SPECIAL EDITION QUAD-MOTOR Cybertruck rumor

[Crissa]

"There really is less and less need for 4x4."

Not where I live.

You mis-read the implication: Drive-by wire means that individual braking and clutching of the drive wheels can be feathered electronically rather than just overpowering the slip like one would traditionally do with an ICE.

Until you're in a situation where you can't shift the weight of the vehicle onto the drive axle - which would be a very slippery inconsistent surface like snow pack or mud - you really don't need on both axles.

And then, when you need power on the greatest surface, you just need two drive axles. The differentials and brakes can be electronically feathered to move drive power to the wheel that grips.

The only thing that 4-motor really gets you is tank turn. And you could probably do that with a special clutch in the differential. It's possible that 4-motor (like the hubs) could simplify the overall mechanical... But that day isn't today.

-Crissa

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[Luke42]

"There really is less and less need for 4x4."

Not where I live.

Where I live (Illinois), FWD and AWD are fine, but RWD and traditional 4WD are terrible.

So, if you buy a pickup truck, you need a 4x4 to compensate for the inferior RWD system. But, if you buy Prius (or another compact FWD car), it's a pretty good all-weather vehicle here, because we're civilized enough to have reliable snow removal where I live.

How do I know? I did a drive-offs between all of the vehicles in the family on snowy winter days.

The reason for the poor performance of RWD/4WD pickup trucks in the snow is due to weight distribution. A pickup truck has roughly a 50/50 weight distribution when fully loaded, which means it's more like 70/30 when unloaded -- and most people drive pickup trucks unloaded a lot of the time. The drive wheels are the wheels which get 30% of the weight.

The other problem is that traditional locking 4WD is lousy in patchy conditions (dry-ish pavement with patches of snow-drift and/or black ice), so you're constantly engaging and disengaging the 4WD system constantly, depending on the road condition and what maneuver you're doing. It makes you think a computer can do a far better job of managing this aspect, which is true. Pickup trucks should be AWD by default in my climate (Midwest).

When I bought my current truck, I changed from Ford to GM, because GM offers a thinly-disguised slip-and-grip system ("4x4 auto") on most of their full-sized pickup trucks. It's a better fit for my environment than the traditional system in the vast majority of Ford trucks.

Tesla's multimotor approach is likely work well with the variety of weather and loading conditions that I encounter.

 

[Crissa]

Tesla's system of multiple motors is to have each motor provide a different torque curve.

That means at the low end, it can apply all the motors it needs - and at the high end, it can disengage the motors it doesn't need.

Rivian and Lordstown are using a system where that's not really possible. Lordstown's truck will have to use all the motors, all the time, or end up with weird drag issues and uneven power. I think Rivian has a method of spreading power across an axle, but I really don't know.

And no one has been under a Cybertruck, so we have no idea what they'll do with the two motors in the back. But it will have electronic braking which allows you to shift power from wheel to wheel using the differential's natural inclination.

-Crissa

 

[MEDICALJMP]

I get that you are smoking some real good shit if you think the Cybertruck is going to have a CD of .25. Pass it over man!

According to this article the Cybertruck is fairly efficient for this class of vehicle. The estimate is CD 0.36 for CT where the Ram 1500 is 0.56 and the F150 is 0.59 CD. ‘’While Tesla hasn’t provided an official drag value yet, Elon Musk has said that “with extreme effort, Cybertruck might hit a 0.30 drag coefficient, which would be insane for a truck.””

https://thenextweb.com/plugged/2019...rucks-aerodynamics-compare-to-regular-trucks/

I have read in another analysis that the CT design with the tonneau cover closed acts as an airfoil. Let’s be honest. This isn’t going to be a fighter jet, but best in class isn’t far fetched.

 

[CappyJax]

There are several real world examples of EVs towing that resulted in about 50% reduction in range. Real world towing examples from ICE trucks pulling 10K-14K lbs trailers are similar (40% reduction). So based on this info & the difference in Cybertruck I have posited that Cybertruck towing might be around a 50% reduction even at 14,000 lbs.

Your prediction of 2,000Wh/mi. that you claim to have made scientifically using your spreadsheet is way out of range.

