Aerodynamic ' Mass' - Equivalency

[aerohead]

Here's yet another product from the tortured-mind experiments of the University of Hard Knox. An outgrowth of a rebuttal to TFLcars.com' 'Tesla Can't Tow' video from the recent past.
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As a co-conspirator in AeroStealth's Chevy BOLT streamlining project, and already in possession of some BOLT guestimates I'll use them to help illustrate this concept.
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TFL's and Engineering Explained's contention was that Tesla's towing problem was an 'electric car' problem, and rooted in 'weight' issues.
My contention was that it was a trailer aerodynamics issue. AeroStealth and I published a You-Tube illustrating the physics of it.
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With the Chevy BOLT, I ran a set of calculations for 100 km/h, estimating road load for some upcoming graphics:
* Based upon the estimated coefficient of rolling force, at 100- km/h, the aerodynamic drag at the traction wheel/road interface, is equivalent to a 2,704-kg gain in mass, or a virtual curb-weight of 9,541-pounds, compared to OEM 3,580-pounds.
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It gets worse!
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At 85-mph ( 137-km/h ) the legal speed between Austin Texas and San Antonio, Texas, due to the cube-law relationship of aerodynamic power, the aerodynamic drag would be the equivalent of adding 5,050-kg added mass to the BOLT, or a virtual curb weight of 14,714- pounds ( 6,674-kg ).
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So, TFL is correct, within a very convoluted context. They completely fail to appreciate the aerodynamic aspects of their towing comparison. It's not the 'weight' of the 'barn' they're towing, it's it's frontal area and Cd of the 'barn' that's the issue.
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Depending on the application, physics allows for a trailer of net-negative drag, which when pulled, actually increases the range of the tow vehicle's solo range. Something completely missed by ours neighbors in Colorado.
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No one can give any thought to ideas unknown to them.

[aerohead]

Using 62-MPH, 90% mechanical efficiency for the Chevy BOLT, and a EPA test weight of 5,880-pounds, I'd reverse-engineered a rolling force coefficient of Cfr = 0.0086862 for the calculations.
In ' Understanding Tractor-Trailer Performance', by Caterpillar Corporation, they published a Cfr = 0.0084375, for an automobile at 60-mph.
Anyone wanting to noodle some comparative numbers for their passenger car, versus aero, at this range of velocity, would have a healthy degree of probability for their numbers reflecting near-real-world values, @ Cfr in this 0.00856185 range average.

[freebeard]

As a co-conspirator in AeroStealth's Chevy BOLT streamlining project,
....
physics allows for a trailer of net-negative drag, which when pulled, actually increases the range of the tow vehicle's solo range.

Is there a Bolt trailer in the works?

[kach22i]

Originally Posted by aerohead

..........No one can give any thought to ideas unknown to them.

Interesting information, and I love the quote above.

[aerohead]

Originally Posted by freebeard

Is there a Bolt trailer in the works?

John's gonna start with a receiver hitch-mounted, aluminum cargo carrier-based tail extension. Janky homemade 'MOON's, rear skirts, rear axle area belly pan section, and diffuser.
The BOLT is Cd 0.308. We're targeting Cd 0.217.
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I won't be building anything until I finish SPIRIT and get it to A2. There, I will simulate a one-wheel, gap-filled, full boat-tail, range-extender trailer, with fully-faired wheel, based off the new boat-tail and new stinger.
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By losing the rear wheel and fairing, I can also get a Cd for a simulated extensible tail.
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Then, by losing the stinger, I can get a Cd for the truncated boat-tail configuration. And I'll have mpg data for this configuration, for the Texas -to- North Carolina roundtrip, to back up the wind tunnel data.
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From this data, we'll be able to compare to the theory, and calculate what the BOLT, or any vehicle will do as a 'full' vehicle. And go from there.
I'll have access to a former Boeing flight test engineer, NASA aerodynamic engineer, former head of race car aerodynamics for Daimler-Chrysler, and former Chief Engineer of Daimler-Chrysler's Aero-Acoustic Wind Tunnel while I'm there.

[freebeard]

I made it to Darko for 'support' (did nothing really), but North Carolina is a bit far.

[aerohead]

My brother in Carson City wants to go, and offered to tow 'SPIRIT' with his truck, should it be dead at the time.
It's a long way, and there's no other family in that direction, or a Bonneville, Battle Mountain, or Mike Cook's 'Shootout.'
I'd sure like the data.
The last trip bankrupted me, and living off Social Security precludes any more sponsoring of another vehicle.
A thousand more man-hours will tell.