Well, you only need to look at racing to realize what it takes to get maximum efficiency in a car. Weight is a critical factor, as is weight distribution, coefficient of drag, etc.

So, auto manufactures are very, very aware of this. However, this is a market driven society and not a society driven by auto manufactures.

What that means is that people want BIG cars and trucks. I am not an advocate of that, but that is the reality here. Here in Florida I am convinced it is the SUV/Truck capital of the world. I see more SUVs and pickup trucks here than I did when I lived up north where there was actually bad weather.

However, I really don't worry about it. It is a self correcting problem. If you let the free market do its job and not artificially manipulate fuel prices, people will change their minds when it hits them in the pocket deep enough.

Finally, as long as there are big trucks and SUVs rolling about there will be resistance to buying a low mass car. Even though SUVs and Trucks are less safe than cars (statistically due to their rollover characteristics), mass usually wins over a compact car.

The big killers are pickup trucks (and many SUVs). They still use a frame rail system for the design and they are usually above the bumper level on many cars. The two rails are deadly in an impact. The worse impacts are when a pickup broadsides a car. The doors on a car can not provide enough energy absorption and the frame rails of the truck are at chest level for the car driver (add to the fact that lateral impacts on the human body are the most deadly).

Broadside impacts force the internal organs to shift and cause aortic aneurisms. Victims look fine with no external injuries, but die at the scene because they rapidly bleed out internally.

Unfortunately, this is just the culture in the US and until gas prices go up and strain the wallets of consumers enough, nothing will change.

I get on the soap box here because my girlfriend is a paramedic and I have been through medical training where we have both witnessed the reality of what we drive and how it kills us first hand.

I agree that reducing vehicle weight would increase MPG. The dilemma for the auto manufacture is to produce this light weight vehicle and still maintain safety standards.

How would you 800 Kg vehicle do in it's impact with 1500 Kg vehicle.

Hi

Good question! But, what's it that we are trying to analyze here?

Our attempt here is essentially to see how best we could reduce the CO₂ emissions due to automobile pollution. If there is any meaning for THAT THREAT leading to a world level catastrophe', then there is no alternative but to work on the premise that, as engineers we need to redesign ALL our systems, to suit and answer this and other REAL problems. We never try to throw the baby along with the water in the tub! So also, here, just because there are "heavier" systems, should we simply forget this greater problems? In the same vein, just because Appollo 13 failed, the NASA and the US government did not call off the space programs, rt?

True, from a market angle, WE NEED to consider some of these things, in the right perspective. And it is here that our (engineers') roles come in - to answer and find solutions, taking all these aspects into consideration

Any suggestions?

Good design would allow different materials for strategic points i.e. titanium for impact resistance and composites for lightweight non-structural components. I believe F1 design is doing this already...at a price.

Vince

Yes! The present day designs and materials engineering do not help us bring out mass produced economic cars/ vehicles. Many technically successful "low eight" cars with high efficiency are running on roads.

But our QUEST here is also to break the ECONOMICS barrier

Any suggestions/ thoughts?

the greatest single factor in reducing fuel consumption in an automobile is weight reduction).

Only in conventional automobiles. High efficiency regenerative braking would greatly reduces the losses due to vehicle mass. The increased energy use due to mass is because of the increased input required to accelerate and grade, recover the Kinetic and gravitational energy on the back end of the process and mass no longer is a primary consideration.

Also, in constant state driving on level terrain, drag is the primary loss. In stop and go driving it is the conversion of the kinetic energy to waste heat through friction braking.

Also, the variable output required of the Prime Mover in conventional processes kills efficiency; average the demand over the entire process and efficiency of the potential chemical energy conversion of the fuel source to the applied work goes up; combined with the associated reduction in the mass and volume fraction dedicated to the prime mover, the overall efficiency of the process is driven up.

The American automobile manufacturers are very slow to pick up on basic changes in the applied science. They love the gee whiz but can't seem to sink their teeth into the meat. Japan and China on the other hand are steaming ahead.

The conceptualization that fuel efficient vehicles have to be small and low performance is about to change, it will be up to the American manufacturers to decide if they want a piece of that pie.

http://www.bestsyndication.com/Articles/2006/c/carter_mark/031206_hybrid_cars.htm

"The Three Fundamental Efficiencies of Hybrid Technology" - (This takes a minute to load.)

The first and primary efficiency has never been applied; while the second and third only at very low efficiency.

I want a vehicle with high accelerative performance and high fuel efficiency; they are not self exclusive.

Gavilan

Hi

While I do not wish to counter any set of arguments on mainly aimed at "high thrust" marketing subjects, as an engineer (and a bit of a scientist too), to me the nearest BEST mathematical presentation that has appealed is in this site:

http://autoblog.xprize.org/

where there is a good analysis of the CAR EQUATION:

F = mgC_rr + ½ρC_DAv² + ma + mgsin(θ)

The essence of the science is that about 80% of the energy that is made available through burning gasoline or otherwise is to counter the weight of the car. Moreover, the efficiency of the burning is so poor (see the original thread at the beginning) that the final engineering economics is ridiculously "costly". And, it is time we engineers do put our heads together and not merely do something, but the global repercussions of pollution are so bad that, for the luxury of a small million people, over 4 billion people who do not even earn US $150 per annum cannot be made to suffer continuously

If we cannot find answers to these, through at least some sacrifice on over engineered luxury, our profession's value is questionable.

Hope we do have POSITIVE realists and engineers with WILL-POWER to break these barriers.

Till now suggestions have not come in that direction

Thnk!

F = mgC_rr + ½ρC_DAv² + ma + mgsin(θ)

This appears to be a sum force equation I recognize the aerodynamic drag force and the accelerating force. It appears the last component is the grading force? What is the first component?

