif Substituting into the equation (air density is 1.2kg/m^3 at sea level), P = 2.41 * 0.3 * 31^3 * 1.2 /2 = 12.9kW (Edit: Please note that you can double-check my calculations HERE. Enjoy, have a play around, it's great!) So, a typical highway load for a standard passenger car is around 13kW. Acceleration requires the maximum load to be 121kW, or such that the average load at highway speed is roughly 10% of rated load. If we look at the above graph and see where the efficiency would typically be for the average engine, it's at roughly 20% out of a total of 28%. Hence the maximum drop in fuel consumption by shifting to a gutless, unroadworthy engine is 32%, and a more realistic drop is 20% by shifting to a more anaemic engine where the cruising load is only 30% of rated load. Of course, in so doing our max horsepower has dropped by 70%, which will not inspire the public. Drop the weight to half and do nothing to the Cd, we can halve the engine size and have the same power to weight ratio, giving the same usable acceleration, lower top-end speed (which most drivers don't see anyway), and a 20% reduction in fuel usage at 70mph. Drop the Cd by half down to 0.15. This means that the power needed for cruising at 70mph jumps down to 6.5kW (won't actually be quite so good because of diminishing returns due to other factors like rolling resistance, but close enough). Now to produce 6.5kW, the engine is 15% efficient. That means that it's consuming 43kW of fuel energy from gasoline (6.5/.15). By contrast, the regular camry is consuming 65kW of gasoline (13/.20). This means that halving drag gives us a 34% reduction in fuel consumption, whereas downsizing the engine gives us a realistic 20% reduction in fuel consumption, and a MAXIMUM POSSIBLE reduction of 32%. Of course, this analysis depends on that curve being correct. Supposedly it was supplied by the Clevelend RTA, whoever they are. I suspect that is at an rpm/throttle point that gives maximum efficiency for a given load. Note that a typical passenger car like the Camry will NOT be operating in this manner because the motoring public (or the journalists) like to have plenty of acceleration in 5th, which means that there could in fact be larger gains made IF THE SAME GEARING IS KEPT (which it probably won't be). Quote:
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But yes, your point remains that it is due to ridiculous drag coefficients on passenger cars that the state of things are where they are today. Drag coefficient is really the low hanging fruit here, waiting to be plucked. I suspect that it's due to the unintuitiveness of Cd, people don't take the time to understand the principles, to study nature, and to refine. They'd rather take a 3-box and tweak it by making it "look streamlined". You might be able to get weight down to about 800kg if you really tried, which will enable almost a halving of engine size for the same performance. This will almost halve city fuel consumption, and as stated before it should have maybe a 20-30% effect (max) on highway FE. All three in combination are best - lowering Cd, lowering kerb weight, lowering engine size, enabling a tall gear for cruising. Quote:
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[quote=Sludgy]
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What's needed is a commuter vehicle, with low Cd, low weight, basically the aerodynamic, weatherproof version of a motorbike. Unfortunately, it doesn't exist outside a few kit cars and concept cars. If you've got that, you can go anywhere for low cost. Regenerative braking is a bonus... however for someone who is concerned about saving money from fuel, losing weight reduces up front cost AND fuel consumption, and adding regen braking adds to up front cost while reducing fuel consumption. So one first, then the other. Unfortunately, rather than encouraging such obvious vehicles, the government is encouraging hybrids. |
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https://www.electricmotorsport.com/EGPR/sales.htm This would fit my needs, IF my commute was in Arizona or southern California. Here in the land of rain, ice and snow, a motorcycle is just a toy with some FE benefits, rather than a practical commuter vehicle. Did I mention that we've had 22 inches of rain so far in May and June of this year?:( Even so, I'm trying to convince a wife who thinks I'm nuts to ride............ |
Wow, I thought this thing looked pretty cool. I think there are a lot of people who would drive a vehicle that looks like this. It's a "love it" or "hate it" design when it comes down to it though.
https://carstyling.ru/resources/conce...pid_esx2_4.jpg Anyway, one thing I have noticed with most of these aero vehicles - no front wheel skirts. Why aren't automakers making them part of the design? |
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Alternatively, the wheels could be pulled further into the car. But in FWD cars, there probably isn't enough room. Finally, using small diameter tires would minimize the wheel well height and width and they might be able to avoid hitting skirts. However, the tires would have to be 10" or smaller, like the old Mini Cooper. It's hard to find small aftermarket wheels. The current vehicle fad is enormous wheels, 18" or more even on small cars. |
All very valid reasoning. You would think that someone would have come up with a steerable front skirt solution. Perhaps there are some stability issues? I really, really want to try my framework idea, but haven't had the time yet. Someone must have tried some similar research for a car company at some point. I wish I could find some test results.
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The Ford V has a flexible membrane, as is mentioned earlier.
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True, but would wheel friction eventually burn/tear right through the material over time? Some kind of flexible rubber material over you wheel well would probably work temporarily, but would tear away over time (I'm considering adapting to current vehicles, not building from the ground up of course).
