Cybertruck Will be a Towing GOD - Part 1: Torque (Newest Video)

[cybertrucktruckguy]

Advertisement

 

[Dids]

Waaaaah waaaaah waaaaah! That's also the sound of people that think a f150 will be better for towing.

 

[Sirfun]

It would be interesting to have comments or video from people who have use their model X towing.

 

[bfdog]

The CT will be a towing God? How much stamina, endurance, and life-span does God status require?

The CT towing 14k+ will be like a champion powerlifter competing in a Crossfit contest. I agree with the comments that up to a certain speed a Tesla torque curve is flat in a good way.

I used an electric weedeater about 40 years ago (yes, in '80s). It was a torque monster. But it was a pain to stretch the cord all around the 1.5 acres. The 2-stroke I finally bought was much better--they still are. 40 years later a battery weedeater still can't really finish that 1.5 acres. The batteries would peter out. And need replacement after 1 season. But my little 80 year old neighbor loves his for light work. He brags that Home Depot keeps taking the batteries back on return after they fail early (lifetime battery on Ryobi?)

Towing EVs are almost in their infancy. But they must get born first. After a pregnancy. The parents haven't even been picked yet. (Isn't Tesla still searching for a site to build the Cybertruck? Isn't Tesla trying to figure out ventilators? While working remotely? Wait, aren't they trying to figure out big rigs? Which reminds me, heck, aren't they trying to figure out batteries?)

I have an electric bike--I love it. For 20 miles. No comparison betwix it and my motorcycles. I have a battery chainsaw and three that are heavy duty (ish) and gas. To make my echo battery chainsaw badass enough to beat my Stihl Farmboss, the echo would last 1-5 cuts.

I am starting to wonder about the wisdom of spending 90K (all in) on a replacement for my 18 year old 7.3 F250. I did rough numbers in my head one day and think battery degradation alone (from abusing the battery towing) in addition to electricity costs will be ballpark 50 cents a mile for towing. I need to do a spreadsheet though with actual guestimates. At a minimum I'm thinking of going back down to 1 motor and keeping the diesel for towing. I mostly just want a "truck" and FSD.

 

[Dids]

The CT will be a towing God? How much stamina, endurance, and life-span does God status require?

The CT towing 14k+ will be like a champion powerlifter competing in a Crossfit contest. I agree with the comments that up to a certain speed a Tesla torque curve is flat in a good way.

I used an electric weedeater about 40 years ago (yes, in '80s). It was a torque monster. But it was a pain to stretch the cord all around the 1.5 acres. The 2-stroke I finally bought was much better--they still are. 40 years later a battery weedeater still can't really finish that 1.5 acres. The batteries would peter out. And need replacement after 1 season. But my little 80 year old neighbor loves his for light work. He brags that Home Depot keeps taking the batteries back on return after they fail early (lifetime battery on Ryobi?)

Towing EVs are almost in their infancy. But they must get born first. After a pregnancy. The parents haven't even been picked yet. (Isn't Tesla still searching for a site to build the Cybertruck? Isn't Tesla trying to figure out ventilators? While working remotely? Wait, aren't they trying to figure out big rigs? Which reminds me, heck, aren't they trying to figure out batteries?)

I have an electric bike--I love it. For 20 miles. No comparison betwix it and my motorcycles. I have a battery chainsaw and three that are heavy duty (ish) and gas. To make my echo battery chainsaw badass enough to beat my Stihl Farmboss, the echo would last 1-5 cuts.

I am starting to wonder about the wisdom of spending 90K (all in) on a replacement for my 18 year old 7.3 F250. I did rough numbers in my head one day and think battery degradation alone (from abusing the battery towing) in addition to electricity costs will be ballpark 50 cents a mile for towing. I need to do a spreadsheet though with actual guestimates. At a minimum I'm thinking of going back down to 1 motor and keeping the diesel for towing. I mostly just want a "truck" and FSD.

When you say electric bike do you mean motorcycle or bicycle? Why do you only get 20 miles? Most electric motorcycles claim in the 200 miles range.

 

[bfdog]

I have a $7,000 Optibike that claimed in the 50 mile range.

 

[Dids]

I have a $7,000 Optibike that claimed in the 50 mile range.

