Tesla Model 3 revealed

[RobDickinson]

98elise said:

To be fair the Tesla also has a motor, gearbox, and speed contol system. Much simpler than an ICE, but you can't ignore it.

The gearbox is literally forward, backward and park. the control system is likewise almost non existent. The motor weighs around 40kgs I think.

Edit - hmm not sure now I found this graph, the roadster motor was 70llbs the model s is twice as powerful but..

Edited by RobDickinson on Wednesday 27th April 20:27

[98elise]

RobDickinson said:

98elise said:

To be fair the Tesla also has a motor, gearbox, and speed contol system. Much simpler than an ICE, but you can't ignore it.

The gearbox is literally forward, backward and park. the control system is likewise almost non existent. The motor weighs around 40kgs I think.

Edit - hmm not sure now I found this graph, the roadster motor was 70llbs the model s is twice as powerful but..

Edited by RobDickinson on Wednesday 27th April 20:27

It was drivetrain cost rather than weight. You can't just look at battery cost, the tesla also has a motor and gearbox, no matter how simple they are. The EV drivetrain is a big expense on a "cheap" car. Put it this way, you can get an entire ICE car for the cost of an EV battery.

I'm a big fan of EV's and have a 3 on order, so I'm not picking holes in EV's. Its just a fact that currently the batteries are a significant cost.

[RobDickinson]

Which is why we need to scale battery production up, cost is going down, faster than predicted too.

Considering the low 'refueling' costs it wont be long until the typical TCO is lower than ICE.

[Slow]

RobDickinson said:

Which is why we need to scale battery production up, cost is going down, faster than predicted too.

Which is why Musk has built a factory and plans on making it even bigger I believe?

[BigBen]

98elise said:

It was drivetrain cost rather than weight. You can't just look at battery cost, the tesla also has a motor and gearbox, no matter how simple they are.

Does it have a gearbox? I can't actually see a need for one. The Zoe has D N R P but I assume N is a legislative requirement to have an interval between D and R and P for a motor start / stop position.

[RobDickinson]

BigBen said:

Does it have a gearbox? I can't actually see a need for one. The Zoe has D N R P but I assume N is a legislative requirement to have an interval between D and R and P for a motor start / stop position.

Yep Model S has a gearbox for forwards(Drive), reverse, neutral and park. not sure why they couldnt just run the motor backwards but I guess they cant

[kambites]

RobDickinson said:

Yep Model S has a gearbox for forwards(Drive), reverse, neutral and park. not sure why they couldnt just run the motor backwards but I guess they cant

Does it have a mechanical reverse gear? I always assumed it just swapped the phases to the motor.

ETA: From the Tesla website: "Unlike an ICE car, nothing changes in the gearbox when you select Park/Drive/Neutral/Reverse; Reverse just spins the motor(s) the opposite way from Drive, electrically. Since Neutral just doesn’t spin the motor (which allows it to freewheel with very little friction), there is no need for a clutch or any other mechanism to disengage the motor from the gearbox. Park actuates the extra rear brake calipers."

Edited by kambites on Wednesday 27th April 21:26

[RobDickinson]

That makes more sense, I saw somewhere that said it had physical gears, seemed a bit confused.

[98elise]

It has a permenant single speed reduction gearbox. It's more like a diff than a traditional clutch + gearbox + diff.

[BigBen]

98elise said:

It has a permenant single speed reduction gearbox. It's more like a diff than a traditional clutch + gearbox + diff.

That makes perfect sense, so like the final drive / diff combo in a RWD car.

[kambites]

BigBen said:

That makes perfect sense, so like the final drive / diff combo in a RWD car.

Basically yes, except it's presumably simpler and more efficient than a conventional diff on a longitudinal engined car because it doesn't need to turn the drive through 90 degrees (as the motors are mounted transversely).

Edited by kambites on Thursday 28th April 08:14

[98elise]

BigBen said:

98elise said:

It has a permenant single speed reduction gearbox. It's more like a diff than a traditional clutch + gearbox + diff.

That makes perfect sense, so like the final drive / diff combo in a RWD car.

Yes. As i understand it the The Tesla arrangement is very much like a transverse motor bolted directly to a differential. Traditional differentials have a single ratio reduction gearing.

There isn't any form of clutch or gear shifting. The motor can reverse direction and free wheel, so you have forward/reverse/neutral with the motor always connected to the wheels.

[kambites]

98elise said:

so you have forward/reverse/neutral with the motor always connected to the wheels.

Which is why you can't tow a broken Tesla with its wheels on the road. You'd be spinning the motor without any coolant flowing through it.

[98elise]

kambites said:

98elise said:

so you have forward/reverse/neutral with the motor always connected to the wheels.

Which is why you can't tow a broken Tesla with its wheels on the road. You'd be spinning the motor without any coolant flowing through it.

Why would cooling be a problem?

I know they need a flat bed but I'd assumed it was because the car is never truly in neutral so there will be motor inertia all the time.

[kambites]

98elise said:

Why would cooling be a problem?

I don't know, presumably the friction in the motor is enough to require cooling? Anything electrical could be shut-off so it must be a mechanical problem of some kind. Whatever the reason, Tesla say you must never tow one of their cars further than a certain distance or at more than a certain speed (which is something like two miles and 30mph, I think).

[RobDickinson]

Digital motor shouldnt produce any real friction, and the cooling system is for the battery..

[kambites]

RobDickinson said:

Digital motor shouldnt produce any real friction, and the cooling system is for the battery..

Well I can't imagine why else towing it would damage the motors?

The motors certainly are liquid cooled. The Model-S has an entire cooling circuit dedicated to the motors and inverters (separate from the battery cooling circuit, I mean).

Edited by kambites on Thursday 28th April 09:01

[Tuna]

kambites said:

Well I can't imagine why else towing it would damage the motors?

The motors certainly are liquid cooled. The Model-S has an entire cooling circuit dedicated to the motors and inverters (separate from the battery cooling circuit, I mean).

Possibly about driving the reduction gearbox 'in reverse'?

[INWB]

Interesting take on why the big three don't get it and how Tesla put one of them "right" on production costs.

The big three are so arrogant. I hope that is their downfall. If Tesla are right and those truly are the battery costs then they are significantly in front of the competition

http://jalopnik.com/how-a-boring-finance-call-show...

[kambites]

Tuna said:

Possibly about driving the reduction gearbox 'in reverse'?

Surely that happens every time you "engine brake"? On a long down-hill section you could easily be regeneratively braking for miles on end at highish speeds.