EDIT: *smack* I'm not thinking. A framework would probably "push" the membrane out of the way while the wheel turned. |
One final thought on an extreme FE car. We should all keep in mind the fact that inexpensive, high FE vehicles have already been built and sold successfully, such as the WV Lupo.
There is no magic to it. The easy, affordable way to big FE numbers is low tech rather than high tech. Nobody will buy an expensive vehicle that is so aerodynamic that it's non-ergonomic. 1) light weight 2) reasonably low Cd / low A, 3) a matched (small) efficient engine, whether gas electric or diesel 4) efficient accessories. |
I think you are right, Sludgy. I think adapting/improving aero mods to older FE cars is the ticket to the highest gains for the cheapest price. Low tech seems to be the way to go.
Designing a fiberglass body to fit a Civic or something may be another option. :D |
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It's like recumbants versus uprights. It's only because the first mover was an upright that people might laugh at recumbants, just like people used to think that those with mobile phones were vain and pretentious. Once something becomes commonplace, the stigma gets removed. Provided that a car fits the required number of passengers in, can accelerate to a given speed, is safe and not difficult to manufacture, then it's the same thing. I don't see why the aerodynamic shape has to be expensive or high-tech for that matter. Consider that the T77a was manufactured in the 1930s with Cd lower than cars today. Consider the curved surfaces of most new cars, and the possibility of using plastic panels. I.e. It shouldn't be difficult or expensive to make a boattail, even if it is dead space, worst case. But there is this false dichotomy that says econo=small box. I wonder if (part of) the reason for this is simply price discrimination. If people were given the option between a heavy "luxury" car and a cheaper, lighter FE car that did almost all the same things, of a similar size, might everyone not buy the cheaper car? I think this might be worth a thread. Quote:
Also, there is the 3-box design legacy to take into account. Almost all the design out there is evolutionary rather than revolutionary. This is unfortunate, because rather than asking "How can I take the most FE design possible and make it practical?", they go from the other end and ask "How can I take an existing car and tweak it to make it FE?" The gulf between what is possible through a revolutionary design and what can be attained by an evolutionary process is immense, as is the time it can take. To get an idea of the problems associated with evolutionary design, look at this. We have the understanding to design for ultra low Cd. We know the basics of what we need to have in a car - room for passengers, room for luggage, an engine, visibility, etc. If we realize the coming need for improved FE now, then it is possible to have a total rethink of everything with the knowledge that fuel concerns will trump most other stuff in future. In addition, such a vehicle will open up other possibilities. For example, if your relatives live a few hours away, going to see them is less of an issue if the cost is minimal. Going to far off places by car becomes easier if it costs next to nothing. |
I can't believe someone posted a picture of The Wraith. What a b!tchin' movie. :)
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Back to the original thought process
In designing a FE car from the ground up, one of the points mentioned is storage space.
I'd like to suggest a matching trailer option. A very aerodynamic trailer. I've read on here before that some vehicles when followed by a well designed trailer allow the vehicle pulling it to get better fuel economy numbers. It would be smallish, lightweight etc. and the car would have to be fashioned with a rinky-dink hitch. something to ponder |
A better idea for storage space is to simply elongate the car, make it bigger.
That way, to can allow a longer taper of the 6:1 fineness ratio in the rear, reducing drag coefficient further. A full size car can more easily obtain a low drag coefficient than an econobox! Think of something as long as a Ford Excursion, but with the height and width of a normal midsize car. Imagine all that trunk space that one could have and all the interior room! |
okay, COD is one thing, but what about weight?
With a trailer option it could be used when necessary. not all driving is on the freeway also, vehicle length isn't something i want to add to my perfect FE vehicle |
Much of the weight in today's cars is useless fluff added to the interior. Many new cars are loaded with 400-600 pounds of unnessessary sound deadener, used as an excuse to inflate the price of the vehicle and compensate for the road noise and improper weight districution caused by a poorly engineered design.
Take note that many of the classic musclecars weigh hundreds of pounds less than the 'lightweight' BMW Z4s and Porsche Boxters of today. Just recently, two cops in my city got into a wreck. The dashboard in their Crown Vic broke and fell onto their legs, snapping their bones like twigs. |
I agree, Toecutter.
Cars are getting bigger on the outside, but smaller on the inside. I sat in a rented new Chrysler "crossover" SUV in Florida a few months ago. It had less room inside than my wife's Corolla. So much for progress. |
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Be careful withthe airplane designs. They ioperate on the principle of laminar flow, as opposed to turbulent flow. Whereas our skies are often free of debris, our roads are an entirely different matter.
A small scratch or dent, even if difficult or impossible to see with the naked eye, is all that is needed to trip the laminar flow into turbulent flow, and all your aero benefits in regard to efficiency go to crap. For a car, I'd recommend staying within the domain of turbulent flow and try to minimize drag from there. That means a teardrop shape, as opposed to a giant penis shape. :p There is a reason solar cars, designed for low drag, do not adopt laminar flow designs as airplanes do. If only there were a way to prevent nicks, cracks, rust, and warping from ever occuring. Then laminar flow might become useful in cars. |
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