In the presentation when Tesla announced the Semi. It doesn't seem to be included on the web site right now.
But the 500 mile range is for 80,000lbs at 65 MPH on the highway.
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Tesla semi is ill conceived...
- Thread starter jr4488
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In the presentation when Tesla announced the Semi. It doesn't seem to be included on the web site right now.
But the 500 mile range is for 80,000lbs at 65 MPH on the highway.
Side wind could push truck out of the road, but it does not increase energy consumption as much as direct head wind. Truck has 5 times air resistance of a car, but mass and rolling resistance is 20 * higher.
Of course information is theoretical, but it makes sense. Tesla needs lot of those trucks to ship cars they make to customers. I guess they are receiving orders so fast that they don't need to advertise it.
Published acceleration tells that max legal US load makes it 4 * heavier.
If you think that CFD calculations aren't conducted for crosswinds, you're sadly mistaken.
A conversation can't be held in abstract terms. If you're casting aspersions on the legitimacy of something I've said in particular, please mention what you're thinking of specifically. If you're just trying to be dismissive in general... that's not exactly a productive avenue of conversation.
It'll be interesting to see their life cycle, period. As with any new motor, it's simply a manner of hoping that the testing has been conducted in a way that accurately encapsulates the full breadth of operating conditions. And this is a new motor. That said, it's not Semi that will be putting the miles on it first, it's Model 3. Yes, different operating conditions, but still nice to at least get real users out there before you start putting four in each truck.
An important thing to keep in mind. While Tesla, as a company as a whole, does not have experience with semis, the people involved in its Semi program absolutely do. This isn't Jerome Guillen's first rodeo, nor a large chunk of the people under him. So let's not assume that the programme is being run by idiots.
T34ME
Active Member
WannabeOwner
Well-Known Member
I know absolutely Jack about it, but I am curious to know the answer.
Can you make an educated guess based on weight on an ordinary Tractor, take away the weight of Engine and Fuel (presumably you calculate your Max haulage load based on having a full fuel tank?) and then adding the weight of 10 x the battery in the MS / MX 100 model?
I'm guessing that body weight will be similar, and electric motors straight substitution for DIFF etc. Dunno if we have to swap gearbox for motors, or if we can swap the weight of that for battery?
Based on a quick Google 1500kg for engine and 500kg for fuel? so 2,000kg in-hand as a starting point.
From what I could find the 85 kWh battery (which is an old thing by today's standards) was 540 kg, and speculation that the 200 kWh roadster battery will be 833 kg
So battery was 600-ish kg/100kWh and is heading towards 400-ish kg / 100kWh.
So 1,000 kWh battery will be between 4000 kg and 6000 kg
So adding between 2000 kg and 4000 kg to existing tractor weight, and commensurate loss of load, less any weight credit we get from removing the gearbox
But only if my assumptions are anything like plausible?
T34ME
Active Member
Cross winds increase drag dramatically, I promise you. Head on you have a sloped surface 8.5ft wide and 13.5ft tall with drag being produced from the same area at the rear.
Cross winds hit the whole area of one side and the front while the whole other side and rear is producing drag. Even if you've never been in a truck chances are you've been in a car that has been buffeted by the blast of air on the leeward side of trucks. Those trucks are using allot of energy to move that air.
Nope, just commenting on what I see.
So far it's sales pitch that those not in the industry are buying. Hopefully for Tesla's sake it's within sight of the truth.
I did some rough math earlier and I came up with a tare weight of about 12,000kg to 14,000kg, a typical highway truck in North America is about 8000kg to 9000kg full of fuel.
I removed engine, transmission, fuel and tanks (about 3000kg). Added a thousand kg for motors, gear trains and controls and about 6000kg for batteries. Rear axles themselves will almost be the same. The frame needs to be heavier as it appears to have go over and under the batteries. The location of the batteries is also a bit of a clue as it appears there's dead space over the front axle hinting that they are very heavy and have to favor the rear of the vehicle.
Quite to the contrary - some of the US's largest fleet operators are not only "buying it", but helped develop it, and had orders ready to go at the launch event.
BTW, my apologies that you got accused of working for the oil industry simply because you come from a different perspective and background. I always try to stick with the Wikipedia principle: "Assume Good Faith"
T34ME
Active Member
T34ME
Active Member
I didn't accuse him of anything, just asking a question like he asked you.BTW, my apologies that you got accused of working for the oil industry simply because you come from a different perspective and background. I always try to stick with the Wikipedia principle: "Assume Good Faith"
TaoJones
Beyond Driven
True, in a sense...
First of all there are only a few trucks, the orders I've seen aren't even pocket change for these companies, this is their "go out and play with" money. They are going to try them out and see if they can make it work.
Second I bet they are going to try these trucks on runs that have light loads, it'll be interesting to see if they can compete with the light tractors they are currently using.
Third, if these companies can improve their environmental image to the public there may be bumps in sales that'll offset potential inconvenience and costs of running these trucks. They'll be going "green".
BTW, my apologies that you got accused of working for the oil industry simply because you come from a different perspective and background. I always try to stick with the Wikipedia principle: "Assume Good Faith"
Actually, it was a question but no problem, I've been called worse
Look, I get the concept, I believe these units will clean up the environment a bit, I don't believe they'll affect man's contribution to climate change but that's another topic. I'm just seeing holes in their claims you can drive these trucks through. I grew up with trucks, been around them all my life, been in them, under them, rebuilt them and driven them. I know how wind affects them as well as many other factors, I also know the bottom half a fuel tank or battery never carries you as far as the top half.
