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sd
Utah
Doctorate in Mechanical Engineering, entreprenuer
Interests: diesel and gasoline engines, cars, aircraft, railroads, electric drives
Recent Activity
Arnold. The Ackermann steering mechanism is a very useful approximation but it is an approximation and is only correct straight ahead and at one steer angle. It gets even more complicated when you consider individual slip angles for the different tires at different cornering loads. If you had individual servo driven wheel steering, you could do a much better job of having a correct solution for different steer angles and for different driving conditions. We build a agricultural harvester and I did the steering design. It has Ackermann steering but it is steer by wire and has 2 hydraulic cylinders but only one sensor. If we added a second sensor, removed the connecting tie rod, and added some more software, we could potentially have a better steering solution. However in our case, in probably will not make a lot of difference as the steering or Ackermann is optimized for the max steering angle. The machine is usually either going straight or making a minimum radius turn at the end of the field. At some point, I would still like to experiment with individual wheel steer. Individual wheel steer would probably make the most difference for high performance or racing vehicles.
I think that the ultimate solution is to have individual motors that can be driven at different torque levels. It would also be best to have individual steering drives so that the wheels can steer independently. The commonly used Ackermann steering mechanism ( http://en.wikipedia.org/wiki/Ackermann_steering_geometry ) is only correct straight ahead and at one radius.
I do not think that an Sonic based EV will compete with the Tesla Model S but it may help to push along EV market if they can keep the price reasonable. I also wish both GM and Tesla well in their EV endeavors and I would agree with Davemart that GM might do better by basing their new EV on a larger platform. However, I do wonder about the long term viability of Tesla. I know that this is heresy among some of the reader of Green Car Congress but currently Tesla's market cap (shares outstanding * share price) is about half that of GM which is not realistic and they are not currently making money so they are funding their continued development and production by selling stock. This is not unusual with startup companies but it can only gone on so long.
Henrik, I think that I can explain why the S60D and S85D out accelerate the S60 and S85. If you have sufficient power to induce wheel spin, you can launch faster with AWD. After the initial launch power when you no longer have enough power to spin the wheels, power to weight is more important.
Slightly off subject but I was surprised not to see an article on this Green Car Congress. Apparently GM has announced that they will have a new electric vehicle. This is from an article in today's NY Times "According to a report by Automotive News, the car — which is expected to appear in 2017 — would be based upon the Chevrolet Sonic and have a range of about 200 miles." Obviously not a competitor for Tesla but it will probably be more affordable for more people.
electric-car-insider.com If you lived where it snows a lot and there are mountains, you might want AWD. I live in Utah and would have a hard time without AWD or 4WD. I have had to chain up all 4 and use low range but admittedly that was for driving on unpaved roads in inclement weather. Anyway, AWD drive would make the Tesla much more attractive here.
What are they using for fuel? The article refers to 320 hp in our petrol (gasoline) configuration but does not state what fuel is used for the 450 hp version. About the highest specific power of any commercially available vehicle is the GM 2 liter turbo with 272 hp. You can get more power with more boost but you will also have to run a different fuel to avoid detonation.
Roger Pham Thanks for the link. I now have a much better understanding of the process. They are using hydraulics to drive a multi-stage piston compressor with a layer of ionic fluid to insulate the piston from the H2.
It is good that they now have direct injection although they seem to be lagging GM and Ford in providing SIDI. What I do not understand is using a CVT. It may be continuously variable and while it will let the engine run at a more efficient point than simple 4-speed transmission, it is also continuously slipping and therefore continuously wearing and continuously wasting power. So while the engine is more efficient, the transmission is not. It would be much better to run a 6-, 7- or 8- speed dual clutch transmission which are both more responsive and more efficient. Also, if you do not think that a CVT transmission in continuously slipping, you need to brush up on your physics and engineering understanding of traction type devices.
I would like to find some more information on ionic fluid compressors but a quick search on the web turned up not much more than was in the above article. I am assuming that the ionic fluid is contained in a cylinder and moved by an electric field? Also, what else can be compressed other than hydrogen? One source suggested natural gas. Probably not air? I would like to see even a simple schematic of this device.