That's terrible expensive bike for such poor performance.

 

[bfdog]

The bike performs well with my fat ass (200 lb) going up my steep hill. It's the difference between riding in these hills and not riding. And I travel 28 mph on flat land (up to 32 some spots if I hump it pedaling). I bought it when my job took me further from work and the bike commute increased by triple.

Thank you for your input on the value of my ebike. I'll file it accordingly.

But the real question is whether a 90K eTruck will be a towing God with (then in two years) current battery technology. Or will the CT be the equivalent of a 5k-7K bike that gets 50 miles range (20-25 with a fat ass in hills (like towing)). Should we believe a 20 minute (part 1) propaganda video that takes 20 minutes to establish: 1. torque is force; 2. electric motors readily have torque; (3) torque is good for towing and acceleration. I much preferred the video of the physicist that discussed the math of energy density. Today I'm thinking of switching to a Bolt but I really want FSD but I don't think FSD will work well so I'm maintaining status quo and continuing to build the CT fund.

 

[Dids]

The bike performs well with my fat ass (200 lb) going up my steep hill. It's the difference between riding in these hills and not riding. And I travel 28 mph on flat land (up to 32 some spots if I hump it pedaling). I bought it when my job took me further from work and the bike commute increased by triple.

Thank you for your input on the value of my ebike. I'll file it accordingly.

But the real question is whether a 90K eTruck will be a towing God with (then in two years) current battery technology. Or will the CT be the equivalent of a 5k-7K bike that gets 50 miles range (20-25 with a fat ass in hills (like towing)). Should we believe a 20 minute (part 1) propaganda video that takes 20 minutes to establish: 1. torque is force; 2. electric motors readily have torque; (3) torque is good for towing and acceleration. I much preferred the video of the physicist that discussed the math of energy density. Today I'm thinking of switching to a Bolt but I really want FSD but I don't think FSD will work well so I'm maintaining status quo and continuing to build the CT fund.

Oh I didnt mean to imply that optibike isn't good, I dont know anything about it. And certainly batteries vs fossil fuel weight for hand tools fossil fuel wins. But power is not just energy, and anyone that thinks how the energy is converted is not important is wrong. I think the video was just laying the ground work by explaining torque and I hope the next videos explain how the power required as load increases is where electric motors excel.
For instance. If a power plant uses 100w to produce 100rpm x 1 ft/lbs of torque.
100=100×1 and another power plant uses 100w to produce 50rpm x 2 ft/lbs
The second power plant has higher torque. If we add an additional load of 1 lbs.
100rpm×2ft/lbs = 200 watts
50rpmx3ft/lbs= 150watts
The second higher torque system can handle the same increase in load but doesn't experience the same increase in energy required. Yes I know this is a gross simplification and that my for instance power plants are horribly inefficient.

 

[ajdelange]

Let's assume that the CT weighs 3,000 kg and that we want to accelerate it to 100 km/h in 5 seconds. 100 km/h is 100,000/3600 = 27.778 m/s so assuming the acceleration to be uniform that would give an acceleration of 27.778/5 = 5.555 m/sec^2. Newtons 2nd law: F = m*a says that the force applied to the vehicle through thrust must be 16,665 Newtons. Since torque is just force times the length of the arm through which it is applied and the radius of the wheels is about half a meter the required torque is 0.5 * 16665 = 8332.5 Newton-meter. That's 6145.7 lb-ft. Thus a couple of things are clear at this point. The first is that the 1000 lb-ft number given for torque is clearly inadequate. The second is that if you are going to tow a trailer that weighs the same as the CT the mass that needs to be accelerated would be 6000 kg and the acceleration, a = F/m, from 6145.7 lb - ft would be half 27.778 m/s. This should be no surprise. You don't go from 0 to 60 as quickly when towing as you do when not.

