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Question Marsbuggy 2 Seater?

Discussion in 'New users start here - FAQ' started by Mars Buggy, Apr 7, 2020.

  1. Mars Buggy

    Mars Buggy New Member

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    Heya, planning my 2 seater buggy, I've not got very far before a question comes up.

    Looking at the completed 6DOF projects I see the rear of the rigs (behind the seat) has the 2 axis points, but with my 2 seater its at the front and 4 at the rear? looking at the sketch below would sim tools be able to adapt the if the 2 axis were at the front?

    Thanks

    upload_2020-4-7_17-10-44.png
    Last edited: Apr 7, 2020
  2. Ads Master

    Ads Master

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  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    Yes SimTools can, it is just a question of axis assignment.
    • Like Like x 1
  4. Mars Buggy

    Mars Buggy New Member

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    Thanks @noorbeast , I'll grind on with the design...

    I can see with a two seater the load (2 fatties) and the height (low garage) could be a problem if I design as above.

    General question to anyone using the Turnigy SK3 motors (kinda hoping @SilentChill , @PeterW or @Carelsbergh_Stijn bump into this thread ) . My thinking about the actuators is to use a timing belt to reduce the overall height and optional gearing if needed for the weight issue. The thing is, having never held or run an SK3 yet, would I be able to add the encoder to the out runner shown below?

    upload_2020-4-9_18-42-41.png
  5. PeterW

    PeterW alias Wickie

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    Hi Mars Buggy
    Yes, it should be ok to add the encoder like shown in your sketches.
    Regarding the high weight of the upper platform, you could think about to have a small reduction from motor to actuator (as an optional feature in case the motor doesnt have enough torque to push your platform). Maybe you can use a littl stronger motor.
    Wickie
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  6. Mars Buggy

    Mars Buggy New Member

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    Thanks @PeterW , the design grind continues.
    This forum is big, I mean massive big. I am wondering if there are many other 2 seat sims up and running. I’ve read loads but not seen one yet I’ll search on but if anyone has a recommendation please share.
    Last edited: Apr 13, 2020
  7. Carelsbergh_Stijn

    Carelsbergh_Stijn Member

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    Hi sir,

    What size motor are you using? And what size ball screw? Any idea how much your upper platform will weigh? Because you want to use 2 seats you will probably need reduction with a belt. I would also recommend using also an outer sleeve around the two pipes or weld the together because the green piece in the tubes will not hold the force and will probably not just bend (pipes coming apart) but even break!

    Also, don't forget about homing switches (or are you going to rely on current peak?) and use a coinical bearing in the bottom.

    Let me know so I can give you more advise.

    Cheers

    Carelsbergh Stijn
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  8. Mars Buggy

    Mars Buggy New Member

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    Heya @Carelsbergh_Stijn

    Conical bearings, I was going to use standard roller bearings, but larger than needed both are rated as ok for axial and radial loads. That being said I have not built a sim and you have so Conical bearings it is - Thanks.

    Homing switches, yup, in my mind I have been playing with using inductive sensors, but then I ask myself, why spend the green on some fancy tech when levered micro switches will do?

    As for the weight, I am still really early on and pulling figures from the sky. Estimating about 300kg - 400kg (2 persons @90kg, seat and rig about 90kg* and a factor of safety about 1.3). Wow that seams really heavy... but has been done.
    * If anyone has an example of rig weight please share?

    Motors will be from the Turnigy
    SK3 range as I believe you've used, as for size I've not calculated anything yet. I want to be happy with the rig frame dimensions first. Thanks for the offer of help greatly appreciated especially as it looks like I am going down the O-drive route.​
    Last edited: Apr 12, 2020
  9. Mike5050

    Mike5050 New Member

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    I can't wait to see a two seater.
    Has anyone built one yet?
  10. Mars Buggy

    Mars Buggy New Member

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    Hey Mike, good question, I’ve been looking for the answer. Commercially there have been loads but I’ve not found a 2 seat DIY version yet.
  11. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    2 seater rigs require a good deal of additional power, given the potential for variable mass, including being unbalanced, so tend to be costly and hence pretty rare in the DIY world, though it could be done. Many 2 seater rigs in the cheaper end of the commercial world tend to be carnival style rides, rather than hard core precision simulators.
    Last edited: Apr 13, 2020
  12. Mike5050

    Mike5050 New Member

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    Hi Mars,
    You got me interested.
    I going to start to look around today and see what i can find .
    I'll Let you know if i find anything
  13. SeatTime

