I think driving a large trucks in tight spaces is hard and stressful. I see a semi backing into a dock and I'm always impressed and glad it is not me at the wheel. Not to mention that car drivers behave like suicidal idiots around large trucks.
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I think driving a large trucks in tight spaces is hard and stressful. I see a semi backing into a dock and I'm always impressed and glad it is not me at the wheel. Not to mention that car drivers behave like suicidal idiots around large trucks.
Trucks will always have to take corners at reduced speeds because of how the trailers are loaded. I don't care how low the center of gravity is in the tractor it will never be low enough in the trailer to take at normal speeds. It's all physics. You sound like you've never seen a fully loaded trailer. The carriers try to maximize space used within the weight limit. That means you have a lot of freight that is a inch or two from touching the roof. This is why sometimes you will see loaded trailers that have rolled at a stop light when the driver tried turning left. We have to go slow because the trailer is much higher than it is wide (8 ft wide x 13 ft and 6 inch high). It's really kind of amazing we don't have more roll overs when you think about it really but the reason we don't is because as a truck driver we know how unpredictable it is to guess how fast as can go on a curve before rolling it. Instead we go slower than we think w e can because it only costs us a few seconds in the grand scheme of things.
By the way some of you sound like you want this thing thing to accelerate like a model S would. That is completely ridiculous and unrealistic. I don't think that could be done when hooked to a trailer(s). I wouldn't want it to either. Think of the freight in the trailer. If you accelerate hard where's that freight going to go? Yes we have to strap and tie freight down but you'd be surprised how easily some skids will fall apart after the driver had to do some kind of emergency braking.
Even though YOU might want a semi to get up to speed at stop lights for your convenience realistically I hope that doesn't happen because semis are currently built to transport freight from point A to B safely and smoothly. It's dangerous to build a semi for performance primarily I believe. If someone wants something fast then a semi is not for them.
A heavy electric semi will have more useful ability to usefully accelerate from a stop due to elimination of the transmission. So fast cornering is , of course, ridiculous. But the ability to keep up with stop and go traffic in an heavy electric truck should improve.
Regen is one of the tricky areas that departs from Tesla cars. Strong engine braking can jacknife a tractor trailer, and strong regen on slippery roads have the same risk. How regen will work in tandem with conventional trailer air brakes is an interesting question.
At a minimum Tesla probably wants to continually measure the angle of the trailer to the tractor. Tesla may require a specialized trailer to maximize performance.
Regen is one of the tricky areas that departs from Tesla cars. Strong engine braking can jacknife a tractor trailer, and strong regen on slippery roads have the same risk. How regen will work in tandem with conventional trailer air brakes is an interesting question.
At a minimum Tesla probably wants to continually measure the angle of the trailer to the tractor. Tesla may require a specialized trailer to maximize performance.
Etna
Member
Not only measure but act on it: you can also do torque vectoring while in regen. This would provide "seriously next level" stability when slowing down on slippery roads. To me it is a given that the Tesla semi will feature this.
Traction and braking should be much improved over conventional trucks. But for me the question is the trailer axles. Can/will Tesla design a tractor without trailer axle sensors? I don't think Tesla will design with batteries in a specialized trailers. But they would benefit from sensors and cameras on the trailer.
For version 1.0 the driver will likely be responsible for engaging regen as they did engine braking. Perhaps a jackknife warning system will be added. More automation will require Tesla to take responsibility for preventing jackknifing.
Etna
Member
My point is that regen torque vectoring can prevent jackknifing under most circumstances - you do not need to power/regen the trailer axles.
Think of it this simple way: your are braking on a slippery road, jackknifing event starts as the trailer begins to nudge the rear axles of the truck sideways to the left. Truck senses this and commands more regen torque on the left side and less on the right side, this basically slides the truck braking force vector to the left of the trailer center of gravity, and realigns the truck with the trailer. Jackknifing movement has been neutralized. The sooner the movement is detected, the easier it is to counterbalance it. In extreme cases such as braking during turns, you can even add a bit of power on the forward right wheel while all the others are in variable levels of regen for extra stabilizing effect.
