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Thread: Technical Violet’s E36 M3 Track Car

  1. #76
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    Attachments aren't coming through.

    What's your goal? What are you going to use the chassis/suspension measurements for?

  2. #77
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    97 M3, 07 X3
    Quote Originally Posted by aeronaut View Post
    Attachments aren't coming through.

    What's your goal? What are you going to use the chassis/suspension measurements for?
    Here are my goals with modeling the suspension arms.

    Determine optimal ride frequency to balance chassis harmonics and prevent resonance

    Obtain theoretical roll centers at various ride heights and plot against CG to determine roll moment.

    Analyze Camber gain and camber thrust

    Choose spring and roll bar rates based on a roll gradient for a given tire. Likely 200tw but ill be able to calculate based on any tire I can find data on.

    Honestly, my goal is to learn, and put it on a resume. Eventually I want to take what IÂ’ve learned and educate others on chassis setup.

    Since my last post. I’ve already noticed some errors. Namely I centered the hub off the lower control arm. Which explains why my camber is off so much.

    Still having issues with pictures… I’ll keep trying

  3. #78
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    If you share, sounds like we'll learn too!

  4. #79
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    I think I got my screenshot to finally work.

    This is a preliminary sketch of my linkage in the front.

    I also don’t have camber plates. So if someone with camber plates and running more camber than stock wants to measure the distance from top of strut to top of strut. It would help give me an idea of the amount of camber adjustment possible.

    CM or MM preferred, but if you give me inches I can make it work.

    Is there a way I can share my work in a group folder? I have made drawings of the seating positions that could help people make their own brackets that could go in there. Along with a brake bias calculator and such.

  5. #80
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    Love it!
    96+, right?

  6. #81
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    Quote Originally Posted by aeronaut View Post
    Love it!
    96+, right?
    Correct this is 96+. The top of the struts measures about 100cm apart. This number will get smaller with additional negative camber.

    My 12.5 mm spacer is also modeled.


    Sent from my iPhone using Tapatalk

  7. #82
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    Aus
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    328i Manual Coupe
    Interested in the brake bias calculator

    Probably best to share on a shared file platform like google drive/dropbox/onedrive

  8. #83
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    '95m3(Avus)/996tt/4.8is
    Here is one my buddy shared with me showing a handful of bias values for different brake/platform combinations:
    https://www.dropbox.com/s/x5uzsttafw...ator.xlsx?dl=0

    Thought it may be a good starting point for the OP, but please share updated versions!

  9. #84
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    I have a spreadsheet, that's undocumented and messy, but has all sorts of inputs to show line pressures, pedal pressures, and bias.
    Inputs are anything and everything that can change the above, such as:
    brake pedal ratio
    booster multiplier
    f & r M/C sizes
    f & r caliper piston sizes and counts
    rotor diam
    pad height
    pad mu
    etc.

    One could put any number in for the pedal ratio and booster efficiency if all you want is bias.

    I'd share if someone pm's me, and would answer any questions, but it's far from ready to publish to all.

  10. #85
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    97 M3, 07 X3

    Technical Violet’s E36 M3 Track Car

    Well, hello again. I should probably apologize for my silence however most of that is due to being in Turkey for the past couple months for work. Thankfully I was on the other side of the country for the Earthquakes and got home safe.

    I returned this weekend to a partially remodeled shower. My wife had taken it upon herself to do all the work herself. I must say I’m very impressed with how far she got. So hopefully I can wrap that up soon and get back to work on the car.

    When I left I was working on the following

    ABS failure
    Painting interior
    Taking measurements of suspension



    Scanning Doors for Custom Panels and Floors




    While I was in Turkey, I focused on the maths:

    Roll Center Height Analysis
    Pretty happy with this one. Although I might have an error in the rear linkage because the lower camber arm is not perpendicular to the subframe. Currently I’m using the full length of the arm. When I find some time ill have to check on this.




    Brake Torque and Bias Calculator
    Previously mentioned. Calculated with DTC-70s front and rear.

    Chassis Spring and Bar Calculator
    This one still needs some work. I followed the book by Miliken and Miliken “Race Car Vehicle Dynamics” and Suspension Secrets supporting articles. I think I have a good value for the rear but the front still seems wrong. Maybe someone smarter than me can identify my errors. This one took a lot of time.

    CG and Weight Estimator
    I used existing values on part weights and started with an estimated curb weight and reduced weight from the car at different locations. I then used the two object method (based around axles) to determine CG.


    You can access these sheets on my google drive. Enjoy! And send feedback if you want!

    https://drive.google.com/drive/folde...X5MG3Ly-93cVGM




    Sent from my iPhone using Tapatalk
    Last edited by TechnicalViolet; 02-16-2023 at 08:15 AM.

  11. #86
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    Good stuff!

    Brake torque calculator:
    - What do you use the outer and inner pad dimensions for? (average/center is all that's needed?)
    - It'd be helpful to many if you allowed 2 bore diameters for the master cylinder.
    Nice job! My homegrown version of this is far too complicated and messy to share.

    Roll Center analysis:
    - I have RC and bump correction, so I'll have to make some measurements, but I like this.

  12. #87
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    Quote Originally Posted by aeronaut View Post
    Good stuff!

