Lets work out the Tesla Semi-Truck Technical Specs

[JRP3]

I feel my numbers are reasonable, but I have no evidence.
The motor will be larger than the Model 3 motor and the gears need to be sturdier. The reason is that the Model 3 motors are used only for short periods at high performance but these truck motors produce high power for extended time. To reach 1M miles these need to be larger. (I don't think Model 3 drive train is designed for 1M miles, that is just marketing).

So you have no evidence and you don't believe what Tesla has said. To increase power output for longer periods of time they can just use more cooling. If 200hp is required for steady state 60mph driving that's just 50hp per motor.

 

[acoste]

So you have no evidence and you don't believe what Tesla has said. To increase power output for longer periods of time they can just use more cooling. If 200hp is required for steady state 60mph driving that's just 50hp per motor.

Not only the cooling. Every part has a specific load it can tolerate for a specific time.

 

[mongo]

Edit: in fact, you can have two motors on the same side of the tractor spin at opposite direction to cancel out some of the twisting, although it may not be needed at all.

For the semi, the drive unit reacts against the outer axle tube, so all the torque gets transferred through to the solid swing arm into the air suspension. So it will try to lift the front via the frame rail, but no side to side twisting.

 

[JRP3]

Not only the cooling. Every part has a specific load it can tolerate for a specific time.

What's the Model 3 motor's max sustained power output? It can do extended high speed driving on the highway, I bet it can put out more than 50hp continuously.

 

[acoste]

What's the Model 3 motor's max sustained power output? It can do extended high speed driving on the highway, I bet it can put out more than 50hp continuously.

Let's say I'm way off and they just put in the Model 3 drive unit. 200 lbs each, plus cabling and cooling 200 lbs. total 1000lbs
Then I can add 500 lbs of battery. That is an additional 38kWh. That would increase my calculated range from 287 miles to 306 miles. Do you feel that's a game changer?



However I will slightly adjust my numbers. This is my most optimistic scenario.

Powertrain 4,080 lbs
300gall fuel 2000 lbs
misc parts (exhaust...) 3000 lbs
- electric motor + inverter -1250lbs (meet in the middle)

and let's say Tesla saved 10% of weight on the remaining of the truck by using lightweight material
Remaining weight = 20 000 - 4 080 - 3000 - 2000= 10 920 lbs
10% of it 1090lbs

that is 8920 lbs for the battery


current battery with case (Model 3) is at ~167Wh/kg. Add 5% for better space utilization in the case (less overhead). = 175Wh/kg

8920 lbs =4046kg
175*4046kg/1000 = 708 kWh battery capacity

Diesel truck:
average 18-wheeler gets 5.9 mpg,
300 gallon x 5.9 = 1770 miles

Electric truck
Model S 100D would get 40-42mpg on diesel at those speeds (~7 times less consumption than truck). Range might reach 350 miles on a 100kWh battery. Let's say Tesla improved rolling resistance and air drag, so I use 6 times the consumption.
That is 350 miles * 708kWh / 100kWh / 6 = 413 miles

 

[JRP3]

Seems more reasonable.

 

[mongo]

Factoids and guesses
Front axle max weight is 12k pounds
Each set of duals max weight is 34k

Semi may be as good as 1.6 kWh per mile.
Tesla specs the range as 500 for long and 300 for standard.

 

[Remus]

For the semi, the drive unit reacts against the outer axle tube, so all the torque gets transferred through to the solid swing arm into the air suspension. So it will try to lift the front via the frame rail, but no side to side twisting.

I understand that. I mean potentially they can have the motors in the front pressing down instead of lift the front. And the motors in the rear pressing down the rears as well.

 

[mongo]

I understand that. I mean potentially they can have the motors in the front pressing down instead of lift the front. And the motors in the rear pressing down the rears as well.

I think what you are describing is pushing the entire axle upward on both sides which would be a displacement, not a rotation.

If you are looking at the left side of the semi with it facing to your left, it accelerates by applying a counterclockwise torque to the tires. This results in a clockwise torque on the axle tube and the axle itself pushes up against the frame rail in front of the axle at the swing arm mount. Also unloads the air bags (I got that backwards up a couple posts). The torque also causes the front motor to shift upward and the rear motor downward as the axle rotates slightly.

