[MattsAwesomeStuff]

Just a note, I purged some personal squabbles from this thread. If you feel it was unfair, and these were beneficial to the community, PM me and we'll discuss it.

 

[electro wrks]

I did not claim that I had better information; I only distinguished between these numbers and real data.

This does not make sense. If you claim to have "real data", then you must think you have "better information". This spreadsheet is what information, and yes assuming some errors, is out right now by one author. By all means, show us more correct and up to date information, if you have it. Or, better yet, do the research and make up a better spreadsheet.

 

[brian_]

This does not make sense. If you claim to have "real data", then you must think you have "better information". This spreadsheet is what information, and yes assuming some errors, is out right now by one author.

Again (and again, and again...) I did not claim to have real data or better information. But thanks for confirming that this spreadsheet contains at least values which are not real data or confirmed information.

Matt, please feel free to delete this round, too...

 

[brian_]

A rational discussion of most of the interesting issues regarding the Tesla Semi, as an update of an earlier discussion:
YouTube by Jason of Engineering Explained: Does The Tesla Semi Make Any Sense? Part 2!

Sources and basis for values and calculations are provided. While there are minor issues, I generally agree with this analysis.

 

[Electric Land Cruiser]

A rational discussion of most of the interesting issues regarding the Tesla Semi, as an update of an earlier discussion:
YouTube by Jason of Engineering Explained: Does The Tesla Semi Make Any Sense? Part 2!

Sources and basis for values and calculations are provided. While there are minor issues, I generally agree with this analysis.

I said that the truck was driving at 55 mph or less for the journey.
I said that the up and down of mountains doesn't matter as long as the starting and ending elevation are the same.
I said that the deficit of the Tesla semi vs. a diesel would be about 5,000lbs.
I said that the majority of loads on the road are less than 73,000lbs.

I should have written it on a white board.

 

[Electric Land Cruiser]

Cool video about the Tesla semi. Some key takeaways from the video:
-aero is not just good but really good
-Plaid carbon fiber cased motors are extremely efficient up to 20k RPM = double RPM range of other electric semis
-3 motors for regen allows for maximum regen (I think this was @brian_'s theory also)
-2 motors optimized for acceleration, 1 motor optimized for cruise
-comes to the same conclusion as others that it only gives up about 5000lbs to a diesel semi in maximum payload

Big thing is that the Tesla semi is roughly 20% more efficient that Volvo EV semi and more than 1.5x more efficient than the EV Kenworth, Diamler, and Peterbilt trucks. It basically humiliates the legacy brands.

It doesn't break the laws of physics it just doesn't have big elephant ear mirrors and a 1970s blunt nose.

 

[remy_martian]

The Semi's efficiency as quoted by Tesla, the company, is the SAME as the Volvo

EV Universe is the source of your Tesla-fanboy Youtube channel's data. He clearly cherry-picked Musk's number, not the official spec from the company, for his cheerleader video.

🤦‍♂️

If you've ever driven a large trailer that totally blocks rear view, you wish you could sit on the cargo mirrors, not in the middle seat, of your truck, for lane changes, backing up, and monitoring the tow. Rearview cameras are not legal in the US, btw, as a replacement for mirrors - were there any mirrors on the Tesla in the wind tunnel, or did Musk order them removed?

 

[Electric Land Cruiser]

I meant to add this graphic to my last post showing all the EV trucks and their efficiency. You can see how much better the Tesla is.

 

[brian_]

Cool video about the Tesla semi. Some key takeaways from the video:
-aero is not just good but really good
...
It doesn't break the laws of physics it just doesn't have big elephant ear mirrors and a 1970s blunt nose.

Mirrors need to be large for safety; reducing their size is a bad idea, and replacing them with cameras is presumably still not legal in the USA. Other than some specialty vocational models, highway tractors have nose shapes from this century (usually revised within the past decade), not the 1970s.

