aerodynamic undertray

Discussion in 'Track Prep & Tech' started by RobT, Sep 10, 2009.

  1. A.N. Other Banned after significant club disruption Dec 5th 2

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    How many do you need? !

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  2. fthaimike Forum Addict

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    Front ones i meant Chris sorry lol to keep with this thread but thanks anyway for those nice pics.
     
  3. RobT

    RobT Forum Junkie

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    interesting thread on undertrays incorporating naca brake ducts and a very cool brake duct/floor arrangement from a racing stasis audi A4

    http://forums.nasioc.com/forums/showthread.php?t=1479376

    Well did the aero work pay off?

    I think it has had some effect.

    At the Aintree race, I beat my PB by 1 sec.....unheard of....and top speed was up also. Car has never felt so planted.

    I have never been to Anglesey before on the new track so hard to judge from that weekend.

    At Curborough, 8/10ths improvement on PB. I struggle to think that aero has so much effect at a slow track like curby but who knows.

    The aero mods have been done along with tyre and gearbox mods also so its hard to exactly know the precise effect, but the feeling of the car at Aintree particularly was fabulous - fast track.

    With the smoothing and front aero work I have done, to reduce drag, I am now getting much higher brake wear as there is less airflow to the brakes. Hence the idea to put low drag ducts into the floor to feed the brakes.

    More info soon.

    Pic from Anglesey:

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  4. jamesa Forum Junkie

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  5. Paul-R New Member

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    Does aero make a noticeable difference on a track car ? I hadn`t thought of that.
     
  6. Mike_H Forum Addict

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    Nice work! Did you do anything at the back end as well? It's on my to-do list for 'sometime' but there's a lot of stuff ahead of it.
     
  7. RobT

    RobT Forum Junkie

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    I have it on quite good authority that modifications to the rear - i.e a diffuser - have the least effect on a hatchback. Thus, that is last on the list. I am currently testing some in-floor front brake ducts - if this works then the front floor will be made in laminated sandwich (carbon top and kevlar bottom for abrasion resistance) with the brake ducts combined. After this, side skirts to stop air coming in at the sides to make the rear end light - to 120mm off the deck like the front floor. If this works, flat floor. Last thing will be a rear diffuser.

    Having the front splitter on hydraulics works a treat - for loading the car on a trailer, the splitter just moved up out of the way. mint.
     
    Last edited: Jun 15, 2010
  8. Mike_H Forum Addict

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    I've heard similar things, Rob. A racer friend told me that it might cause me problems with understeer too, on a FWD car. I guess that depends on the rest of the suspension and aero setup too.

    Do you have a 120mm clearance rule in your sprint class, or did that just seem like a good height to you?

    I someone making the parts for you, or are you building up some top end fabrication skills?
     
  9. RobT

    RobT Forum Junkie

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    the sprint class allows 40mm min clearance but says that nothing must touch the floor if the tyre deflates, so that was I seem to remember something like 80mm - but as I still occasionally drive the car on the road, I chose 120mm too give some possibility of going over curbs etc - this simply comes from ride height and position of suitable mounting points off the ground, nothing particular about it

    I made the floor in plywood to see if it would survive road and track use, and loading to trailers - it has.

    I didn't want to spend getting a carbon floor until I knew this - lot of money to smash off!

    The floor will need properly vacuum bagging and cooking to make it as light and strong as possible, so I will take my plywood template to a specialist for this final step - there's a few of them about but I am using these lads as they are hillclimbers also

    http://www.fibre-lyte.co.uk/
     
  10. pascal77uk Paid Member Paid Member

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    Sounding good Rob.

    Rear diffusers can cause you more problems than good if not done right. Que wind tunnels and extensive testing against the clock etc
     
  11. RobT

    RobT Forum Junkie

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    I'm not convinced I need more rear grip - lots of people go to lengths to reduce rear grip on a hatchback to make it neutral - I am aiming to leave rear grip standard, and get more front grip to get it neutral - its getting there.....the rear end let go at Anglesey in practice and its getting more 'pointy' all the time - there is still some optimisation to be done with front geometry on my new (radial) tyres and I reckon this, combined with side skirts to reduce high speed rear lift, might just about do it.

