Tesla semi is ill conceived...

[WannabeOwner]

How much can regen contribute to braking? Like can it literally slide the tires if allowed to?

Not in a Model S, no. I would describe it as more than engine-braking [on a stick shift], and less than normal reasonably-heavy braking. To use it, and not use the brakes at all, I have to lift-off sooner than I would start to slow down in an ICE using brakes. That's fine, I keep a bigger gap to traffic in front, and as I am approaching slowing / stationary traffic I lift off and slow down (on full regen) as I approach the traffic; if I'm still travelling too fast I have to use the brake, but 95% of the time I can drive without using the brakes. (In MS Regen only works down to about 8 MPH, so I have to use the brakes below that, but e.g. the Bolt can get to a stop on Regen only)

But that is a factor of the amount of Regen energy that Tesla has decided to harvest on an MS. They could harvest significantly more (on a Semi). On MS its one-pedal driving - lift off and you get regen. It could be done using brake pedal instead - press brake pedal and get regen, until the point where you are pressing the brake pedal hard enough that you have exceeded regen ability and you get physical brakes too. If Regen will be "huge" on a Semi then maybe they will make it a function of Brake pedal, rather than one pedal driving. Much as I love one pedal driving I would be very happy if Regen was on brake pedal. In MS: if battery is cold or 100% charged then Regen is limited or non-existent; opportunity to get caught out by that by lifting off and expecting Regen but getting none! whereas if it was all on Brake pedal you'd press that and get Regen, if available and sufficient, otherwise you would get brakes.

The Bolt has a High/Lo switch for regen (so does the MS but its basically "almost nothing" and "normal" to allow Newbies to convert), so perhaps Tesla will provide Regen adjustment no the Semi - e.g. if trailer is empty or fully loaded.

Are you anywhere near a Tesla sales centre? If so I'd recommend getting a test drive. Whilst on the one hand driving a Tesla is just like driving any other car there is also a difference, and its hard to describe. The whole one-pedal-driving thing, with Regen, the lack of noise, the smoothness ... they are all "different" to ICE, and to my mind way, way better. I expect some of that will translate to driving an EV Semi, and you'd have a better feel for that if you had driven one. Look sufficiently interested in the MS / MX and talk Tesla into lending you one for the weekend for an extended trial perhaps?

In Europe, the situation is even more extreme

Plus the benefit that the price differential of Electricity / Diesel is more pronounced than USA

 

[mongo]

Well, putting the battery pack as far back as they did tells me they either have extremely heavy batteries or they don't have a clue how to design a truck for proper weight distribution.

Not sure what you mean, battery pack center is forward of the midpoint of the front and front rear axle. So >50% weight on front axle.

How much can regen contribute to braking? Like can it literally slide the tires if allowed to? I assume the car has cruise control which would use regen automatically without you even knowing it?

The motors can theoretically create as much regen as acceleration. Cruise can be programmed to coast vs regen when over the target speed (likely based on how much over the tractor is 0-2 coast >2 decelerate)

 

[KarenRei]

I wonder if he thought the motors were batteries?

It's interesting looking at the diagram, too, in that it makes it very easy to envision a sleeper cab variant: the extra length means an extra row of batteries and extra range. About 750mi per charge at 80k lb GVW @ 60mph for an extra ~$30k (plus the cost of fitting out the sleeper). It'll be great having limitless power and silent, no-hassle heating and cooling in there. A lot nicer than an APU.

 

[AZ Desert Driver]

I thought I saw a bunch of styrofoam models showing variants of the Tesla Semi. Where I saw it was a youtube video and the camera quickly swept over it. Does anyone have a good shot of those variants? Might go a ways toward settling speculation.

 

[jkn]

Ever driven truck in a heavy crosswind?



Well, putting the battery pack as far back as they did tells me they either have extremely heavy batteries or they don't have a clue how to design a truck for proper weight distribution. It's claimed Elon has a crack team of truck engineers working on this so my vote is it's freekin heavy. It also fits nicely into his anti jackknifing spiel.
If they slid the batteries in the front they could have used conventional frame rails instead of having to build around the battery pack and they would have used up dead space and added weight to the front axle. This also would have opened up a huge market to retrofit existing equipment and power new trucks.



Very heavy, you've just sacrificed 6% of your payload (revenue) to batteries. Thing is I don't believe the truck is even nearly that light. Their acceleration claims could be from that Frieghtliner in the video floating around which probably has a battery pack good for a ten mile range which would make the battery pack 50x lighter and boost empty weight acceleration substantially.

No, for me truck driving is theoretical, but I do understand that theory very well. I have lot of practical experience cycling in strong wind. Head wind is much worse than cross wind. Truck is of course longer, so wind can push it off road. This causes lot of extra work for driver, but not for engine. Crosswind will increase air resistance, but not as much as headwind.