Back to regenerative braking, The mass related components are recoverable on the back side.

Now take that sum force equation and multiply it times the displacement. We now have calculated the work. Divide the work value by time and we have the averaged applied power through the process. It looks to me like we drag around a LOT of excess mass and volume because we put real time demand on the prime mover.

What do you think?

Gavilan

The first component is the Rolling Friction

Essentially, even without going into much mathematical details, we need to recognize the following:

(1) Moving any material body needs energy, and this energy is directly proportional to the mass of the body

(2) From a Global angle, when the body to be moved is of higher mass, the the involvement of materials utilization is also high. For example, steel, aluminum, plastics et. all.

Now, for a mass that is low, the energy required to propel it is low; so also the materials required. This lower materials consumption has great significance.

We know that a ton of steel needs the mining and conversions of over 5 to 10 tons of materials (iron ores, dolomite, coal). The temperature of conversion involved is about 1800 deg C. We have a system where the huge amounts of energy and resultant pollutions created in these manufacturing activities have wrought great havoc to the environment. All these would reduce automatically, when the weight is reduced... the logic goes in this fashion!

And it is based on these scientific TRUTHS that we have now come to conclude: WEIGHT REDUCTION IS A MUST

But How? At what economics?

Instead of answering these and trying to bring overall efficiency in materials/ energy phenomena, the automobile manufactures seem to be creating "manufactured" demand for high weight, high "guzzlers" ... something Kenneth Galbraith had indicated in the 60's, about how markets for "un-necessary" things are made possible through playing to the baser sensibilities of the human psyche.

Be that as it may, this writer is not interested in these philosophical musings; but is very seriously working on the idea of "weight reduction"

But engineering themes and concepts are needed, to make it happen, so that the ultimate consumer NEEDS are not overlooked

But "weight reduction" has to be attempted for optimum materials/ energy/ comfort/ economics

Any "out-of-the-box" thinking?

"Be that as it may, this writer is not interested in these philosophical musings; but is very seriously working on the idea of "weight reduction""

That's a little myopic, don't you think?

So, what's the plan? Are we supposed to force automakers to our demands and make them use carbon fiber, titanium, aluminum foil, and reintroduce Yugos?

Are we going to force people to buy these cars because we are not interested in their philosophical musings and yearning for big cheap cars?

Oh, and are we going to force the people to pay higher prices for the use of exotic materials to trim weight? Won't that hurt the poor the most?

Okay, so I am a little cynical, but do really think that those things don't matter? It's like saying that I am not interested in the philosophical musings of acceleration in the equation F=ma, so the new formula is F=m, folks.

Am I wrong to conclude that this question you posed has only one right answer; that is weight reduction? We can think out of the box, but only if it is weight reduction.

Again, maybe I am being cynical, but my point is that it at least appears that this thread isn't very open to all the ingredients in the problem, only mass, and you only want to acknowledge responses that reinforce your point of view on it. Again, this is only a perception and may not be your real intent, so don't take this as a personal attack, please.

Hi pvhramani,

Not too long ago, I posted a few clarifications on the Automotive X Prize site re the equation you reference. That equation gives a force, namely the tractive force, required to move a car at a certain instant. Its terms are what you'd expect: rolling resistance (related to mass and tire construction), aerodynamic drag (related to shape, frontal area, and instantaneous velocity) acceleration (related, obviously to mass and acceleration) and grade (also dependent upon mass). In calculating fuel efficiency, we need to add a velocity factor (again) to get from force to power. And we need to account for how the power is produced and delivered -- another equation altogether. Although we often think of an ICE as having an efficiency of 25%, in use, these engines produce efficiencies from about 30% down to zero (when they are idling).

Clearly, mass has a significant effect, but it is not the primary factor in fuel efficiency. If it were, you'd expect to see 400 lb motorcycles getting extraordinarily high mpg figures -- but their figures (40 mpg for those snazzy looking "crotch rockets") are no better than some small sedans of 5-6 times the mass. One part of the reason is that motorcycle aerodynamics are atrocious, with even the faired racy looking ones having a Cd around .65. But another part of the problem is not addressed in the equation presented by John Shore (at AXP) at all. An ICE operates in a very wide wide range of specific fuel consumptions, burning from about .25 kg/kW/h on up to many times that as the load decreases. If the load is zero, then all of the fuel spent in idling the engine is entirely wasted. Motorcycles engines are very lightly loaded at ordinary road speeds.

So, actual fuel efficiency depends upon many factors, with weight, as you say, being a critical one. But weight is not the critical factor. In my own X Prize contender vehicle, 40 mph is the speed (on a level road) at which aero drag predominates over rolling resistance. (The real speed is actually lower -- I've overestimated rolling resistance in the interests of conservatism) At 80 mph, aero drag consumes 4 times the power consumed in overcoming rolling resistance.* But your point is well taken: start to climb a hill, and mass has a very large effect (of course, with regeneration, some of that energy is regained on the way back down, just as acceleration energy is regained in stopping.)

Good aero can be a "cheap" way of improving fuel efficiency. The Aptera is a good example of what can be done. If you dig far enough into their website, you will find that they get 120 mpg under steady state conditions with their plug-in hybrid (not the 330 they originally suggested, nor the 230 they got with a diesel in direct drive). That is a very good figure, and it owes its being largely to great aerodynamics, with a claimed Cd of .11 (which is probably correct, if they really did get 230 under diesel power). In general, good aero can result in less material usage than bad: smooth shapes have less surface area than boxy ones, and smaller cars have less frontal area than larger ones. So good aero can both reduce cost and mass. Dealing with mass alone, can offer increased costs: light strong materials are typically more expensive that heavier materials, with carbon fiber and titanium being extreme examples.

