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2Dof +Traction loss - Its Finally Starting!

Discussion in 'DIY Motion Simulator Projects' started by Ian Pace, Feb 18, 2021.

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  1. Ian Pace

    Ian Pace Member

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    Back in November 2019 I started buying stuff to have everything in hand for Christmas week and the Monster Motos I had ordered never made it. I had wanted to have everything in hand prior to starting work on the project and for some reason I shelved the project.

    I have now re ordered the Monster Motos and still awaiting delivery, however I will be starting the frame tonight and also have everything ready so that they will eventually make it from China, it will be a matter of just connecting the boards and get it all configured and fine-tuned.


    The rig will be running x3 50:1 PGSaw motors and frame will be built from 20mmx20mm and 50mmx30mm metal hollow sections.

    Mainly it will be built based on DOF reality H3 design, however just as a base as it will have ‘some’ modifications


    I still need to figure out how to get the seat and steering to be adjustable (easily) for my 7 year old, without sacrificing stability…… but I guess ill figure that out as I go along


    I will keep this thread updated with all the progress…. But it might take a while, as free time isn’t on my side

    Let the fun begin!
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    Last edited: Feb 18, 2021
    Ian Pace, Feb 18, 2021
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  2. Ian Pace

    Ian Pace Member

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    Today managed to dedicate a few hours and this is the current state.

    sidewithseat.jpg base.jpg
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    Ian Pace, Feb 20, 2021
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  3. Ian Pace

    Ian Pace Member

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    Im sure im missing something....... does the below make sense for a PGSAW 50:1 motor?

    upload_2021-2-21_9-20-21.png
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    Ian Pace, Feb 21, 2021
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  4. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    The CTC is way too big, 40-60mm is more likely about right, depending on the intended design.
    • Useful Useful x 1
    noorbeast, Feb 21, 2021
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  5. Ian Pace

    Ian Pace Member

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    intended design is based on dof reality p3.
    Ian Pace, Feb 21, 2021
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  6. Ian Pace

    Ian Pace Member

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    Hahah now I realized that it’s 800!!!! Should have typed in 80! That’s what happens when you are in a rush!
    Ian Pace, Feb 21, 2021
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  7. Ian Pace

    Ian Pace Member

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    That's more like it :)
    seems i have a bit of lee way where to play around at least. I will obviously try and shorten the ctc as much as possible.

    upload_2021-2-21_18-9-34.png

    upload_2021-2-21_18-9-58.png
    Ian Pace, Feb 21, 2021
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  8. Ian Pace

    Ian Pace Member

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    another small update


    1.jpg 2.jpg 3.jpg 4.jpg 5.jpg unnamed.jpg

    The Universal joint is from a Land Rover defender and i replaced the bearings with new ones, for peace of mind. I guess its an over kill :)
    Just need to support it a bit more as its with diagonal supports just to be safe.
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    Ian Pace, Feb 22, 2021
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  9. Ian Pace

    Ian Pace Member

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    Small update :)
    Took a day off next week, hopefully I can spend the whole day working on the rig and get moving.

    D6E09E9E-7F5F-425A-A5BA-8FFD60E4CD97.jpeg
    Ian Pace, Feb 26, 2021
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  10. Ian Pace

    Ian Pace Member

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    Some more progress :) :) 2E0A23DA-96A9-4269-805F-437BFCEEBEB3.jpeg C4753DFF-05C0-4675-B3C3-12DBA765C8A2.jpeg 99DF42A6-D0C0-4712-872E-E215EE910ED0.jpeg 9B88EE27-2388-48F0-B697-F57C77577D05.jpeg C4753DFF-05C0-4675-B3C3-12DBA765C8A2.jpeg 9B88EE27-2388-48F0-B697-F57C77577D05.jpeg
    • Like Like x 1
    Last edited: Mar 3, 2021
    Ian Pace, Mar 2, 2021
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  11. Ian Pace

    Ian Pace Member

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    A7FDA64C-F849-4525-B02E-5E0A62923C70.jpeg 29001344-279D-4DBF-8DC2-B3F9E4095100.jpeg 62D9C8A0-E7A9-43CF-8C0F-0C873A4A8412.jpeg
    Ian Pace, Mar 4, 2021
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  12. Ian Pace

