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compact 2 DOF build - convertible

Discussion in 'DIY Motion Simulator Projects' started by Chlumpi, Mar 20, 2015.

  1. Chlumpi

    Chlumpi New Member

    Joined:
    Feb 1, 2015
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    Occupation:
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    My Motion Simulator:
    2DOF, DC motor, Arduino
    Hi everyone,

    as announced, I hereby start my building thread - may the fun begin.

    I started this project in anticipation of the OculusRift and my revoked interest in PC gaming.

    Starting out with buying a T500 RS steering wheel, I am currently assembling the parts to start my build for a 2DOF with optional 4DOF later on. I intend to build a convertible that can go either as full frame or seatmover as space is an issue which will hopefully be resolved in the coming years.

    I bought a used leather seat from an Alfa Romeo Spider, knowing it will add some unnecessary weight to my build (20 kg in total, racing seats at reasonable prices are around 10 kg), however the looks convinced me and the adjustability allows for many different riders. In addition, it has a sturdy automotive grade seat slider included, which will allow for easy adjustment of the pivot point in shaker and full frame configuration

    The electronics will be based on:
    2x 90ZYT with MCP4 1:60 worm gear motors (http://www.ebay.co.uk/itm/380956910371) (left and right handed)
    2 x monster moto shield
    1 x arduino uno
    1 x 930W DELL server power supply (should i opt for a second one?)
    1 x massive universal joint from ebay (2x22° maximal angle each pitch and roll; it's protecive paint, not rust)

    DSCN2162.JPG


    I started with sketches of my frame, which will be made of aluminum and some structural steel plates and held together by screws or bolted. In addition to what is shown in the picture, i will also add collapsible feet for a larger base area to avoid tipping over. There will not be a monitor mount for now, as I want to use an Oculus Rift or a similar head mounted display eventually. The motor mount is not final yet, but i intend to use a 4-6 mm steel bracket on right angled aluminum profiles.

    Motorhalter_45_45.png
    Motorhalter_45_45_ohni.png
    Motorhalter_45_45_close.png

    I originally wanted to build it close to @noorbeast 's pretty build, but I am currently struggling with the orientation of the motors and the possible maximally attainable angles. The reason i wanted to go for a 45° orientation relative to the seat is that i think that it would lead to a more uniform movement in both roll and pitch. Also, I can project the maximal angle with both levers in opposite directions in 2D for the calculations of lever length (CTC).

    As i have found to be rather poor in rigid body physics, I would like to have some advice on the maximal attainable angles by these motors if i use a full 180° for lever hub. My ideal configuration would have approximately 20° of roll and pitch, similar to the Blue Tiger Motion simulator



    although i know most people recommend less movement to improve response. I am also playing with the idea of using to different motor positions/CTCs for racing and flying simulation, to allow for different maximal angles.

    Now for the engineers in the audience:
    The motors are rated with a peak torque of 30 Nm (80 RPM), the total mass of moving weight would be around 100-110kg. I expect the center of gravity to be approximately 40 cm above the pivot center. The maximal angle (45° from center) would be 27.8° at 20° pitch and 20° roll.

    - Question 1: Can the motor move the weight at full extension?
    - Question 2: If 1 = no, what is the maximal attainable angle?
    - Question 3: Whats the damn formula? ;).
    - Question 4: Is there a good, free, easy to use software to calculate these "easy mechanics"?

    In anticipation of some great answers, really hoping to soon be able to start building,

    Chlumpi

    Attached Files:

    • Like Like x 1
    Chlumpi, Mar 20, 2015
    #1
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Nice project @Chlumpi.

    Try your power supply but you could go for another PSU as they are cheap on Ebay and those motors can draw plenty of amps during spikes.

    Question 1: Can the motor move the weight at full extension? - That depends entirely on the design, the weight you are trying to move and with what leverage. The greater the design leverage, the less weight and the more powerful the motor then the better it is. Keep in mind that compact designs like mine trade leverage and hence need fairly powerful motors and will move less weight than say a shoulder mount design that maximises leverage.

    Question 2: If 1 = no, what is the maximal attainable angle?

    You are correct that the maximum attainable angle is a property of the design. That said most of us don't use anywhere near the maximum attainable angle that our rigs are capable of. Larger movement arcs can work in gentle flight sims but are not that great or realistic for racing or even combat flight. This is particularly so with the Rift where the haptic motion cue is far more powerful than trying to simulate a g-force, which is not possible anyway.

    Question 3: Whats the damn formula? ;).

    Have a look at my math here, though that question was about heave the same formula applies: http://www.xsimulator.net/community/threads/question-about-heave-calculations.6353/#post-70692

    Question 4: Is there a good, free, easy to use software to calculate these "easy mechanics"?

    There are likely others and this is not free or cheap but is specifically for designing motion sims: http://www.fly.elise-ng.net/motionplatformdesigner

    You can link SketchUp with SimTools and drive a design model: http://www.xsimulator.net/connect-simtools-sketchup/
    • Informative Informative x 1
    Last edited: Mar 20, 2015
    noorbeast, Mar 20, 2015
    #2
  3. Wanegain

    Wanegain Active Member

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    My Motion Simulator:
    DC motor, Arduino, Motion platform, 4DOF
    Nice project @Chlumpi !

    20° seems to be not easy because of ball joint. Usually the max angle is 18°.
    Wanegain, Mar 20, 2015
    #3
  4. momoclic

    momoclic Active Member

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    My Motion Simulator:
    DC motor, Arduino
    In view of the engine power, would it be more effective to position a motor on each axis?
    Here the two axes are mixed, so the effects are mixed.
    The setting of movements would be simplified.
    momoclic, Mar 20, 2015
    #4
  5. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    If your design goal is very large movement angles then you want a design that allows the leverage for that, with a capacity to move say up to 120kgs really quickly. Hence, it would be more effective to place the motors so that they have greater leverage.

    I will be honest and say a compact design is not the best for doing that. So I guess the key question to ask yourself is what is your primary design aim. You can get an idea of the speed and range of what a compact full frame can do from having a look at the videos of my build. I would suggest that is about as far as you can push the movement without going to more powerful motors that have higher RPM and greater torque.
    noorbeast, Mar 20, 2015
    #5