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Old 10-11-2020, 12:11 PM   #1 (permalink)
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1922 Rumpler "teardrop" limousine

(Starting at page 17, "Aerodynamics of Road Vehicles, Fourth Edition"):
Quote:
CD = 0.28; A = 2.57 m^2

The value of this cD is particularly noteworthy because the wheels of Rumpler's vehicles are totally uncovered. _____ ... this must have increased drag by 50%.
So, might a similarly shaped car with the drag due to the wheels minimized be about 0.14?


Last edited by sgtlethargic; 10-11-2020 at 11:42 PM..
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Old 10-11-2020, 12:38 PM   #2 (permalink)
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Closer to cD = 0.19, I think.

0.28 = 1.50x

x = (0.28) / (1.50) = 0.1866... = 0.19
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Old 10-11-2020, 03:44 PM   #3 (permalink)
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Quote:
Originally Posted by Vman455 View Post
Closer to cD = 0.19, I think.

0.28 = 1.50x

x = (0.28) / (1.50) = 0.1866... = 0.19
Oh, not halved. I overlooked that tricky percentage language.
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Old 10-11-2020, 03:57 PM   #4 (permalink)
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The two that remain are just stunning in the flesh.





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Old 10-11-2020, 04:45 PM   #5 (permalink)
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Quote:
Originally Posted by JulianEdgar View Post
The two that remain are just stunning in the flesh.
That's cool. What about the aerodynamic strategy(ies) used?
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Old 10-11-2020, 05:07 PM   #6 (permalink)
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Quote:
Originally Posted by sgtlethargic View Post
That's cool. What about the aerodynamic strategy(ies) used?
Well, fantastic for 100 years ago, but pretty pedestrian today.
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Old 10-11-2020, 08:23 PM   #7 (permalink)
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Quote:
Originally Posted by JulianEdgar View Post
Well, fantastic for 100 years ago, but pretty pedestrian today.
Are there any modern cars of that relative size (looks like it might seat 7-10 people) that has a (theoretical for the Rumpler) 0.19 cD?
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Old 10-11-2020, 10:03 PM   #8 (permalink)
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Quote:
Originally Posted by sgtlethargic View Post
Are there any modern cars of that relative size (looks like it might seat 7-10 people) that has a (theoretical for the Rumpler) 0.19 cD?
In a modern wind tunnel it had a measured Cd of 0.28 and a frontal area of 2.57m^2.

As far as I know, they were five-seaters.

0.19 Cd and 7-10 people is how misinformation spreads!
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Old 10-11-2020, 10:11 PM   #9 (permalink)
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Quote:
Originally Posted by JulianEdgar View Post
In a modern wind tunnel it had a measured Cd of 0.28 and a frontal area of 2.57m^2.

As far as I know, they were five-seaters.

0.19 Cd and 7-10 people is how misinformation spreads!
You've misread the thread!
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Old 10-11-2020, 10:16 PM   #10 (permalink)
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Quote:
Originally Posted by sgtlethargic View Post
You've misread the thread!
I don't think so.

There's no justification for the 0.19 Cd figure - it's not the result of any measurement and is just a guess. As far as I know, the 7-10 people figure is wrong.

As I say, this is how misinformation starts and then spreads!

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