Davemart Do not confuse HarveyD with science or engineering.
Hey John! Did you know that there is a wind turbine accident about every other day with a blade failure, outright tower failure or a major fire about every week now. Some of the blade failures have resulted in blade parts being throw more than a mile. http://www.caithnesswindfarms.co.u/AccidentStatistics.htm I would far rather live near a nuclear power plant than a wind farm.
Lad, If you were mayor, it would be smart to have your emergency responders well trained but you would have not authority to conduct inspections as that is the FRA (Federal Railroad Administration) jurisdiction. The Bakken crude is so called light, sweet crude which is the more desired crude and while it is more flammable than heavier crudes, it is not as flammable or dangerous as other materials being transported. Every few days, we have a unit train (~100 cars) of sulfuric acid go thru town. Also, gasoline, propane, chlorine, ethanol, and ammonium nitrate are all transported by truck and train. The really dangerous material in my opinion is LNG. Sooner or later we will have a major accident with a large LNG tanker but hopefully not in the US. I did the math on this once and the largest ocean going tankers have about a mega-ton TNT equivalent energy potential. Hiroshima was less than 20 kilo tons so these tankers have about 50 times more energy potential.
I should add that fuel cell research has been going on since 1838 and we still do not have practical fuel cell vehicles.
I expect that Lithium-Sulfide will be the next breakthru in battery technology. There are a number of people working on the problems and they seem to be making good progress. It is also good to see a major automotive company seriously working with Li-Sulfide. Lithium-Air might render the IC engine to dustbin of history but that is an much harder problem. I agree with SJC and Treehugger on most people not understanding how much time and effort it takes to get a new technology to market. I remember attending a seminar 45 years ago when I was a ME graduate student at MIT. The speaker had a new magnetorheological fluid and demonstrated some of the properties but stated that he had no idea what it could be used for. At the time it was just a laboratory curiosity. It took 30 years or so but now some of the Cadillacs and Corvettes have tunable magnetorheological shock absorbers along with a host of other applications. LED's have been around since 1962 but only in the past few years have they made major inroads in lighting.
Roger Pham I work as an engineer and am also a principal of a small company that builds a relatively high tech agricultural harvester. We use a hydrostatic transmission which is what you are describing for the wheel drives. Electric would be more efficient but a relatively small amount of the total power is used for traction. We also use some hydraulic motors and cylinders for other functions such as conveyor drives and lifts but where we are different is that all of the high speed positioning is done with 375 V electric servo motors. The use of the electric drives gives us a substantial efficiency and maintenance advantage over our competitors. As we go forward, we will be electrifying more of the functions and may add ultracaps to recover some of the available power from deceleration.
Engineer-Poet Your are right in that power is pressure * flow rate and with a variable displacement motor, it is possible to reduce power without throttling losses by changing the flow rate. You do need a variable speed transmission as the pressure gives you torque and the displacement gives you rotational speed. No matter what you do, you will have a less efficient system with hydraulics than you would with electric. However, the hydraulics may have a lower initial cost but would probably require more maintenance.
Would this work? Yes, but. I tried make some reasonable (maybe even generous) estimates and then do some calculations. If you do like my estimates put your own in but no fair ignoring physics. I assume that is a hydraulic accumulator type hybrid but it does not really matter. Anyway, energy is change in Press * Volume. I assumed that change in pressure is about 2000 PSI or 14,000,000 Pa (Newtons/m**2) and the tank volume is 50 liter or 0.050 m**3. Multiplying the two, yields 700,000 Nm or 700,000 Joules. Remembering that a watt sec is a Joule, so a watt hour is 3600 J and a kilowatt hour is 3,600,000 Joules. Anyway, with my assumptions (which may even be generous), you end up with about 0.2 kilowatt hour equivalent. OK, so this would work if you were doing most stop and go but you are not going to get far on just the stored energy. One other fly in the ointment and that is efficiency. With electric power, you can chop the current or use pulse width modulation to control the power. Full on for a few micro seconds and then full off for a few micro seconds. You can not do this with hydraulics. You have to throttle the flow. Even if the system was 90% efficient at full power (which I doubt), it would only be 45% efficient at half power. And we have not even worried about the heat that is lost if we do not immediately use the power. Anyway, this might work OK for mail delivery or trash collection where you start and stop every 50 meters but, even then, my money would be on electric power with ultra caps. This is also how John Deere and Caterpillar bet with their hybrid excavators. Bottom line -- I do not think that this is break-thru technology.
