03-21-2021, 12:45 AM
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#11 (permalink)
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Quote:
Originally Posted by somerandomguy
Good evening,
I would like to know how can i calculate the drag coefficient of a 1990 toyota corolla with the height and width measurements?
Thanks
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There is no accurate way without putting the car in a professional wind tunnel.
Coast-down testing is notoriously inaccurate.
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03-23-2021, 12:32 AM
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#12 (permalink)
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Quote:
Originally Posted by somerandomguy
Good evening,
I would like to know how can i calculate the drag coefficient of a 1990 toyota corolla with the height and width measurements?
Thanks
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Total drag is CdA. In other words, the coefficient of drag X frontal area. The height and width would be used for the Area. The coefficient of drag has to be measured in a coast down test, or a wind tunnel. |
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03-23-2021, 01:45 AM
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#13 (permalink)
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Nobody likes my spring-on-a-tow-rope idea. 
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03-23-2021, 03:05 AM
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#14 (permalink)
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Quote:
Originally Posted by freebeard
Nobody likes my spring-on-a-tow-rope idea. |
Sounds good to me!
I forgot that DIY tests (spring scale tow or coast down) only work if wind is basically zero.
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03-23-2021, 03:30 AM
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#15 (permalink)
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Quote:
Originally Posted by freebeard
Nobody likes my spring-on-a-tow-rope idea. |
To be honest, I assumed that people were ignoring it because it doesn't measure aerodynamic drag. |
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03-23-2021, 01:36 PM
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#16 (permalink)
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Quote:
Originally Posted by JulianEdgar
To be honest, I assumed that people were ignoring it because it doesn't measure aerodynamic drag.
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I think the idea is to measure rolling resistance. Cost down tests measure rolling resistance + aerodynamic drag. So the hard part is usually separating the two.
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03-23-2021, 01:41 PM
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#17 (permalink)
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Originally Posted by Isaac Zachary
Subtract any force you believe or know rolling resistance takes up. You could push a pressure operated scale against the car and see how much force it takes to push the car in neutral and convert the number into newtons.
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Once you've subtracted the rolling resistance, what's left?
[five minute delta]
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03-23-2021, 02:45 PM
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#18 (permalink)
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Ok freebeard you made me comment on this:
I first thought that this spring scale was an excellent method until I thought about it some more and came up with many issues with repeatable results and myriads of conflicting things that would show up as increased or decreased scale readings. Kinda like torque does not relate to PSI holding values in a screw.
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03-23-2021, 03:16 PM
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#19 (permalink)
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I accept the criticism.
It was a thought experiment.
Which lead to further thoughts about averaging the data. What if the spring were pulsed with a solenoid to give a fluctuating reading, said fluctuations greater than the noise?
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03-24-2021, 12:57 PM
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#20 (permalink)
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Corolla
* The 1988 Corolla GT-S was Cd 0.33, @ around 18.302-sq-ft frontal area.
* The next-gen Corolla was jointly produced by Toyota- General Motors, as the Corolla / Geo PRIZM, I believe, at the New United Motor Manufacturing, Inc. ( NUMMI ) factory in Fremont, California, where Tesla Motors presently resides.
This car, in 1992, had grown to 20.8 sq-ft frontal area, at Cd 0.33.
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