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SMC3 based DIY 2DOF from NZ

Discussion in 'DIY Motion Simulator Projects' started by James Robbie, May 25, 2017.

  1. James Robbie

    James Robbie Member

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    My Motion Simulator:
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    Can you please explain the thinking and theory behind this? As you can see, things are welded pretty solid so would be a hefty job to achieve this. I'm guessing I have missed something or overlooked something...
  2. mariano68

    mariano68 Active Member

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  3. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
    3DOF, DC motor, JRK
    On the physics side a joint on the bottom will put huge stress on the motors as the seat travels through a large arc and the geometry involved is also very problematic in terms of accurate control.
    • Useful Useful x 1
  4. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
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    Agree with @noorbeast , I would also add that you have decreased the roll center height, which can feel very unnatural and could cause nausea. Ie. Like driving your car with your seat near the roof.
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  5. James Robbie

    James Robbie Member

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    My Motion Simulator:
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    Thanks for the feedback everybody, most appreciated. I wish getting SMC Utility and proving my motors was an as easy task... Grrrrr...
  6. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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    Hang in there, it is all new first time around and we all make mistakes that we learn from.
    • Agree Agree x 1
  7. James Robbie

    James Robbie Member

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    My Motion Simulator:
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    :cheers :cheers :cheers :cheers :cheers

    WE HAVE SUCCESS!!! Motors are now running and responding in SMC Utility. I do have to swap the POT wiring as i have managed to wire them both up so they are opposite to the motor... But, I am happy that's all I have to do! I am very super stoked to finally get things responding and happening, so SO relieved. The solution to the problem of not having motors moving via SMC Utility was a double barreled issue and I am kind of embarrassed about it as it was a couple of silly things. But i understand it now so cant complain about learning I guess.

    First problem - I didn't understand/realize that the POT feedback had to be within the Clip Input and Max Limits settings. Yes this sounds silly but as I am bench testing and don't have my POTS mounted to the motors yet. They were always off/set to min and not centered unless i was moving them but this is where the second part i failed at made a big difference. I was moving them across the scale and they were responding accordingly but didn't click on the correlation to the limits set.
    Second problem - I wasn't clicking the "OFF" button to turn the motor on when the POT feedback was within the limits. I vaguely remember reading the guidelines to the Utility software but I wrongfully assumed that when the button is showing "OFF", that is what the motor state is rather than clicking the button to put it in the opposite state. So in my head, i assumed "the motors were always on and ready so why would i want to click the "OFF" button when its not moving anyway". But also, this wouldn't be as much of an issue if the limits weren't in place as the POT wouldn't have to be within them.

    It wasn't until i read and re-read threads and tutorials and FAQs today at work that I realized all of this so i came home from work with a plan! When i read what i have just described as my problems, it sounds silly now that i know and understand but i tell you, it wasn't through lack of trying that i was mis-understanding the process required.

    Motors and electronics proven, now to modify my frame and mount the motors and POTS to it all!
    • Winner Winner x 5
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  8. James Robbie

    James Robbie Member

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    My Motion Simulator:
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    I am getting closer and closer to wiggle time!

    All of the electronics are now housing and ready for plugs to be connected. I used an old half size PC PSU case and rewired the fan to a manual switch. I designed and 3D printed a little housing/holder for both the MM and the Arduino Nano. You can see the interior picture with the flash showing the 3D housings better. Surely with how i have positioned things, the MM and heat sink should get ample airflow... Some might call it an overkill! :D The PSU is housed in a cheap plastic box, nothing special but its hidden and contained. Need to drill a couple of holes in the lid for air flow but I will get around to that. Quite happy with the concept of it.


    IMG_0875.JPG IMG_0871.JPG IMG_0873.JPG IMG_0880.JPG IMG_0878.JPG IMG_0882.JPG


    And now the new motion frame and my existing rig are ready to mate and caress for the first time. All of the flat plate shown in the pictures is 5mm/6mm steel so it might not look it but its solid as a tank. All though there are no pictures yet of them, the armature is complete with tie rod ends/rose joints and they sit inside the rear corners of the frame by bolting through. I listened to advice and went through a few cutting disks and flipped my driveshaft joint so the pivot point is now at the top.


    IMG_0846.JPG IMG_0849.JPG IMG_0850.JPG IMG_0851.JPG IMG_0852.JPG IMG_0848.JPG


    Once I have tested it and am happy with it all working, all of the welding will get a tidy and the steel will get a paint bucket thrown at it so don't freak too much about the aesthetics at the moment. Yes I understand there is probably things wrong and things are exactly how they should be but this is all learning and part of the process for me. Half of the enjoyment is building it and so now its time to just bolt it all together and see how I get on. Only issue with that is I have to tackle the scaring software setup and settings debarkle........ :think
    • Like Like x 4
  9. armpit

    armpit Active Member

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    Looks very tidy, and those motor mounts are slick! Glad you flipped the universal joint, too. Probably saved you from a headache down the road.
    • Agree Agree x 2
  10. James Robbie

    James Robbie Member

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    My Motion Simulator:
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    2 x steps forward and 1 x step backwards...

    So mounted my rig to my motion base and found a slight design floor/oversight. I can confirm that my COG is accurate with me in it and its balanced nicely................ Only problem is, I am 125kg ish. So when I am not in my rig, 99% of the weight is at the opposite end of the rig over the feet and away from the COG pivot point. And with the motors being at the rear, that means there is a lot of weight putting constant strain on the motor shafts and armature which I am not happy with at all.