Thus our concern with torque is that it is converted to thrust (by dividing by the wheel radius) and it is thrust which accelerates the vehicle. Power taken from the motor is the product of the torque and the wheel speed. So when one steps on the accelerator at a standstill very little power is required, at first, to accelerate at 5.55 m/sec^2 but 8332.5 N-m is from the very beginning. This is the reason torque is specified. The vehicle may have plenty of torque to overcome drag at cruising speed but if it doesn't have that same torque or more at 0 speed the vehicle will take forever to accelerate. And here is where an electric motor shines. It can deliver its maximum torque (or close to it) down to 0 rpm. In fact torque stays constant up to the point where we must limit power to the motor in order to avoid burning it up. We have to limit torque in oder to keep the product of torque and motor speed within limits - it's not a fundamental torque limitation of the motor. ICE engines, con versely, cannot deliver any torque at 0 speed. They must be run at some appreciable speed in order to be able to deliver any torque and geared down to make that torque available at low wheel speed.

Note that we figured out what the torque would be from the mass and acceleration only. IOW we don't really need to even consider torque to determine the performance of the vehicle. Thus torque really isn't that important. I think it is given because truck buyers expect to see it. Note that it is not given on the reservation web page. If you want to know what it is for each of the models figure it out as I did above (of course they don't give the weight either).

Given this I'm not sure the video clarifies or muddies the waters.

Will the CT be fantastic for towing? Sure. It's 0 to 60 spec insures that it has the torque and it's 500 mi EPA range insures it has the range if you are satisfied that a 500 mi range truck is sufficient for towing. Note that some of the ICE vehicles offer 700 to 800 mi range through auxiliary fuel tanks. Electronic torque vectoring without the use of fancy mechanical differentials or the friction brakes promises improved towing stability. And you have all the other advantages of a BEV over ICE.

 

[bfdog]

Let's assume that the CT weighs 3,000 kg and that we want to accelerate it to 100 km/h in 5 seconds. 100 km/h is 100,000/3600 = 27.778 m/s so assuming the acceleration to be uniform that would give an acceleration of 27.778/5 = 5.555 m/sec^2. Newtons 2nd law: F = m*a says that the force applied to the vehicle through thrust must be 16,665 Newtons. Since torque is just force times the length of the arm through which it is applied and the radius of the wheels is about half a meter the required torque is 0.5 * 16665 = 8332.5 Newton-meter. That's 6145.7 lb-ft. Thus a couple of things are clear at this point. The first is that the 1000 lb-ft number given for torque is clearly inadequate. The second is that if you are going to tow a trailer that weighs the same as the CT the mass that needs to be accelerated would be 6000 kg and the acceleration, a = F/m, from 6145.7 lb - ft would be half 27.778 m/s. This should be no surprise. You don't go from 0 to 60 as quickly when towing as you do when not.

Thus our concern with torque is that it is converted to thrust (by dividing by the wheel radius) and it is thrust which accelerates the vehicle. Power taken from the motor is the product of the torque and the wheel speed. So when one steps on the accelerator at a standstill very little power is required, at first, to accelerate at 5.55 m/sec^2 but 8332.5 N-m is from the very beginning. This is the reason torque is specified. The vehicle may have plenty of torque to overcome drag at cruising speed but if it doesn't have that same torque or more at 0 speed the vehicle will take forever to accelerate. And here is where an electric motor shines. It can deliver its maximum torque (or close to it) down to 0 rpm. In fact torque stays constant up to the point where we must limit power to the motor in order to avoid burning it up. We have to limit torque in oder to keep the product of torque and motor speed within limits - it's not a fundamental torque limitation of the motor. ICE engines, con versely, cannot deliver any torque at 0 speed. They must be run at some appreciable speed in order to be able to deliver any torque and geared down to make that torque available at low wheel speed.

Note that we figured out what the torque would be from the mass and acceleration only. IOW we don't really need to even consider torque to determine the performance of the vehicle. Thus torque really isn't that important. I think it is given because truck buyers expect to see it. Note that it is not given on the reservation web page. If you want to know what it is for each of the models figure it out as I did above (of course they don't give the weight either).

Given this I'm not sure the video clarifies or muddies the waters.

Will the CT be fantastic for towing? Sure. It's 0 to 60 spec insures that it has the torque and it's 500 mi EPA range insures it has the range if you are satisfied that a 500 mi range truck is sufficient for towing. Note that some of the ICE vehicles offer 700 to 800 mi range through auxiliary fuel tanks. Electronic torque vectoring without the use of fancy mechanical differentials or the friction brakes promises improved towing stability. And you have all the other advantages of a BEV over ICE.