So, I agree that weight is a key issue, but every facet of automotive fuel efficiency deserves attention. My own vehicle and the Aptera are similarly efficient. Either one will do well as a commuter car. To nudge these vehicles over 100 mpg, however, has taken attention to every aspect of design: limiting the "mission," limiting payload, limiting size, limiting weight, improving aerodynamics, dramatically improving engine cycle efficiency, and devoting a lot of time to improving crash resistance, given the hazards of low mass.

But as engineers, what can we do, other than starting our own car companies? We have to influence the market as best we can. In the US, peoples' buying habits say "We honestly don't care. If we did, Priuses would outsell Ford F150's 6:1 rather than the inverse." I'd love to think the the Apteras and Pod Ones (my own vehicle) of the world will have an easy time in the market, but that is anything but assured. It is mainly a marketing issue, given competent engineering. As engineers, if we can help influence management to produce, and make an effort to sell, more efficient vehicles, we will have done a good thing for the planet. Unfortunately, doing so is a very very hard sell. Big heavy vehicles have a lot of profit. The few nutcase engineers out here who think they can sell small, highly-efficient vehicles are all on their own, starting their own companies.

Engineers, with an understanding of what can be accomplished must influence manufacturers and society to act more responsibly toward energy. Make the case for efficient products. Otherwise management and politicians will stick with the same high consumption/high profit mindset. In the US we use 8 times as much energy per capita as the average world wide, and twice as much per capita as is used in Europe. I've spent quite a lot of time in Europe, and cannot see that, in any way shape or form, we in the US are enjoying a higher standard of living because we consume more. If anything, the reverse appears true -- we are near the bottom in math and science education (no doubt, part of the problem re energy usage), and don't even provide universal health care (the norm in developed countries).

* You might think, at first glance, that the power should go up by a factor of 8: four because of V squaring, and twice again because of the velocity doubling the required power. But, in fact, rolling resistance, which remains fairly constant, also requires twice the power for twice the speed.

Hi Blink ... thank you for your experienced and serious presentation.

I am NOT a car manufacturer, nor am I a car designer. Further, I am also NOT interested in any competition, although I learnt certain FUNDAMENTAL scientific facts by visiting the Automobile X Prize site, which also happened after a forum discussion in Just-auto-dot com. My intention of studying the design/ performance/ efficiency aspects of an automobile is to see and arrive at PRACTICAL and GLOBAL methods by which the automobile could be made a more benign and more environment friendly vehicle to the majority of people in the world (not merely to the small groups in countries such as US or other highly "energy guzzling" nations). For example, in countries such as China and India, cars within about 75 to 80 bhp, and capable of comfortably seating 4/5 people would be accepted in large volumes if the average fuel consumption is about 35 to 42Km/ L (82 mpg to 100 mpg). There the price factor is of great importance. I expect the price level of such a Car to be in the range of less than $9, 000, to hit the market in a big way. Today the "best" cars in this range do NOT give a mileage of even 60 mpg. It should be noted that if such a car is brought out, the annual potential in a country like India alone for such a car would be in the range of 2.5 to 3 million per annum, in the next 5 to 7 years

Whether any one understands and accepts or not, the IC engine based (including CNG as fuel) car will not be outwitted for another decade and a half, although new hybrids would make much inroads. Thus, all my PRACTICAL attempts would be to work on that premise, and not on any "as yet untried/ untested" systems being forced down through marketing. But, as an engineer, I AM NOT pooh-poohing these latest technical "beauties". But to me they are only beauties now.

I wish to get DESIGN inputs so that in a practical way, the final design could be readied for prototyping, and later to reach the commercialization level.

In this, as a COMPOSITES development engineer, I have specialty LOW cost composites that would rival steel and even the so-called high strength Carbon fibers. My Composite cost would be (in molded form) not more than $7 or $8 per Kg. For example, a front bonnet molded in such a material, for the car defined above, would have a weight of about 6 Kg (including the stiffening frame work) and would not cost more than $45; and the product/ component would come out from mold, ready without any finishing needs.

To what extent you could give me inputs with your experience is what I am eager to know, and shall be happy and thankful to you for the great help.

What you think we as engineers should do?

We should stop buying/using unnecessarilly large/heavy/overpowered/unaerodynamic cars for day to day use.

Del

My favorite car was a little '79 Honda Civic. I think smaller cars are more practical for the most part. The larger cars tend to be more durable at higher speeds across rough roads. I think we should convince ourselves that going slower has a lot of merit.

Engineers, scientists, attorneys, accountants, doctors ... and the various other professionals have a code of conduct ... normally unwritten ... that we would all work for the common cause of the society without self aggrandizement. This writer wishes to think and act in that fashion, and ... may be certain words/ phrases used might have indicated different connotation to some.

At this moment, from a purely scientific angle, the "car equation" definitely indicates the TRUTH that weight is the single biggest factor in considering the energy needs of a vehicle. If this is NOT so, this writer IS prepared to change this stance. There is no DOGMATISM ... but it is purely science.

With that aspect being taken centrally, we need to work on the idea of "out-of-the-box" solution ... also taking into consideration some or all of the other societal and consumer preferences and needs. Further, although we do note that every car manufacturer is in fact vying with one another in developing and creating more and more "energy guzzlers", we engineers have not taken cognizance of the dichotomy: on the one side we need to do something to reduce GHG's; but on the other side there are marketing themes that conflict with this. It is this fact of dichotomy that becomes the opportunity for "out-of-the -box" thinking - something to be accepted by both "warring" groups!

This discussion was initiated on the theme: reduction of CO₂ and GHG in the atmosphere inflicted by automobiles, and as the basic "car equation" suggests a causal connection between energy needs and weight, that becomes the central theme.

