Steering rack picture info. For the record | FerrariChat

Steering rack picture info. For the record

Discussion in '360/430' started by 24000rpm, Jun 22, 2020.

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  1. 24000rpm

    24000rpm F1 Rookie

    LH, 360 Challenge race car OEM rack.
    RH, F430 coupe OEM rack, which is practically the same as 360 oem

    so the teeth are really the same for these 2 racks.
    From that , and the fact that the challenge car has quicker turn, I deduced that the pinion must be different from challenge car to regular road car.

    Just for the record.


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    tifosi101 likes this.
  2. mwstewart

    mwstewart F1 Rookie

    Feb 5, 2014
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    The pitch of the RH rack looks to be slightly coarser but perhaps it's just the photo?
     
  3. mwstewart

    mwstewart F1 Rookie

    Feb 5, 2014
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    P.S. the pinion is matched to the rack.
     
  4. 24000rpm

    24000rpm F1 Rookie

    it is coarser because the car it belonged to was barbecued;).


     
  5. 24000rpm

    24000rpm F1 Rookie

    wow, how's that possible, the challenge car is quicker than the road car , that's for sure

     
  6. mwstewart

    mwstewart F1 Rookie

    Feb 5, 2014
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    Perform a quick test to validate the ratio: turn each rack to full lock and measure the distance between the rack body and the end of the rack, then turn the pinion 360 degrees and re-measure each steering rack. Mark the pinion to ensure the rotation is exactly 360 degrees on each rack.
     
    imahorse and 24000rpm like this.
  7. 24000rpm

    24000rpm F1 Rookie

    report back:

    f430 rack: fully extended to one side: tip to body: 106mm , 360degree later: 42mm
    360 challenge: fully extended to one side: tip to body: 100mm , 360degree later: 40mm

    I have no idea how to interpret these data

     
  8. mwstewart

    mwstewart F1 Rookie

    Feb 5, 2014
    2,624
    England
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    Okay, great. Looking at the basic rack travel:

    F430: 106mm - 42mm = 64mm of travel per 360 degrees.
    Challenge:100mm - 40mm = 60mm of travel per 360 degrees.

    The F430 rack moves 32mm per half turn on the steering wheel and the Challenge moves less; 30mm, so, actually the F430 rack you have there is lower or 'quicker' mechanical ratio than the Challenge rack that you have. When comparing two racks of equal dimension the further a rack moves per degree of pinion rotation the 'quicker' it is i.e. it moves the wheels more per turn than a higher ratio 'slower' rack.

    What makes things a little trickier here is that the Challenge rack is shorter; this is a design choice to affect the steering geometry and maximum/minimum angle of deflection of the wheels. Although the mechanical rack ratio is higher than the F430 the different rack length serves to create a lower steering ratio than the F430 at the expense of lock/overall travel i.e. a three point turn in the F430 is likely to take many more turns in the Challenge.

    I can't get any more detailed than the above without measuring wheel travel and steering wheel angle, but hopefully it answers it.

    The ideal solution for a road car is the same rack dimensions but a different rack and pinion.
     
  9. 24000rpm

    24000rpm F1 Rookie

    i think i got something wrong, it should be "after travel per 180 degrees". but your analysis still holds.

    I guess i'll have to remove the pinion to compare

    maybe the rack and pinion are really identical it is something else that makes the challenge car turns quicker

     

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