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need help for 2DOF full frame

Discussion in 'New users start here - FAQ' started by ivan jack, Oct 9, 2020.

  1. ivan jack

    ivan jack Member Gold Contributor

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    Hello everyone!

    This is my first post here, i'm novice in the term of motion but not a total noob.
    So lets get to the point!
    I built a static rally cockpit and now i want to make it 2dof motion sim. The structure with all the gear and me in it weighs about 150 - 200 kg, the structure is made with rectangle iron tube . I found out that the center of gravity with all the stuff mounted and me inside is right under the chair so i guess i was lucky with this one! hahah please help me decide what motors to use, how far to put them from center of gravity or if i put them in the back or front. I have a problem finding a low cost drive shaft to use for pivot(100 $ second hand in my country) so please give me some other options cause i don't want to spend that much Also be aware that i'm building this in my home , i don't have a garage or acces to big equipment like a welder for example. I built the whole thing with a hand saw and a drill. here you can see it. 1,5 m length, 70 cm width, 1,2 m height. Thanks !

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  2. Ads Master

    Ads Master

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  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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  4. ivan jack

    ivan jack Member Gold Contributor

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    I made some modifications to the frame to be lighter, corected the Fov too and I build a mini replica 2dof to understand better mechanics. I wont use wipers , they are too weak, but i don't know yet what motors to use and i read every thread here and can't decide. Can you please, help me ?I need 50:1 ratio motors or 25:1? not to expensive, but good enough to pull. Is the 12V direction to weak for what I have? Should I go 24? I didn't understand much from simcalc, maybe a quick video tutorial is needed for noobs like me.Thank you! IMG-20201026-WA0003.jpeg IMG-20201026-WA0010.jpeg 20201102_122748.jpg

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  5. Christian Doehl

    Christian Doehl Member Gold Contributor

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    Hi Ivan,

    with the modifications the rig seems to be similar weight than a lot of other already realized. I'm also building my rig out of iron square tubes and I use wormgear motors from China (https://www.ebay.de/itm/153756777639) and they have a lot of power. For the joint you can also have a look to used farming equipment as the have huge kardan-shafts.

    BR
    Chris
  6. ivan jack

    ivan jack Member Gold Contributor

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    hello there! so yesterday I managed to build the base , I found Uni joint on farming equipment website cheap and new. I didn't put it right under the seat because the rig is heavy in front due to design and monitor stand, so that's the center point with all the gear and driver inside. Today I wait for motors to come , I bought VW transporter wipers. hope they can last at least 2 or 3 months. (daily driver). Now I have a small problem . I didn't find any moto monster shield in my country , but I found 2 single channel based on same chip. Hope they are good. (see photos) I need help wiring these and help with the code cause I'm not sure if is the same as for the shield. Had some projects with arduino but code was provided by simhub or other app. Other concern that I have is the Idle state of the rig , how it will sit when the rig is powered off? the motors will hold weight steady ? Do I need to build a spring system for under ? So many questions in my head right now..."I can't..... get.... no sleep " :)))

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  7. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    I suspect the motors will be back driven by the weight of the rig, in other words they won't hold when unpowered.

    I am not sure about the boards you have but there are alternatives if necessary:

    Ibt2s: https://www.xsimulator.net/community/faq/ibt2.371/

    Cytron: https://www.xsimulator.net/community/faq/cytron-md13s-for-smc3.358/

    As an aside the uni joint should be placed as close to the seat base as possible, to lessen the strain on motors and avoid introducing some weird geometry, so perhaps consider flipping it over: https://www.xsimulator.net/community/faq/universal-joint-placement.108/

    Looks like a lot of mass, so I am not sure how the motors will go, where do the motors mount and how much design leverage do they have?
  8. Christian Doehl

    Christian Doehl Member Gold Contributor

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    Hi Ivan,

    looks like the Mini Monster Moto Shield. See the Pinout on the attached picture. I guess you have to connect 5V, GND, ENA, ENB and PWM for Motor 1 of your UNO R3 with 5V, GND, INA, INB, PWM of your driver board. The Arduino Uno wiring is for the SMC3 code of @RufusDufus, So I think this code should work for your setup as well. I use the dual Monster Moto and this works well with just one Motor wired as explained.

    NO GUARANTEE !!

    To the motors, I don't know your motors in detail, but my ones are blocked when unpowered, so the seat stays in position.

    Nice progress in sum, go ahead, it will be worth it.