I don't know how much weight front wheels should have. Engine and gearbox are mostly on front wheels, so front wheels on Tesla semi could be lighter. Those rear motors can steer truck. So even if front wheels lose grip truck turns as driver wants. For that I have practical experience, because I have driven tractor with separate brake pedals for each rear wheel.

Motors on rear wheels with help of computer can reduce risk of jackknifing, but I don't believe they can always prevent it.

I realized that 5 s 0-60 mph for empty truck could be limited by traction. Some of weight is on front wheels and truck tires do not have as good grip as car tires. (Must be made from stronger, harder rubber.) So truck weight could be lot less than 20 000 lbs.

Those accelerations are possible only with large battery. Tesla model S with 100 kWh battery accelerates faster than S with 90 kWh battery (or smaller).

Panasonic NCR18650B weights 45.5 g
100 kWh battery has roughly 8000 of roughly similar cells. = 364 kg
800 kWh battery would have 3000 kg of cells. Add case, cooling, cables, ...
Truck is build around battery, so battery case is part of truck frame.
Tesla probably has new higher energy density chemistry.
-> battery is not enormously heavy.

 

[SMAlset]

Very much interesting Podcast from an owner of a truck company in Canada who did an order for the Semi.

Blubrry PowerPress Player

Thanks for posting a link to this podcast, about 22 minutes in length. Chase, the interviewee, provided an interesting perspective on how he and his partner made the decision to make a reservation. Good questions too from the interviewer. For some background Chase and partner work in the oil fields in Canada doing off road type of hauling of equipment generally. When he reserved their truck during the event, he didn't know what the pricing structure would be so it was interesting to hear what he felt would work for them. Don't know how many people listened to the podcast back when this was originally posted in the thread but really feel worth a listen.

 

[Big Earl]

A cross wind will also increase rolling resistance, as the wind wants to push the truck out of its lane, increasing the tire load.

 

[KarenRei]

Ironically, the opposite can also happen; crosswinds are used by sailboats and land yachts to move faster than the windspeed itself (relying on the keel or wheels, respectively, to resist lateral movement). While as a general rule crosswinds increase drag, the details of the interaction are nontrivial and can be counterintuitive.

 

[scaesare]

How much can regen contribute to braking? Like can it literally slide the tires if allowed to? I assume the car has cruise control which would use regen automatically without you even knowing it?

It's largely a software defined curve, given the momentum to turn the rotor at a specific speed.

Tesla limits regen to a constant deceleration force... I've heard ~0.3 Gs, up to a limit. On my RWD S, that's about 60KW. Not enough to slip the tires under normal conditions.

Traction control prevents breaking loose in slippery conditions by cancelling regen.

 

[AudubonB]

I thought I saw a bunch of styrofoam models showing variants of the Tesla Semi. Where I saw it was a youtube video and the camera quickly swept over it. Does anyone have a good shot of those variants? Might go a ways toward settling speculation.

I posted a pic in this post from Tuesday morning: Tesla Semi

 

[Farmertom]

No, for me truck driving is theoretical, but I do understand that theory very well. I have lot of practical experience cycling in strong wind. Head wind is much worse than cross wind. Truck is of course longer, so wind can push it off road. This causes lot of extra work for driver, but not for engine. Crosswind will increase air resistance, but not as much as headwind.

Well, come for a ride in a heavy crosswind and I promise you'll be reprogramming your computer. It is possible even for empty trucks to have problems achieving the speed limit in heavy crosswinds due to power limitations, turn straight into the wind and load lightens up on the engine. Anybody that's driven a truck can tell you this.

I don't know how much weight front wheels should have. Engine and gearbox are mostly on front wheels, so front wheels on Tesla semi could be lighter. Those rear motors can steer truck. So even if front wheels lose grip truck turns as driver wants. For that I have practical experience, because I have driven tractor with separate brake pedals for each rear wheel.

12,000lbs in the US. If the Tesla is lighter they are wasting potential net load unless they can move the fifth wheel forward enough.

You think you can steer a semi with the rear wheels? Please call us when you do, this is entertainment we wouldn't want to miss

Motors on rear wheels with help of computer can reduce risk of jackknifing, but I don't believe they can always prevent it.

Your rear wheel steering will cause far more than it'll prevent...

I realized that 5 s 0-60 mph for empty truck could be limited by traction. Some of weight is on front wheels and truck tires do not have as good grip as car tires. (Must be made from stronger, harder rubber.) So truck weight could be lot less than 20 000 lbs.

Traction?

It could be I don't know the finer points of racing but for the most part truck tires on dry pavement are not a huge traction issue...

Those accelerations are possible only with large battery. Tesla model S with 100 kWh battery accelerates faster than S with 90 kWh battery (or smaller).