    Brake torque calculator:
    - What do you use the outer and inner pad dimensions for? (average/center is all that's needed?)
    - It'd be helpful to many if you allowed 2 bore diameters for the master cylinder.
    Nice job! My homegrown version of this is far too complicated and messy to share.

    Roll Center analysis:
    - I have RC and bump correction, so I'll have to make some measurements, but I like this.
    Not a bad idea about the master cylinder. Right now I use pressure which is extremely hard to measure. I just assumed common pressure for all the lines, however 2 bore master cylinder would need to be handled differently.

    Inner and outer pad radius gives you the center and also accounts for unused area on the rotor. If used properly, not sure I have the pad clearances correct enough for this to be accurate.

    I can also share my sketches of the suspension but its real busy.


    Sent from my iPhone using Tapatalk

  13. #88
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    Good stuff.

    Unused pad area doesn't change the braking force though. It's a bad decision by the person using that pad/rotor combo, for sure.

  14. #89
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    97 M3, 07 X3
    Rear subframe out! Time to weld up reinforcement plates.

    And fix the two bolts I broke...

    One bolt was on the exhaust connection between midpipe and header, which I’m not too worried about.

    I’m not sure how to tackle the broken rearmost RTAB pocket bolt yet. Both sides were pretty bad, must have been collecting moisture for decades. Initial thought is to try drilling and tapping. If tapping fails, ill cut into the fender and weld a new nut on top. If theres a different approach, let me know please.


  15. #90
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    Quote Originally Posted by aeronaut View Post
    Good stuff.

    Unused pad area doesn't change the braking force though. It's a bad decision by the person using that pad/rotor combo, for sure.
    What I should have said is its calculating surface area of the pad, based on the measured clearance.

  16. #91
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    Got a pick of the rtab bolt failure? No way to weld a nut on the underside?

  17. #92
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    Quote Originally Posted by olemiss540 View Post
    Got a pick of the rtab bolt failure? No way to weld a nut on the underside?
    I will take one tonight. Its the location in the bottom center of the image below. You do have to cut into the chassis to access it, but I saw a forum post of the work completed last night.

    The bolt broke off about 3/8 into the hole, so it would help pilot the drillbit. Just unsure if tapping would be successful after all that.

    Yay old cars.


  18. #93
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    Just saw this in case it's any help https://grassrootsmotorsports.com/fo...1/#post3675053

  19. #94
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    ∞FX37,M3a/4,94 332
    Punch the center if you can.
    Drill all the way through it with a 1/8" drill bit.
    Spray through that hole with whichever lube of preference.
    Keep stepping up to the next drill bit size and lubing each time.
    Repeat
    Repeat
    Do Not Use a Tap!!! Ever!!

    If you break the tap off in what's left of the bolt being broken off 3/8" of deep, you can't drill anymore.

    It does not take long with fresh bits and lube to hollow the bolt down to nothing.
    [IMG][/IMG]

  20. #95
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    Quote Originally Posted by AJLM34A View Post
    Punch the center if you can.
    Drill all the way through it with a 1/8" drill bit.
    Spray through that hole with whichever lube of preference.
    Keep stepping up to the next drill bit size and lubing each time.
    Repeat
    Repeat
    Do Not Use a Tap!!! Ever!!

    If you break the tap off in what's left of the bolt being broken off 3/8" of deep, you can't drill anymore.

    It does not take long with fresh bits and lube to hollow the bolt down to nothing.
    *slowly puts tap back in box

    Thank you! You are totally right, if I break a tap off in there I’m royally F’ed.

    I am trying to come up with a plan to pilot the bore and punch the center. If I figure something out ill let you know.

    To be clear, you are thinking that I can eventually degrade the bolt down to nothing and reuse current threads? Worst case I can weld a nut on top.

  21. #96
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    You could also use left handed bits. Once you get the bolt drilled with a couple sizes, they can help to back the rest out of the threads I believe.

    Worse case, is there enough meet on the mount to drill/tap one size larger?

  22. #97
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    Quote Originally Posted by TechnicalViolet View Post
    To be clear, you are thinking that I can eventually degrade the bolt down to nothing and reuse current threads?
    * I was thinking of an eas-out type bolt extractor but wrote tap by mistake.

    Yes.

    If you can punch the center and drill as parallel to the remaining threads as possible, there will be so little left you can use a tap (by hand) then to deburr the threads.
    Last edited by AJLM34A; 03-07-2023 at 05:07 PM.
    [IMG][/IMG]

  23. #98
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    Quote Originally Posted by olemiss540 View Post
    You could also use left handed bits. Once you get the bolt drilled with a couple sizes, they can help to back the rest out of the threads I believe.

    Worse case, is there enough meet on the mount to drill/tap one size larger?
    I have used left hand bits with success on bolts this size. May have to play it by year and see.

    The constraint would be the RTAB pocket. The slot probably couldn’t get any bigger. Im also concerned about any type of dimension change effecting the rear toe alignment.

  24. #99
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    Quote Originally Posted by AJLM34A View Post
    * I was thinking of an eas-out type bolt extractor but wrote tap by mistake.

    Yes.

    If you can punch the center and drill as parallel to the remaining threads as possible, there will be so little left you can use a tap (by hand) then to deburr the threads.
    Either way. You bring up a great point about breaking a tap. Need to give myself the highest chance of success.

  25. #100
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    Buy a transfer punch set to get a centered starting dimple for drilling.

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