Think of it this simple way: your are braking on a slippery road, jackknifing event starts as the trailer begins to nudge the rear axles of the truck sideways to the left. Truck senses this and commands more regen torque on the left side and less on the right side, this basically slides the truck braking force vector to the left of the trailer center of gravity, and realigns the truck with the trailer. Jackknifing movement has been neutralized. The sooner the movement is detected, the easier it is to counterbalance it. In extreme cases such as braking during turns, you can even add a bit of power on the forward right wheel while all the others are in variable levels of regen for extra stabilizing effect.
At least in the US, highway speed limits for trucks are significantly lower than they are for cars, and for good reason. Yes, drivers routinely exceed speed limits but even so, truck traffic typically moves slower than car traffic on the open road. I am not worried about sharing highways with EV semis. In fact I welcome them for many reasons, including the fact that they will be able to brake more effectively and therefore will be safer.
If Tesla can show trucking fleet operators that the Tesla Semi is more economical to operate than conventional diesel trucks the operators will buy thousands of them. And based on yesterday's Q1 2017 Earnings Call, Elon clearly believes the Tesla Semi will offer a compelling value proposition.
The big question in my mind is how a Tesla Semi with a, for example, 1,000kWh battery will be charged. I expect that when Elon reveals the Tesla Semi he will also announce that Tesla will be creating new dedicated Supercharger stations that charge at well over 300kW peak.
Skotty
2014 S P85 | 2023 F-150L
Here's a slightly off topic question for you semi experts. Why do semis hauling cow trailers always go faster than other semis? Is it because they hate the stench of their trailers as much as everybody else and can't wait to get rid of it? Seriously, I think it's probably because it's a lighter than typical load. But without fail, they are always traveling faster than other semis. They might like to have the Tesla semis. 
The biggest advantage to a Tesla semi is no diesel storm clouds when taking off from a stop. Really, dump trucks are worse. They should make a Tesla dump truck.
The biggest advantage to a Tesla semi is no diesel storm clouds when taking off from a stop. Really, dump trucks are worse. They should make a Tesla dump truck.
Once Tesla convincingly demonstrates that a long haul commercial BEV semi truck is more economical than the traditional ICE trucks, other companies will be motivated to develop other truck types as BEV vehicles. Tesla can't do everything, they just have to lead the way just like they are leading the way in the vehicle markets they currently compete in.
Here's a slightly off topic question for you semi experts. Why do semis hauling cow trailers always go faster than other semis? Is it because they hate the stench of their trailers as much as everybody else and can't wait to get rid of it? Seriously, I think it's probably because it's a lighter than typical load. But without fail, they are always traveling faster than other semis. They might like to have the Tesla semis.
The biggest advantage to a Tesla semi is no diesel storm clouds when taking off from a stop. Really, dump trucks are worse. They should make a Tesla dump truck.
Dump Truck drivers are drivers who have too poor of a driving record to be hired by a trucking company.
Cow Haulers are by far the worst on the road by far. Some are good drivers but as a percentage they are the worst out of all truck drivers. The reason why is because they more times than not are just farmers who own a truck. They don't have the training or the care to drive like the rest of us professional drivers. They have uncovered trucks and violated traffic laws more often then the rest of truck drivers because they have no risk of losing their job if they get any violations or complaints.
As a professional driver these drivers give us all a bad name.
I believe Tesla Bjorn (Bjorn Nyland on YouTube) has demonstrated that the Model X with towing configuration has software programming to do what you are talking about. IIRC he had some episodes where he is towing with his Model X in the weather of Norway and specifically talks about how he feels the SUV is reacting to the road conditions and compensating as he is towing, making him more stable.
It has "anti-sway" built in. Whether or not it works the way @Etna describes, I cannot say. For that matter, Tesla has also been unwilling or unable to explain how it works when asked directly.