The US Tier 4 Final and the Euro 6 compliant engines are quite clean. In some places, the exhaust make actually be cleaner than the intake air. The real problem is the older engines especially the engines that predate common rail electronic injection. Also, until recently, the EU standards were more lax than the US standards.
HarveyD According to the CIA, the estimated 2014 birthrate in Canada is 1.59/woman. https://www.cia.gov/library/publications/the-world-factbook/rankorder/2127rank.html This is well below replacement which needs to be about 2.2 - 2.3 to account for those that die before reproducing. The US is about 2.01 which is still below replacement. Even Mexico is down to 2.29. Most of the countries with really high birthrates are in Africa and the Middle East. Even India is down to 2.51. Anyway, I will stick with my PC suggestion for more education for women. War is so messy. I could suggest getting rid of religion but that is probably not PC. On your other comment, the US is not likely to have high speed rail any time soon except on the coasts as the population density and the distances traveled will not support it.
HarveyD I more Politically Correct (PC) approach would be to support women's education. With education, the population growth rate would fall, the demand for resources would fall in the long term and we might even have fewer wars.
Not sure what this has to do with sustainable mobility but it is interesting. I suppose if I had mounted on my truck, I could eliminate those old smoking vehicles that cross my path. I actually worked briefly on a predecessor to this vehicle almost 45 years ago. It was a tracked vehicle designed to destroy aircraft with a lot power for the laser but the technology was not well enough developed for it to be practical.
There is an interesting commentary in the current New York Times concerning a test drive of a VW Diesel Golf. "But no crossover, and no hybrid for that matter, can do what I managed in the new diesel-power Golf TDI: 60.6 miles per gallon over 75 highway miles along the Jersey Shore. That’s my personal highway m.p.g. record for any American-market car I’ve tested, including the Toyota Prius." "In stark contrast to a Prius, a car in which I feel my life force oozing away with every mile, the VW isn’t a sluggish chore to drive."
I have no idea if Lux knows what they are talking about or not. I have not taken a Tesla Model S out for a test drive It looks like a nice vehicle but is not what I currently need. I do hope that Tesla makes it in the market place but I would not buy their stock as there is no way that their current market capitalization of $35.4B (number of outstanding shares * share price) makes sense when Ford has a maket cap of $68.3B and GM is $55.8B. Tesla as a company is just not worth half of Ford or 5/8s of GM despite what you might think of Ford or GM. By the way, I am not an anti-EV troll and worked on an Electric Vehicle as far back as 1968 when I was a grad student at MIT.
HarveyD I wish you were correct and it was so easy. However, the largest on-shore wind turbines, I could find were 3.2 MW from GE and 3.3 MW from Vestas. There are limits to how large a blade can be and still be transported and how large the diameter of the tower can be and still be transported. Vestas has built a 8 MW off-shore wind turbine and that apparently is the largest to date. Most commonly, the on-shore wind turbines that are presently being installed are about 1.5 MW. These numbers are the rated power and for on-shore wind farms, you are doing very well to average 20% of the rated power. So if you take 1000 MW for a new nuclear plant and 2.5 MW for a very large on-shore wind turbine and then take the average output to be 20% of that or 0.5 MW, it will take 2000 of these wind turbines to equal the power of the nuclear plant and I think that I am being generous with the numbers. I would like to see a verifiable reference for wind turbine power being produced at 2.0 cents to 2.5 cents per kWh As I said in a previous post, about a month ago I flew in a private plane from Utah to Wisconsin and back. We flew low enough so that it was easy to see the wind turbines on the ground in Wyoming, north western Nebraska, and southern South Dakota and Minnesota. Almost none of the turbines were rotating and I think I could have counted the turbines producing power on my fingers.