 

[Silent Ludicrosy]

Factoids and guesses
Front axle max weight is 12k pounds
Each set of duals max weight is 34k

Semi may be as good as 1.6 kWh per mile.
Tesla specs the range as 500 for long and 300 for standard.

1.6 kWh/ mile would be really impressive.

A typical semi uses about 200 hp at 60 mph assuming 0.6 drag coefficient, which works out to 2.5kwh/mile. About half of that is aerodynamic and the other half rolling resistance. 1.6kwh/mi would be really good, you’d need something like .4 drag coefficient and low rolling resistance tires. Source: http://electracold.com/CAT.pdf

 

[MP3Mike]

A typical semi uses about 200 hp at 60 mph assuming 0.6 drag coefficient, which works out to 2.5kwh/mile. About half of that is aerodynamic and the other half rolling resistance. 1.6kwh/mi would be really good, you’d need something like .4 drag coefficient and low rolling resistance tires. Source: http://electracold.com/CAT.pdf

I guess it is good that the Tesla Semi has a drag of 0.36 then. (Under the 0.4 that you say would be necessary.)

Tesla is only quoted as saying that it will be under 2kWh/mile. And 1.6 kWh/mile is under 2.

 

[JRP3]

the Tesla Semi has a .36 drag coefficient, compared to the standard of .65-.70.

Tesla Semi Unveiled: 500+ mile range, Bugatti-beating aero, 2019 production

 

[acoste]

Tesla Semi Unveiled: 500+ mile range, Bugatti-beating aero, 2019 production

Ah, these typical Elon tricks. He doesn't mention anything about the trailer. That can make a big difference.

And also comparing it to a Bugatti which is designed to be a reverse wing to keep the car on the road at high speeds. That's like saying this has better cd than an airplane.

 

[Silent Ludicrosy]

Tesla is only quoted as saying that it will be under 2kWh/mile.

Did they say at what speed?

 

[MP3Mike]

Did they say at what speed?

I'm pretty sure that was quoted for 60 MPH with a total weight of 80k lbs.

 

[Silent Ludicrosy]

With .36 Cd, energy required to overcome aerodynamic drag at 60mph would be .76 kWh/mi.

With the lowest rolling resistance Coefficient (.0051) wide single tires, energy to overcome rolling resistance is .81kWh/mi.

Overall that’s 1.57kWh/mi at the wheels. Assuming 90% drivetrain efficiency, that’s ~1.75 kWh/mi at the battery. Anyone seen any actual efficiency numbers from a Tesla permanent magnet motor?

 

[acoste]

With .36 Cd, energy required to overcome aerodynamic drag at 60mph would be .76 kWh/mi.

With the lowest rolling resistance Coefficient (.0051) wide single tires, energy to overcome rolling resistance is .81kWh/mi.

Overall that’s 1.57kWh/mi at the wheels. Assuming 90% drivetrain efficiency, that’s ~1.75 kWh/mi at the battery. Anyone seen any actual efficiency numbers from a Tesla permanent magnet motor?

Motor itself is at 97%. From Battery to wheels it's at 93%. The Longest-Range Electric Vehicle Now Goes Even Farther

 

[Tobyw]

They said 1 mile can be done with less then 2kW
They said they have a 500 mile reach
2kW*500miles=1000kWh, So that sounds to me like a Megawatt powerpack, which is what I already estimated for quite some time.
Somehow I didn't expect all of it fitted in the truck alone, I thought some of it would be placed in the trailer. On top of that, I expected the trailer to be regenerating, that would have made jacknifing impossible for sure, on top of it, if the wind blows hard, trailers won't, or much harder, get blown over, I think the chances of that happening are still there with the current trailers.

Multiple trailers should be possible to use with autonomous controls. Imagine parallel parking with two or three trailers. Cutting the frontal area in half should come near cutting the high speed drag in half.

 

[Tobyw]

Multiple trailers should be possible to use with autonomous controls. Imagine parallel parking with two or three trailers. Cutting the frontal area in half should come near cutting the high speed drag in half - i.e. half-height, twice length, small tires.

 

[Tobyw]

Ah, these typical Elon tricks. He doesn't mention anything about the trailer. That can make a big difference.

And also comparing it to a Bugatti which is designed to be a reverse wing to keep the car on the road at high speeds. That's like saying this has better cd than an airplane.

Lift (+/-) increases drag.