Aerodynamics

Discussion in 'Discussion Forum' started by Dr.Jeff, Feb 4, 2020.

  1. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Aerodynamic related topics seem to come up in various discussions; obviously when talking about things like spoilers, but also in conversations like the flow of air through the engine bay, radiator, etc. The subject has been raised many times, including some very recent threads.

    Unfortunately the science of aerodynamics is extremely complex and beyond the ability of most hobbyists (myself included). Without sophisticated modeling technology and wind tunnel testing we are really only guessing. Particularly with older obscure vehicles like the X1/9 where the path has not been paved very well.

    The following article was posted in today's newsletter form Grassroots Motorsports Magazine. It was printed in last December's issue. Unfortunately it does not offer much real help, but it does address a couple of common misconceptions. So I thought it might be worth a look for those (like myself) who like to modify our X's:
    https://grassrootsmotorsports.com/a...ampaign=GRM+Daily+Newsletter+Automation+Email

    I'm sure there are many other resources that are much better and offer greater assistance on the subject. The ones that I have reviewed in the past were written by and for aerodynamic engineers, and therefore much too complex. Especially when I am not really trying to improve the aerodynamics of my street cars, but I like to add body modifications to give a "track" look to the car (i.e. purely for style). It would be nice however to know just how much good or harm I am doing when making such changes. Anyone have good articles written for the masses that might be useful?

    In my opinion this is what not to do:
    62eb41f4059c50bc5fbcde27ab8571d4.jpg
     
  2. fastx19

    fastx19 Administrator Moderator

    Location:
    Santa Clara, CA
    That would be exactly what you would want to do for a Amod hillclimb car, or even an amod autocross car. But, for the rest of us in everyday land, I agree with you.
     
    Dr.Jeff likes this.
  3. Cratecruncher

    Cratecruncher True Classic

    Location:
    Austin
    Years ago I did a series of coastdown tests on one of my vehicles as a school project out at a closed airport. The basic idea is to record the time interval required for the car to slow down from say 80 to 60 mph with transmission in neutral. Then do it again from 30 to 10 mph. Over a series of runs you will get a fair estimate of both rolling/drivetrain friction and aerodynamic drag coefficient using some simple formulas. While not NASA accurate the data are good enough to tell you a ballpark number and fun to see the effects of various changes. With so many cool apps now available you may be able to get speed and elapsed time in graphical form right on your phone in real time. That's something we could only dream about 35 years ago.
     
    twincam69 and Dr.Jeff like this.
  4. bpimm

    bpimm Brian Pimm

    Location:
    Washougal, WA
    Dr.Jeff likes this.
  5. NEG

    NEG True Classic

    Location:
    UK
    I wonder if they ever stuck that car pictured above in a wind tunnel...it looks more like a styling exercise than something serious...
     
  6. bpimm

    bpimm Brian Pimm

    Location:
    Washougal, WA
    it actually looks like a time attack car, they go a bit crazy on the aero.
     
  7. JimD

    JimD Waiting for Godot... Moderator

    Location:
    Missouri, USA
    I was thinking "upscale snow plow". Of course, it is snowing here lately, so snow is on my mind.
     
  8. Bobkat

    Bobkat 1979 x1/9

    Location:
    Calgary Alberta
    I am it the process of putting the x in some CFD software. I have to take some time and simplify a model.
     
    autox19, mkmini and Dr.Jeff like this.
  9. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Brian is exactly right, the caption for that pic (on Google image) said it is a time attack car. Goes along the lines of what "fastx19" said earlier.
     
    Bobkat likes this.
  10. mkmini

    mkmini True Classic

    Location:
    Latvia
    please share You results after that :)
     
    Bobkat likes this.
  11. myronx19

    myronx19 True Classic

    Location:
    Toronto, ON Canada
    Bob Nelson has a pretty sweet ride, some interesting aero - he has some great vids on Facebook & Instagram.

    I borrowed this picture of his car off Facebook - really nicely built, K20 - and he keeps making it faster and faster every year!

    upload_2020-2-7_17-0-22.png
     
  12. At least it looks as though it has sufficient horsepower to overcome the aerodynamic drag ;)

    If you are serious about aerodynamics, then nothing beats the BT46 "fan car":

    [​IMG]

    Interestingly, I noticed that there is a new design being proposed based on this idea (with even more extreme aerodynamics):

    [​IMG]

    Ciao,
    Dom.
     
    autox19 likes this.
  13. MikeHynes

    MikeHynes True Classic

    Location:
    Goodfield, IL.
     
    mkmini likes this.
  14. NEG

    NEG True Classic

    Location:
    UK
    Duh, not serious look at the tyres...
     
  15. Bobkat

    Bobkat 1979 x1/9

    Location:
    Calgary Alberta
    Gordon Murray's new T50 design uses through body fan aero.

    [​IMG]
     
  16. carl

    carl True Classic

    Location:
    Virginia
    Doc, if you are going for the look without concern for function, you can do whatever you want whether it makes aero sense or not. I don't know what the streets are like in Sin City but out here they tend to be in bad shape so low front splitters and fancy undertrays will just be ripped off. Big wings will get you all manner of comments as my snorkel seems to confound "normal" folks and I constantly get asked what that thing is.

    I like the early stock front spoiler and want a rear ducktail as the aero for my car.

    Kind of depends what you want, period correct look for a race X or a modern time attack look which might be out of place on an X.
     
  17. ecohen2

    ecohen2 True Classic

    Location:
    Arlington Va
    @carl is right, around the DC metro area even a Corsa kit is constantly in danger of getting ripped off by uneven road surfaces...

    I WANT A SNORKEL!
     
    mkmini likes this.
  18. carl

    carl True Classic

    Location:
    Virginia
    Be careful what you yell for, I can send my wife to the dollar store and get you a kids swimming snorkel.
     
  19. ecohen2

    ecohen2 True Classic

    Location:
    Arlington Va
    Some how that wouldn't surprise me... :)

    I want a snorkel that goes on the back of my X1/9 and looks similar to the one FAZA produced!!
     
  20. carl

    carl True Classic

    Location:
    Virginia
    If you know someone with good fiberglass skills you can borrow mine to make a mold.
     
    Brayden_connolly likes this.

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