But aerodynamics certainly are important, and the Tesla Semi probably has lower drag than trucks using the same cab as their diesel counterparts. Part of that is managing airflow under the truck, which means a smooth bottom (almost automatic for much of the length within the wheelbase due to the battery cases) and minimizing the amount of air which gets under there. All of the experimental trucks built in the past couple of decades (with diesel engines) have substantial aerodynamic improvements, but one reason that their designs don't go into production intact is that the low nose and shallow approach angle needed to effectively keep air out from under the truck are not practical in operation.

PepsiCo's use of their Tesla Semi fleet in actual commercial operation has led to some interesting opportunities for information, including how these trucks are towed when they break down; it's different from the manufacturer carrying them around on lowboy trailers. I'm not concerned about the breakdowns - stuff happens, especially in early production vehicles - but this recent photo shows a challenge for the tow operator:

(from a Facebook post)

It appears that the orange tow loop was used with the tow truck's wheel lift to pull the Semi onto the ramps, to get it high enough to fit the wheel lift under the Semi. I have to do something similar with my Triumph Spitfire, driving it onto shallow ramps (regular garage ramps are too steep) to get an ordinary floor jack under it... but that's a tiny sports car, not a truck.

It looks like the Semi would benefit from air suspension in the front (most heavy trucks have air suspension in the rear, but basic old leaf springs and beam axle in the front), so the nose can be lifted as required.

By the way, the legally required markings on the door confirm the 82,000 pound GCWR. Here trucks are also required to display their tare weight, which would be great information to have about the Semi, but Colorado apparently doesn't require that.

 

[remy_martian]

The electric semi trucks lower the suspension at highway speeds, so not your grandaddy's leaf suspensioned Mack truck.

If the Tesla lost power at highway speed, there would be no way to crank it back up again.

 

[remy_martian]

I meant to add this graphic to my last post showing all the EV trucks and their efficiency. You can see how much better the Tesla is.

View attachment 135481

The number being used for efficiency is not Tesla's official 2.0 kWh/mile, but cherry-picked by the Youtube fanboy from an interview where Musk is bullshitting he sees 1.7 and sees a path to 1.6.

The other CEOs have established truck businesses and dare not ad lib bs numbers, whereas Musk lives for his stock options these days and has been pouring the BS on pretty thick on this one. Tesla's number is indistinguishable from Volvo's. Three motor to one blah blah blah can you call me a tow?

There's also no data to say whether these packs are using the prototype 4680 cells, or the production Semi's Model 3/Y cells.

 

[Duncan]

Mirrors need to be large for safety; reducing their size is a bad idea, and replacing them with cameras is presumably still not legal in the USA.

Thinking about that
If you legally NEED the mirrors - but have the cameras anyway - why would you fit large mirrors?
Would you be able to fit dinky little aerodynamic mirrors to comply with the law while using the camera system
For a truck one of the main uses is when reversing - and todays camera systems are massively superior

 

[remy_martian]

We also don't allow laser headlights here.

You especially notice these idiots right after spending a couple of weeks driving in places like Germany. Drivers in the US are very undisciplined, don't know the rules of the road, they flip you off when they take your right of way, they undertake when passing, hog the fast (passing lane), and will speed up to block a signaled lane change.

And you want to make cameras legal?

😂

 

[cricketo]

We also don't allow laser headlights here.

You especially notice these idiots right after spending a couple of weeks driving in places like Germany. Drivers in the US are very undisciplined, don't know the rules of the road, they flip you off when they take your right of way, they undertake when passing, hog the fast (passing lane), and will speed up to block a signaled lane change.

And you want to make cameras legal?

😂

Cameras will be legal eventually. May take a few dead (natural causes) senators first though.

 

[Duncan]

We also don't allow laser headlights here.

You especially notice these idiots right after spending a couple of weeks driving in places like Germany. Drivers in the US are very undisciplined, don't know the rules of the road, they flip you off when they take your right of way, they undertake when passing, hog the fast (passing lane), and will speed up to block a signaled lane change.