I don't think anyone should rely on that claim without more validation.
If you do not want to backup it up with anything that is fine too.

Carl Sagan: Extraordinary Claims Require Extraordinary Evidence

Show me an EV pulling a 14,000 pound 5th wheel losing only 50% of their range. Show me evidence of an ICE vehicle only losing 40% of range pulling a similar trailer.

I provided the evidence in the form of actual physics. Now you provide evidence of your claims.

 

[TVBtesla]

I heard Elon tell Joe rogan he would be driving a plaid CYBRTRK, my 1st or 2nd will be one when available

 

[Luke42]

Tesla's system of multiple motors is to have each motor provide a different torque curve.

The torque curve isn't so dramatically different that it won't allow you to get unstuck, though.

You can start a car out in 1st or 2nd gear on snow (or on dry pavement if you're careful with the clutch), but it still moves.

If the front wheels are in 1st and the back wheels are in 2nd (with two engines), the vehicle will overcome static friction and start moving if either the front or the back wheels are on something solid. Add in some proper traction control, and the driver won't even notice the difference.

You won't win any drag races this way, but the car will still be able to get rolling gently, which is what you really need in that situation.

 

[firsttruck]

Show me an EV pulling a 14,000 pound 5th wheel losing only 50% of their range. Show me evidence of an ICE vehicle only losing 40% of range pulling a similar trailer.

I provided the evidence in the form of actual physics. Now you provide evidence of your claims.

The actual physics of energy use per mile does not care if vehicles are BEV (kwh) or ICE (mpg). If same total weight (tow vehicle + trailer), same cD, same frontal area you get same answer from formulas.
If ICE + trailer total weight is 14,000lbs, cD .55, frontal area X has 40% mpg loss.
then BEV + trailer total weight is 14,000lbs, cD .55, frontal area X will have same 40% kwh loss.

Below are examples of how much worse energy use is (40-50%) when towing large trailers.
Even shows how towing 5th wheel trailer is more energy effecient than similar ball hitch travel trailer.

------------

Ford F-150, curb weight 4,995lbs, non-towing range 15-18 mpg

Ford F150 that tows 10,000 lbs., Eco-Boost - iRV2 Forums
https://www.irv2.com/forums/f45/ford-f150-that-tows-10-000-lbs-eco-boost-433691.html
03-08-2019, 10:04 AM #11
tscarps, Senior Member, Location: Omaha, NE
Mallard travel trailer with a dry weight of roughly 8,000 lbs. loaded up closer to 9,000.
total 14,000 lbs
towing the Mallard travel trailer got about 8 mpg.

Open Roads Forum - Travel trailer "vs" fith wheel -- MPG to tow
2016
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29131182/print/true.cfm
Posted By: Padlin on 12/18/16 05:10am
both trailers were 10.5 ft high
5th wheel trailer was 1 ft longer, 2" wider and 900lbs heavier.
10 mpg ball hitch Travel Trailer, 20 ft, 3,500 lbs, 10.5 ft high
13 mpg 5th wheel trailer, 21 ft, 4,400 lbs, 10.5 ft high, 2 inches wider
17 mpg without trailer
17 mpg is more than 40% better than 10mpg

.....
Posted By: StirCrazy on 12/20/16 12:51am
my experience was similar to a couple.
towing old travel trailer (29 foot, 7500 lbs) with my 99 7.3I got about 11.4 mpg.
same truck a month later with a new 38-foot, 5th wheel 11,500 lbs trailer I got 15.7 mpg. exact same trip route. As mentioned the more aerodynamic front end of the 5th and being closer to the truck cab makes only one drag zone instead of two with the typical ball hitch travel trailer.


