OT: Tesla Road Test

If you're completely cycling the battery on every hill, it's not going to last very long.

I walk on a treadmill and drive a V8 pickup for the rest. Gas is cheap.

I get half that, depending on where I buy gas. Gas is cheap.

Of course, like every other communist, you lie.

The Saudis see to that. When they're not busy engaging in their favorite side hobby of smashing aircraft into skyscrapers

You really _are_ as stupid as you sound. Snowflakes are.

On Tuesday, June 27, 2017 at 9:51:14 AM UTC-7, snipped-for-privacy@yahoo.com wrote: ..

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In the BMW i3 500lbs of the weight is the battery. The chassis is aluminum and the body is carbon fiber. It doesn't have power seats and a few other things to save weight.

A lot of the weight in modern vehicles is required to provide occupant prot ection - the difference between vehicles of just a few years ago to now is significant in terms of the probability of being seriously or fatally inju red.

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The motor weighs about 50kg - that could be shrunk although with a single s peed transmission you still need the motor torque to provide starting accel eration and hill-climbing. Providing that torque without limiting the top speed puts a constraint on how light the motor can be. Some of the weight reduction in electric motors for EVs has been by designing the motors to to lerate higher RPMs - the Tesla motors are designed for 15,000RPM max, those in the current generation of the Prius are designed for 17,000 RPM.

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Yes that impressive - but we'll see if it becomes practical - diesel is not in favor currently because of noxious emissions.

Partly, although the aerodynamics don't have a large factor in the EPA test and its weight is less than the Prius (3,000lbs) or any other plug-in hybr id such as the Volt (3,800 lbs).

A significant cause of the inefficiency is the fact that it is a series hyb rid with a ~20% loss in power transmission from the engine to the wheels (s tate of the art inverter/motor efficiency is about 90%).

ine that is 250% larger gets in the high 50's.

I record all my fuel-ups and my average over 3,500 miles is 54.5mpg. My no rmal local trip mileage is about 58mpg but the average was reduced by a 130

0 mile trip to Oregon with sustained high speeds (~75mph). For that trip t he average was 51.5mpg. My Mazda3 on a similar trip achieved 39mpg.

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The Tesla Model S and Prius are the best cars on the market currently with values of 0.24 and 0.25.

uld only be improved by 15-20%.

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They could do that now but styling and practicality take precedence once re asonable values have been achieved .

Although the Cd is important tire losses are as great or larger than aerody namic ones at most speeds, even on a freeway.

Modern tires have a rolling coefficient of ~1%.

ared to a parallel hybrid because of the ~20% loss in the dual conversion f rom mechanical to electrical and back again. A parallel hybrid avoids this .

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The Toyota/Ford hybrid system as used in the Prius does not have a conventi onal drive train. They use two motors balancing the engine torque using su n and planet gearing to allow it to transition between series and parallel operation with no changing of gears while allowing the engine to be operate d at its optimum point for the instantaneous power requirement. ...

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The pricing of limited production cars like that is artificial - but it is unlikely that it could be sold for $20,000.

cheers

kevin

I believe this is reflected in the death rate in autos. It is at an all time low having dropped below the rate of deaths by guns. We started down that road (so to speak) in the 60's with the introduction of seat belts and continued to improve safety equipment since. I would have expected that once we got nearly everyone to wear seat belts we would have gotten the lion's share of the reduction in death rate available, but that is not right. The auto industry has taken safety seriously and continues to make cars safer and safer adding more protection features. I think the final step will be to remove the driver from the equation and let the cars do the driving. Then we will find cars to approach the safety levels found in mass transportation.

I don't follow this trade off. How is providing low end torque counter to providing top speed? Are you saying that making the motor bigger limits the RPM?

It is a concept car. It's not really intended to fit any market segment. They have to sell a lot of any car to justify producing it. I don't think this one would sell enough to meet the requirements. Rather concept cars are built to test ideas. Some of those ideas (like the minimal power train) may survive to show up in production vehicles. But I can't imagine a tandem car will ever be remotely popular.

I take it the Mazda 3 has a regular ICE? That's one of the things that bug me. The Mazda 3 gets about 40 mpg or 2.5 gal/100 miles. The hybrid at 50 mpg is 2 gal/100 miles, not a huge improvement. Both cars are not remotely large although I have to admit I've not been in a Prius or Volt. I suppose they aren't as small as the Mazda 3. Then there are the all electric cars that get better economy even if the original source of the energy is considered with MPGe ratings of around 100 or I would assume 1 gal/100 miles equivalent. I'm not totally sure how they come up with that number, but the point is the energy savings is real.

I'm going to wait on test driving the Tesla model 3. It should have everything I want (depending on the size) and be cost effective. If they can get me a version with 300 mile range I may take that. 220 miles is not enough to get to my destination and return if there is some issue that I can't stay. With a car like the Volt it would be hours to add enough charge to get me back. It's not different with the Tesla unless there was a supercharger nearby which there isn't. So I would want closer to 300 mile range. So I would likely get the larger battery pack if it is available for the model 3.

I'll let the makers worry about how they get the efficiency. I am happy looking at the final MPGe numbers.

But drag coefficient is not the same as drag resistance. The coefficient gives an idea of how optimal a shape is while the drag resistance tells you the energy it takes to move through the air. So two vehicles with the same drag coefficient may not use the same energy at speed due to the different sizes.

Practicality is most important. No one wants to lay down in their cars.

A planetary gear set may allow the two motors to turn at different speeds, but that ratio and the ratio to the output shaft is fixed unless the set is extended to include other combinations. This does not allow for the gas engine to be run at a specific RPM at all times.

If it can be sold at all, given the very small market for such a vehicle.

