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Thread: Shock Sensors - Reverse readings?

  1. #1
    Join Date
    Nov 2016
    Posts
    3

    Default Shock Sensors - Reverse readings?

    Is there a way to reverse the way the software reads the position of the travel sensor?

    For example, the sensor position is at 4" as the car sits static. Downward motion (compression) results in a higher number, upward motion (extension) results in lower number. It's a bit confusing. Seems backwards to me.

    Is there a way to reverse it? I tried changing the settings, from 0=0 & 5=8 to the opposite, but got some really weird readings.

    To take it a step further, could the static position be set to read 0, and up be positive and down be negative?

  2. #2

    Default Re: Shock Sensors - Reverse readings?

    You can make a math channel to achieve this.

    For myself I have a math channel that I can enter a number that sets each channel to zero. This way you can see the position above/below the car at rest height.

    If you do this you can then use the wheel motion ratio to calculate wheel movement. Happy to post some screen shots if that would help.

  3. #3
    Join Date
    Nov 2016
    Posts
    3

    Default Re: Shock Sensors - Reverse readings?

    I'd really appreciate that!
    Thanks

  4. #4

    Default Re: Shock Sensors - Reverse readings?

    Quote Originally Posted by nbman
    I'd really appreciate that!
    Thanks
    Have a look on the Team Racepak facebook page https://www.facebook.com/teamracepak/ and the Racepak Community facebook pages https://www.facebook.com/groups/Racepakcommunity/ as there is a lot of helpful advice there and you may get a quicker response I am a member of Team Racepak for 2018 and data is my passion!

    Hope this helps, note I work in metric...

    This is a math channel I have (there is one for each sensor:
    ('RR Shock Pos'/0.6944444444444444)-117.9

    RR Shock Pos = VNet sensor raw value
    0.6944444444444444 = the calculated motion ratio for this sensor. I have calculated this for each wheel.

    This gives the wheel movement then -117.9 from this value gives the car at rest.

    I will quote from a forum member now...
    With regards to if the shock velocities are positive during compression or rebound, it depends on how you have the position channel calibrated and if you multiply the shock velocity channel by -1. The shock travel becomes more positive (towards larger values) as the suspension is compressed Therefore, during compression your shock velocity would be negative...

    To calculate the motion ratio I put the car on stands, remove the wheels and measure to the ground, record this measurement and the sensor measurement. Jack the suspension up say 50mm and take the measurements again. Divide the 2 and you have the motion ratio. The result will be like the screen shot below


  5. #5
    Join Date
    Nov 2016
    Posts
    3

    Default Re: Shock Sensors - Reverse readings?

    OK, I'm going to give it a try.
    Thanks very much.

  6. #6

    Default Re: Shock Sensors - Reverse readings?

    Quote Originally Posted by nbman
    OK, I'm going to give it a try.
    Thanks very much.
    Not sure how often you get on Facebook as I just made a post about the shock sensors https://www.facebook.com/teamracepak...8499077767345/. I only just noticed that the last 3mins is blackness however the first 3mins is useful

    If you need to read up some more, try Competition Car Suspension by Allan Staniforth, it is a great reference book to have.

    Some points to consider:
    1) Ride height is ground to the Chassis reference.
    2) When a shock is in compression it records a positive (increasing) value and in rebound a negative (decreasing) value.
    3) Calibrate damper pots to what you see at the springs.
    4) Unsprung weight (wheels, tyres, brakes, wishbones, uprights etc - Competition Car Suspension by Allan Staniforth)
    5) Sprung weight (Total weight - unsprung weight)
    6) Motion Ratio - the movement of the spring for a given amount of wheel movement (the shock travel can be used for this value, however the spring ratio will also be needed). This has been previously done for both the dampers and the sensors.

    Ride Height Measuring
    1. Measure to a point on the body (fender) with the tyres at normal pressure and with its normal weight in it (driver).
    2. Also measure to a point on the lower control arm. Not important where but must be used all the time. For this I use a longacre ride height tool as it has a magnet that holds the tape to frame. Indicator shows height as the car moves up and down. This is locked off at a measurement (not critical).
    3. Jack the car off and remove the wheel.
    4. Lower the car so that the measurement in (1) is the same.
    5. Raise the lower control arm to match the measurement at (2).
    6. Measure the ride height from the point that you want to use. For my purpose I used the bolt that attaches the hub.
    Mine:
    RL - 177 mm FL - 162 mm
    RR - 175 mm FR - 163 mm






    My next big job is measuring up the car.
    https://youtu.be/-IbmL-UKWOo

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