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_Gus's 6DOF Project

Discussion in 'DIY Motion Simulator Projects' started by _Gus, Jul 19, 2019.

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  1. _Gus

    _Gus Member Gold Contributor

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    I'm trying to get the game to sync up with my sim right now, and I'm incredibly confused.

    The game is patched for motion, and the tuning center shows the telemetry from the game, and when I look at the virtual axes tab, it shows roll, yaw, etc. moving and everything. The issue though is that it doesn't move the sim itself. The weird thing is though that if the game isn't running, and I go to the Output Testing tab and manually move the sliders, the sim moves fine. I'm not sure what I'm doing wrong. From everything I've read, it should just work.
  2. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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    I don't know what game you are testing, can you please advise.

    If it is LFS did you first run a race in first person mode befor patching it for motion, as that generates some required files.
  3. _Gus

    _Gus Member Gold Contributor

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    Sorry—I should have mentioned that!

    I’m testing with Assetto Corsa.
  4. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
    3DOF, DC motor, JRK
  5. BM114

    BM114 New Member

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    I noticed you used some flange couplers for your output shaft to lever adaptation. I wanted to leave a link here for anyone following this project in the future. I was able to find something very similar at
    https://www.rainbowprecisionproducts.com/h-18mm-p-2401.html for only $10 a piece plus shipping. I got all 6 for about $80 and they arrived in 5 days. (USA)
    • Informative Informative x 1
  6. _Gus

    _Gus Member Gold Contributor

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    Game not moving the sim:
    I have min/max values in the tuning center, so the rig should move some at least. I'm less worried about actually tuning it once it moves, but instead that it doesn't move at all.

    Motor torque:
    I've cut the levers shorter, from 5", to the 3 5/16" that I mentioned earlier, all seems good with that.

    IMG-5812.JPG

    My issue however is that it still won't move me, and I don't even have the seat on right now, which will weigh an extra 40 pounds. I did the math, and my motors should be able to move 400 pounds with the current lever arm length (25.4Nm motors), however it won't move me, even though I weigh 260 pounds, and so combined with the frame it would be lifting like 310ish pounds, far less than the 400 maximum.

    First, I was also having a issue where if I moved the axis slider too quickly in SimTools, the motors would all freeze, and an occur would occur on the 2x32 board. I solved this by going into describe and limiting the max amps to 10, and max volts to 24, as these are 200w motors. It should be noted that before this, I was able to lift myself very slowly via SimTools, however it would have trouble if I tried to use the heave slider.

    The strange thing is I was able to, using the SMC3 Utility, have a single motor lift 5 extremely heavy toolboxes, which in all weighed 143.2 pounds, plus it was also moving the frame. The motor wasn't moving slowly or anything either. This, along with the math, leads me to believe that SimTools simply isn't using the full power of the motors.

    Here's my math btw:

    CTC = 0.086 m --> (8.6 cm)
    Motor torque = 25.4Nm

    Max weight = torque/CTC (N)
    Max weight = 25.4/0.086 (N)
    Max weight = ~295N
    295N = ~30kg

    30kg/motor * 6 motors = 180kg
    180kg = 397 lbs

    As you can see, the math and SMC3 both point towards the motors being more than capable at this CTC length, so I'm hoping that one of you can help me with figuring out what the issue is with SimTools.

    Also, as I forgot to mention earlier, the gearbox produces 25.4Nm of torque at 72RPM.
  7. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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    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 0.3 m/s needs 30 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

    You also can't assume that the mass is evenly distributed, at times only some of the motors have the majority of the load.
  8. _Gus

    _Gus Member Gold Contributor

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    Well that sucks. I guess either I'm going to have to make the CTC even shorter, or I'm going to have to buy a more reduced gearbox, which sounds like it will only cause more problems. Just so its clear, these are the motor specs I have, and I am using the 30:1 reduced gearbox (7th column of data).
    HTB1oIm3dNUaBuNjt_iGq6xlkFXaR.jpg

    Noorbeast, what is a typical CTC length people use, and do you know what RPM their motor spins at?
  9. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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  10. adgun

    adgun Active Member

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    Hi
    One watt is one NM with a speed of one meter a second.
    Motor is 200watt with a speed of 72rpm
    72/60=1.2x2xpi=7.54meter a second
    200w/7.54 m=26.5Nm without loss
    i-30 wormgearbox is somewhere about 70% efficient
    26.5x0.7=18.55NM
  11. BM114

    BM114 New Member

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    Where did you source your motors?
    I have a very similar motor, but instead it is a 300w(output at gearbox) rated at 18rpm with a 100:1 ratio.
    Depending on your ctc arm length you may not need such a high output rpm. You may consider changing out gearboxes for a better output torque with slower rpm.
  12. _Gus

    _Gus Member Gold Contributor

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    Thank you guys, this helps a lot. I'm pretty sure I'm going to need more powerful motors.

