Vrakpant

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METRIC SYSTEM FTW! -cough- in your face. (edit: realizing this is still 2020. no coronies. cough was entirely for dramatic effect. The cough wasnt directed at your face and I was wearing my mask. why am I even explaining this? Is all virtual anyway. anywhoo..)

What an awesome video! If the cybertruck has that kind of fuel efficiency it is simply ridiculously good. I do hope the calculations for batterypack size is with the "offroad" tires though, because I'm greedy like that. The weight of the truck is of particular interest to us europeeans as it relates to what kind of licence is required to drive it. I guess you could downgrade the loading capacity on paper to get it under 3.5tons(METRIC!)for a standard drivers licence. but that reduces the loading capacity from 1500kg(3500lbs) to about 1000kg. Not to mention the limitations on towing. Total allowed combined weight of car plus trailer is 4250kg on standard licence B. Will have to upgrade to licence BE anyways for a decent size trailer. But at least it is looking good for me not needing to get a category C1 licence (light lorry) for my truck. happy days.





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Humanoid1

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There are still a good number of us who were born before a certain date and possibly the right country in the EU who can drive up to 7.5 tons on our standard license too.
Certainly this was the case in the UK if the test was passed before 1997. Same for Australia and likely other countries with close links to the UK.

Mnay of those that need the additional test will be happy enough to take it to gain access to their Cybertrucks :)
 

KrodEKid

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No. You'd notice it less because every other component - like drag - would be lessened, but rolling resistance actually goes down with speed (his formula didn't show this but... It's even more complicated!) as the centrifugal 'force' pushes out on the tires. Then they heat up and that creates yet another increase in stickiness but a decrease in the stiffness... It's complicated!

But no, if a tire has higher rolling resistance, it pretty much always does. However, if you're ever spinning your tires without doing 'work' then that's waste, too.

-Crissa
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ajdelange

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He refines rolling resistance, then totally ignores slip, intertial and gravitational losses and the fact that drive train loss is not fixed. Thus his estimates are low as are his battery size estimates. But, even so, given all the unertainties (the CT is going to weigh less than the X?) he's probably not all that far off.
 

fritter63

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So this is just really exciting. Was a little bummed about going back to a "gas guzzler" even if it was charging off solar. This means that it's just not the case. It will be be almost as efficient as driving the 3 (I am averaging 260 wh/mile)
 

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7,000 pounds is a more realistic weight knowing what we know on the weight of other Teslas.

A CoD closer to 0.4 is more realistic based on the evaluations that some other have already made.

A CRR of 1.5 is more realistic for an off road tire.

I think we are closer to 500W/mi than 400W/mi.
 

Dids

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7,000 pounds is a more realistic weight knowing what we know on the weight of other Teslas.

A CoD closer to 0.4 is more realistic based on the evaluations that some other have already made.

A CRR of 1.5 is more realistic for an off road tire.

I think we are closer to 500W/mi than 400W/mi.
Except that Elon said it wasn't heavier than f150. But maybe he was lying.
A CRR of 1.5 is massively unrealistic for a kevlar tire. The kevlar replaces the steel bands. They are lighter tires and stronger and they have a lower rolling resistance than a steel radial. They also are typically a higher pressure tire which again helps keep them round.
 

SentinelOne

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So this is just really exciting. Was a little bummed about going back to a "gas guzzler" even if it was charging off solar. This means that it's just not the case. It will be be almost as efficient as driving the 3 (I am averaging 260 wh/mile)
[/QUOTE]
wow, lifetime avg on my m3p is 316 wh/mi....so diff traffic, weather and driving styles do make a big diff
 

CappyJax

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Except that Elon said it wasn't heavier than f150. But maybe he was lying.
A CRR of 1.5 is massively unrealistic for a kevlar tire. The kevlar replaces the steel bands. They are lighter tires and stronger and they have a lower rolling resistance than a steel radial. They also are typically a higher pressure tire which again helps keep them round.
Sure, maybe the smallest battery backCT will weigh the same as an F150. I based my numbers off a tri-motor.

Kevlar doesn't change the rolling resistance. Tire pressure is based on the tire size and load the tire is carrying. Having a higher pressure in the same size wire will reduce the rolling resistance, but it also reduces your traction and increases center tire wear.

My mistake on the CRR. I meant .015.
 

Dids

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Sure, maybe the smallest battery backCT will weigh the same as an F150. I based my numbers off a tri-motor.

Kevlar doesn't change the rolling resistance. Tire pressure is based on the tire size and load the tire is carrying. Having a higher pressure in the same size wire will reduce the rolling resistance, but it also reduces your traction and increases center tire wear.