So round figures, your 3kg truck produces 310 HP to do 0-60 in 5 seconds. And requires a force of 16.7 kN or 3754 lb. With 33 inch tires that requires motor torque of 5162 lb-ft.

And 535 HP to do 0-60 in 2.9 seconds (which pulls almost exactly 1 G)? So, if you drive a 3M toward a wall 41 meters away and drop a 3M from a height of 41 meters, they will hit the ground/wall at almost exactly the same time (assuming a spherical chicken) going 62 mph? To achieve that acceleration requires a force of 6520 lbs. If I want to pull that off with one motor driving 33 inch tires I need 9K lb-ft of torque? If I use the motor from the slow truck (5161 lb-ft of torque required), I need two additional 1850 lb-ft motors.

It takes a lot of force to get a mass to accelerate. By definition.

 

[ajdelange]

Here are some more musings on torque which I hope will help in clarifying some of the confusing material in the video. Perhaps an edit or two is possible.

The motor(s) in a truck are there for the purpose of providing a force on the truck in the direction of desired travel. This force does several things but the most significant of them is getting the truck moving that is, accelerating it to desired speed. Force is also needed to lift the truck up hills and push air out of the way but lets focus on getting the truck moving for now. The required torque is the required force multiplied by the wheel radius (this is the definition of torque) and the required force is the product of the mass of the truck and the desired acceleration. In symbols this is F = m*a which is Newton's second law and the basis for all classical mechanics. Since torque is simply force multiplied by arm (the technical term, here the wheel radius) we can multiply both sides of F = m*a to get F*r = T = m*r*a from which it is clear that the faster we want to accelerate the more T, torque we will need. The more torque we can obtain the faster we can get from 0 - 60. Thus we want all the torque we can get but there is a limit to what drive train components will tolerate before failing. In the sketch below the maximum available torque, let's mark it T, is denoted by the solid horizontal line in the "Torque Limited" part of the diagram which plots torque on the left vertical axis against wheel speed.

Now lets go back to the Newton law and multiply all terms by w, the angular speed of the wheel. This gives F*r*w = T*w = m*r*w*a. As r*w is the distance the car travels in a unit time, i.e. it is the speed of the vehicle, and as force times distance is energy and energy per unit time is power each of those terms is the Power transferred to the truck. The dashed line shows how that power, read off the right vertical axis, varies with speed . When the torque is held constant It increases linearly with speed. Eventually a point is reached where the motor's power capacity is reached. It cannot, or cannot safely, produce any more power and at speeds above this critical speed the power is constant at the maximum value the motor can produce. As power is the product of torque and wheel speed the torque must go down as speed continues to increase and this is shown by the solid curve in the "Power Limited" part of the chart. As acceleration depends directly on torque it is clear that the vehicle will not accelerate as swiftly in the power limited region as it does in the torque limited region. An electric motor, conversely, has a torque characteristic that is quite like the sketch.

I don't know how good a job I did of explaining this but a whole lot of the story is tied up in this graph.

 

[Dids]

Sweet god in heaven make it stop

 

[bfdog]

And

Sweet god in heaven make it stop

To sum up the graph, the Tesla pulls like a freight train with the same maximum force until about sixty mph then force drops off (the amount of acceleration) because power output or horsepower has limits. You can see it in drag race videos also of Teslas racing Porsches. The ICE cars start overtaking. I saw Tesla torque curves somewhere and they were nicely flat until 60 as I recall.

The video was frustrating. I used Engineerstoolbox for my calculations. I learned and used and could derive all those equations in the early 90’s. It’s on a website now. Plug and play.

 

[Keeney]

People have spent a lot of time talking about the range when towing, but there is another factor that comes into play. We know the CT can put out super high torque and power for 2.9 seconds at a time. What can it do for an hour at a time? Is it going to overheat (or thermally-self-limit) its motors or batteries or electronics pulling a heavy load up a sustained uphill road (through a mountain pass)?

Non-HD ICE trucks often fail this test - they have enough peak power available, but their cooling system is sized only for intermittent peaks at that power level, and it cannot sustain that amount of power without overheating.