    I got them from China via AliExpress. They were the ones SilentChill recommended I get... Here's the link: https://www.aliexpress.com/item/328...&terminal_id=946e480d49ff4a97a9fa588b83dfad9d.
  13. SilentChill

    SilentChill Problem Maker

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    Hmm seems strange, I was using 12v 125w motors at 100rpm with 100mm levers and it lifted me and my platform fine.

    Yours are 24v 200w and only 72rpm I cant understand why they are not powerful enough ??

    Sorry if I've given you the wrong advice but I would of been certain they would of been easily powerful enough :(
  14. _Gus

    _Gus Member Gold Contributor

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    Can anyone let me know what the max weight a SCN5/6 actuator can lift is?
  15. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    My Motion Simulator:
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    Max 60kg, depending on motor and screw pitch, but I don't consider them a good or cost effective option for a 6DOF: https://www.miraiintertech.com/home/scn6.php
  16. _Gus

    _Gus Member Gold Contributor

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    That's too bad... I believe each actuator/motor would need to be able to lift about 90 kg. To double check that with you guys though, my platform weighs ~50lbs, the wheel/seat setup weighs another ~50lbs, and I weigh ~270lbs. In all, would a 60kg-capable actuator be able to lift ~400 lbs at all of the angles a 6dof would be operating at?

    By the way, right now these are the motors I'm looking at, with a 40:1 gearbox, which, assuming the gearbox was 50% efficient, would yield around 125 Nm of torque, which should be able to deal with the 90kg/motor max load. (note that the 90kg load per motor would be assuming the whole weight is being supported by 3 motors, as it would be in an extreme pitch, sway, or surge.)
  17. joe extraknow

    joe extraknow Member Gold Contributor

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    Perhaps, the PT-actuator is better option. The pt16:
    http://www.pt-actuator.com/proshow.asp?strID=126

    cheaper than SCN6, and uses Servo motor with 150kg load capacity...., I believe cost at about $500 - $600 each. Or the pt 12 with only 100mm stroke, but even cheaper:
    http://www.pt-actuator.com/proshow.asp?strID=163

    That will overcome common 3-shortcomings by an ac gear motor like yours:
    1: non-linear
    2: low resolution (no servo high-res encoder)
    3: backlash (using gear box).
    Last edited: Aug 12, 2019
  18. BM114

    BM114 New Member

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    These motors are very similar to the motors I bought off Ebay. (Mine was listed at 300w though) One of the things that isn't shown on the aliexpress description is that 9A is the required current for no load running. According to the Ebay seller I talked with the motor requires up to 30A to run at full load. You may check in on the power supply, I went with a 720w to do my testing for the motor to ensure it wasn't current limited.

    For comparison I know my '300w' motor run at 24v can lift 75lb with some strain at 110mm ctc and a 100:1 gearbox ratio. Mine was rated at 200kgcm or ~ 40lbs@110mm based on the Ebay listing, but lifted 50lbs easily enough. Assuming you ran a 110mm ctc lever and we simplify by saying the gearbox losses are the same then each of your existing motors would strain to lift (40/100)*75= 30lbs each. That gearbox ratio might be a bit low for your needs.

    Lastly I wanted to bring your attention to the rpm output. Using an online rotary to linear speed calculator; an output speed of 75rpm at 100mm ctc will give 785.4mm/s. From what I've read you want to be somewhere around 200-300mm/s. Given this information you have plenty of leeway to trade some speed for torque using a higher ratio.

    Hope all of this information helps. I haven't been able to get anywhere close to finishing mine(emergency vet visits are $$$$), but I'd really like to see yours succeed so I can be confident mine will too.
  19. _Gus

    _Gus Member Gold Contributor

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    Thank you guys for all the feedback.