------------

From your spreadsheet what answer do you get for

1. total weight: 11,000 lbs ( 4,990 kg )

--- (tow vehicle, 2 people (400lbs), bags (400lbs), misc stuff (120 lbs), trailer ( 6,000lbs)


2. Coefficient of drag for tow vehicle: 0.25

3. Coefficient of drag for trailer: 0.55

4. area of front of tow vehicle: 25 square ft ( 2.31 sq meters )

5. area of front of trailer: 76.5 sq ft ( 7.124 sq meters = 2.60m x 2.74m)

6. speed: 56 mph ( 90 k/h )

 

[CappyJax]

The actual physics of energy use per mile does not care if vehicles are BEV (kwh) or ICE (mpg). If same total weight, cD, frontal area you get same answer from formulas.
If ICE + trailer total weight is 14,000lbs, cD .55, frontal area X has 40% mpg loss.
then BEV + trailer total weight is 14,000lbs, cD .55, frontal area X will have same 40% kwh loss.

Below are examples of how much worse energy use is (40-50%) when towing large trailers.
Even shows how towing 5th wheel trailer is more energy effecient than similar ball hitch travel trailer.

------------

Ford F-150, curb weight 4,995lbs, non-towing range 15-18 mpg

Ford F150 that tows 10,000 lbs., Eco-Boost - iRV2 Forums
https://www.irv2.com/forums/f45/ford-f150-that-tows-10-000-lbs-eco-boost-433691.html
03-08-2019, 10:04 AM #11
tscarps, Senior Member, Location: Omaha, NE
Mallard travel trailer with a dry weight of roughly 8,000 lbs. loaded up closer to 9,000.
total 14,000 lbs
towing the Mallard travel trailer got about 8 mpg.

Open Roads Forum - Travel trailer "vs" fith wheel -- MPG to tow
2016
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29131182/print/true.cfm
Posted By: Padlin on 12/18/16 05:10am
both trailers were 10.5 ft high
5th wheel trailer was 1 ft longer, 2" wider and 900lbs heavier.
10 mpg ball hitch Travel Trailer, 20 ft, 3,500 lbs, 10.5 ft high
13 mpg 5th wheel trailer, 21 ft, 4,400 lbs, 10.5 ft high, 2 inches wider
17 mpg without trailer
17 mpg is more than 40% better than 10mpg

.....
Posted By: StirCrazy on 12/20/16 12:51am
my experience was similar to a couple.
towing old travel trailer (29 foot, 7500 lbs) with my 99 7.3I got about 11.4 mpg.
same truck a month later with a new 38-foot, 5th wheel 11,500 lbs trailer I got 15.7 mpg. exact same trip route. As mentioned the more aerodynamic front end of the 5th and being closer to the truck cab makes only one drag zone instead of two with the typical ball hitch travel trailer.


------------

From your spreadsheet what answer do you get for

1. total weight: 11,000 lbs ( 4,990 kg )

--- (tow vehicle, 2 people (400lbs), bags (400lbs), misc stuff (120 lbs), trailer ( 6,000lbs)


2. Coefficient of drag for tow vehicle: 0.25

3. Coefficient of drag for trailer: 0.55

4. area of front of tow vehicle: 25 square ft ( 2.31 sq meters )

5. area of front of trailer: 76.5 sq ft ( 7.124 sq meters = 2.60m x 2.74m)

6. speed: 56 mph ( 90 k/h )

Anecdotal stories are not evidence. And if an ICE loses 40% of its range, the BEV will lose more because the BEV does not use energy to maintain combustion. Therefore, an ICE doesn’t use twice the fuel for twice the power to the wheels, it uses something less. In addition, ICE engines are often more efficient at higher power settings.

 

[firsttruck]

Anecdotal stories are not evidence.

There is way more real world DATA like that.

You can get the same 40% loss seen in real world ICE non-tow vs tow using physics formulas.
If that was NOT true what would be value of using the formulas.
If the formulas are good then they help us understand the real world and predict what might happen in the real world. That is what science tries to do.

the BEV will lose more because the BEV does not use energy to maintain combustion.

"maintain combustion" & " ICE engines are often more efficient at higher power settings" is nothing special. At a steady speed it is just one of many constant & consistent factors that are all summed up in total energy to wheels efficiency that provided the traction. You have similar loss factors in BEV. We do not worry about every individual bearing loss in the many many more bearings in ICE vs BEV. We use the total efficiency of about 35% for ICE & 85% for BEV.

 

[Crissa]

You won't win any drag races this way, but the car will still be able to get rolling gently, which is what you really need in that situation.