Elon doesn't know anything about trucks, that's a given and if Jerome knows as much about trucks as people seem to think on here he would also know how important weight is to the people that buy these units. Acceleration and the ability to climb hills at posted speed is cool but fleet operators couldn't care less, their goal is to get as much product per load from point a to point be cheaply and reliably. Every manufacturer claims their equipment runs cheaper and more reliably than the others, one of the reasons Freightliner is so successful is they build some of the lightest trucks on the road, Jerome should know this.
I choose when to engage regen by modulating the accelerator pedal on my Model S all the time. Not hard to learn how to simply not dump the go-pedal.
Besides which I would expect an option to move regen from pedal to hand-initiated control would be easy to implement.
A little more on aerodynamics from my flight training days
Angle of attack - Wikipedia Slip (aerodynamics) - Wikipedia
A highway truck and box trailer is basically the shape of an airfoil or the fuselage of an aircraft, driving straight into the wind is like a well trimmed airfoil or aircraft, the wind parts and flows smoothly around the vehicle. As the angle of attack increases turbulence forms on the upper side of an airfoil or on the leeward side of the aircraft fuselage or truck, as this angle of attack increases the turbulence gets worse and drag increases. This is beneficial for aircraft in certain instances (increased rate of descent, increased lift to a point) but requires lots of power to overcome drag, for trucks it just uses more power, thus more energy, basically no benefit unless you're traveling down hill.
Angle of attack - Wikipedia Slip (aerodynamics) - Wikipedia
A highway truck and box trailer is basically the shape of an airfoil or the fuselage of an aircraft, driving straight into the wind is like a well trimmed airfoil or aircraft, the wind parts and flows smoothly around the vehicle. As the angle of attack increases turbulence forms on the upper side of an airfoil or on the leeward side of the aircraft fuselage or truck, as this angle of attack increases the turbulence gets worse and drag increases. This is beneficial for aircraft in certain instances (increased rate of descent, increased lift to a point) but requires lots of power to overcome drag, for trucks it just uses more power, thus more energy, basically no benefit unless you're traveling down hill.
Truck has an advantage over an aircraft. Wheels cancel sideways force without adding energy consumption. Because of this headwind causes more drag than crosswind.A little more on aerodynamics from my flight training days
Angle of attack - Wikipedia Slip (aerodynamics) - Wikipedia
A highway truck and box trailer is basically the shape of an airfoil or the fuselage of an aircraft, driving straight into the wind is like a well trimmed airfoil or aircraft, the wind parts and flows smoothly around the vehicle. As the angle of attack increases turbulence forms on the upper side of an airfoil or on the leeward side of the aircraft fuselage or truck, as this angle of attack increases the turbulence gets worse and drag increases. This is beneficial for aircraft in certain instances (increased rate of descent, increased lift to a point) but requires lots of power to overcome drag, for trucks it just uses more power, thus more energy, basically no benefit unless you're traveling down hill.
I believe Tesla semi is not heavier than diesel truck. Battery back of MS is heavy because of protection plate under it. You don't need increase that when increasing capacity. They can back 200 kWh into a small car, so batteries are not enormously heavy. I expect larger capacity batteries for S&X soon.
Published acceleration tells that max legal US load makes it 4 * heavier. Is 20 000 lbs heavy or not?
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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.
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?
Quite to the contrary, that would be unexpectedly heavy. Model S/X battery packs are ~180Wh/kg. Model 3 is supposedly ~150Wh/kg. As a general rule, the larger you go, the higher the Wh/kg as more of the weight is comprised of cell mass rather than overhead. Take ~180Wh/kg and 900kWh. That would be 5 tonnes (11k lbs). Do you honestly think that everything else is 9k lbs? Especially given that Tesla tends to do things like build primary structural support with ultra high strength steel rather than mild steel? Given how light the drive units are? Given the lack of the diesel engine, transmission, pollution controls, and everything else associated?
No.
Furthermore: throughput payload mass divided by time to delivery. Time to delivery can be limited by speed limits, but more often fuel consumption considerations. Make the "fuel" far cheaper and you can afford to drive faster. In terms of throughput mere 5mph speed increase outweighs a 6% decrease in payload. And has already been covered here, given:
14h window
11h max driving in that window
30 minute break no more than 8 hours in
500mi @ 60mph** + 400mi @ 60mph (in a 30 minute break) = 900mi @ 60mph = 15h = way more than 11h, meaning you're doing the normal 11h+0,5h.
We don't have data for higher speeds. But something like:
420mi @ 70mph + 336mi @ 70mph (30 minute break) = 765mi @ 70mph = 10,93h driving + 0,5h charging
335mi @ 80mph + 268mi @ 80mph (30 minute break) + 268mi @ 80mph (30 minute break) = 871mi @ 80mph = 10,89h driving + 1h charging
** Some people here have been saying 65mph. But Musk very clearly said 60mph in the presentation. The press kit doesn't say either way.
In urban driving, range becomes essentially irrelevant, since total range increases while the speed at which you rack up the miles decreases. Meanwhile, while the truck is constrained by speed limits, the huge acceleration advantage will shave off time - dramatically where stop and go traffic is significant. Once again: time is inversely proportional with throughput; less time = more throughput.
In Europe, the situation is even more extreme. Because rather than 14h/11h/30m, it's 4,5h/45m: for every 4 1/2 hours of driving, a driver must stop for at least 45 minutes. So with electric, you always want to hug those speed limits, because you have downtime galore and your energy is cheap!
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