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RiftFlyers 6DOF Platform

Discussion in 'DIY Motion Simulator Projects' started by RiftFlyer, Apr 22, 2014.

  1. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    Hi Guys,

    I want to introduce my proposed 6 DOF build and draw on your experience and hear feedback, comments and suggestions.

    I am planning a 24volt DC build using Sabertooth controllers.

    I have been researching motor and gearbox options for a while and have come up with this as the leading contender:

    - Worm gearbox and motor 4.6Kg
    - Output Speed 30RPM
    - Output Torque 41.50Nm
    - Motor Current 15amps
    - Full load time 25Mins
    - max radial load 600N
    - Max axial load 120N
    - Gearbox Efficiency 0.52 at 30RPM

    There is a 300step/revolution encoder option for the motor but at £60 I think I will more likely go with single turn 10K pots.

    I hope to use the Kangaroo boards to complete the feedback loop. I have purchased one to test.

    My AUW of the upper platform will be between 100 and 120KG (Including me). The platform will be used for helicopter simulation (X-Plane and DCS). I intend to use it with the Oculus Rift and not lift monitors.

    Please let me know what you guys think. Especially the motor/gearbox option. Thanks
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  2. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
    DC motor, Motion platform, 6DOF
    From what I have seen/experienced (I'm sure other more experienced members will chime in) six 360W motors at 30rpm should drive it OK if you are careful with the weight of your platform. What will the sim be used for Race Car/Plane (I see aircraft), as there may be an issue in the amount of movement or speed that you can get out of the motor arms before you overload the motors (The DC motor are driving arms and not a BFF actuator?)? I'm currently going through a similar design process for my new sim (Rift on order), but have decided to build a working scaled model (to test out the design/software configs) before committing to the real thing.
    Last edited: Apr 23, 2014
  3. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    Thanks for your reply SeatTime. You are correct the sim will be for x-plane for the most part and the motors will be driving arms. I'm not certain of the arm length but based on my platform weight of 120KG or less I think I could be ok between 10 and 15cm.
  4. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
    DC motor, Motion platform, 6DOF
    A 100mm arm at 32 RPM should give you a speed of 167mm Sec. The amount of platform movement will be dependent on where you mount your motors to the base and arms to the platform. The more movement/mass you have to move the more torque you will need. It is one big balancing act. When I built my first sim it was based on mainly tried and tested ideas, so I felt comfortable in just jumping in even though I went for a four motor design. With these 6 DOFs I see the risk as higher, especially using smallish DC motors. If this is your first sim you will have quite a big learning curve and lets be honest costs$$ especially in building a 6DOF (Basically 6 x everthing$). All the best though and I will be watching your progress with interest. Hopefully the Sabertooth and Kangaroo experienced guys can jump in and give you a hand. The boards I use will not be suitable for you.
  5. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    My Motion Simulator:
    2DOF, DC motor, JRK, SimforceGT, 6DOF
    Motors should have enough torque if you have your cg (with you aboard) directly in the center of the top frame. People have tempted this with wiper motors, but twice as quick as you are thinking. 240v units range upto the same speeds, not bad for flight but totally useless for driving.
    To me you levers will be way too long for the motors to cope. I would come down to 85mm max even that will push them, Remember the stall current of the motor is important part too, ie being rated at 15amp they are likely to stall at a min of 30amps so the sabertooth need to put out this at least on its peaks. This happens when levers change direction. And on a sim that about 80% of its time , changing direction.
  6. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
    DC motor, Motion platform, 6DOF
    This is why I am building a working model. Similar to my current seatmover, the length of the motor arm is only one part of the equations, if you have a large/small torque angle to your attachment point then you will get a smaller/higher movement in that direction with a required less/more torque irrespective of the length of the arm. I'm sure I could work all this out in a modeling program, but I like to see things actually working.
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  7. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    85mm max.... Hmmm. Now I'm having doubts. I was basing my calculations on the rated torque figure which puts it at about 40Kg on a 10cm arm. Do you guys think that will give enough platform travel for descent effects at <85mm? At that rate I'm looking at 1 second from min to max deflection for a total travel of less than 170mm vertical.

    As stated earlier this is for helicopter simulation with x-plane.
  8. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    My Motion Simulator:
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    Here is a unit running wipers you can see the amount of movement he is achieving with relatively
    short levers.

    Another

    Your motors will be a little slower wiper tend to come in at 50-60rpm if you are lucky.
    But you will have at least 3 times the torque, which should result in a very nice motion in flight.

    This is why a model is handy to build, but too touch your toes in the water, I would test one motor for speed , torque and control, get this right before spending 5x that.

