Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 06-22-2021, 06:58 PM   #11 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,562
Thanks: 7,738
Thanked 8,554 Times in 7,041 Posts
I can see how they could test the front spoiler easily. But, were the five data points modifications to a complete test shell? Full scale?

__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 06-22-2021, 07:04 PM   #12 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by freebeard View Post
I can see how they could test the front spoiler easily. But, were the five data points modifications to a complete test shell? Full scale?
Yes, they were testing full scale with the cars made from polystyrene and having interchangeable bits.
  Reply With Quote
The Following User Says Thank You to JulianEdgar For This Useful Post:
freebeard (06-22-2021)
Old 06-22-2021, 07:45 PM   #13 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,562
Thanks: 7,738
Thanked 8,554 Times in 7,041 Posts
Thanks.

It always bothers me when they reduce a compound curved surface to a single angle. You can do a lot with three or four points on a Spline Curve.

Quote:
In the computer science subfields of computer-aided design and computer graphics, the term spline more frequently refers to a piecewise polynomial (parametric) curve. Splines are popular curves in these subfields because of the simplicity of their construction, their ease and accuracy of evaluation, and their capacity to approximate complex shapes through curve fitting and interactive curve design.

The term spline comes from the flexible spline devices used by shipbuilders and draftsmen to draw smooth shapes.
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
Old 06-23-2021, 01:01 PM   #14 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
'smaller'

Quote:
Originally Posted by JulianEdgar View Post
I am going to post some aero cars - not every day, as the thread name implies, but whenever I feel like it. (Unlike the Random Aero Cars thread, I will always try to provide some measured data.)

All the cars are covered in my book - A Century Of Car Aerodynamics (link below).

Today's car - the 1983 Fiat Uno.



The Uno was a low-cost car made in huge numbers – over 8 million were built. Most interesting from an aerodynamics perspective, it was a small hatch. The smaller the car, the harder it is to achieve a low Cd. And since a hatch will always have a large wake, with that shape we have another aerodynamic negative. But Fiat took great care to optimise the aerodynamics – especially drag – at a time when few manufacturers were bothering much about the aerodynamics of their cheapest cars.

Cd was 0.34 (standard car), 0.33 (economy special) and 0.30 (Turbo). Lift figures were also good - and across the whole range of yaw angles.

One might want to provide some context with respect to a qualifying adjective as 'smaller'.
We know from verisimilitude that there exists no prohibition from 'shrinking' the proportions of a very low drag vehicle, creating a 'smaller' vehicle of identical Cd.
An example would be Morelli, who took a small, 1976 FIAT of Cd 0.44, and turned it into Cd 0.23.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 06-23-2021, 04:21 PM   #15 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by aerohead View Post
One might want to provide some context with respect to a qualifying adjective as 'smaller'.
We know from verisimilitude that there exists no prohibition from 'shrinking' the proportions of a very low drag vehicle, creating a 'smaller' vehicle of identical Cd.
An example would be Morelli, who took a small, 1976 FIAT of Cd 0.44, and turned it into Cd 0.23.
Most people understand what a smaller car is. I don't know of any smaller production car that looks exactly like a big one but is just shrunk proportionally in all directions.
  Reply With Quote
The Following User Says Thank You to JulianEdgar For This Useful Post:
aerohead (06-23-2021)
Old 06-23-2021, 04:52 PM   #16 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
1975 Porsche 924



Aerodynamic development of the 924 began using one-fifth scale models that were tested in Paris Laboratoires Eiffel. The results gained from these tests were then applied to full-size prototype that was optimised in the Volkswagen wind tunnel.

With the headlights retracted, the Cd was 0.36. With headlights up, it increased to 0.38. Projected frontal area was 1.76m2, giving a CDA of 0.634m2 with the headlights down, and 0.669m2 with the lights raised.
  Reply With Quote
Old 06-23-2021, 05:19 PM   #17 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
I don't know of........

Quote:
Originally Posted by JulianEdgar View Post
Most people understand what a smaller car is. I don't know of any smaller production car that looks exactly like a big one but is just shrunk proportionally in all directions.
That's not even germane to the topic.
If you're going to make a simplistic, overgeneralized comment about 'small', then It's my opinion that you haven't properly served the reader.
The 1987 Renault Vesta-II remains one of the lowest drag 'cars' ever created, in spite of it's 139-inch overall length.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 06-23-2021, 05:28 PM   #18 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,562
Thanks: 7,738
Thanked 8,554 Times in 7,041 Posts
Is there enough data to make the 924 the next car of the week?
Quote:
Most people understand what a smaller car is.
Quote:
History - Another look at the Cord 810 | Page 2 | The H.A.M.B.
https://www.jalopyjournal.com/forum/....772659/page-2
Pray went on to make some very highly regarded Auburn Speedster replicas, while the company he started managed to make about 100 Cord 8/10″ cars, as they were branded, reflecting the fact that they were 8/10th scale replicas of the original Cords.
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
Old 06-23-2021, 11:17 PM   #19 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Very interesting ad for the 924:

  Reply With Quote
The Following 2 Users Say Thank You to JulianEdgar For This Useful Post:
COcyclist (06-26-2021), freebeard (06-24-2021)
Old 06-24-2021, 03:25 AM   #20 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Re the above ad. It's interesting on a bunch of levels.

1. It gives the power to propel the car at 55 mph - 15hp.

2. It gives the lift forces at front and rear at 100 mph - 46 and 105(!)lbs, respectively.

3. From the above, and knowing the projected frontal area, we can work out the front and rear lift coefficients, and so work out lift forces at all speeds.

4. It states that the lateral centre of pressure is behind the centre of gravity, so we know it has decent straightline stability

5. It shows the centreline surface body pressure measurements, including in the wake (but not, unfortunately, under the car) so we can see how much of the upper surface of the car is experiencing low pressure (ie lift - see #2 above.)

Good ad!

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com