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Rick C

On Wednesday, June 28, 2017 at 12:39:09 PM UTC-7, rickman wrote: ...

le speed transmission you still need the motor torque to provide starting a cceleration and hill-climbing. Providing that torque without limiting the top speed puts a constraint on how light the motor can be.

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No - the opposiite.

Motor size is related to torque. Since all current EVs use single speed ge aring if you want acceptable take-off and hill climbing either the motor ne eds to be large, or you limit top speed.

For example if a lower torque motor is used the gear ratio has to be increa sed, then the top speed will be limited by the max RPM of the motor.

The EV manufacturers are continually increasing the max RPM of the motors - in the current generation Prius the motor RPM limit has been increased to

17,000 so they can increase the gear ratio and reduce the motor size and we ight. Even on the Tesla they have a 15,000 RPM limit which I find pretty high for a large motor.

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That is on the freeway - under commute conditions the Prius gets >60mpg the Mazda ~30mpg

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The Prius is slightly larger than the Mazda which is larger than the Volt ( which is based on the Cruze platform). I found the Volt rear seat unaccept able and the trunk too small because the battery raises the floor by severa l inches.

I find the Prius is very effectively packaged with quite adequate space for 4 people and good flexible cargo capabilities. >Then there are the all electric cars

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Under commute conditions the Prius uses about the same energy as my Spark E V that did 4.7mi/kWh overall from the wall (5.7mi/kWh from the battery). Th e average engine thermal efficiency is very close to 40%.

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I'm also on the waiting list for the Model 3 and I agree the 75kWh battery would be my favoured option.

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Agreed - although the cars being compared are similar in cross-section. In that article I linked both the Tesla and the Prius have a CdA of 6.2sq f eet.

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The engine RPM is constrained as you say but the range is large enough to n ot be a significant limitation even with the single gear set of the Prius.

With the current generation the ICE can be stationery up to road speeds of

68mph and at the other extreme the ICE can run up to 3-4000 even when the r oad speed is zero. The high RPM limit of the electric motors has help exte nd these limits compared to the previous generation. The maximum road spee d has also been increased to 112mph from the 103mph before.

Toyota's high-end hybrids do have dual speed gearsets to allow a wider rang e of operation.

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kevin

Ok, I understand the trade off you are talking about, it actually has to do with selecting a gear ratio. But still this surprises me. I've never heard of an electric car that didn't have superior starting performance because the torque of electric motors is maximum at start. I don't think this is the limitation being fought.

More likely the limitation is the power/torque generated at higher RPM where the max torque is falling off. To run with a single gear ratio this ratio is set by the max RPM of the engine and the max car speed desired. Then the motor size is determined by the power needed to run at speed. It's not about the low end at all.

A Prius or Volt won't do it for me in terms of the electric range. My weekly commute is 120 miles each way. I'd be on gasoline about when I reached the highway (35 miles).

You say 75 kWHr like they have told anyone what they are offering. I can't find anything that is actually verified.

I'm surprised. Both Teslas are fairly roomy and the model X is a bit taller. Heck, the S can seat 5 adults and 2 kids. The X can have seating for 7 people. I guess they are just longer. Gotta have some place to put all those batteries.

Not sure I care about doing 112 or even 103 mph. I tend to drive around 60 on the highway even when the limit is 65 or 70 just to get the better economy.

Not sure what you mean by "wider range". Do you mean higher speeds? I can't see a reason to do that. As I mentioned, you can set the gear ratio to match the max RPM to the max required road speed. Then the power/torque of the engine is set by what is required to operate at that speed. Once you do that, why would you need a lower gear? A car needs less power and the same torque at low RPM and an electric motor has *more* torque at lower RPM with the max at standstill. Why would a lower gear be needed? What would it accomplish, reving the engine at higher RPM at low speeds?

I suppose you might set the gear ratio so the car was a bit underpowered at high speed, then have a lower gear to give much better acceleration at low speeds. Then it would feel more like an ICE with limited acceleration at road speeds.

Now the Teslas are clearly over designed with much more power than needed, but the one I drove accelerated at 60 like my truck did at 20. I believe the model 3 will only be somewhat slower, still a sports car compared to anything I've driven lately.

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Rick C

We know why krw thinks that. Krw thinks that anybody who doesn't share krw' s fatuous delusions is "stupid". "Well-informed" would be more accurate, bu t krw isn't in any position to assess that - he thinks that he knows everyt hing that anybody needs to know, and that what he thinks he knows is always right, and everybody else knows it.

This is decidedly comic, or would be if krw didn't own guns.

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Bill Sloman, Sydney

Miss-informed might be more appropriate. Since the statement implies that the Saudis government, who is responsible for the oil, is also responsible for actions of a few terrorists. I am no fan of the Saudis, but can't really accuse them of such.

Yeah, the royal family doesn't personally climb into the aircraft.

So, you still believe the Saudis royal family is behind it? What is the motive?

the House of Saud is thousands od people add Wahhabism and it isn't totally impossible that some of them decided building mosques all over the world wasn't enough

It's usually good to talk about something you know something about. Slowman knows nothing. Ignore him.

The Saudis can only *wish* they controlled oil. That alone proved how stupid Shorty is. No one cares what Slowman says.

Krw knows even less. Ignore him too.

The Saudi's control enough oil wells to have an appreciable effect on the oil price. Obviously they would like to have more, but they do have enough influence to make it worth their while to exercise what influence they do have.

Krw can manage true-or-false dinstinctions (though he gets a lot of them wrong). Matter of degree are beyond him. People do care what krw says - they are afraid that people who don't know what an ignorant twit he is might take him seriously.

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Bill Sloman, Sydney

I guess they control (limit) the down side, but not the upside. If they did have involvement with 9/11, it would be stupid for them to scare people away from buying money (fuel) in the sky.

burning money in the sky