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DIY G29 Hydraulic Load Cell brake

Discussion in 'DIY peripherals' started by niterida, Jun 17, 2020.

  1. niterida

    niterida Member

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    Actually I give up on this setup.
    I have tried different ratios on the pedal arm, different return spring strength, different length of push rod and although each of them gives a different feel and I can get it to feel exactly like a real brake it has one fatal flaw.
    I cannot get the feeling of just touching the brake and having it register. If I make it sensitive enough to do this then full braking comes in too easy and it locks up. If I set it so I get full braking without locking too easy then I have to press too hard to get that initial braking and then I can't judge how far to ease off the brake for trail braking.
    And when I look at my telemetry it is this transition from full braking to trail braking and trailing the brake all the way into the corner where I am losing all my time. And I mean ALL my time - I can brake at exactly the same point with exactly the same brake force as the Professional driver telemetry from VRS, turn in at exactly the same point, hold exactly the same line and accelerate out at exactly the same time, but between turn in and accelerating out I lose about 10kmh because I can't ease off the brakes without losing all braking so I have to hold them a bit harder and then come off them too soon because I have lost too much speed :(
    Thrudtmaster TLCM pedals are now on my shopping list - unless anyone has nay better ideas or (affordable) options ?
  2. niterida

    niterida Member

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    I have found the issue - the current setup doesn't start registering until there is 2v output. I read that this is standard for the G29 pedals - any idea how I can rectify this ? Is it something in the pedals that doesn't send a signal to the game until 2v or is it something in the software, PC or game ??
    Maybe thats why people use an arduino board instead of just the INA122 amplifier ??
  3. niterida

    niterida Member

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    D'OH - the issue was very simple to fix.
    I have a Leo Bodnar Logitech to USB converter and there is software to calibrate the converter - once I did that it was registering just a slight pressure on the pedal so now I can trail brake like a pro (well almost.....)
    I still think the wii fit loadcell is not the right option and will try a disc type loadcell. The cheapest one I can find is on back order so I won't get it for 6 weeks or so. Will report back if that makes any difference.
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  4. niterida

    niterida Member

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    Update time :)

    I redid my wii fit loadcells by taking 2 of the bare loadcells (without the pressed steel bolt on bits), placed them back-to-back in a X and then dropped them in my caliper. This got rid of any flex that the pressed steel bits had (and they ended up bending out of shape anyway) and made the pedal a lot harder.
    Then I tried different pedal arm leverage ratios and found it is very dependent on getting that just right. Too much leverage and the pedal is too soft and spongy and not enough and the pedal is like standing on a brick.
    I have it just about right but would like it a tiny bit harder - unfortunately can't do that unless I build new pedals with infinitely adjustable leverage ratio.

    Just did a quick race at Spa in a M3 and got straight down to 2:20's where I was usually in 2:21 bracket. Did one lap at 2:19.8. Braking was just so natural and trail braking all the way into the apex felt the most realistic yet.
    In fact I would say it absolutely felt exactly like real brakes :)

    I think I might fork out $80AUD and get a 200kg button type loadcell. When I went from one wii loadcell (50kg) to 2 (100kg) it made a huge improvement. So I am thinking a 200kg one might be even better. Also it will fit in the caliper better :)

    Stay Tuned ........

    IMG20211013200146[1].jpg IMG20211013200238[1].jpg IMG20211013200315[1].jpg IMG20211013200328[1].jpg
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    Last edited: Oct 13, 2021
  5. sedesa tatasa

    sedesa tatasa Member

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    Good idea. I also use the wii fit load cell.
    I think it 500kg to 1000kg.
    You should check with scale before using the $ 80 AUD.
  6. niterida

    niterida Member

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    there are 4 in the fit board and the board is only rated to 150kg and allowing for some safety factor I assume each loadcell is 40-50kg - no way is it 500-1000.
    I have also tried the cheap 50kg eBay loadcell and the wii ones have about the same sensitivity.
    I am pretty sure a 200kg button style loadcell will be the best option. They don't bend and are a true pressure style measurement. i think the tiny bit of flex in the current setup is detrimental and will be my last area of improvement (apart from continually fiddling with the pedal leverage ratio)
  7. niterida

    niterida Member

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    Another quick update.

    I put the pedal back to the lowest lever ratio (from 3:1 to 2:1 roughly) so it is hard to push - even on the middle setting it was too soft and had too much travel and I was struggling to trail brake properly.

    I was also trying to use the variable resistor on the Derek Speares loadcell amplifier board to adjust the sensitivity. If you set it so it is really really hard to get full braking (F1 car) and then adjust it lower for Gt or road cars it then increases the bottom of the range. Sometimes so much that the brakes are on when you don't even touch the pedal. And you have to adjust it between cars or the F1 cars lock too easy if you have it set for GT cars.
    So now I have figured out that you adjust the resistor so it only read max when you are at max pressure you can physcially apply and leave it alone.
    I have a Leo Bodnar adapter for the Logitech pedals to Thrustmaster wheel and in the software you can adjust the pedal range (same as the brake range in AC etc). I set the minimum slider so that when you take up the master cylinder slack the signal sent to the game is around 100 (or 10%). This will stay the same for any car now.
    Then I adjust the maximum value to suit the car - 1024 for F1, 910 for GT and 800 for road cars (lower number means less pressure to reach 100% in game)

    Just took another 3/10th of my M3 Imola best :)
    Last edited: Oct 15, 2021 at 12:24
  8. niterida

    niterida Member

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    More updates - just in case anyone is still following my ramblings.......

    Turns out my X shaped loadcells wasn't the best execution - as they were only glued together and the glue I used wasn't very good so they would move in the caliper. This then meant that the loadcell sensor and wires would sometimes get caught by the caliper piston and one of the sensors failed.

    So I machined (well used a grinder actually) a 1mm notch in the back of one the loadcells so the other one would slot into and stay at exactly 90deg and used a better glue. Then put that into the caliper with one of them upright (like a Cross) rather diagonally (like an X).

    Now it is just about perfect and my settings had to change because the readings were more stable and they didn't change as I used them since they were no longer moving etc.

    So I now have the minimum brake range set so that at rest it is on zero in game. That way the master cylinder free play takes up the slack (where you would normally set minimum brake in game above zero to avoid lockups) so when you first feel the brake pedal resistance in game reading will be around 10-15% (I have it at 15%). Then set the maximum brake range to where you apply your own max brake pedal force. And adjust from there to your liking and/or car.
    Obviously the actual in game settings should then be 0-100 brake range and 1.00 brake gamma

    Attached Files:

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