Let us not be emotional or very personal. Instead, let us discuss if there are solutions to this central theme. Or, is the theme itself WRONG?

I will concur that mass is the most significant variable in other than steady state driving, but only because the base power process efficiencies of currently applied prime mover ICEs are so low, and the importance of this variable decreases as regenerative efficiencies increase. But reducing vehicle mass is hardly "thinking outside the box."

Consider a steady state operating velocity of 25 meters/sec for 1 hour on level terrain. Is mass still the most significant factor in energy use of the system? No, the aerodynamic cross-section and coefficient of drag is. Reduce the volume fraction required for your prime mover and you can reduce the overall volume of your vehicle, which in any design will translate to reduced aerodynamic cross-section as well as reducing your focus variable, body and prime mover mass; in short; use power averaging; and yes I understand that the volume and mass fractions are partially offset the required storage medium.

The gravitational and kinetic components of the total energy conversion equation become recoverable. The energy is recovered through the process of regenerative braking instead of being lost through conversion to heat and dissipated. In short, use regenerative braking.

There is but one mass dependent component of your equation which is not recoverable, that being road drag. The aerodynamic component is not directly mass dependent.

Now you can muddy the water with your reference to the mass of materials used in production, but I think you may find that modern composite materials are quite energy dense in production.

I don't believe it unreasonable to focus, for now, on the power process and aerodynamic design of the vehicle itself.

Gavilan

Yes Gavilan! Now we seem to be coming round to (perhaps) the first stage in moving toward an "out-of-the-box" solution! While mass is NOT the "be-all" and "end-all" here, it definitely is PRIME. Even in our analysis on "drag", the cross section/ volume do in fact finally pertain to mass/ weight.

In attempting to plan and organize new designs, we may first have to consider some parameters as being constant; and then work on the various other parameters. We may have to "go round and round" ... and then only may we arrive at a final optimum, commercially acceptable design (for both the enterprise as well as the consumers/ society).

Here, for example, let us talk of ONE initial POWER value as being constant. Then how do we go about? What should be the beginning? Also, we may note that our FIRST design may not have all the BEST set of end results... these may have to come over a period.

Could propose some starting point?

"our analysis on "drag", the cross section/ volume do in fact finally pertain to mass/ weight."

Really? What about a ship's sail? What has mass to do with drag?

There may be a loose correlation, but not a causation. So, I would disagree.

I do not like small cars, I have to carry a lot of stuff around and I like the extra feeling of safety. I buy cars with a good shape, eg low wind resistance, not like those boxy SUVs for example with the wind resistance of a house brick!!

My car weighs almost 2 tons, but has an economical diesel engine that gives me around 50MPG on a long run (UK Gallons).

Nothing is perfect and a better MPG than that would be best of course......

I also like the point that Diesel is nowhere near as easy to start burning as petrol is and rarely "EXPLODES"......in the event of a leak or an accident....it just smells terrible though!!

Hi Andy ... You seem very straight ... explaining what you like as a consumer. Now it is for all engineers to understand these needs and find answers. Of-course, any answer would have to consider our main thrust of the discussions: that of reducing CO₂ and GHG

So here we are:

1. Andy the consumer likes BIG cars ... and safety is his main need, apart from the need to carry loads.
2. He now gets 50 mpg British gallon (= about 60 mpg US)
3. He wants better mpg for better economics

Now come on "thinking" engineers, let's design an optimum Car that Andy needs

Hi all engineers! shall we set the mpg target for Andy as 80 mpg (US)?

What now?

D'uh?

Are we now designing everything in the world based on one nutter's () requirements?

I hardly think a sample size of one is statistically significant.....plenty of idiots don't want seatbelts...but they are a good thing and mandatory.

Maye there should be sensible legislation for various 'classes' of vehicle, to give maximum efficiency for each class...so Andy can still have a 'load carrier' ...and a nice efficient one...someone else can have their 'city car'.

And please don't anyone whinge about 'legislation'...it is already there in the form of lighting, emissions, seatbelts etc.....

Del

Hey Del! ... let's not be emotional. Andy's requirement may not be the universal need. But it still specifies some things which are normally NEEDED by most.

As engineers, we can THINK of any starting point for a DESIGN, which could be refined/ modified to arrive at "acceptable" optimization. Further, there are already in place a high level of data on "legislations" and parameters which need to be considered in designing appropriate cars. Andy's NEEDS are to be juxtaposed with those.

In this connection, please visit this site:

http://auto.xprize.org/

Although the details there are for a world wide competition, that would offer millions of dollars in prize money, the different parameters and legislative requirements have been delineated very well. The dead line is 2009.

But this writer is not looking at those prize money/ competition and all. Here we are talking about how we may reduce CO₂/ GHG emissions, and yet have both the manufacturer's and consumer's needs satisfied, at the mundane level.

In the light of these, what Andy suggested could definitely be a starting point ... not that we wouldn't have better "definitions". But this could be the starting point for engineering thoughts and actions

May be you could throw some TECHNICAL light on these, for further discussions. Taking up the challenge?

"Here we are talking about how we may reduce CO2/ GHG emissions."

Most people (if not all of us in some fashion) buy a vehicle on emotional needs. Andy's requirement is but one sample point, as mentioned before. You can take a poll of a large cross section and gather data, but the real factor that drives peoples' buying habits for vehicles is based on emotions.

They buy based on emotions and then justify their purchase with facts that they cherry pick to support their emotional argument.

This behavior is not limited to purchases of automobiles, but is pervasive in everything we do right down to the arguments we make.

This suggests that the real "out of the box" approach has more to do with changing culture paradigms and less to do with changing mass.

Point 2. above is completely and utterly wrong as a US gallon is much smaller than an Imperial gallon......!!! I would have expected anyone with "superior" knowledge to either know this automatically, or at least to have the intelligence to check the values out exactly before writing......