    I also have some new michelin radial slicks to try which will be very interesting - in a supersoft compound that they have developed for the berg cup apparently

    then there's steering geometry mods ;) but thats a storey for another day

    too many things to try, not enough time :lol:
     
    Last edited: Jun 15, 2010
  12. fthaimike Forum Addict

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  13. Paul-R New Member

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    Rob, what are the `gas struts` you used ?
     
  14. RobT

    RobT Forum Junkie

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  15. RobT

    RobT Forum Junkie

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    interesting read about the next gen Ford Focus which will use active radiator ducts which close when the engine doesn't need cooling and reduce drag / increase mpg. Also small flaps which lower out of the front edge of the front wheel arch to reduce drag created by the front tyres at speed.

    'Ford Active Grill Shutter System'

    Well cool stuff and possible competition application
     
  16. idrivemyself New Member

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    Well done on the splitter Rob! :thumbup:

    That Ford active radiator bit could be had fairly easily... Wire up an ECT with a servo motor and a flap or two out front. Could even have a dash mounted variable resister in series to over-ride the ECT. Or take it a step further and wire in the VSS to a control module to alternate flap position based on speed. Too many thoughts for the off season....
     
  17. RobT

    RobT Forum Junkie

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    Bump from 2010.

    Latest version of front splitter on my Ibiza sprint car. Whole thing is now detachable to aid service access, with only 2 clevis pins to hold it on, so removable in <5mins easy. Now slightly longer at front, and with much larger under-car area than previous, and also lower to the ground (80mm). Attached to chassis rails with two large ali plates. This version is not attached to the front bumper at all so dead easy to remove.

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    with windows to allow access to pins removed

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    infinity and Dex like this.
  18. gingernuts Forum Member

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    Very interested in this rob as Im doing full front splitter, skirts, diffuser and rear wing over the closed season. Do you have any more pictures of the attachement points of the splitter Ie where it ties to the bumper bar and subframe, And any pictures of the splitter bare in general and its fixings. Looks a very good base design for me to start building. I can get an off the shelf one for a rado but it might not incorporate the foor and maybe be better to build my own and tweak it to the required spec.
     
  19. RobT

    RobT Forum Junkie

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    Will take some more pics when its off next, very hard to see with it all fitted. Basically there are two ali plates bolted to the outside of the chassis rails that hold the front, which you can see in the pics, and the rear slots into what is a long thin letterbox shape bolted to a strutbrace which runs between the front wishbone bolts.

    More here

    http://www.seatcupra.net/forums/showthread.php?t=349916&page=7
     
  20. Prawn Forum Member

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    Looks great Rob!
    I hope you don'd mind me adding a bit to this, after following Nige's threads for years, and stealing a good hour or more of your time at GTI international this year looking over the ibiza, I finally got on with making something similar for my own car.

    I started by getting the car up on the ramps, I need to remove the bumper to drive it up the ramps, so that came off first:

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    And up she goes:

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    I took a measurement along the sill line to see where the car was sitting, this will become my target angle for the splitter to ensure it's parallel to the ground when finished, or slightly nose down if anything.

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    I marked up the centre line, and drew around my existing LCR splitter to get a rough outline shape.

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    Then added 100mm all round for the splitter projection, this should suit, as the sides of the LCR splitter curve in tighter than the bumper, so total projection on the sides ends up around 50mm.

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    And out came the Jigsaw:

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    Next up came the rear piece, all cut out and finished:

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    The idea of making it in 2 parts, is that the front section is fairly likely to get damaged at some point, and also, if it were a single piece, I'd be unable to remove it and take it home if it were damaged. By making it this way, it can be removed and put in the back of the car if needed.

    Like so: (hole is to clear the dog bone mount)

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    Held up for a test fit:

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    (angle not set here)

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    Hinges fitted to join the two halves (these will be bolted up in the finished product)

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    I left a 2mm gap between the sections, which is just enough to allow adjustment of the splitter angle without the two parts binding.

    Rear section test fitted, this is bolted through the two captive bolts that hold the lower subframe brace in place. it's absolutely solid here!

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    But as an extra, I added tie rods hanging down from the chassis rails to take extra weight

    I welded M8 nuts to the end of the thread bar, then ground it all down so there's as little as possible sticking down to catch

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    I later scraped that fixing method for the tie rods, because it was awful, requiring the whole bar to be turned to remove, and the car to be lifted too high. useless.

    Getting there:

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