And you want to make cameras legal?

😂

Cameras are SAFER than mirrors - especially on a Tesla with the computer putting a flashing icon around anything that it thinks you should look at

 

[remy_martian]

Loss of 12V is probably the reason.

 

[Duncan]

Loss of 12V is probably the reason.

Lose the 12v and your diesel stops working

 

[smokeycanadian]

sorry if I don't have anything to really say about tesla due to taking a "sit and wait&see" position literally..even then I do kinda have to agree that a tesla tractor being difficult to get towing is a bit of a poor design oversight, even kneeling-stuck city buses still can be made towed off by a conventional heavy wrecker as I have seen at least once for real

but anyhow just as a silly small friendly nitpick to @Duncan - typical newer engines yeah but the ones vintage enough to fit this picture could literally keep going without any glow heat needed at all (just as long as that was a mechanical instead of electronic fuel pump that was bolted onto it tho of course)

 

[Electric Land Cruiser]

Mirrors need to be large for safety; reducing their size is a bad idea, and replacing them with cameras is presumably still not legal in the USA. Other than some specialty vocational models, highway tractors have nose shapes from this century (usually revised within the past decade), not the 1970s.

But aerodynamics certainly are important, and the Tesla Semi probably has lower drag than trucks using the same cab as their diesel counterparts. Part of that is managing airflow under the truck, which means a smooth bottom (almost automatic for much of the length within the wheelbase due to the battery cases) and minimizing the amount of air which gets under there. All of the experimental trucks built in the past couple of decades (with diesel engines) have substantial aerodynamic improvements, but one reason that their designs don't go into production intact is that the low nose and shallow approach angle needed to effectively keep air out from under the truck are not practical in operation.

PepsiCo's use of their Tesla Semi fleet in actual commercial operation has led to some interesting opportunities for information, including how these trucks are towed when they break down; it's different from the manufacturer carrying them around on lowboy trailers. I'm not concerned about the breakdowns - stuff happens, especially in early production vehicles - but this recent photo shows a challenge for the tow operator:
View attachment 135483
(from a Facebook post)

It appears that the orange tow loop was used with the tow truck's wheel lift to pull the Semi onto the ramps, to get it high enough to fit the wheel lift under the Semi. I have to do something similar with my Triumph Spitfire, driving it onto shallow ramps (regular garage ramps are too steep) to get an ordinary floor jack under it... but that's a tiny sports car, not a truck.

It looks like the Semi would benefit from air suspension in the front (most heavy trucks have air suspension in the rear, but basic old leaf springs and beam axle in the front), so the nose can be lifted as required.

By the way, the legally required markings on the door confirm the 82,000 pound GCWR. Here trucks are also required to display their tare weight, which would be great information to have about the Semi, but Colorado apparently doesn't require that.

That's a lot of words to say that the Tesla is very aerodynamic and the other semis are not

The picture you posted was not from Colorado, FYI.

Take a look at the Tesla semi and then look at the Volvo, it's next best competitor. Blocky vertical nose, two sets of mirrors, fiberglass wind deflector, open sides, eyebrow overhang, etc etc. Like I said before it still even has bulges where the stock fuel tanks are. It follows the same basic design as every semi since the 1970s.

You biggest criticism is that is difficult to tow?? Really that's where we are now? Luckily EV technology is several times more reliable than ICE.

 

[brian_]

Thinking about that
If you legally NEED the mirrors - but have the cameras anyway - why would you fit large mirrors?
Would you be able to fit dinky little aerodynamic mirrors to comply with the law while using the camera system
For a truck one of the main uses is when reversing - and todays camera systems are massively superior

Yes, that's one solution, and it is available: small mirrors with cameras mounted in them, and interior monitors for the cameras. See the Digital Mirrors section of Kenworth's T680 web page, for instance. Gee, imagine one of those diesel-building dinosaurs offering advanced systems...