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First Build - need advices

Discussion in 'MA' started by Alex Soon, Jul 8, 2020.

  1. Alex Soon

    Alex Soon Screw

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    I had previously posted my FL build for the rear bumper.

    Now i am trying to build the front part of the MA chassis. I noticed there is a challenge as the bottom of the front part of the MA chassis is actually of ascending angle.

    I had built a FL bumper for the front chassis too but am worrying if the 2 protuding front rollers will pose a problem when the car climb up steep slope (i.e. front wheels lose contact with the ground).

    The ground clearance for the front (without brake/sponge etc) chassis is 1.5mm

    Most of all, the burning question i have is whether the "contraction" is sufficient (i.e. the part where both 'arms' swing toward the front wheels). The sole reason for such build is to counter the rocking straight section of a track.
     

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  2. ltr74

    ltr74 FRP H-Bar

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    Honestly if you are worried about rocking straight then front pivot bumper and rear anchor is the best option. It's sturdy, relatively cheap to build and not difficult to build. If I ever have to deal with rocking straight again, I'll be using my old pivot bumper from 2018. I've got a lot more newer builds but they are much too fragile to deal with the rocking straight.

    I see several issues with your current work.
    1. no angle on the front rollers. This will cause you to crash out on corners.
    2. Front ground clearance is really low and won't allow you to add brake to the front if needed. 3mm before brake is a good goal
    3. Front rollers are much too far forward
    4. Your frp that is mounting the front rollers needs to be trimmed or it will hit the track.

    See Roscoe's video here for front pivot tutorial. I don't use his AT system but lock down the roller stay instead and I use carbon(2019/2020 J--Cup front carbon stay) for the center piece of the roller stay. He also has a followup with some fixes to his design and somewhere he has an anchor system video.
     
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  3. Alex Soon

    Alex Soon Screw

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    I had re-built it again but now met with another problem.

    The rear brake clearance from the ground is 7mm and the rear bottom rollers seems too low for the rear brake to work. I have no problem building a underguard using item 15242.

    Do I adjust the bottom roller a bit higher to be on same level as rear brake OR do i attach some popsticle to the bottom tail section of the rear break to make it closer to ground (like 3mm cleance from ground) so that it can work without the bottom roller screw touching/dragging the track? Which option is better?


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    Last edited: Jul 16, 2020
  4. ltr74

    ltr74 FRP H-Bar

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    I would mount the silver brake on the bottom of the chassis using the lower mounting holes. Then figure out a way to mount the whole system on the silver brake. Using the upper mounting holes is not a very common build for open class. I am not sure why you have springs and spacers in between the silver plate and the roller stay? But brining down the silver plate and then building up is the more common way to build. The silver brake wills till be a little high since you are using 26mm tires, but it will be more manageable.

    I go much more pancake style than a lot of racers, but my goal when building is everything except for stabilizers are even with the chassis. You can see it with my newest build. body damper sits on top of the chassis, but all other parts, roller stay, AT system, sliding dampers, hardware, all sit very low.
    IMG_7235.jpeg
     
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