    After considering all of the options and re-evaluating the current setup of my rig, this is my plan:

    Motors
    I'm going to buy six 600W motors which can be found here, and pair them with a 100:1 gearbox from the same seller. These motors seem to be quite well priced, and my contact via the Alibaba chat offered me a 5% discount, which is pretty good, especially on such a large amount. Each motor/gearbox pair will cost me $226.10 after the 5% discount, and shipping for the whole order is likely going to be around $350, leaving a total of around $1706.60 for the entire motor/gearbox purchase.

    As for the details of the motors, they are rated at 600W, and I believe this is the output, as the motors themselves are 24 volts at 31.25 amps, which means at max they will draw 750W. The motor, before the gearbox, is rated at 1.91 Nm of torque, at 3000RPM, and to be on the safe side, I am assuming I will only get about 80% of the rated torque due to inefficiencies in the motor, meaning I expect ~1.53 Nm @ 3000 RPM. After the gearbox, which I will conservatively assume has an efficiency of 50%, I will have an output of ~76.4 Nm @ 30 RPM.

    I plan to use 4.5" (11.43 cm) CTC arms, which will give me ~668.4 N of lifting force per motor, at 30 RPM. I am conservatively assuming that each motor will need to lift ~50 kg (49.9 kg) based off of measuring the weight distribution of the sim, and adding some additional buffer. The 50 kg would yield a force of -489.5 N due to gravity. This leaves me with a net force of 178.9 N, or enough to accelerate the platform at 3.59 m/s^2, or in other words just over 1/3 of a g. I believe this should be plenty. The 4.5" CTC arms will allow for a maximum upward linear speed of around 359 mm/s, which should be more than enough.

    The good thing about using these 600/750W motors instead of the 1KW motors that I was looking at, is that in addition to being cheaper themselves, they will allow me to continue using my 2x32 Sabertooth motor controllers, which means I don't have to spend $600.00 on new 2x60 controllers.

    Power supplies
    Enough about the motors though; the other expensive parts that I'll need to replace in my rig are the power supplies, which are currently only 480W. For the new motors, I will be purchasing these 1500W, 24v power supplies. This will allow me to run the motors at max power, giving them the full 750W if it is needed, and will also allow me to prevent any overloading of the power supplies.

    Each power supply is $146.00, and luckily shipping appears to be free, which is always good. This means that purchasing the three PSUs will run me $438.00, which is also a lot less than if I had gone with the 1KW motors.

    Other stuff
    There's also some other stuff that I'll need to get, for instance some 4 AWG wire and terminals for the beefier power supplies, some extension cords, materials to create new potentiometer brackets, as well as new motor key hubs to allow me to attach the CTC arms to the shafts. I'm expecting this all to run me around $100-200, and so that's not that bad.

    I also want to reinforce where I'm mounting the motors to the bottom part of my rig, as right now I think that's the only structural weakness of my design. To do this, I'm going to order some 0.5"x2"x24" aluminum plate for McMaster-Carr, and mill it so that I will be able to bolt it into the frame, and then bolt the motors to it, which should be quite effective at further spreading the load across the mounting area, and should prevent the motors from shearing out of the wood. This isn't very costly, I just wanted to mention that I was going to do it. It should cost about $36 between the metal and shipping.

    Finally, stuff always comes up, and so I'm guessing I'll end up spending another $100-$200 or so on random things like bolts, washers, and all that good stuff.

    Summary
    Basically, I'm going to be spending around $2500 to fix this project, which is effectively doubling my expected budget. Luckily I can afford to do this, however I am not at all happy about it. It's going to take a lot of time to fix, even after I spend the money.

    If some of you guys here could evaluate whether the parts decisions I've made make sense, that would be great, as I want to be 100% sure what I buy will work before I spend the money this time.

    If anyone wants my old motors!
    If anyone is interested in purchasing my current motors and gearboxes, send me a PM. The motors are 24 volts at 11 amps, spinning at 2200 RPM, and the worm gear reducer is 25:1. I'm guessing (don't quote me on this) that they would be fine for a 2dof or similar rig which doesn't need to support the full weight of the user. I purchased these motors for ~$160 each, and I'm willing to negotiate a good price for anyone interested, as I would really like to recoup what I've spent on them.
  20. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
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    Umm - That link is for Brushless DC motors. Is that what you are after?
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