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TECHNIC BUILDERS: Collaboration on large scale vehicle design

Building large scale vehicle and have spent countless hours working on suspension; particularly independent w/ drive and issue of wheel camber when shocks are depressed. In many MOC vehicle builds the suspension is not "true" as depression of the shock absorber either causes the body of the vehicle to drop unrealistically or the tire to lose contact with the "road" surface. TLG has fixed this problem with some vehicles i.e. #8070 using specialized components. But those elements are insufficient for large scale models. In #9398 the problem is readily apparent. Specifically I wanted a large wheel/tire to remain perpendicular to road service even as it travels up and down due to "shock absorption". TLG released an element in several sets which I thought might be used to address the issue and I think the design I'm displaying here may be a possible solution. Would welcome all thoughts and if there is a need for better photos please let me know.

Comments

  • rancorbaitrancorbait Manitoba CanadaMember Posts: 1,850
    The reason your wheels won't remain perpendicular while moving up and down is because you only have one control arm holding it, which causes the wheel bearing to pivot freely with only the shock to keep it somewhat straight.

    I'm no Technic expert, but if I understand you correctly, you are trying to get something like this:

    2014-06-23 22.48.29

    2014-06-23 22.52.11

    2014-06-23 22.52.52
    CCC
  • TechnicNickTechnicNick Berkshire, UKMember Posts: 277
    @Davian07, what you've made looks like a VW Beetle-esque swing axle arrangement, with all the camber changes on compression that implies... @rancorbait's four link design would serve your purpose. By tweaking the lengths and pivot points of the links you'll be able to give it any camber characteristics you like.
  • Davian07Davian07 Member Posts: 19
    Thanks, Rancor and Nick. Rancor's design certainly solves the problem of offset camber and maintains the wheel/tire in the proper plane.. The potential issues I can see are the limitations of travel (unless the length is significantly increased), the bulk, and the (with no offense intended) unrealistic appearance. One of the goals is to solve the problem while also maintaining as much as possible a "real world" look.

    I will today post images of the chassis with the wheels mounted and with the shocks compressed. Due to the ball joint the drive axle remains parallel to the "road" surface and the two tie rods maintain it's centering and limited travel. Admittedly, I have not tested in a "real world" world scenario i.e. weight and motion over uneven terrain.
  • kyrotekkyrotek Southampton, UKMember Posts: 212
    edited June 2014
    Turn the shock absorber over and link it further back on the top arms of the parallel assembly. You may have to move the upper link for the shock slightly higher, perhaps into the body of the vehicle a bit like real mounting would be achieved.

    Only thing to watch out for is if it comes into contact with the drive shaft but that could be avoided by adjusting the distance between the upper and lower parallel arms. This could be set as an adjustble feature for greater travel of the suspension overall. A crossover between rancorbait's lower assemby and your upper shock mount might be the best course.
  • iancam33iancam33 Member Posts: 407
    Do some searches for Baja suspension systems. This might help you out. also, it might be the suspension stiffness is not high enough for what you plan to do. Use two shocks per wheel.
  • Davian07Davian07 Member Posts: 19
    Thanks to everyone who offered assistance; invaluable in helping me build upon and refine the design. Part of my goal was to utilize the new LEGO ball-joint assembly as I felt this would lend more to the idea of realism i.e. CV joints in a real car. I searched and could not find these being used in such a manner. While these are certainly too large to be used in many MOC models, for the size vehicle I am constructing they were perfect. Below are images of the remodeled suspension assembly including some with the shock compressed. The drive axle remains parallel to the surface plane and the entire structure has been secured to the chassis in a way so as to offer the most strength.
    rancorbait
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