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Student Project - 3DoF w/Traction loss

Discussion in 'DIY Motion Simulator Projects' started by Joel Magill, Aug 28, 2017.

  1. Joel Magill

    Joel Magill New Member

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    Hello to all,

    Totally new to sim rigs and to the forum. I am a senior mechanical engineering student at Georgia Southern University in Statesboro, GA. As a capstone project myself and a group of students are building a DIY 3DoF sim rig with traction loss. This is going to be done using a mini late model dirt track car which will be mounted on top of a steel frame. Our design will include a front universal joint with worm gear motors in the rear for articulation and traction loss. Fabrication will begin next week! We are excited to build this rig and I am sure we will be using this site as our main source of information/question asking.

    Just wanted to introduce myself and give a little insight to our project. Much more to come!

    -Joel
  2. Ads Master

    Ads Master

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  3. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    I will be looking forward to following your project.

    It sounds like there is going to be a fair amount of mass to move and manage, what sort of motors and controls are planned?
  4. Joel Magill

    Joel Magill New Member

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    We are designing the motion portion of the sim rig to be a maximum of 1000lbs with the driver. We are still in the design phase so we are currently researching what motors and motor controllers will be strong enough and fast enough to work effectively with our rig.

    Any recommendations for worm gear motors that could work for our application are very much welcomed. Like I said above, we are greenhorns when it comes to sim rigs

  5. Joel Magill

    Joel Magill New Member

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    Sharp Chassis.png

    We will be using one of these cars for the rig. (Made by Sharp Chassis.) A race ready car, with the driver, is approximately 930lbs. We will be able to shave significant weight from the car as it will not have a motor, suspension, fluids, etc. Our goal is to create a sim rig with a large range of motion with regards to traction loss to mimic dirt track racing.
  6. sim2go

    sim2go New Member

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    Not long ago I posted almost same questions. To my narrow understanding the motor choice will heavily depend on how the frame will be constructed. I suggest put more time on thinking, projecting construction part, things will come out clearer.?
    • Agree Agree x 1
  7. Gadget999

    Gadget999 Active Member

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    i think you may need hydraulics to move that amount of mass freely

    consider a much lighter design perhaps you could construct a simple frame and use the body panels to make it look the same
  8. Joel Magill

    Joel Magill New Member

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    We should have a much better idea of what the rig will actually weigh by this weekend. @Gadget999 do you have an idea of a weight to aim for? We want to avoid using hydraulics.
  9. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    It comes down to physics, which encompasses design, mass and inertia determining what will be required to move it through a range and at a speed suitable for motion.

    It would be a good idea to spend a bit more time researching and planning. There is some good information and handy told in the FAQs like SimCalc that can help you get your head around the fundamentals.
    • Like Like x 1
    Last edited: Aug 30, 2017
  10. Joel Magill

    Joel Magill New Member

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    Thanks @noorbeast! Ill download SimCalc and see if I cant learn some more about this. I am still working on the CAD drawings but I will post them when done to get some opinions
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  11. Joel Magill

    Joel Magill New Member

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    With hurricane Irma hitting the eastern United States, school was cancelled for a good while. Here are some updates on our progress.

    Here is the frame we intend to use. Our manufacturing facility on campus took delivery of a new CNC machine, so the frame it came on was up for grabs. The swivel on the front is a 1000kg rated swivel. The arc is the path for traction loss.

    Step2.PNG

    Sub-frame design. Will be using castor wheels for traction loss, but to save time on the drawing I didnt include them.

    Step3.PNG


    Race car chassis on subframe

    Step4.PNG

    Here it is with the motors and rods simulated. Most everything ive seen sim related has the motors mounted behind the actual sim rig, with the rods pushing towards the front. Has anyone tried this? bad idea? I did it this way to try and keep the final product looking clean and well put together. The body panels should hide the motors and rods nicely.

    Step5.PNG

    Also, we will be using a universal joint (not pictured) to mount the front of the chassis to the sub-frame. The pivot point is the hole cut into the cross member above the swivel.

    Traction loss



    Home position
    Top_home.PNG

    Full swing

    Top_max_traction.PNG

    trac loss home_seethru.PNG

    trac loss max seethru.PNG

    Here are the SimCalc calculations for the model above.

    SimCalc.PNG

    The hardware we are considering is below.

    We were looking at Motion Dynamics worm gear motors
    Specs:
    600W
    24V
    150Nm torque
    30rpm
    25amp

    power supply (AK-1000-24)
    1000W
    24V
    40amp

    Sabertooth motor driver
    dual 60amp
    120amp peak

    Kangaroo motion controller

    I would love to hear some opinions on the traction loss setup. What should be the max length of the motor arm to simulate the traction loss? We want a good bit of travel to simulate dirt track racing, but im afraid the motor arm will be too long at 8in-10in.

    Sorry it took so long to update! Looking forward to some feedback.

    -Joel
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    Last edited: Sep 18, 2017
  12. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    Something that pivots around a central point is yaw, not traction loss. TL pivots from the front.

    Keep in mind that simulation is about exploiting perceptual and processing weaknesses, in other words tricking the brain. Don't overdo axis movement travel at the expense of speed and precision, particularly if VR is ever going to be used.
    • Agree Agree x 1
  13. Joel Magill

    Joel Magill New Member

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    Ideally I would have located the pivot point right under where the front axle would be, but because this rig will be on the heavy side, I moved it back to alleviate some of the weight on the rear motors. Additionally, a driver of these cars recommended this location for the pivot point, however he is a race car driver, not a simulation builder.

    LEFT SIDE.jpg


    The pivot is further forward than center, but just slightly. Im wondering if this needs to be redesigned now...the traction loss aspect is very important for this rig as dirt track cars stay sideways most of the time.
  14. PiaMan

    PiaMan Active Member

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    Your ujoint supports the weight. The traction pivot goes at ghe front axle. Since the frame willve supported with rollers or something traction loss doesnt add any weight to rear seat shaker motors
  15. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    I would have thought TL was very important for the project, and clearly your driver may know a lot about racing this style of car but little about simulating it.

    I said in another student thread that mass for the sake of aesthetics could be dealt with by doing things like replicating the frame in carbon fiber. High mass and inertia complicate simulation and need lots of power, and hence money, to help mitigate the effects.

    But it is your project, myself an other will just toss in our own views for you to consider.
    • Agree Agree x 1