    Now the unintended, unplanned next step is to make a brace/support to take the weight when I am not in the rig that is on a hinge so it can be levered out of the way when I hop in and then put in place before i hop out.

    This wont be attempted for another week or so because I am lucky enough to be the proud new owner of a OSW DD wheel so I am going to have to adjust my rig for that also. Seems silly to spend two weekends building when I could do it all in one.
  11. MarkusB

    MarkusB Active Member Gold Contributor

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    Yes, I know what you mean and I did something similar. You will probably miss it in the post, so here is the picture again. The red arrow points to the peace of wood that I can bring into an upright position for locking the seat. The arrow head points to the hinge.
    SeatLock.jpg

    Unfortunately I tended to forget to unlock the seat, even after applying this nice tag. Guess the motors did not like working against the lock. :)
    Remove.jpg
  12. James Robbie

    James Robbie Member

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    So update time... Days and months and even over a year since my build thread had anything attached...

    Not even sure where or how to start this update other than - its still not a completed working rig :(:mad::confused:

    Current situation is i have everything tethered and cable tied together to make sure my rig doesn't move. I eventually got everything working to a good enough extent that my partner could sit in the rig and get bounced around a little bit but with my fat ass in there, the wiper motors didn't have enough holding power. Even with my partner in it, the holding power wasn't fantastic but that exaggerated when I tried. The motors, for a short period when in unison, worked but as soon as they got hot or weight was moved to one motor rather than the other, the holding power failed and the motor basically locks itself because it goes to the bottom of the rotation and cant pull/push itself back to center.

    With that in mind, i have tried to put my rig on a weight loss scheme and attached it with an angle grinder which is less painful than taking an angle grinder to myself. This will have adjusted the center of gravity but I wouldn't think it would be enough to upset the overall balance to a point where that is the cause of my issues.

    I am now running off a car battery off a trickle charge system instead of server PSU's as I fried a few and since moving to the car battery concept, i have got ample consistent power supply so highly recommend do this from the start.

    To get up to speed now, i have designed a counter leaver system on paper based on the fulcrum theory but i am yet to build that into something physical i can test with. To be honest, I have lost motivation at the moment because of how many issues i have run into trying to do it DIY and cheap. I am looking into linear actuators at the moment and whether its a route i will go down instead of trying to redesign my rig for the lever idea. Its something i want to finish but disassembling my rig to try another method in the hope it fixes using cheap DIY parts doesn't give me much hope and unfortunately, buying a solution isn't an option.

    I will keep plugging on
  13. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    You look to be trying to build a compact full frame design with limited inherent design leverage. Wiper motors are not particularly well suited to such a design because of limited torque. For example I use 200w DC motors with 60:1 gearboxes on my compact rig.

    Have you considered switching to a choulder mout design, as that would give the wiper motors far more design leverage.
  14. James Robbie

    James Robbie Member

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    I am living and learning the hard way trying to push the boundaries of DIY, cost and design... And at the moment, it hasnt paid off.

    So putting a hoop on the back of the rig and mounting the movement arms from the motors up higher? Guessing if I was to do that, I should move all the mounts out wider as well? Both bottom and top?
  15. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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    • Like Like x 1
  16. James Robbie

    James Robbie Member

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    My Motion Simulator:
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    Now that I have finished my last project (450L fish tank setup), I am allowing myself to let my mind wander back into the motion project. I have done research over the last 4-6 weeks around the shoulder mount setup that @noorbeast has suggested and this will become my main focus to achieve. I have already put a plan in place and I have played around with the SimCalc which is a great tool so I will get some accurate measurements and start doing instead of reading! Exciting times!

    This has given me motivation to get back into it now. Wish i had of looked harder and found that SimCalc tool earlier and I wish i had of understood more of the concepts but as mentioned a couple of posts above - its a big learning experience! Hopefully over the next week or so, I will separate my rig from my motion platform and start the "doing"
    • Like Like x 2
  17. James Robbie

    James Robbie Member

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    My Motion Simulator:
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    Small update but still working away on getting things moving :grin

    I have managed to build an extension of my frame to accommodate rear mounting the motors and "shoulder" mounting the pivot arms. Unfortunately I haven't had the funds to be able to buy more steel and I have built the add-on with left over steel and off cuts which means its probably still not ideal but surely it cant be worse off. Two factors i have kept in mind while doing the add-on is "ease of having to break down and shift the rig" and trying to keep the overall size of the rig down.

    I have also removed all unnecessary steel work that was used for triple screens etc for when I initially built the rig. So there is less weight overall in the frame and that weight has been removed in height so hopefully that helps things in some way as well. One other thing I have done is sat my seat up so my body weight compared to the mounting points has improved greatly. COG was always in the right place originally but again, hopefully something else that has to help improve things.

    Here are a couple of progress shots of where i am up to:

    IMG_2653.JPG

    IMG_2656.JPG


    I have done some calculations comparing before and after with the new mounting positions. The CTC parameters are just default options for arguments sake

    Inboard compact design figures:

    Motion - inboard compact stats.jpg

    Shoulder mount design figures:
    Motion - shoulder mount stats.jpg

    Yes ideally the shoulder mount would be higher and possibly wider and moving the motors out wider to allow for better roll control but there is where the size and moving limitations came in to play.

    IF this all works = cool
    IF this all doesn't work = crying material
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