Tesla robo taxi drag?

[aerohead]

Originally Posted by Phase

Here

The rear axle isn't narrowed to match the greenhouse as in some other lower drag vehicles, but the Tesla goes most of the way there, at least satisfying Dr. Teddy Woll's, of Mercedes-Benz, requirement of the above-the-beltline streamlining.
Perhaps something will show up one day at SAE International's website.

[aerohead]

Originally Posted by Piotrsko

Cooling plate is otherwise ise known as "heat sink" wonder how well that works in LA$ Vega$ or Phoenix or even in your neck of the woods during summer?

It's a good point! At present, I don't know anything about BEV coolant temperatures experienced at SAE standard 60-F atmosphere, during EPA dynamometer certification testing.
The BTE-e for BEVs is given at 95%, so, we're looking at a 5% waste heat-flux that must be rejected to ambient conditions to protect the motor, pack, and power electronics.
That's 3412-Btu / KW, or 2546 Btu/ horsepower of waste heat.
My BOLT is absorbing 20.77- hp @ 65-mph.
On a 60-F day, the radiator would be required to reject 1.09-hp worth of heat ( 2,783-Btu/ hour ), or, 46.4-Btu/ minute.
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For air conditioning, we'd need the average mean heat transfer coefficient of the cabin envelope, its total surface are, metabolic heat load of the passengers, and solar gain from exposed, glazed fenestrations; knowing the insolation transmittance and radiative emissivity criteria.
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My present, Kitchen Aid, Energy Star-rated refrigerator has only cooling plates, compared to the Sears Roebuck fridge that it replaces, which had almost a 'whole-dimension', convection-driven, exposed heat exchanger on it's backside.

[Piotrsko]

Well for starters, my 5 gallon coolant battery tank only gets about 10 degrees hotter than ambient during discharge. Don't monitor it charging as I'm asleep, but suspect another 5 degrees. Not hot enough to use as a defrosting source either way. Is enough to get pack to 55 f on a frost morning with a hundred foot wire pipe heater set to 40f.

Spitballing, figure the motor and controller is dissipating a KW worth of heat at full throttle as it takes about .25KW to idle

[aerohead]

* I picked up Jamie's computer rendering of the Robo Taxi Monday afternoon.
* I placed it on the light table and compared it's roof contour to everything I had.
* The 'Robo's' roofline is most like the Electra Mechanica 'Solo' BEV three-wheeler.
* In side elevation, the 'aft-body' constitutes 43.33% total body length.
* At its trailing edge, the uninterrupted roof contour's down-slope angle is 20.5-degrees to the horizon.
* In ground reflection mirror image, the car forms a 'free-stream' body of L/D = 2.198:1 fineness ratio when the tail is extrapolated to its conclusion; very close to the drag minimum reported in Sighard Hoerner's 1951, 'AERODYNAMIC DRAG'.
* At the ground plane, the tail's maximum slope angle is 25-degrees ( dimpled golf ball separation point )
* The Tesla's Vejungungsverhaltnis is 1.45.

[freebeard]

Vejungungsverhaltnis is a ratio of what to what?

[aerohead]

Originally Posted by freebeard

Vejungungsverhaltnis is a ratio of what to what?

The distance between the roof apex and rear of the vehicle ( aft-body ), is divided by the [ total vehicle height (H), minus the ground clearance ( GC ), yielding the body-only height divisor ( h )]
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V = (aft-body / h)
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'V' is a convention created by Baron Reinhard von Koenig-Fachsenfeld which shows up in his 1951 book, 'Aerodynamiks des Kraftfahrzeugs', covering his research at the FKFS, and Braunschweig Technical University, up to the beginning of WW-II
This value is an important component of dimensional analysis, used to 'steer' research.

[Vekke]

Originally Posted by aerohead

* I picked up Jamie's computer rendering of the Robo Taxi Monday afternoon.

* The 'Robo's' roofline is most like the Electra Mechanica 'Solo' BEV three-wheeler.

Did you try MB EQXX?. In my test that was very close match. Just cutted to shorter length.

[aerohead]

Originally Posted by Vekke

Did you try MB EQXX?. In my test that was very close match. Just cutted to shorter length.

The best side elevation photograph of the EQXX that I could come up with, short of a 'blueprint', indicated that it's tearing edge intersected the roofline contour of the 'Template Part-C', as did Lightyear Zero, Hyundai IONIQ-6, Tesla Model 3, with optional carbon fiber rear spoiler, and some others.
If we had wind tunnel smoke-flow imaging of the these cars, we could see the point, and elevation of where the lowest streamline filament begins to deflect, above, or below the nose, which would also indicate the elevation where a 'long-tail' would terminate, and the streamlines would rejoin there original, un-disturbed location in space. This would also allow measurement of the total distance traversed over or under the body, closest to the surface boundary, allowing calculation of instantaneous velocity and pressure at any point along the pathway.
The wake areas versus frontal areas, and Cds would allow comparisons to the results PhD Jeff Howell et al, at Loughborough University experience in their 2D, and 3D Windsor Body boat-tailing research.

[aerohead]

This plan-view image of GM's Impact-EV1 isn't as technically accurate as a blueprint, but you can discern that AeroVironment/GM did elect to narrow 'all' of the aft-body for pressure recovery.
In development, I believe that it was 'Impact-4' which achieved Cd 0.185, with a single door mirror.
https://ecomodder.com/forum/member-a...-1-showing.jpg