For the future, please memorize the following information so that you will not make such a simple mistake again:-

1 US Gallon = 3.785412 Liters

1 Imperial gallon = 4.546092 Liters

You seem very sarcastic in your manner, I cannot imagine why, so you should try and make sure that you get out of the bed on the right side each day in the future.....

If you had read with some deeper understanding, you would have noticed that I actually never wanted a "heavy" car, its just that the cars I need are heavy.....I have to carry some large and heavy objects several times a week and I need power to pull either a caravan or one of several trailers that I use......a mini won`t do it for me.....

I would be only too happy if it were possible to reduce the weight, without any significant loss of crash worthiness or towing qualities, but as the caravan I tow is nearly 1.5 metric Tons, and the German law is adamant about the weight of the tow car versus the weight of the trailer, a lighter car would not help me much.....I am sure the laws are laxer in this respect in many parts of the world, but I like to be as law abiding as possible, I live here!

You show also little thought to the problems of accidents, when a big heavy (old) car hits a modern light car, usually the light car suffers the most. We cannot expect that suddenly all heavy cars are taken out of usage though, and we would still have trucks anyway if we did......

It is a big problem.

I personally see the 6 stroke engine, in a Diesel format as being the engine of the next generation, but development is too slow at the moment. Once achieved, this would result in a significant reduction of weight with regards to both the engine and its ancillaries and some significant improvements in fuel economy. Something to look forward to in the future.

Of course car body weight must be reduced and I hope that this can be performed in a slow and careful manner....at the same time a further reduction in fuel usage which would significantly benefit all mankind.

India is a country where modern cars are not seen as often as one would hope, for the reasons already mentioned. Many are British built cars (so I am informed) of the 50s and 60s still without the slightest regard to accident safety for the occupants or the pedestrians....seat belt law is often ignored and people are killed daily because of that point alone, though 50s cars, did not always have mounting points either....

There is an area where your energies could be put to a good use in raising the levels of education for all Indian people, not just those with a caste and the money which allows it. India is a wonderful county and I have had many good friends from there, but it has not been improved much since it got its freedom from Britain in 1948 and many say, it has actually only got worse. The division between the haves and have nots is not getting any smaller, why not?

I think therefore that you should cast your eyes closer to home and get some of the inherent problems that India has fixed before aiming your sarcastic guns at people in other countries......or were you trying to make a joke out of it??? Did I somehow "miss the point"? A joke (if that is what it was) not maybe your strong point!

I think in the future you should radically think about reducing your sarcasm to the level of your knowledge in the matter concerned, which in this case appears to be very elemental indeed......

I wish you a Good day sir.

I think a good place to start is with the passenger compartment and ergo-metric design of the controls/ safety etc. A ICE/electric design allows the elimination of drive train including the transmission if the process uses wheel hub integral motor/regenerators. This means that the prime mover can be placed so as to optimize center of gravity. In short, the vehicle can be designed "around" the passengers.

It is very important that we consider the aerodynamic cross-section and coefficient of drag when designing the body. Given the operating velocities and the square relationship of drag to velocity this will be a primary factor.

A quick scan of the AXP website did not give the grade, grade length (or maximum delta elevation), or sustained grading velocity. Without these known performance variables it would be difficult to use Pyhramani's sum force equation to begin to estimate storage and prime mover requirements.

Because aerodynamic drag will be such a significant factor, we need to decide what our maximum cruising velocity will be. Without that, we can not calculate the most significant drag component.

In the real world, stop and go driving is the norm and would greatly benefit from regenerative capability and power averaging. Proper quantification of the drive motors and storage device when combined with a good Loading Control Program should allow for very high performance acceleration while maintaining storage capacity for regenerated energy.

We will not impact emissions if the design of the vehicle is unacceptable to the consumer. Make it Safe, Fuel Efficient, and High Performance. With a properly designed hybrid process, non of these things need be self exclusive.

Gavilan

I fundamentally agree with the weight shedding...

How many cars still have cast iron blocks?..madness.

Weight shedding is a self justifying process...the more you shed ...the more you can take off...a lighter car doesn't need such heavy suspension, stiff chassis etc....

These road cars with huge wide wheels and tyres are a nonsense, they increase rolling resistance,drag, unsprung weight ...they are a mere fashion statement unless you are trying to corner too fast or going off road.

There is my design input gratis...

Del

Well put as usual....thanks.

You were not alone either.....some other good posts too....

I wonder how the Indian "Chappie" would have reacted if I had told him that I drove a lorry and not a car, because I need the weight/load carrying possibilities, he would have probably died of heart failure on the spot!!

Or coming from India, he might have thought that it was a better idea.....who knows?

Hi all

1. First of all I wish to unconditionally apologize to Andy if he felt there were any "sarcasm" (as he felt) in the expressions made

2. To me what he has expressed is still a PERFECT example to start with, in terms of NEED for weight reduction

3. Yes! here is another terrible mistake I did make, and again I unconditionally apologize. .. that concerned with mpg. in fact my typing got reversed ... Instead of 50 mpg (British) it should have been US, and vice versa for the other

Now all these DO NOT obliterate our original discussion theme of "weight reduction in automobiles to reduce CO₂/ GHG"

Again, coming back to the said car (a big SUV) is the starting point (even if it be only a "concept" one), the 2000 Kgs is the first thing to look at. On the basis of works which I am personally doing in specialty COMPOSITES (not Carbon Fiber/ Boron Fiber and other high cost ones), it is possible to reduce as much as 750 to 800 Kg from the original 2000 Kgs - the final weight being about 1200 Kg (Note: Unlike the high cost Carbon fiber materials, which may cost anything above $80 per kg of component part, these new composites are expected to cost not more than $6 to 8 per Kg of finished component)

Add to this the excellent technical inputs by Gavilan ... we should have a STARTING point to continue our technological discussions on: "Weight reduction in automobiles to Reduce CO₂/ GHG"

Post Script: Let us not become emotional and very personal. Bringing in ethnicities of individuals and taunting are not in the ethos of scientists and engineers. All of us are bound to make some mistakes (inadvertent) often. But we all work on principles of science, which are universal. The "laws" of Gravity and Thermodynamics, for example, do not respect ethnicities and national boundaries ... they work universally

"Man masters nature not by force but by understanding; this is why science succeeded where magic failed; because it has looked for no spell to cast over nature" ... Dr J Bronowsky in "Science and Human Values" - Penguin

I enjoy imagining a aerodynamic slick single piece solid under-body. The under-body is often neglected when considering the aerodynamics of an auto.

