Tesla Semi

[ggr]

That isn't saying one on each wheel... (There are normally 8 wheels on a Semi Truck.) Maybe he his just going to put two motors on each drive axel. (For a total of four.)

We don't know what "a bunch" means.

I don't know where you get 8 wheels from; that would be a very unusual configuration. Usually there are front steering wheels (2), then two axles of dual wheels, for a total of 10. Maybe you just meant the driving wheels. Anyway, we'll find out one day...

 

[jhm]

Bunch of Motors for Semi

Had to make it a poll.

 

[kenliles]

US oil production is recovered - post Harvey

 

[ValueAnalyst]

Less than a half hour ago, I purchased shares of Old Dominion Freight Line (ODFL). It was recommended in the newsletter I received this morning from Craig Johnson of Piper Jaffray. It was Johnson's TSLA recommendation in his 2013 JAN 28 newsletter that motivated me to research Tesla and Elon, and purchase my initial TSLA shares at less than $38 each.

ODFL is a member of the SmartWay Transport Partnership which promotes fuel efficiency and reduced emmisions. I'm betting on ODFL buying Tesla semi-trucks and greatly benefiting.

Old Dominion Freight Line
Old Dominion Freight Line - Wikipedia
SmartWay Transport Partnership - Wikipedia

Could you please explain why Tesla would share the cost savings with ODFL instead of pricing its semi just below the ICE alternatives, and even if it did, why ODFL would be able to keep the savings to itself instead of having to pass them onto its customers due to competition from other freight liners who will also be able to purchase Tesla's semi?

 

[D-egg-O]

Integrated axle & electric motor design (Not Tesla)
Charged EVs | AxleTech and TM4 partner to produce fully integrated electric axles

 

[dhanson865]

I don't know where you get 8 wheels from; that would be a very unusual configuration. Usually there are front steering wheels (2), then two axles of dual wheels, for a total of 10. Maybe you just meant the driving wheels. Anyway, we'll find out one day...

And even though it is 10 wheels it is only 6 positions / 3 axles. The double wheels on the 2nd and 3rd axle act as a single unit and can even be replaced by a "super single" even though it is inferior.

6×4 (drivetrain) - Wikipedia

A 6×4 drivetrain (six-by-four) is a vehicle with a drivetrain of three axles delivering power to two wheel ends on two of them. It is a form of four-wheel drive but not one of all-wheel drive.

It is the most common form of drivetrain of semi-tractors and heavy haul fixed-chassis cargo trucks.

On a traditional ICE rig, the two rear most axles are being driven and the front wheels are steering and brakes only (brakes on all 3 axles)

You know Tesla will delete the old transmission and driveshaft and fill the area between the first and second axle with battery pack modules.

For it to be a "bunch" of motors it'll have to be 3 minimum (one per axle) but it could easily be 4, 5, or 6 if they want to go that far.

In the vote thread I went for 3 and 5 as my two answers (3 for a low spec, 5 for a high spec). But before I'd seen his "bunch" tweet I'd have guessed 2 for the low spec and 3 for the high spec.

Elon and JB have both said in the past that it didn't make any sense to do 4 motors on a sedan or coupe. So I thought that was still in play on this concept until the "bunch" quote.

 

[D-egg-O]

I am most interested to see how Tesla designs the brake system. Semis use air to have cheap, reliable, and easy connections for the trailer brakes. Air pressure is supplied by an air compressor on the engine. The air is also used for a bunch of accessories (i.e. air suspension, cab suspension, seat height adjustment, horn, etc.).

Edit: video for more background

 

[dhanson865]

I am most interested to see how Tesla designs the brake system. Semis use air to have cheap, reliable, and easy connections for the trailer brakes. Air pressure is supplied by an air compressor on the engine. The air is also used for a bunch of accessories (i.e. air suspension, cab suspension, seat height adjustment, horn, etc.).

Edit: video for more background

Maybe just a air tank with no compressor or maybe a weak electric compressor that could run while you are charging the packs?

Compressed air isn't my forte, I have no idea how viable that is.

 

[D-egg-O]

Maybe just a air tank with no compressor or maybe a weak electric compressor that could run while you are charging the packs?

Compressed air isn't my forte, I have no idea how viable that is.

They definitely need a compressor to create the pressure needed. It will just be electrically powered. S and X should have one of these for the smart air suspension, so they could use this design architecture. Maybe even just use multiple S and X compressors.

I'm willing to bet they still use air for the brakes in order to be able to connect to any conventional trailer (and thus controlling the trailer brakes). The difference will be in how the brake signal travels to the brake valves and modulators. I think this signal will be an electrical one, aka brake by wire, rather than actual air providing the signal. This will improve brake timing, provide better ABS control, and thus improving stopping distance and safety. It will reduce the complexity in air lines in the truck as well.

 

[AudubonB]

...and don't forget how effective all those motors can be in regenerative braking - obviating the need for quite so much available compressed air that today's semi tractor-trailers must maintain.

 

[D-egg-O]

...and don't forget how effective all those motors can be in regenerative braking - obviating the need for quite so much available compressed air that today's semi tractor-trailers must maintain.

The more motors installed, the higher the regenerative braking power available.