Yeah, of course!

When slipping, torque doesn't help. Nor does it help with range! That's why you'd want to be able to change the amount of power required to produce the least amount of torque needed - then put it where you need it,

Anecdotal stories are not evidence. ...

Yeah, BEVs technically are using no more power to do most things (except provide heat) because an ICE is always wasting power idling or providing the wrong amount of torque. A BEV stuck in traffic is not losing range, but an ICE is. It still takes just as much power to move the same trailer. You just notice it more because the BEV is so efficient otherwise (and contains so little energy).

As an example, my motorcycle contains 1/4 gallon of gas in energy. But it can get 80 miles range! Sure it only goes half that at freeway speed - but that's because air resistance. It's not like an ICE bike magically is doing better - if it went its optimum speed (instead of freeway speed) it would go twice its range, too. My spouse's scrambler get 50mpg and contains two gallons. You ride it at freeway speed and you're only going to get 80 miles. Ride it in the moutains here and you can go almost twice that. But ride it side by side in city traffic, and my bike goes further.

-Crissa

 

[firsttruck]

At 55 mph on level road, 50% range increase (300 wh/mi reduction) due to better aerodynamics of new trailer.

-------------

Tesla Model X LR+, 100 kwh, 5,421 lb (2,459 kg), 350 miles range
2021 Apex Nano 194bhs 22', 4,800lbs, 55mph, 800 wh/mi 108 mi between charge
2018 Airsteam Bambi 22', 4,500lbs, 55mph, 489 wh/mi, 177 mi between charge
Able to go about 50 more miles before having to charge using Airstream Bambi.
50% range increase.

Other vehicle:
2017 Ford F-350 15-17 mpg, 8-10 mpg towing ( 50% loss)
2019 Grand Design Reflection 312BHTS 37ft 10,000lbs trailer

An Airstream and an EV || Tesla Model X Towing an Airstream Bambi
Oct 11, 2020
All Electric Family


Tesla Towing an Airstream || Part 2
Oct 18, 2020
All Electric Family

 

[CappyJax]

At 55 mph on level road, 50% range increase (300 wh/mi reduction) due to better aerodynamics.

-------------

Tesla Model X LR+, 100 kwh, 5,421 lb (2,459 kg), 350 miles range
2021 Apex Nano 194bhs 22', 4,800lbs, 55mph, 800 wh/mi 108 mi between charge
2018 Airsteam Bambi 22', 4,500lbs, 55mph, 489 wh/mi, 177 mi between charge
Able to go about 50 more miles before having to charge using Airstream Bambi.
50% range increase.

Other vehicle:
2017 Ford F-350 15-17 mpg, 8-10 mpg towing ( 50% loss)
2019 Grand Design Reflection 312BHTS 37ft 10,000lbs trailer

An Airstream and an EV || Tesla Model X Towing an Airstream Bambi
Oct 11, 2020
All Electric Family


Tesla Towing an Airstream || Part 2
Oct 18, 2020
All Electric Family

Your “evidence” supports my statement more than yours.

 

[Luke42]

When slipping, torque doesn't help. Nor does it help with range! That's why you'd want to be able to change the amount of power required to produce the least amount of torque needed - then put it where you need it,

Behold TCS! The torque electric motors produce is why even our humble 2004 Prius had fantastic traction control software.

According to the paper EV designs I've done over the years, all of that low-end torque means it's easy to build an EV that can do a burnout, but which can't keep up with highway traffic.

As for range-impact, slip-and-grip happens rarely enough that being inefficient while slipping shouldn't impact the range very much. If I drive for an hour on a slippery day, I probably spend less than a minute actually slipping and sliding. That's why you can get away with using brakes to simulate a limited-slip-differential in slip-and-grip systems. Slipping and sliding has big impact on how I perceive things, but it's not a constant thing.

The offroad community tends to be dismissive of slip-and-grip systems, but I find them pretty much perfect for the conditions I encounter.

 

[firsttruck]

Your “evidence” supports my statement more than yours.

The new trailer had almost the same weight but much better aerodynamic.

What part supported your prediction?