Multiple Gear Ratio Options

[Red Sage]

God. Why do I bother clicking on these threads?

Sure. You can change gearing to accelerate faster, and have a lower top speed. You can change gearing to accelerate slower, and have a higher theoretical, potential top speed... But using the same powerplant and power source, you will not necessarily reach a significantly higher top speed due to wind resistance. And, given a rather limited energy reserve, your range would be greatly reduced on any high speed run.

There is no reason to build a 250 MPH Tesla Motors product if you cannot drive it at that speed for a minimum of two hours. And do so without a pit crew trailing you. And complete the trek without killing the car. Or needing to replace 90% or more of the drivetrain components from rubber and wheels to drive shafts and motors. Trust that attempting a 250+ MPH in a Bugatti Veyron SS is not an inexpensive endeavor.

Keep in mind that 'overheating' in an EV is not the same as in an ICE. A 'cold' ICE motor may run, badly, at internal temperatures under 200° Fahrenheit. An air-cooled ICE may entertain temperatures as high as 400° Fahrenheit. Liquid cooled ICE typically prefer to be below 250° Fahrenheit.

The individual Lithium-ion battery cells in a Tesla Motors battery pack have a very narrow optimum operational temperature. It is between about 65° and 95° Fahrenheit. It is highly unlikely you will ever get a HEMI to perform well with its internal parts never going over room temperature on a Spring/Summer day. Over 120° Fahrenheit, or under 35° Fahrenheit, the batteries are effectively useless. Because of the priority of allowing you to continue driving the car, the battery management system in the Tesla Model S is designed to protect the vehicle from misuse. Safety. Reliability. Durability. These are of paramount importance. Trust that if Tesla wanted to build a one-off, single use Model S that completed the Nürburgring well ahead of a Panamera Turbo S, AMG S-Class, or 7-Series Alpina in a single flying lap -- but needed a crane to load it on a flatbed afterward -- they could.

When a battery cell technology arrives that can survive a wider temperature swing without reduction in capacity or capability... Or, when a cooling system that can keep battery cells within the narrow effective range regardless of the voltage draw upon the battery pack... Then will be the time to take on the Naysayers who spout, "Yeah, but it CAN'T be tracked!"

 

[doubeld]

God. Why do I bother clicking on these threads?

Because you love it. And you love giving us your excellent opinions. And you're addicted to the TMC/TM forums. You might want to check that out

I'm worried that you're going to get an ulcer if I keep feeding you, so I'll stop with any more questions/comments directed at you.

Now for the rest of you, one more question... just kidding. I think my question is answered.

 

[bxr140]

There is no reason to build a 250 MPH Tesla Motors product if you cannot drive it at that speed for a minimum of two hours.

That makes absolutely no sense. Of the many reasons why one should/could/would not build a 250mph tesla, the duration at which it could sustain that speed is all but irrelevant.

 

[Laserbrain]

The Bugatti Veyron cannot hold its top speed for longer than 12 minutes, because then the 100 litre gasoline tank is empty... :tongue:

 

[tga]

The Bugatti Veyron cannot hold its top speed for longer than 12 minutes, because then the 100 litre gasoline tank is empty... :tongue:

And you need to change the tires anyway (only good for 15 min at top speed, or something like that).

 

[Red Sage]

That makes absolutely no sense. Of the many reasons why one should/could/would not build a 250mph tesla, the duration at which it could sustain that speed is all but irrelevant.

The Bugatti Veyron cannot hold its top speed for longer than 12 minutes, because then the 100 litre gasoline tank is empty... :tongue:

And you need to change the tires anyway (only good for 15 min at top speed, or something like that).

Precisely my point. The idea is to prove that electric cars are 'better' by a wide margin. Not 'almost as good'. Not 'about the same'. Not 'a little bit better'.

You finish 35 laps of the Nürburgring, or complete the Daytona 500/Indianapolis 500 without stopping in under two hours and the world will bow at your feet.

 

[bxr140]

Precisely my point. The idea is to prove that electric cars are 'better' by a wide margin. Not 'almost as good'. Not 'about the same'. Not 'a little bit better'.

You finish 35 laps of the Nürburgring, or complete the Daytona 500/Indianapolis 500 without stopping in under two hours and the world will bow at your feet.

I'm not sure you understand how the world quantifies "better". In context, more range (which is what all your suggestions boil down to) does not amount to a hill of beans.

That's why performance of the P cars is so impressively 'better'. Nobody cares how many times a P can do the 0-60 or the 1/4 mile, when the power will be heat limited, etc. They are easily the fastest cars in the world in class. 2.8 impresses car people. 11 seconds impresses car people.

Lap time at the ring, top speed...they impress car people.

 

[Red Sage]

Every time Tesla Motors does anything that Naysayers claimed it was 'impossible' to do with an electric vehicle, they move the goal posts. That is, they first decry EVs, then try to point out flaws in their execution. Eventually, all of those protests will go away. It just takes time. And the time will come sooner than many expect.

 

[SΞXY P100D]

I believe we should consider having transmissions in EVs not solely based on achieving higher top speeds or faster acceleration, but also in terms of reducing motor RPM and possibly increasing battery energy efficiency and cooling management. I'm no physicist or engineer, but having a transmission to reduce the motor's workload seems like a good idea to me.

I found this discussion about magnetic transmission to be very interesting: Magnetic Transmission | Tesla Motors

 

[jaguar36]

I believe we should consider having transmissions in EVs not solely based on achieving higher top speeds or faster acceleration, but also in terms of reducing motor RPM and possibly increasing battery energy efficiency and cooling management. I'm no physicist or engineer, but having a transmission to reduce the motor's workload seems like a good idea to me.

The OP was originally suggesting different gear options, not adding a transmission.

A transmission however doesn't reduce the motors workload, it actually increases it by adding additional sources of friction into the drivetrain. A transmission allows a motor to work at its optimal RPM range and still provide enough torque or not exceeding the max motor RPM. The electric motor in the S works well at a very wide RPM band, therefore its not worth the cost and drivetrain losses to add a transmission.

 

[loviik]

I want to know why we need even single gear if we can control torque and speed with current and voltage

 

[Gerasimental]

I want to know why we need even single gear if we can control torque and speed with current and voltage

Torque capacity basically scales with size of the motor. Since the Model S uses a 8:1 reduction gear, if I remember correctly, the motor would need to be 8 times as large to provide the necessary torque without a gear. This is obviously impractical in terms of size, cost, and mass, but also has the problem of a huge rotor inertia.

 

[Red Sage]

I want to know why we need even single gear if we can control torque and speed with current and voltage

A reduction gear is required to keep the car from doing the sort of things that people are supposedly 'so afraid' of seeing happen if powerful electric cars reach the hands of the untrained masses. Because you have a reduction gear, you get the instantaneous response, without the sort of lack of control you see in ICE vehicles that crash before they can leave the parking lot at an 'independent franchised dealership'. Oh, and you don't melt your tires and wheels down to the hub by applying 18,000 rpm from zero instantaneously -- though I'm sure there would be a certain contingent of the U.S. populace that would be very entertained by such a prospect. Even more so whenever someone had extremely expensive carbon fibre or magnesium wheels.