    Ian Pace Member

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    Hi All,

    I dont know if its because i am tired or if its really the case that i made a humongous mistake with my calculations.
    Do the below values in simcalc make sense for my design?
    are the negative values correct (based on the fact that the rod mount is below the uni joint)
    CTC Value is not the current one installed as its currently at 30mm but considering changing it to 70mm for more rotation.
    as built.jpg


    Currently its as below
    upload_2021-3-4_23-14-53.png

    your help would be greatly appreciated as i am clueless.
    Ian Pace, Mar 4, 2021
    #12
  13. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    I suspect your CTC of 70 is a bit optimistic, likely is will be more like 40 - 50 to have the required torque to drive a fully loaded compact full frame rig.

    Disregarding mechanical loss, to know what Newtons it will take to move something it will be Mass (kg) x Acceleration (m/s) = F (N). So to move 100kg at 0.7 m/s needs 70 N. It takes 9.8N per kg to counteract gravity. Keep in mind there is significant mechanical loss in things like the gearbox, depending on the ratio you may want to allow between 10% to 50% loss for worm gears and the greater the gear ratio the higher the % loss is: http://www.meadinfo.org/2008/11/gear-efficiency-spur-helical-bevel-worm.html
    noorbeast, Mar 5, 2021
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  14. Ian Pace

    Ian Pace Member

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    hi noorbeast,

    thanks for your reply. Can you please confirm if the numbers make sense with the negative value? As I am not sure how it can achieve that much efficiency in pitch and roll.

    what is the general consensus of the ideal degree of roll and pitch. This will be used mainly for racing with the very occasional flight sim. I can’t seem to get it greater than it is. Is there anything I can change to get the degrees up a bit?
    Ian Pace, Mar 5, 2021
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  15. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    • Like Like x 1
    noorbeast, Mar 5, 2021
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  16. Ian Pace

    Ian Pace Member

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    hahah i did try to read that last time but got lost after a few seconds :)
    Ian Pace, Mar 5, 2021
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  17. Ian Pace

    Ian Pace Member

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    I am trying to calculate based on the above figures - 9.8N per kg, however this rig is balanced on the UJ, which means that not all the weight is on the motors.
    Lets assume that the total weight it has to move is me plus the frame and accessories, lets also assume that that would add up to approx 150/160kg. Do you think the below is sufficient?

    According to the CTC lever calculations i have approx 916N of output force (without calculating worm gears losses) that would amount to 93kg of dead weight with no losses and approx 69kg with a 35% loss.


    upload_2021-3-6_20-41-6.png

    upload_2021-3-6_20-41-32.png
    Ian Pace, Mar 6, 2021
    #17
  18. Ian Pace

    Ian Pace Member

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    excuse me for another post but i really need to sort this out.........

    this is another option that increases drastically the degree of movement and also the pitch force at the cost of a bit of roll force. Would love your views on both options.

    upload_2021-3-6_21-58-34.png

    upload_2021-3-6_21-59-20.png
    Ian Pace, Mar 6, 2021
    #18
  19. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    My view is that you are unlikely to use the full range in race simulation, though you may in general aviation, which is much slower. If VR is used speed and precision are way more important than range of axis movement, with surprisingly little of the latter needed.

    In other words you are better off focusing on ensuring torque than wild axis rotation degrees.

    A pivot will balance a weight, but becomes a point of rotation for mass with momentum. In a sim rig that mass momentum has to be effectively arrested and precisely reversed all the time. Think of yourself as the pivot, holding a bar with bucket of water on the end while you spin it around one way, then try and reverse and go the other, the reversal is where you would really be straining, as you are arresting the mass momentum. On a sim rig that reversal also tends to happen when the levers on the motor are at the max number of degrees they can be from the rest state, which is where they are least effective in terms of torque utilisation.
    • Informative Informative x 1
    noorbeast, Mar 6, 2021
    #19
  20. Ian Pace

    Ian Pace Member

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    Thanks once again noorbest for your very detailed reply! Its impressive how you are so quick to answer everyone on this forum!

    What would you settle with for degrees? It will mainly be used for racing on a triple screen setup (fixed screens) but with the occasional use of VR.

    What torque figures would you settle for with regards to pitch an roll assuming a 160kg load in all (a bit exaggerated) considering the fact that i am using a 50:1 gearbox
    Ian Pace, Mar 6, 2021
    #20
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