Author Topic: Lift or Down Force ?  (Read 8529 times)

0 Members and 1 Guest are viewing this topic.

Offline SaltRat

  • Full Member
  • ***
  • Posts: 150
Re: Lift or Down Force ?
« Reply #15 on: December 05, 2010, 09:59:32 PM »
Thanks for the note. 

My hood bulges at highway speed and the steering feels light 130-150mph.  I want to know if the front is lifting.  Hitting a bump won't affect the "paperclip" that indicates lift, will it?


Deducing aero forces from suspension travel is a dodgy endeavor unless the suspension rate is relatively low.  Many LSR cars have very stiff suspension and/or travel limits for the express purpose of restricting body movement and attitude changes.

The problem with the o-ring or ty-wrap technique is what happens when driving over a bump.

For one-off testing and instead of an LVDT* and data system, one could inexpensively rig up a common rotary potentiometer and read or record the variation with an ohm meter.

*LVDT = Linear Variable Differential Transformer.
It is highly likely that the “linear potentiometer” shown earlier is, in fact, an LVDT.

SaltRat
When (if?) this baby hits 88mph, you'll see some serious poo.

Offline johnneilson

  • Sr. Member
  • ****
  • Posts: 502
Re: Lift or Down Force ?
« Reply #16 on: December 06, 2010, 10:34:34 AM »
FWIW;

Putting a data logger in the car is not that much money now a days, 15 years ago was another story.
But, you would not believe the uses you can find for one besides the std tach/speed/temp and pressure logging/display.
With a standard 0-5v analog channel you can use std instruments, for instance, I monitored ram air inlet pressure to our car while on Cal Speedway (sports car).

With some of the talk about traction control, I could easily see throttle position/rpm/speed data as necessary.

John
As Carroll Smith wrote; All Failures are Human in Origin.

Offline Cajun Kid

  • Rajun Cajun Racing E/CGALT 5690
  • Hero Member
  • *****
  • Posts: 3189
  • Venable Rod's & Racing #805 Studebaker, #806 Ford
Re: Lift or Down Force ?
« Reply #17 on: December 06, 2010, 11:13:42 AM »
any reccomendations on which data logger ?  and then what I need to log ?


The only data I have ever gotten was from the

Seat of the Pants, Eyes, Ears, Hands and Right Foot.   :cheers:

Maybe I need ELECTRONICS now ??

Charles
ECTA Record Holder Maxton
E/CBFALT, E/CBGALT, E/CGALT, E/CFALT, A/CGALT, C/CGALT, D/CGALT, C/CBGALT, B/CBGALT, C/CFALT
OHIO
B/CGALT, C/CGALT

LTA Record Holder and 200 Club Member
A/CBFALT, B/CBFALT, C/CBFALT, C/CFALT, C/CGALT,   E/CGALT, E/CFALT

Fastest Standing Mile at Ohio  203.343mph
Fastest Standing Mile at Maxton 196.967mph
Fastest Standing 1.5 Mile at Loring 213.624mph
Fastest Standing Mile at Loring 204.109mph

http://s261.photobucket.com/albums/ii43/cajunkid5690/

Blog    www.venablerodsandracing.com
email   venableracing@gmail.com

Offline johnneilson

  • Sr. Member
  • ****
  • Posts: 502
Re: Lift or Down Force ?
« Reply #18 on: December 06, 2010, 11:43:59 AM »
Charles,

I personally use Pi Research, this from investment 10+ years ago. Good equipment works for a long time, multiples of cars and karts.
A few years ago I worked with a fellow who ran CDS, Competition Data Systems eq. If and when, I will look this direction.

I have also been looking in the direction of Racepak, I believe the same folks as MSD in Tx. Or owned by the main company.

Not to advertise but these folks are very good www.veracitydata.com

One note: the software to anaylise the data is a tool, take a look at it also.
A very good book on data was published by the SAE, I forget the author. Can be usefull to show you what systems can do.
I will look up the author later today when I go to shop.

John

As Carroll Smith wrote; All Failures are Human in Origin.

Offline Cajun Kid

  • Rajun Cajun Racing E/CGALT 5690
  • Hero Member
  • *****
  • Posts: 3189
  • Venable Rod's & Racing #805 Studebaker, #806 Ford
Re: Lift or Down Force ?
« Reply #19 on: December 06, 2010, 12:06:53 PM »
John thanks for the info.