I wonder if recycled plastic could be reinforced using some type of cord? Like recycled tire cord or something. I wonder how the strength to weight ratio would compare to that of steel?

Can somebody tell me how that is measured?

The under-body could be molded with mounting blocks for mounting the primary prime mover and drive components. The primary components are mounted and then another single molded piece, the passenger compartment, is then set onto the under-body and finished with control and seating components. Using fly by wire technology to eliminate as much of the mechanical linkage components as possible. Then the outer body shell is set over the passenger compartment and fastened to the under-body. Three molds for three pieces.

Access panels could be used for general maintenance and access to control components; bringing the vehicle into a garage and reversing the process to access major components for replacement. Pull the component connection plugs and lift the passenger and outer shell off the under-body to access the major drive and suspension components.

The car I want will have a prime mover that operates at a near constant output feeding a primary averaging storage unit. The control circuits will feed power from the primary storage unit to the three or four independent tractive controlled wheel hub integral motors. When I brake the integral motors will regenerate; feeding power either back into the primary averaging storage unit or an auxiliary tempcap for the next acceleration. Thats when I'm just cruising round town regular like.

But when I want to git, I can just dump everything I got from the averaging storage unit, tempcap, and prime mover output into the drive motors. At ought to give me a little kick up in speed fer a bit, or to make the hill anyway. If I just dump it all into the motors I'll git like a lit cat fer a bit then fall back to where my max prime mover power balances against grade and drag. Yup pilgrims, thats a what I want.

Is there anyway you engineers can git something like that in the showrooms so when I finally get my neadermobile paid off I can buy me a real automobile? I mean, don't get me wrong, the gee whiz gizmos in my neadermobile look really cool but dang, the basic concepts of the power process ain't much different than what Mr. Ford was putting out for my granddaddy; and I'm neert 60.

Its fun to think about the possibilities.

Gavilan

Hi Gavilan

You have good knowledge and experience in science/ engineering of the propulsion and related fields

To begin with, we need to DEFINE our CAR parameters.

I still feel, although Andy felt a bit annoyed and emotional, his idea could be a beginning ... may be with some modifications. And, I had indicated that if the Original car weight is 2000 Kg (even if it is a "heavy duty SUV), we could definitely reduce the weight to 1, 200 to 1, 250 Kg.

Your idea: The under-body could be molded with mounting blocks for mounting the primary prime mover and drive components. The primary components are mounted and then another single molded piece, the passenger compartment, is then set onto the under-body and finished with control and seating components. Using fly by wire technology to eliminate as much of the mechanical linkage components as possible. Then the outer body shell is set over the passenger compartment and fastened to the under-body. Three molds for three pieces. ... is great, but would need some analysis and definite conclusions, after arriving at the END Parameters

What are the other DEFINITE PARAMETERS to be defined?

Hi all!

There seems to be a sudden lull in the discussion.

In this it will be attempted to present certain definite FACTS:

1. The CAR Equation:

We did talk about the Car equation earlier:

F = mgC_rr + ½ρC_DAv² + ma + mgsin(θ)

Explanation:

F = force required at the wheels of the vehicle
m = mass of the vehicle
C_rr = coefficient of rolling resistance between tires and road surface
ρ = density of the ambient air
C_D = coefficient of drag of the vehicle in the direction of travel
A = cross-sectional area of the vehicle
v = speed in the direction of travel
a = acceleration of the vehicle
g = local acceleration of gravity
θ = angle (relative to horizontal) of the road surface

For over three decades the main thrust on increasing fuel efficiency has been through attempts to improve the drive train system. For the last decade and a half there is much work going on to look at different energy systems instead of the IC engine. Of late there has been innovations through "capturing" back the kinetic energy lost while breaking; and now electric hybrids are examples.

The basic Car equation is the mathematical expression of how the propulsion force is balanced by the Car as a system. It is clear that of the four force-systems that are to be overcome by the propulsion force, three are directly dependent on the MASS (weight) of the car. And, although the aerodynamic Drag force component does not directly show the involvement of weight, it is clear that this "drag" is dependent on the surface area, 'A' that "pushes" against the "wind effect" responsible for drag. And further, although the car velocity (which is under "driver control") influences drag, it is obvious that a reduction in 'A' would automatically reduce this drag and hence the weight.

It is, thus, evident that weight is the main factor in the CAR equation.

2. Other factors:

Of prime concern is the safety factor - not only that of the inmates in the car but those outside. Thus, when we talk of weight reduction, it would have to be done against this trade-off. This is so on the basis of present day technologies available for safety. However, if we could develop new safety engineering methods, to be effective even at very low weight levels, weight reductions could be pushed to the limit - which would be the most optimum for fuel efficiency, and incidentally to reduce CO₂/ GHG.