    SeatTime Well-Known Member

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    I expect you have a suitable budget, skill and space to build a Stewart Platform to safely throw around 400Kg. Massive forces involved :eek:.
    Link to a two seat sim - note that he is replacing the old 3 phase motors in the pictures with 130ST 2.6Kw matched servo systems (obviously thinks its worth it ;)).
    https://www.xsimulator.net/community/threads/amc-aasd15a-servo-controller.13945/page-5
    Big Sim.jpg


    As a cheaper/simpler alternative you could build a single or side by side 2DOF seatmover with a big front screen + some G systems (Harness tensioner etc ) to better convey the constant forces. Would work well IMO , although not as 'impressive' as a big stewart platform in motion :).
    Last edited: Apr 14, 2020
  14. Carelsbergh_Stijn

    Carelsbergh_Stijn Member

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    Hi

    1. Magnetic switches are clean and not hard to build, but normal switches are simpler

    2. I'm using keda 6364 motors from Hobbyking but they are not available anymore, I would suggest to use the sk3 6374 motor or even bigger

    3. As for weight, my upper frame weighs in at about 60kg

    4. About the power usage, yes this will draw some power, but to begin with, you are using BLDC motors and they are pretty efficiënt and also, if it's possible to have the upper mounting points at the height of the center of gravity I would suggest doin' it, because this helps a lot in reducing power draw (long story short, when you rotate around the center of gravity, you only need rotational energy)

    5. You should use sfu2005 or sfu2004 if they exist, diameter 16 is not enough for your machine

    Cheers

    Let me know if there's anything else

    Carelsbergh Stijn
  15. Mars Buggy

    Mars Buggy New Member

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    Thanks @SeatTime and @Carelsbergh_Stijn ,
    I’ll have a read of the thread, that thing looks way overkill for my garage. I’ve found this example on robotdigg more the size I was looking at. Although I doubt its ability to have the full 6dof movement without a frame clash.
    upload_2020-4-16_7-40-27.jpeg
    Looks like my frame weight guess is not far off. Thanks @Carelsbergh_Stijn for sharing. I’ll keep those upgrades specs in mind.
    Last edited: Apr 21, 2020
  16. Mike5050

    Mike5050 New Member

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    Hi Mars,
    Is that yellow motion sim commercial or self made?
    where did you get info?
  17. Mike5050

    Mike5050 New Member

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    sorry didn't see you posted robotdigg
  18. Mars Buggy

    Mars Buggy New Member

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    Moved on a little bit, not much but a bit. Got to say, Wow optimising the hexapod geometry is a tough one...
    Any suggestions on the sketch so far, will be awesome? Tried SimCalc for a little bit but its set up for 2dof and pinion arms (unless I have an old version). How have you guys attacked the balance, GOG calc's.
    Space and the 2 seater is forcing me to be sitting above the platform. Hopefully looking for a proven method to optimise the hexapod dims now that I have a good idea of my actuator travel?
    Thanks for sharing.
    upload_2020-4-24_18-57-28.png
  19. rick surette

    rick surette New Member

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    Hi Mars Buggy, I am not building a 6 DOF but will be following along with your build because I will be using odrives.
    I bought them before really understanding that they are not noob friendly. Seeing the other builders get them working gives me some hope and I hope you share your experience setting them up.
    Thanks
    Rick
  20. Mars Buggy

    Mars Buggy New Member

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    Heya @rick surette ,

    Chances are you'll be ahead of me. I'm still asking questions and information gathering/sharing. Although its good to know that we could be going through the O-Drive pain at about the same time - keep in touch , I'll share what I can but at this time I'm most likely to be exposed as a noob. The real build thread will supersede this when I have completed the design.

    I've set my mind to a 2 seater, but every day I think, hmm, I could go single seat and have it easy! (edit - ahem 'easy' who am I kidding ) I am still playing with thoughts about Nema 32 BLDC at 48v and the codes @pmvcda (FlyPT) has shared. Long way to go still.
    Last edited: Apr 28, 2020
  21. Mars Buggy

    Mars Buggy New Member

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    If anyone can help thanks in advance, I am looking at proximity sensors for the actuator. First question, the detection range is from 1mm to 10mm (there are others) but most are about 4mm sensor range, would 4mm be enough to stop an actuator moving at 480mm (extreme case) per sec, if not what has been used successfully?
    Second question should the sensor be Normally closed, I think so, to cut the power to the motor on a open circuit would be, either limit reached, or a fault in the circuit. A fault in the circuit for Normally Open and I will not be able to sense the limit. (OK mind made up don't answer 2nd question)

    Thanks

    M