 

[neroden]

I am most interested to see how Tesla designs the brake system. Semis use air to have cheap, reliable, and easy connections for the trailer brakes. Air pressure is supplied by an air compressor on the engine.

Electric-powered air compressors are not a problem. In fact, I think there's one on my air-suspension model S already. You can get very high powered ones.

I presume for compatibility there will be an air compressor to power the trailer brakes. Whether it will also power the tractor brakes, dunno, but probably -- I think that means they don't need hydraulics at all, which would be a savings, right? The regenerative braking would be the primary "light duty" brakes with the air brakes only being used for serious heavy braking anyway.

 

[bxr140]

The more motors installed, the higher the regenerative braking power available.

Not to get too pedantic, but I don't think that's a real factor--once you have a motor on an axle, you have enough regen for that axle.

Regardless, we all agree there's a lot of energy to be recovered in a semi. No doubt tesla is going to harvest as much of that a possible in a safe (for people) and healthy (for the vehicle components) manner.

 

[TMSE]

Not to get too pedantic, but I don't think that's a real factor--once you have a motor on an axle, you have enough regen for that axle.

Regardless, we all agree there's a lot of energy to be recovered in a semi. No doubt tesla is going to harvest as much of that a possible in a safe (for people) and healthy (for the vehicle components) manner.

Why does an EV semi need axle?

 

[skitown]

I've never been in a semi, let alone driven one. With that out there... anyone have any ideas what sort of braking scenarios would likely be beyond what the regen braking could handle? We're all used to seeing "No Compression Brakes" signs as we enter small communities from highway speeds; think 65 MPH down to 35, etc. Will that noise pollution become a thing of the past? Would compression brakes more than likely just been used when the driver hasn't had time/warning to brake under normal driving conditions; and/or say on long descents, or when the battery pack is too full or unable to accept more regen? TL;DR, what are the likely limitations of the regen system in a Tesla Semi?

 

[bxr140]

Why does an EV semi need axle?

Doubling down on pedantry? I like it.

As you and everyone already know, it was not reference to the physical component. To wit: A model S has two axles; everyone understands what that means.

Internet fun aside, there's loading characteristics that could easily drive tesla semi's solution to the EV equivalent of solid axles...not unlike ICE vehicles, where increasing loads demand solid vs independent axles.

That structural member of a semi axle shares the bending loads from the wheels on either side. Decoupling the left and right could easily result in more total structural mass to achieve the same loading margins.

Remember that even with Tesla's vision, Semi is still going to be goal oriented just as the trucking industry is goal oriented. A lot of the physical/hardware solutions on Semi will resemble those on traditional ice semis, because decades of trucking has proven those solutions maximize their goals. The most unique [physical] parts of Semi will be where the EV drivetrain allows tesla to step function the performance of a legacy equivalent.

 

[SwTslaGrl]

I think the advantage of Tesla Semi is a new kind of planning software could be used. For example on route 1 the truck has x payload, expected y regen, need to start with z energy stored in the battery and w energy stored at the destination. Route 2 follows route 1 and starts with w energy stored and so on..

 

[TMSE]

Doubling down on pedantry? I like it.

As you and everyone already know, it was not reference to the physical component. To wit: A model S has two axles; everyone understands what that means.

Internet fun aside, there's loading characteristics that could easily drive tesla semi's solution to the EV equivalent of solid axles...not unlike ICE vehicles, where increasing loads demand solid vs independent axles.

That structural member of a semi axle shares the bending loads from the wheels on either side. Decoupling the left and right could easily result in more total structural mass to achieve the same loading margins.

Remember that even with Tesla's vision, Semi is still going to be goal oriented just as the trucking industry is goal oriented. A lot of the physical/hardware solutions on Semi will resemble those on traditional ice semis, because decades of trucking has proven those solutions maximize their goals. The most unique [physical] parts of Semi will be where the EV drivetrain allows tesla to step function the performance of a legacy equivalent.

If I understood correctly, axle is the metal rod/link that connects left and right wheels. Correct?

In the ICE world, no matter what the vehicle is, whether a semi or a car, you have only one engine. So you need axles and transmission to transfer power to all wheels. Right?

In the EV world, when each wheel can be fitted with a relatively inexpensive electric motor, why do we need axle? We know transmission isn’t there, same way with axle. Model S has axle because one motor is shared to control both left and right wheels.

 

[Off Shore]

If I understood correctly

You didn't, but it's understandable, because the definition you cited is correct. It's also standard practice in the trucking industry to use the same term to mean essentially everything from the left wheel to the right wheel.

 

[mongo]

If I understood correctly, axle is the metal rod/link that connects left and right wheels. Correct?

In the ICE world, no matter what the vehicle is, whether a semi or a car, you have only one engine. So you need axles and transmission to transfer power to all wheels. Right?

In the EV world, when each wheel can be fitted with a relatively inexpensive electric motor, why do we need axle? We know transmission isn’t there, same way with axle. Model S has axle because one motor is shared to control both left and right wheels.

The axle assembly supports the load as well as transfering the motive force. A solid axle with leaf springs or air bags is about as simple as it gets. Semi trailers do not provide motive force and still use axles (without axle shafts) to support the left and right wheels.