Reducing rolling resistance cannot be at the expense of "grip"; and aerodynamic efficiency cannot be at the expense of carrying capacity, passenger convenience and on some "ugly" looks

Having said this much, we now need to arrive at a "practical" DEFINITION of our CAR. This could be based on either an existing car or based on a new Design. This writer feels that it would be better for us to consider an exiting car as the standard. As already noted earlier, this writer is wishing to take up the Challenge of converting even a 2, 000 Kg level Heavy Duty SUV into a 1, 200 Kg vehicle.

Could any one suggest a Practical beginning please?

see #21.

Aluminium block with the most weight efficient cylinder number/arrangement.

Actually research the optimum wheel size...not just the biggest, chosen for show.

Improve the aerodynamics.

Have tyres that can run flat to save on the spare.

Remove the driver.

Del

Hi Del

Interesting and "thinkable" suggestions. But to what extent "remove the driver" could work in city conditions is doubtful...May be we could have a modular system that helps change from "driven car" to "driver-less" car ... for highways.

yes! Engine weight needs to be reduced. A magnesium/ aluminum alloy would be an optimum choice for the present, and magnesium is becoming a bit cheaper than before

Aerodynamic improvement is a MUST, but not at expense of passenger convenience (already stated) and being ugly (already stated)

I am not able to understand "running on flat tires" ... But definitely we NEED to redesign Tire systems and also the Size of the tire

Now the question is: How do we define all these as an operative definition for engineering?

"running on flat tires" ...

Tyres..obviously inflated in normal use...but if you get a puncture they should be able to get you home when flat...this would avoid carrying a heavy spare wheel.

Hi Del! Understood...

I confused the idea as a "new design for cars to run on flat tires!"

However, we may also think of total redesign of the "good old" tire ... may be ... using some of the new Polymer/ Elastomer materials

As far as the Structure and body are concerned, I look at "unitized" molded systems in Composites - not the Carbon fiber system off-course (already indicated earlier), and something in the manner proposed by Gavilan

We now need to "operationalize" these into a systematic DESIGN theme, with the various variables and other parameters that impact on the end performances.

I am not well versed in such a CAR design... Any one to HELP please?

1. The CAR Equation:

We did talk about the Car equation earlier:

F = mgC_rr + ½ρC_DAv² + ma + mgsin(θ)

Explanation:

F = force required at the wheels of the vehicle
m = mass of the vehicle
C_rr = coefficient of rolling resistance between tires and road surface
ρ = density of the ambient air
C_D = coefficient of drag of the vehicle in the direction of travel
A = cross-sectional area of the vehicle
v = speed in the direction of travel
a = acceleration of the vehicle
g = local acceleration of gravity
θ = angle (relative to horizontal) of the road surface

First component = road drag force.

Second component = aerodynamic drag force. Please note the square relationship between velocity and drag force.

Third component = vehicle kinetic accelerating force.

Fourth component = grade force.

So now take your instantaneous sum force and multiply it times the velocity. You now have the instantaneous power requirements.

The 55 mph sustained velocity on 7.5 percent grade is probably going to be the limiting requirement of the AXP. I could do this with a hybrid system through a limited change in gravitational potential and meet the other parameters, but not if my prime mover must produce continuous sustained power at that rate. The change in gravitational potential (the total height of the grade) needs a reasonable limit before I could go any further.

Gavilan

Sorry, this is a late reply but I just cam across this post.

When did CO2 become a green house gas??? Now, I'm no environmental scientist but I thought CO2 was needed for our precious plants. Not to mention, CO2 is what we spew out when we go on and on about topics like this.

Sorry, if you couldn't tell, I'm one of the skeptics. I think it's a valid argument but I just wish everyone would look at the facts and state them correctly.

Hello Guest!

Very RIGHT indeed, when you say CO2 is needed for our precious plants! This writer would appreciate your reading the first presentation, wherein it is mentioned:

"the heating of the atmosphere has to be understood as increasing not only due to these GHG's but also due to the spewing of a great amount of heat by IC engines and other heat engine sources"

The important matters here are:

(i) About 80+ % of the original heat input inside any IC engine is lost during the course of the energy-transfer from the initial burning of the fuel till the propulsion enregy turns the wheels

(ii) CO2, NO2, SO2, CO and various other gases and many other noxious particles are spewed through the exhaust gases/ matter ... all of which are in some way very dangerous to us (let us not go deeper into this subject, for that forms a different science altogether, including your idea on NEED for CO2, which this writer too subscribes)

(iii) The "car equation": F = mgC_rr + ½ρC_DAv² + ma + mgsin(θ)

http://cr4.globalspec.com/comment/148443/Re-Weight-reduction-in-automobiles-to-reduce-CO2-GHG

... is our most useful "tool" in studying and arriving at appropriate designs for improving the Car performance.

It is not known why a very serious discussion that was brought forward so that engineers and scientists could discuss on the practical way we could answer the original "questions/ queries" suddenly "stopped"... and there seems to no takers for the Engineering CHALLENGES involved.

Pvhramani,

Fair enough, but I have 2 more cents to add... I agree with you in regards to CO, NO2, etc. but I believe that CO2 is as harmful and/or benificial as O2.

Now, in regards to the inefficiecy of the automobile, I couldn't agree more. I am involved in a couple projects that should result in a bit more efficiency but nothing to get too excited about. I've been involved as a consultant on a few automotive projects with small private companies. I will say this, I think there is hope, a lot of small steps in the right direction.

Hi Guest

It is interesting and nice to note that you are involved in improving the efficiency of the present day automobile.

It is suggested that you may carefully study the threads in a different discussion (yet closely related to this subject here):

http://cr4.globalspec.com/thread/14733/The-2008-Green-Car-Awards

... and here is one specific discussion in the same subject line:

http://cr4.globalspec.com/comment/152542/Re-The-2008-Green-Car-Awards

This writer is disappointed that all discussions stopped after the last thread presentation. Perhaps you could offer something through your experience and knowledge

Best wishes

pvhramani

I'm really not at liberty to discuss the projects as I don't want to tip toe around what I can and can't say. I have sent some emails to the companies to ask them to chime in.