    BR Chris

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  9. ivan jack

    ivan jack Member Gold Contributor

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    thanks for the fast reply . I put the uni joint there because of the design of the front that includes multiple bars . i weigh only 67 kg I'm not that heavy. I took a round bar and put it under the rig , i got inside and moving the rig back and forth i found that the center of gravity is right there with all the gear plus my weight. and the seat. I'll try and if is not working right i can change its position very fast. made some holes under the seat too as a second try. I'll place the motors behind , today i will build a frame for the motors and moun it to the base , still waiting motors to arrive. the boards are moto monster but single channel. here the specs http://qqtrading.com.my/monster-moto-driver-vnh2sp30-30amp
  10. ivan jack

    ivan jack Member Gold Contributor

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    Thank you so much , I'll try this on motor arrival.
  11. ivan jack

    ivan jack Member Gold Contributor

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    I tested as you said and the code works , ran the SMC utility and i receive data from the pot. Now I have another problem . Do I need to mount the pot onto motor shaft to test the utility ? I think I do something wrong , followed the smc tutorial , but i didn't find anywhere if the tool needs the pot to be mounted or not. I managed to make the motor turn using the utility , but just that. The bad news is that the motors are weak but i'll keep them to test the hardware maybe use them for a next 2dof seat for my friend who helped me with the welding. I think I need something Industrial grade cause this weighs a ton. Back to square 1 on this one!

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  12. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    I did flag that the motors may struggle, given the apparent mass.

    Yes mount and attach the pots, as they provide positional feedback, some sort of flexible coupling is often a good idea: https://www.xsimulator.net/community/faq/how-to-connect-protect-a-potentiometer.13/

    You will also need heatsink and fan for the board.
  13. ivan jack

    ivan jack Member Gold Contributor

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    thank you , then I leave everything for now and I ordered some couplers as you said and heatsinks for boards. I have lots of fans from previous computers. I bought a 12V 30A PSU but I saw that the fan doesn't spin when i turn it on . is this normal or it has a thermal throttling system ? I need to know so I can return it if is faulty .
  14. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    If correctly wired I would expect the fan to spin when connected to a power source.
  15. ivan jack

    ivan jack Member Gold Contributor

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    yeah , everything is wired correctly . I guess i will return it then or change the fan cooler. Anyway, I'll test everything tomorrow with the couplers and post the results. thank you for the help! Good day!

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  16. Christian Doehl

    Christian Doehl Member Gold Contributor

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    Hi Ivan,
    following the tutorial you have to User the pots unmounted first. When the motors are turning you have the blue line in SMC for the motor Signal. Now turn the related pot until the green Targetline matches the blue line and the motors should stop. Now mount the pots (take care not turning the pot) and switch (lower left) to motion. The Targetline will start struggeling and see if the blue line follows the green one. If so, everything seems correct. If it turn opposite change pot wires +5V and GND.

    Good luck.
  17. ivan jack

    ivan jack Member Gold Contributor

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    Nice! that's the thing i didn't understand how to do ! I'll try when the couplers arrive tomorrow and post the results. Thank you!!
  18. ivan jack

    ivan jack Member Gold Contributor

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    What if i put a 3rd wiper motor in front , yeah I know will be 2 dof because of the pivot, but i think it can help the other 2 from the back right? can be less stress on the other 2 motors...can I do this with SMC? just thinking....
  19. MarkusB

    MarkusB Active Member Gold Contributor

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    I don't think that this will work.
    With motors on both sides of the pivot, you would have to precisely synchronize the motor movements, because otherwise the motors would work against each other.

    Example: When both back-side motors move their levers downwards, the front-side motor would need to move its lever upwards by exactly the same amount.

    Maybe you could use a flexible coupling between the levers and the rig in order to add some tolerance, but this in turn may have other side effects, like imprecise movements or bouncing.
    • Agree Agree x 1
  20. ivan jack

    ivan jack Member Gold Contributor

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    I understand, I'll stick with 2 and maybe in the future after more learning i will make a 3 dof. I'll buy stronger motors for now and use the wipers for testing and learning how all system works, I already did a mini replica of 2dof with micro servos and works great. but with wipers it's a little different but I'll figure it out eventually , I started play with simcalc and I'm trying to understand better mechanics.
    • Like Like x 1
  21. ivan jack

    ivan jack Member Gold Contributor

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    I did it!!!! and after that i tested the motion tab, everything works now ! thank you ! need to tune some settings , here is a video of my progress.



    still trying to figure how to ground isolate my motors, I didn't understand much from the FAQ , my motors have only 2 wires , the contacts have a T shape on the end and part of them were inside the case (see photo), but i took them out before testing the hardware. What to do ?? Do I need to open the motors? can I use them like this on a metal frame? should i put the contacts back ? Sorry for asking so many questions , but I don't want to damage the parts or do something I will regret. Thank you guys so much for helping me!
    Turns out the PSU Is ok , I didn't read on it : "NOTICE: This psu have a built-in fan control circuit! Fan automatically starts acording to working temperature !" silly me :)))

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