A traditional way of eliminating sway is to apply the trailer brakes to build back tension between the towing vehicle and the trailer. Tesla's anti-sway most assuredly doesn't interact with the wire harness between the aftermarket brake controller and the trailer, so this method is unlikely what they refer to.
To confirm: a few months ago I asked my local Tesla Service manager if the Model X Towing option package software controlled the trailer brakes through the trailer harness and was told "No" and that the anti sway control was done with the Model X brake system.
Back to the Tesla Semi: is Tesla going to build special Supercharger stations just for their truck? Since the Tesla Semi is likely going to have a battery pack of 1,000kWh or more, today's Superchargers that max out at 135Kw or so will take many hours to charge them.
If it becomes a reality it'll be truck stops and Carrier facilities that will place them on their property. As a truck driver I'm quite skeptical to say the least that Tesla will be successful in this market. Like I've said before without 700 miles worst case scenario range and 80% charge from very low in 30 minutes I don't see it happening. Trucks move too much and sit too short of time to make this economical without meeting those two requirements that I've set.
Skotty
2014 S P85 | 2023 F-150L
If trucks had full autonomy on highway (as in, driver not required) they wouldn't have to stop to sleep, and this would allow more time for charging. A bit far fetched maybe? Actually, maybe the concept will be charge while you sleep. Truck has to run a pretty long haul between charges under that scenario though.
adiggs
Well-Known Member
The long haul trucks you're speaking of here - do you know roughly what % of them are running with 2 person teams, or otherwise changing drivers to keep the truck moving while the driver is sleeping / not working?
My notes form earnings call on Tesla Semi:
- will manufacture themselves without partner, uses a bunch of Model 3 motors, able to use high volume components from Model 3
- will have fairly high gross margins, appealing product at low cost
- JB: incremental complexity of building it is a lot less than you might think
- will sell to fleet operators - that is how it will occur. Operators look at economics (cost per ton per mile) - if it's better, they will buy a huge number. Elon confident it will be better
- will manufacture themselves without partner, uses a bunch of Model 3 motors, able to use high volume components from Model 3
- will have fairly high gross margins, appealing product at low cost
- JB: incremental complexity of building it is a lot less than you might think
- will sell to fleet operators - that is how it will occur. Operators look at economics (cost per ton per mile) - if it's better, they will buy a huge number. Elon confident it will be better
adiggs
Well-Known Member
Now THIS is a business model that appeals to me, and is exactly what I was hoping to see from Tesla Semi. Keep their capital investment focused on building more vehicles, and let other people like the fleet operators figure out the capital / financing for owning them.
Thanks for the notes @tlo.
I'm not sure how just three M3 motors is going to provide enough power for the Semi to out-torque. Six, maybe. I think 1500hp would be a minimum. Anyone have a theory?
adiggs
Well-Known Member
Maybe the motor's HP/torque output is more limited by the rate at which power can be dumped into the motors, than the motors themselves. In which case, maybe 3 motors can get closer to the 1500HP you're looking for, simply because Tesla Semi will have better power delivery from the battery(s).
To an earlier point about sports car semi's - for in town driving and getting stuck behind a slowly accelerating semi from a stop, simply having 1 or a very small number of gears and a flat torque curve that allows steady (if low) acceleration with no gear changes will be a nice improvement for traffic. It's not just the low acceleration - it's also the accelerate 5 more miles of hour, shift, accelerate 5 more mph, shift, ..., that drags out the acceleration process. And that sounds like something electric motors do a lovely job of helping with
To an earlier point about sports car semi's - for in town driving and getting stuck behind a slowly accelerating semi from a stop, simply having 1 or a very small number of gears and a flat torque curve that allows steady (if low) acceleration with no gear changes will be a nice improvement for traffic. It's not just the low acceleration - it's also the accelerate 5 more miles of hour, shift, accelerate 5 more mph, shift, ..., that drags out the acceleration process. And that sounds like something electric motors do a lovely job of helping with
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