I have pasted a couple links below about an (intended) zero emissions Mini. This Mini uses electric hub motors for power. This is not a project that I was involved with but this little Mini is what got everyone thinking.

This Mini uses four motor, one for each wheel. With a little reduction in weight the vehicle does not necessarily need all four motors. That combined with some different theories on the method of charging batteries makes for some promising possibilities.

http://www.treehugger.com/files/2006/08/the_hybrid_mini.php

http://www.pmlflightlink.com/archive/news_mini.html

And another thing...

I skimmed over the posting you referred to, the one with the picture of the heavy congestion in one Indian city. In my opinion the photo is definitely "Photo shopped". Someone added a lot of black smoke to the air above the vehicles. I can't take anything seriously that refers to a fake picture.

Hello

First of all, it is wished to thank the Guest for the useful information provided through the "link", presented in a previous thread.

Please note that the the photo presented is NOT fake. In fact, if you have any American/ European friends who have traveled to India (visiting and trying to drive in cities such as Bangalore, Kolkatta, Chennai ...), they would tell you that what you see in the picture is only "small smog", which are usually far more!!!

This writer is pained to note that there always seems to be a certain amount of "skepticism" about the veracity of materials provided by many of us in the EAST, and many of us ARE forced to go extra length to prove that we mean and tell FACTS only.

The ignorance of the western world about the extreme conditions in the POOR nations of the East is frustrating, especially when observing that very highly learned people seem to have absolutely no idea about the wretched conditions in which men and women in the East and South East Asian countries live ... and many of them just pass "off-hand" comments, ignoring what psychological effects such things inflict on men and women of Honesty, sincerity and dedication!!!

PS: It is hoped that this "GUEST" would try to read through the data presented about this writer in Member profile:

http://cr4.globalspec.com/member?u=11231

... and try to observe the serious and sincere works being undertaken by the writer (aged about 60 now) for over 36 years! It is also hoped and wished that such "GUEST" would not pass off-hand comments, ignoring etiquette and general decency.

Best wishes

pvhramani

I do have to plead ignorance when it comes to driving in Indian cities as I've never been. However, knowing my way around Photoshop I still would guess that photo to be altered. I would have no problem admitting to be wrong if it is a real photo but I would need to see the source. I'm not at all trying to suggest that polution isn't bad there. I've seen photos and I've grown up around Los Angeles smog. I'm just having trouble taking that picture on face value, no offense intended.

I think skepticism is necessary in our (engineering/scientific) world. If it wasn't for a little skepticism we would still think the Earth is flat.

I don't mean to take this thread off topic. I think the need for reduced emmisions and/or more efficient vehicles are very necessary and more people should be talking about it and working on it.

Hello Guest

Your point on "source" of the photo is well taken. The photo is a scan copy of a "clipping" sent to the writer by a friend (Original News Paper: THE HINDU - published in India;of Dec 10, 2007). Perhaps the "compression" brought about in the CR4 system might have slightly distorted the original. Please see this:

http://www.adrive.com/public/39e496e84f0b0cd953a4b504ff927413a8beb208e2e3ea3975434844835a468a.html

You would get a better and clearer illustration

Best wishes

pvhramani

When did CO2 become a green house gas???

Billions of years ago, I suppose. Joseph Fourier is credited with formulating the atmospheric greenhouse* concept in 1824. Svante Arrnhenius is credited with quantifying the greenhouse effect of CO2 in the atmosphere in 1896. CO2 was well-recognized as a greenhouse gas when I was in grade school in the 1950's.

I don't think the original poster is misstating the facts by suggesting that CO2 is a greenhouse gas.

* Of course glass greenhouses do not operate on the effect we call the greenhouse effect when discussing the atmosphere.

First off, we need to REDUCE the amount of automobiles in our world cities, not increase the numbers. The low overall efficiency of our transportation technology is as much a factor of gridlock than low Carnot Efficiency.

Second, to enhance overall efficiency does not require re-inventing the technology; we could make significant impact just by sequencing the traffic lights. Our view of the problem must widen beyond the beauty of the elegant to the drab but important obvious.

We need to develop mass transit or people moving technologies and re-engineer our societies by reducing the socio-economic demands that drive us away from our homes and family and into the streets of overcrowded cities.

Pvhramani is very well versed in the energy use by the industrialized nations in comparison to the under-industrialized nations. I believe that comparison would be more fair if contribution to Gross World Product was factored into the metrics.

There will always be an intrinsic relationship between economics, politics, science, and engineering. The problems that we face as a species may be more closely related to our nature than our technology; more specifically, our inability to recognize and mitigate the misdirection of our technology brought about because of our collective human nature.

Until all of our children begin to value the health of their planet more than the status related to their personal transport methods the spiral into gridlock and environmental degradation will continue. The problem may be more a socio-engineering problem than a techno-engineering problem.

Gavilan

In the late 1970's I proposed the following.

Laying cable just below the surface of the roadway that could be accessed by automobiles through the process of induction instead of direct contact.

Tonight, rethinking the possibilities, I would add a storage device so that the automobile could be driven off grid and a onboard meter to bill the operator. I would use the 50 or 60 Hz cycle commercial power grid as the power source.

I would also take emag and turbine propulsion off the rails and out of the sky and put it in evacuated tubes; replacing most air travel with this technology. Under evacuated conditions the potential speeds would dwarf that of a modern airliner. New materials science has me rethinking the possibility of neutrally buoyant tubes, suspended at optimum depths to cross large bodies of water.

Gavilan