Charles
ECTA Record Holder Maxton
E/CBFALT, E/CBGALT, E/CGALT, E/CFALT, A/CGALT, C/CGALT, D/CGALT, C/CBGALT, B/CBGALT, C/CFALT
OHIO
B/CGALT, C/CGALT

LTA Record Holder and 200 Club Member
A/CBFALT, B/CBFALT, C/CBFALT, C/CFALT, C/CGALT,   E/CGALT, E/CFALT

Fastest Standing Mile at Ohio  203.343mph
Fastest Standing Mile at Maxton 196.967mph
Fastest Standing 1.5 Mile at Loring 213.624mph
Fastest Standing Mile at Loring 204.109mph

http://s261.photobucket.com/albums/ii43/cajunkid5690/

Blog    www.venablerodsandracing.com
email   venableracing@gmail.com

Offline Dynoroom

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 2192
Re: Lift or Down Force ?
« Reply #20 on: December 06, 2010, 12:47:46 PM »
Edelbrock has a system called Quick Data. Easy to use, windows based software, and $$ friendly. Has all the things you need and more.
Michael LeFevers
Kugel and LeFevers Pontiac Firebird

Without Data You're Just Another Guy With An Opinion!

Racing is just a series of "Problem Solving" events that allow you to spend money & make noise...

Offline Cajun Kid

  • Rajun Cajun Racing E/CGALT 5690
  • Hero Member
  • *****
  • Posts: 3189
  • Venable Rod's & Racing #805 Studebaker, #806 Ford
Re: Lift or Down Force ?
« Reply #21 on: December 06, 2010, 12:52:20 PM »
Edelbrock has a system called Quick Data. Easy to use, windows based software, and $$ friendly. Has all the things you need and more.

Thanks Michael, talk to you tomorrow night on chat.

Charles
ECTA Record Holder Maxton
E/CBFALT, E/CBGALT, E/CGALT, E/CFALT, A/CGALT, C/CGALT, D/CGALT, C/CBGALT, B/CBGALT, C/CFALT
OHIO
B/CGALT, C/CGALT

LTA Record Holder and 200 Club Member
A/CBFALT, B/CBFALT, C/CBFALT, C/CFALT, C/CGALT,   E/CGALT, E/CFALT

Fastest Standing Mile at Ohio  203.343mph
Fastest Standing Mile at Maxton 196.967mph
Fastest Standing 1.5 Mile at Loring 213.624mph
Fastest Standing Mile at Loring 204.109mph

http://s261.photobucket.com/albums/ii43/cajunkid5690/

Blog    www.venablerodsandracing.com
email   venableracing@gmail.com

Offline johnneilson

  • Sr. Member
  • ****
  • Posts: 502
Re: Lift or Down Force ?
« Reply #22 on: December 06, 2010, 10:06:03 PM »
Charles,

the book is written by Jörge Segers, Analysis Techniques for racecar data acquisition
published by SAE

It goes from the basic data logging to full on theory and creating math channels.

Again, I will mention the anaylist software tool is a must.
I am very skeptical of any SW that is updated every month and a "free" download.

John
As Carroll Smith wrote; All Failures are Human in Origin.

Offline jl222

  • Hero Member
  • *****
  • Posts: 2955
Re: Lift or Down Force ?
« Reply #23 on: December 07, 2010, 01:25:59 AM »


   Charles...have you measured from the floor to bottom of front wheel rim and to bottom of body in front of wheel? This should answer half of your question.

               JL222 :cheers:

Offline krusty

  • Full Member
  • ***
  • Posts: 252
Re: Lift or Down Force ?
« Reply #24 on: December 07, 2010, 05:41:28 PM »
^^Well?^^     vic

Offline Cajun Kid

  • Rajun Cajun Racing E/CGALT 5690
  • Hero Member
  • *****
  • Posts: 3189
  • Venable Rod's & Racing #805 Studebaker, #806 Ford
Re: Lift or Down Force ?
« Reply #25 on: December 07, 2010, 05:58:31 PM »
 :?  The distance from the bottom of the rim to the floor should not change much, not sure why that is a factor? Tire is not going to change much is it ?    Now from bottom of front air dam to the ground is the ride height at rest, but at speed from the pictures it is hard to tell what that measurement is at the finish line.

