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Old 01-29-2021, 01:09 PM   #1 (permalink)
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CYBERTRUCK range pulling tadpole trailer = approx. 870-miles

I've had a little time to run the calculator through some more paces.
Ever since Cybertruck was announced, and TFL cars.com began their Tesla attack, AeroStealth and I have been doing thought experiments, working out performance predictions for different scenarios, all based upon data from empirical testing of the Tesla Model X.
One scenario includes pulling a fully-boat-tailed, accordion gap-filled, tadpole trailer, which creates the sought after, but impractical 'elongation' necessary for really low drag. Rear wheel skirts and suite of blending mods.
Lowest suspension setting.
I've detuned the truck / trailer to Cd 0.10.( Hucho gives Cd 0.07 as 'floor' )
Frontal area taken at 36-sq-ft.
All-up weight = 6350-pounds
I've allowed 78% useable capacity of a 200-kWh pack
Rolling force coefficient is the same as, and was reverse-engineered from the Model X. ( 95% of pickups will never see 'truck duty' )
Since the Cybertruck is rated to 130-mph, I ran numbers for up to that velocity.
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* In California, where trailer towing is limited to 55-mph, calculation indicates 179-Watts / mile, and 870-miles range to battery exhaustion.
* At 65-mph, 779-miles.
* At 75-mph, 694-miles
* At 130-mph, on the autobahn, 513-miles.
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# The Cybertruck pulling the trailer at 130-mph has the same road load as:
- The F-150 shape at 76-mph
- The RAM 1500 shape at 79-mph
- Cybertruck (naked) at 85-mph
- Tesla Model S shape at 90-mph
- Lightyear-one shape at 100-mph
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With an additional weight penalty, the trailer could carry a secondary pack. It's conceivable that, a family could take a roundtrip camping excursion without ever requiring a stop for recharging. Bladders would dictate the length of any trip segment duration.

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Old 01-29-2021, 05:48 PM   #2 (permalink)
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They announced the truck will be redesigned now.

I hope they just add some character lines, round some edges that need it, and add air curtains.
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Old 01-29-2021, 06:42 PM   #3 (permalink)
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Hope not.

The longitudinal edges generate vortexes that wrap and then unwrap along the top edge. Simple curve surfaces and curved butt-welds.


https://external-content.duckduckgo....6pid%3DApi&f=1
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Old 01-30-2021, 06:25 AM   #4 (permalink)
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Seeing as you are obsessed with BSFC, have you considered how much less efficient the motor and controller get at higher speeds and lower loads. It seems like a critical oversight for you to ignore.
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Old 02-01-2021, 03:25 AM   #5 (permalink)
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Quote:
Originally Posted by Cd View Post
They announced the truck will be redesigned now.

I hope they just add some character lines, round some edges that need it, and add air curtains.
Can't wait to see the new design. The current one looks hideous.
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Old 02-03-2021, 12:11 PM   #6 (permalink)
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oversight

Quote:
Originally Posted by AeroMcAeroFace View Post
Seeing as you are obsessed with BSFC, have you considered how much less efficient the motor and controller get at higher speeds and lower loads. It seems like a critical oversight for you to ignore.
After the press have an opportunity to conduct tests on the actual vehicles, we'll have more data to work with.
If you are in possession of bona-fides, then I petition you to release the raw information, from the source.
A BSFC-e motor map would be extremely insightful!
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Old 02-03-2021, 01:50 PM   #7 (permalink)
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Tesla at speed

Wikipedia has some info on the Model S.
* At 70-mph ( 110-km/h ) power absorbed is 10 kW ( 14-hp )
* At 100-mph ( 160-km/h ) power absorbed is 31 kW ( 42-hp )
* Comparison of cubing the velocities, at 100-mph, aero power requirement would increase by 2.9154-X.
* Tesla engineers told CAR and DRIVER to expect optimum range for the Model S, at around 56-mph, low 70s-F, dry, calm, no air conditioning.
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Old 02-04-2021, 07:19 AM   #8 (permalink)
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Quote:
Originally Posted by aerohead View Post
After the press have an opportunity to conduct tests on the actual vehicles, we'll have more data to work with.
If you are in possession of bona-fides, then I petition you to release the raw information, from the source.
A BSFC-e motor map would be extremely insightful!
Why would I release them even if I had them, I believe them to be insignificant, for EVs and ICEs. A simple search for Leaf motor efficiency tells you that the percentage change is around 7%, but that is not analogous necessarily.