Panasonic NCR18650B weights 45.5 g
100 kWh battery has roughly 8000 of roughly similar cells. = 364 kg
800 kWh battery would have 3000 kg of cells. Add case, cooling, cables, ...
Truck is build around battery, so battery case is part of truck frame.
Tesla probably has new higher energy density chemistry.
-> battery is not enormously heavy.

Again, this is all theory.

 

[Farmertom]

Not sure what you mean, battery pack center is forward of the midpoint of the front and front rear axle. So >50% weight on front axle.

Almost a hundred percent of the engine and transmission weight is over the front axle on a diesel powered truck plus over fifty percent of fuel. Tesla is going at least fifty percent on the rear axles. The drawing may not be true placement of the batteries either, video shows a solid wall right in front of the rear wheels. One picture actually shows empty space forward of the batteries.

The motors can theoretically create as much regen as acceleration. Cruise can be programmed to coast vs regen when over the target speed (likely based on how much over the tractor is 0-2 coast >2 decelerate)

That's what I was thinking. Controls work exactly like engine exhaust and retarder brakes on diesels.

 

[mongo]

Almost a hundred percent of the engine and transmission weight is over the front axle on a diesel powered truck plus over fifty percent of fuel. Tesla is going at least fifty percent on the rear axles. The drawing may not be true placement of the batteries either, video shows a solid wall right in front of the rear wheels. One picture actually shows empty space forward of the batteries.

Numbers here are ballpark for people who don't deal with semis (like me).
It will be interesting to see how much the tractor weighs, and what they can get on the front axle to achieve max GVW.
Current tractors are about 11k on steer and 9 k on drive. Max legal is 34 per tandem, so the trailer can have 25k front and 34k rear, 59k max of which 46-48k is cargo.
If the tractor is lighter, they would not reach 80k, but could still hit the max cargo a diesel tractor can haul. Also don't have a load penalty due to fuel.
I'd love to find a breakdown of component weights to start a comparison. Any idea where I could get that info? Or can you grow out some general numbers for engine, transmission, differential?

 

[Farmertom]

Not in a Model S, no. I would describe it as more than engine-braking [on a stick shift], and less than normal reasonably-heavy braking. To use it, and not use the brakes at all, I have to lift-off sooner than I would start to slow down in an ICE using brakes. That's fine, I keep a bigger gap to traffic in front, and as I am approaching slowing / stationary traffic I lift off and slow down (on full regen) as I approach the traffic; if I'm still travelling too fast I have to use the brake, but 95% of the time I can drive without using the brakes. (In MS Regen only works down to about 8 MPH, so I have to use the brakes below that, but e.g. the Bolt can get to a stop on Regen only)

But that is a factor of the amount of Regen energy that Tesla has decided to harvest on an MS. They could harvest significantly more (on a Semi). On MS its one-pedal driving - lift off and you get regen. It could be done using brake pedal instead - press brake pedal and get regen, until the point where you are pressing the brake pedal hard enough that you have exceeded regen ability and you get physical brakes too. If Regen will be "huge" on a Semi then maybe they will make it a function of Brake pedal, rather than one pedal driving. Much as I love one pedal driving I would be very happy if Regen was on brake pedal. In MS: if battery is cold or 100% charged then Regen is limited or non-existent; opportunity to get caught out by that by lifting off and expecting Regen but getting none! whereas if it was all on Brake pedal you'd press that and get Regen, if available and sufficient, otherwise you would get brakes.

The Bolt has a High/Lo switch for regen (so does the MS but its basically "almost nothing" and "normal" to allow Newbies to convert), so perhaps Tesla will provide Regen adjustment no the Semi - e.g. if trailer is empty or fully loaded.

Are you anywhere near a Tesla sales centre? If so I'd recommend getting a test drive. Whilst on the one hand driving a Tesla is just like driving any other car there is also a difference, and its hard to describe. The whole one-pedal-driving thing, with Regen, the lack of noise, the smoothness ... they are all "different" to ICE, and to my mind way, way better. I expect some of that will translate to driving an EV Semi, and you'd have a better feel for that if you had driven one. Look sufficiently interested in the MS / MX and talk Tesla into lending you one for the weekend for an extended trial perhaps?

Sounds like driving a Tesla car is more like driving a heavy truck if you want to avoid using the brakes.

I'd love to test drive a Tesla, I have no doubts about the drivability, quietness and smoothness. I'm actually considering one for local commuting. The biggest issue is range, I live out in the country that will be it's limiting factor.

As for the semi, we could probably do around fifty percent of the work we currently do with diesel powered trucks, for the rest we would be limited by either range or weight. This is only if we purchase two charge stations as well as the trucks.

Range is never what's advertised and weight hasn't even been mentioned yet in Tesla's case.

 

[electracity]

Range is never what's advertised and weight hasn't even been mentioned yet in Tesla's case.