To get the air dam to floor measurement I need to put the air dam back on and it is COLD and the air dam is in the nose of the trailer out on the back forty.  Will get mounted and measured this weekend.

Charles
« Last Edit: December 07, 2010, 06:00:35 PM by Cajun Kid »
ECTA Record Holder Maxton
E/CBFALT, E/CBGALT, E/CGALT, E/CFALT, A/CGALT, C/CGALT, D/CGALT, C/CBGALT, B/CBGALT, C/CFALT
OHIO
B/CGALT, C/CGALT

LTA Record Holder and 200 Club Member
A/CBFALT, B/CBFALT, C/CBFALT, C/CFALT, C/CGALT,   E/CGALT, E/CFALT

Fastest Standing Mile at Ohio  203.343mph
Fastest Standing Mile at Maxton 196.967mph
Fastest Standing 1.5 Mile at Loring 213.624mph
Fastest Standing Mile at Loring 204.109mph

http://s261.photobucket.com/albums/ii43/cajunkid5690/

Blog    www.venablerodsandracing.com
email   venableracing@gmail.com

Offline jl222

  • Hero Member
  • *****
  • Posts: 2955
Re: Lift or Down Force ?
« Reply #26 on: December 07, 2010, 06:23:15 PM »

  The tire could grow some at speed but assuming it doesn't if front end is higher in the shop than rim, you have lift
and downforce if less  8-) eyeball engineering :-P

Offline Cajun Kid

  • Rajun Cajun Racing E/CGALT 5690
  • Hero Member
  • *****
  • Posts: 3189
  • Venable Rod's & Racing #805 Studebaker, #806 Ford
Re: Lift or Down Force ?
« Reply #27 on: December 07, 2010, 07:01:33 PM »

  The tire could grow some at speed but assuming it doesn't if front end is higher in the shop than rim, you have lift
and downforce if less  8-) eyeball engineering :-P

Hmm, I would have thought that if the bottom of the air dam was lower or even with the lower edge where moon meets rim at rest, then looking at the pics that would mean front end has lift at speed ?

I will get exact measurements over the weekend,,, But going through and zooming in on a dozen or so finish line pics and as many at rest as well,,, it looks like the front is lifting just a little (maybe 1/2 to 3/4 inch at the most)  and the rear may have a bit of down force as it looks just a smidge down at speed.

I guess some precise measuring and a wind tunnel test is in order for Feb/Mar. That way I can try out my step pan and various spoiler lip length's and angles as well as adjusting rake.

Charles
« Last Edit: December 07, 2010, 07:06:48 PM by Cajun Kid »
ECTA Record Holder Maxton
E/CBFALT, E/CBGALT, E/CGALT, E/CFALT, A/CGALT, C/CGALT, D/CGALT, C/CBGALT, B/CBGALT, C/CFALT
OHIO
B/CGALT, C/CGALT

LTA Record Holder and 200 Club Member
A/CBFALT, B/CBFALT, C/CBFALT, C/CFALT, C/CGALT,   E/CGALT, E/CFALT

Fastest Standing Mile at Ohio  203.343mph
Fastest Standing Mile at Maxton 196.967mph
Fastest Standing 1.5 Mile at Loring 213.624mph
Fastest Standing Mile at Loring 204.109mph

http://s261.photobucket.com/albums/ii43/cajunkid5690/

Blog    www.venablerodsandracing.com
email   venableracing@gmail.com

Offline johnneilson

  • Sr. Member
  • ****
  • Posts: 502
Re: Lift or Down Force ?
« Reply #28 on: December 07, 2010, 07:32:01 PM »
Or you could install the data system, make a run and see how much lift/squat you have and at what speeds.............
Also, during the acceleration, you can see the amount of squat in the rear end.

Just an observation, John
As Carroll Smith wrote; All Failures are Human in Origin.

Offline MAZDA1807

  • Full Member
  • ***
  • Posts: 137
Re: Lift or Down Force ?
« Reply #29 on: December 08, 2010, 03:36:49 AM »
IMO a little lift goes a long way, most time the wrong way.
80ci,264.7 RWHP, 19.2sq.ft. of frontal area, 175.611, NOTBAD