Double standards here from aerohead again. Factors that supposedly invalidate throttle stop testing are ignored when it is a calculation done by aerohead.



Have you considered the extra effects of switching losses in the mosfets/IGBTs and thermal performance changes?
Have you considered the effects of temperature affecting internal resistance in the cabling and motor?
What about 12v accessory load? The dc/dc converter will change efficiency with different battery voltage.
The motor efficiency and powertrain losses won't be consistent so by your metric can't be assumed to be consistent.

You claim that throttle stop is invalidated by factors and then ignore the same factors when it is your calculation. Which is it? You omitted factors because they are irrelevant and you are wrong about throttle stop testing or you have double standards? I see no other option

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Old 02-05-2021, 11:02 AM   #9 (permalink)
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High-rpm electric motor BSFC-e

1) Porsche addresses the issue with a two-speed transmission.
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2) The Institute of Electrical Engineering, Karlesruhe Institute of Technology, Germany, reports that the issue of high-rpm electric motor operation and efficiency stem from divergent rpm Lorentz force, versus Reluctance force rpm optimization requirements, which Martin Doppelbauer and Patrick Winzer resolved in their laboratory R & D.
Today's 12,000 - 20,000 rpm motors may soon yield to 30,000 - rpm motors, currently under development.
Something like 49,000 member organizations of the Institute of Electric and Electronic Engineers, globally, are actively addressing this issue.
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3) Typically, in mechanical engineering, it's common to assume a constant BSFC, with respect to predictions surrounding road load hypotheticals. As a mechanical engineer you would know that.
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4) My illustration for the Cybertruck / tadpole configuration, with the exception of correcting for higher rolling resistance, isolates only the delta- road load response based upon Cd. It absolutely assumes the efficiency demonstrated by Tesla performance. And I'll make absolutely no apology on account of that. You'd suffocate on the margin of error.
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Old 02-05-2021, 12:51 PM   #10 (permalink)
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Quote:
Originally Posted by aerohead View Post
1) Porsche addresses the issue with a two-speed transmission.
--------------------------------------------------------------------------------------
2) The Institute of Electrical Engineering, Karlesruhe Institute of Technology, Germany, reports that the issue of high-rpm electric motor operation and efficiency stem from divergent rpm Lorentz force, versus Reluctance force rpm optimization requirements, which Martin Doppelbauer and Patrick Winzer resolved in their laboratory R & D.
Today's 12,000 - 20,000 rpm motors may soon yield to 30,000 - rpm motors, currently under development.
Something like 49,000 member organizations of the Institute of Electric and Electronic Engineers, globally, are actively addressing this issue.
--------------------------------------------------------------------------------------
3) Typically, in mechanical engineering, it's common to assume a constant BSFC, with respect to predictions surrounding road load hypotheticals. As a mechanical engineer you would know that.
--------------------------------------------------------------------------------------
4) My illustration for the Cybertruck / tadpole configuration, with the exception of correcting for higher rolling resistance, isolates only the delta- road load response based upon Cd. It absolutely assumes the efficiency demonstrated by Tesla performance. And I'll make absolutely no apology on account of that. You'd suffocate on the margin of error.
1) What is the relevance to your calculations? Tesla used to use the front/rear power split to maximise efficiency as the motors had different efficiency bands, I don't know if they still do.

2)Relevance?

3)True, apart from the fact I am not an engineer

4)Assumptions of constant efficiency are perfectly adequate,(assuming you know that there is a small margin of error) we can agree there also. Thanks for clearing that up.

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