    Your idea is sound, myself I don't trust the motor specs on most sale sites, until I have tested it and pushed its limits or seen it tested to limits. For one motor worth a look, your hunch might be spot on. And they may just deliver the power required. Hell they got to do better than the wipers for power, they got way more torque.

    A little hint when building, design the lever with a few holes for testing, make the connecting rods extendable, handy for initially setting up the rig. Then you can test with different centre and find your sweet spot for your sim, they and we all are different.
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  9. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    I had just been watching those videos when I got notification of your reply :)

    I will take your advice. I'll purchase one motor gearbox combo and do some testing with the Kangaroo and sabertooth when it arrives.

    Can I ask how you arrived at 8.5cm arm length? Just wondering if there are some formulas that can be applied or if you base that figure on experience from other examples. Thanks for your input.
  10. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    My Motion Simulator:
    2DOF, DC motor, JRK, SimforceGT, 6DOF
    5 years and 11 odd builds of various styles, have not done a 6dof yet, personally don't like the resulting feel. Im addicted to me seat mover, who's getting a drift frame under her now.
    But from using many different frames, configurations and motors and drivers, I have found that most aim to high for the power they think they can supply, best to aim in the middle and surprise ya self when it goes way better, hence because this will probably be the first build alone these lines - 24v - kangaroo - 6dof. You are stepping into an area that's not totally discovered,
    pioneer on my friend.
    We are here to support your venture.
    • Like Like x 1
  11. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    Thanks for all the feedback so far.

    I have changed the spec of the motor and gearbox and ordered 1 unit for testing. The new motor is lower speed and will give 52Nm of torque.
  12. telfel

    telfel Active Member

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    Hi @RiftFlyer

    If your going to use the Kangaroo I would order the motor with the encoder, you get much less noise etc than using a pot, even the hall effect ones show jitter. You also only need to then work out top and bottom limit switches.

    regards Terry
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  13. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    Thanks Terry,

    I had read the issues posted in the Kangaroo thread so I ordered the motor with a 300 step encoder. Hopefully they will play nice together.
  14. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    Ah the increased torque for a little less speed wont hurt and your getting 6x more torque, in a way, so it adds up, Will love to see a test run of one motor will show you how strong or fast it will be. Please keep us all informed on how it all goes. Thanks.
  15. trent

    trent New Member

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    Hi Riftflyer, What make and model of motor are we talking about? I'm looking to build a 6dof similar to Full Motion Dynamics for flight simming, and I've been trying to find a motor as powerful as the 613 watt smartmotor they used.
  16. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    @trent

    The motor and gearbox are from cobalt controls in the UK. The latest specs were given over the phone today and are not listed on the website. I'm awaiting an email with full specifications. I'll post more details when I have them. I'll be waiting a few months for the test motor. It has to come on the slow boat from the supplier (probably China). Prices are higher than the motion dynamics solution and watt rating is maybe lower! If I factor shipping and import duties on the Australian unit it may balance out though. Price is in the £200 to £250 range. Cheaper than anything I could find here in rip off Ireland.

    EDIT: Sorry I see you said full motion dynamics not motion dynamics (Australian Company). I don't know the specs of the motors they used. If you have more details on what they used please share a link. Thanks
    Last edited: Apr 24, 2014
  17. RiftFlyer

    RiftFlyer Active Member Gold Contributor

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    @trent I think I found the motor you are referring to. The uber sexy Moog Animatics servo motors. I'd imagine they are brushless and a lot more efficient than brushed PMDC motors. I'm too scared to check the price!
    Last edited: Apr 25, 2014
  18. BlazinH

    BlazinH Well-Known Member

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    A little clarification; hall effect pots are noiseless as they are a digital device. If you have noise on the output, it is coming in thru the wiring or elsewhere. But I think the “jitter” referred to above is not noise, but normal operation for these. When using the 360 degree model for example, there will be a +- .1 degree variance in the output that sometimes looks like noise because when it’s on the edge between say 2.31 and 2.32 volts (represents degrees position), it can keep switching back and forth between the two and it looks like its jittering.

    That being said though, encoders are probably the easier method to use with the kangaroo when you consider the problems it has in dealing with an analog signal the way use it even though the adding of limit switches may be a little harder to do than not.

    Btw The kangaroo manual says that you must have it near center position at power up to tune with limit switches but that's the only requirement other than having it weighted also.
  19. trent

    trent New Member

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    DC motor, 6DOF
  20. trent

    trent New Member

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    Last edited: Apr 25, 2014