My mistake on the CRR. I meant .015.
https://www.prweb.com/releases/2009/07/prweb2638794.htm
“Such an enormous weight reduction would lead to significant lower levels of rolling resistance and fuel consumption"
Reccomeded tire pressure is more a function of the suspension set up then it is of tire size or tread wear. Pickup trucks often reccomend lower pressure because they have a stiffer suspension to be able to handle load, they also have traction issues because the back end is so light. Ford got into trouble doing this once.
CT will have a more even weight distribution than F150, it will have a variable suspension. Therefore logically they can run a higher pressure while still having traction and not bouncing when empty.
 

ajdelange

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So this is just really exciting. Was a little bummed about going back to a "gas guzzler" even if it was charging off solar. This means that it's just not the case. It will be be almost as efficient as driving the 3 (I am averaging 260 wh/mile)
You have grabbed on to the wrong conclusion. What you should have taken from that video is that consumption is determined by a lot of factors the most important of which is the details of the individual drives over which it is measured. e.g.

wow, lifetime avg on my m3p is 316 wh/mi....so diff traffic, weather and driving styles do make a big diff
I do get 260 on my X in Virginia in the winter but up in Quebec during the summer it is more like 285 (in direct conflict with the assurances that I have been given that I'll lose 20- 30% of my range in cold weather). It definitely depends on how, where and when you drive but, of course, it also depends on the vehicle parameters. The six loads are drive train, inertial, gravitational, rolling resistance, slip and drag. To calculate their absolute and relative magnitudes (and signs) you must know the vehicle mass, slip coefficient, rolling resistance coefficient, drag coefficient, temperature, effective frontal area (not the actual frontal area), airspeed, velocity and first derivative of velocity and grade. Thus in order to calculate the energy used in a trip you must have the vehicle speed history, The speed history is obviously complex influenced by such things as slowing down for traffic and stop lights, accelerating to pass and so on and it tends to be, except when on auto pilot, complex. The picture below shows recorded Wh/mi for the most recent 30 miles I've driven.

IMG_1418.jpg

The total energy used in those 30 miles is represented by the shaded area under the curve. That energy, divided by 30 miles, is the average consumption (252 Wh/mi). The high frequency oscillations are from speed adjustment. The slower trends relate to terrain. The graph represents a 10 mile trip to a destination and return over the same route some of which was on freeway. The trip involves going up a hill (higher than average consumption) followed by going down the hill (lower consumption - regen was on).

The point is that the actual Wh/mi used would be virtually impossible to calculate even if I had a terrain profile because of inability to predict traffic conditions, wind, wet pavement etc. And so the best we can do is speak in terms of averages. On the graph the heavy horizontal line labeled "Rated" represents the average consumption Tesla measured during a prescribed (EPA) test. Although I cannot find the numerical value attached to that line documented anywhere it's value can be determined from the graph as 272 Wh/mi. Multiplying by the 351 mi rated range of this vehicle we find that the available discharge battery energy for this version of the X to be .272*351 = 95.47 kWh.

If we go to ABRP and select Model X LRP we find that ABRP thinks this vehicle's consumption is 332 Wh/mi at 65 mph. That is, in our experience, a bit high. In any case the rated consumption (determined at lower speed) is 81.9% of that. Now assuming that ABRP is reasonably skilled at doing what they do we look at their 65 mph prediction of 485 Wh/mi for the TriMotor CT and apply that same 81,9% factor to it to get an estimate of 397 Wh/mi for the rated consumption of the TriMotor. Since the CT is obviously going to be a bigger vehicle and as the drag goes up as the square of linear dimension and as the drag is the largest load given regen we feel comfortable in the gut with that number. But since gut feel is not very certain we think we should probably attach at least 10% uncertainty to that and think about 397 ± 40 Wh/mi. This leads us straightaway to battery size estimates of 500 times this or 198.5 ± 20 kWh. So 180 to 220 kWh for the TriMotor. This estimate is based on nothing more than how an exisitng X performs and a WAG as to how the CT might differ. If I do elaborate calculations of the 6 loads based on Monte Carlo trip models I come up with about the same numbers. Take it or leave it.
 
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CappyJax

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https://www.prweb.com/releases/2009/07/prweb2638794.htm
“Such an enormous weight reduction would lead to significant lower levels of rolling resistance and fuel consumption"
Reccomeded tire pressure is more a function of the suspension set up then it is of tire size or tread wear. Pickup trucks often reccomend lower pressure because they have a stiffer suspension to be able to handle load, they also have traction issues because the back end is so light. Ford got into trouble doing this once.
CT will have a more even weight distribution than F150, it will have a variable suspension. Therefore logically they can run a higher pressure while still having traction and not bouncing when empty.
Here is some advice. Don't reference marketing materials as your evidence. A 20% weight reduction in tires will mean a total of 40 pounds in at least a 5,000 pounds vehicle. That is 0.8% difference. That will not impact rolling resistance in any significant way.

Tire pressure has zero to do with suspension setup. It has only to do with the total weight of the vehicle. You want to match the weight of the vehicle to the tire pressure so you get the optimum footprint with the best traction to fuel economy ratio. You increase the pressure above this, you will get better efficiency but with increased center tread wear. You decrease the pressure below this and you get better traction with increased side thread wear.

The max tire pressure of a Wrangler tire with Kevlar is 80psi. Same max pressure as without kevlar.

Pickup trucks may have lower recommended tire pressures because they have wider tires which provides a larger surface area for which that pressure to be applied. This is why a very heavy monster truck with huge tires only needs 10psi, but a bicycle with skinny tires might need 100psi+. But as you increase the load on the truck, you increase the tire pressure to increase a consistent footprint of the tread on the surface.
 

fritter63

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You have grabbed on to the wrong conclusion. What you should have taken from that video is that consumption is determined by a lot of factors the most important of which is the details of the individual drives over which it is measured. e.g.
[sam Eliot voice] ain’t my first rodeo, son.

I’ve known that for decades. 😎
 

Newton

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I hope tesla offers road tires standard.

It would be funny to see skinny tires on the CT, sure would increase efficiency a bit.
 

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