The head of semi development said the design goal was equal weight to diesel. This is another indicator of a generation of batteries beyond the model 3.

Not sure what you mean, battery pack center is forward of the midpoint of the front and front rear axle. So >50% weight on front axle.

They had the option of more batteries over the front axle. But they met the design weight distribution with a cleaner design.

 

[WannabeOwner]

for the rest we would be limited by either range or weight

This is the first release of Tesla Semi model. The first Model S was far less range than the S100 of today ... so if First Version Semi matches 50% of Diesel I reckon that's pretty good, as it can only get better as Battery technology advances

 

[jkn]

Well, come for a ride in a heavy crosswind and I promise you'll be reprogramming your computer. It is possible even for empty trucks to have problems achieving the speed limit in heavy crosswinds due to power limitations, turn straight into the wind and load lightens up on the engine. Anybody that's driven a truck can tell you this.



12,000lbs in the US. If the Tesla is lighter they are wasting potential net load unless they can move the fifth wheel forward enough.

You think you can steer a semi with the rear wheels? Please call us when you do, this is entertainment we wouldn't want to miss



Your rear wheel steering will cause far more than it'll prevent...




Traction?

It could be I don't know the finer points of racing but for the most part truck tires on dry pavement are not a huge traction issue...

Again, this is all theory.

Thanks for invitation, but wrong continent. It is easier to ask young relative when I seem him. I guess he drives heavier truck than you, but not one of these:
104-tonninen monsterirekka aloitti puunkuljetukset Lapissa
Total 104 000 kg
cargo 77 000 kg
length 33 m
fuel usage 65 - 80 l/100 km
Fetches wood from 68°39′N, 027°33′E, so not easiest conditions. Next sunrise at end of January.

I have newer seen or heard truck driving slower than legal limit 80 km/h, because of wind. You say crosswind is worse than headwind. Normal truck has gaps between truck and trailer and under it. Crosswind going through those gets accelerated to speed of the truck. This increases engine load. In Tesla semi those gaps are closed. So crosswind has less effect than headwind for Tesla semi.

If I understood correctly: If steering axle has less than 11 klbs on it, truck cannot weight full 80 klbs. Moving fifth wheel forward would help. But they don't need to do it. It takes years before they can produce even 1% of new trucks sold. They don't need to make truck for everybody. Truck for 1% is enough for years. They need hundreds trucks to transport their own products. Can they produce those in one year?

Steering car with electric motor on each wheel has been done and it works well. For example Rimac: Rimac Automobili Concept_One

Of course it will work with semi. I'm certain Tesla has tested it and found it prevents jackknifing, but I don't believe they have found all possible conditions.

If all weight is on driving wheels, 3 s 0-60 mph causes no traction problems. For faster acceleration softer tires are needed. Those do not last long. Truck tires should last long under heavy load, not so good under light load. I don't know acceleration times on those videos or what they have done for tires. It is interesting to see effect of motor torque on truck frame.

Lithium batteries are not only theory. We know what they can do. We can roughly estimate what truck needs. Answer is not exact, but we know it is not enormously heavy.

 

[oneday]

I don’t think I would have thought this until I owned an electric car and truly lived the superior torque of electric motors, but the exhaust coming off of those trucks is so disgusting, inferior, and primitive.

It really thrills me that Tesla is going after the semi market. I think it will really drive the point home to the masses that the electric drivetrain is superior in every way. And eventually it will be superior in every way with no compromise, lots of investing still to be done however. The rest of the manufacturers just need to jump on board.

 

[Farmertom]

Well people, basically Tesla and batteries have three criteria to meet, performance, range and weight, so far it appears they can only meet two. Nikola has seen this, hence the hybrid.

It's good Elon is trying to build a truck, it's good Trevor is trying to build a truck. They both have major challenges to overcome, one or maybe both will succeed.

I wonder if they are selling components to each other? Nikola one supplies gear trains and axles for Tesla and Tesla supplies batteries and, motors and controllers for Nikola one? I don't know, isn't Elon big on sharing technology? Cooperation would be good in my opinion.

Is the Tesla semi ill conceived, I'd have to say no. Rushed a bit maybe but not ill conceived. As was said, if nothing else and the truck doesn't make it into mainstream goods transportation, Tesla will have a fleet to move components and finished product, the trucks look good and fit nicely with Tesla's goals to electrify transportation. They will also be good for development and refinement of batteries and drive train components.

 

[oneday]

Well people, basically Tesla and batteries have three criteria to meet, performance, range and weight, so far it appears they can only meet two. Nikola has seen this, hence the hybrid.

Nope, Tesla has met all three for more than half of all trucking needs in the US, provided they provide the charging infrastructure (something they’ve proven to be more than capable of).

As to Nikola, I wish they didn’t include “fool” cells, but wish them luck.