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In depth post on motion and different setup's. Well worth a read

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Trigen, May 15, 2020.

  1. Trigen

    Trigen Active Member

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    Came across this post on another forum that may spark some idea's. There's a lot of very good info there

    https://www.isrtv.com/forums/topic/...AWf9oAaF5WdE4_bJMT873H_WmzN0kqatLaT1PcOicQS58
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  2. Ads Master

    Ads Master

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  3. pmvcda

    pmvcda aka FlyPT

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    My Motion Simulator:
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    Agree with Joe. That's the objective of making my software, Mover.
    But I don't think we need 25 computers for motion cueing with toy simulators, that send strange and some very limited info about it's physics.

    Also never understood the logic behind 4 actuators in sfx100 or dbox setups. Maybe it seems better to the eye. People think it's the 4 wheels suspension, and then they get data from all the car body motion.
    I think that maybe dbox is making it, but not sfx setups.
    And when I make it in Mover, I have to calculate the tilts to keep the 4 feet on the floor.
    Could be here all night...
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  4. Trigen

    Trigen Active Member

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    I agree with you there and had i not read this post i would be ignorant and gone for 4 actuators. Thankfully i did so now i will go with 3 when i eventually do my SFX-100. Another thing i also noticed experimenting with a 1 actuator type setup (spring assisted heave) is using pitch speed (with your software) over vertical acceleration and that gives a far superior 1:1 representation of what the car is doing. He also mentions something along those lines. I think if you are on a very tight budget you can easily get away with 2 actuators in the back and while you wont quite get that thump in the front (and lack some pitch height front/back) when that pitches up first the lowering of the back ones gives a very good representation.
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  5. Gary R Tree

    Gary R Tree New Member

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    The link is a great read. Thank you for posting it up. As an engineer, the 3 actuator sim rig makes sense. Putting 4 on a rig creates conflicts, no question. Three points create a plane, adding a 4th means there needs to be a boundary condition to constrain the movement of all 4 actuators. That is unnecessary and confuses the motion.

    I am currently researching which DIY motion rig I want to build. At this point, I will be basing it on 3 actuators. I am thinking of using SFX actuators with longer throws so I can use it with a Flight sim and a racing sim.

    Can some of you point me towards some good examples of DIY 3 actuator SFX style rigs on 8020? I know longer throws can create a tip-over condition.

    My desire is to start with 3x -3DOF and add TL if I can find some good examples. I have chosen to do this in 8020 because it is so modular and because I found a bunch at a salvage yard. :)

    Thanks in advance for your help.
  6. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    Check out @Hoddem's 3DOF here: https://www.xsimulator.net/communit...-rig-v2-3-dof-sfx-vr.14304/page-2#post-199895
  7. cfischer

    cfischer Active Member Gold Contributor

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    You may have already seen this thread. I talk a little about my long travel 3 actuator rig and my current thoughts on its limitations and things I would change.
    https://www.xsimulator.net/communit...actuator-and-using-4th-motor-for-surge.14793/
  8. Gary R Tree

    Gary R Tree New Member

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    Thanks Noorbeast and CFischer.
    I am now watching those threads.

    I am thinking about 3 each - 350mm actuators, limited to 200mm movement on a rectangular 8020 frame, 2 rear and 1 front. Based on what I am reading, there is a potential tipping issue. Does anyone have any references to people who have tackled this issue already? I hope to set this up with long smooth strokes for flight sims and then dial the movement down for racing sims. Obviously, this is all conceptual right now.
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  9. cfischer

    cfischer Active Member Gold Contributor

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    Long strokes are going to be a problem in pitch and roll with the center of roll under the rig. Its going to feel like surge and sway.
  10. Gary R Tree

    Gary R Tree New Member

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    Is it possible to use longer strokes with slower speeds in flight sims and then short strokes at faster speeds in Racing sims? Or is the problem with long actuators the distance from the floor to the CG of the rig & driver.
    This is all brand new to me.
  11. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    In SimTools you an create motion profiles for race and flight, and they will be considerably different: https://www.xsimulator.net/community/faq/steps-to-create-a-motion-profile.228/

    For a flight sim, say a commercial heavy on a basic 2DOF, you can have a much larger axis allocation for the likes of pitch and roll, as it is very unlikely you will be using the full extent of those axis allocations at the same time. Similarly, you would use much larger Tuning Center values, as for a commercial heavy you primarily have long slow axis movements. You would do the reverse for a 2DOF race profile, but even there in Game Manager profiles you would likely run larger TC values for something like a Cobra or street sedan, compared to an F1 or Indy Car.

    Design does play a role, in terms of the type of rig and its axis range. For traditional motion rigs how many DOF and what axis range, in what configuration, can influence what cues are possible and what sort of accuracy they have. I suspect the likes of @SeatTime would argue that G-Pressure System type rigs can provide even more relevant and accurate cues than traditional rigs.
  12. Gary R Tree

    Gary R Tree New Member

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    I am thinking about starting simple and then expanding my motion rig as I learn more about the technical aspects and limitations. I'd like a dual-use rig with long smooth strokes for flying. I prefer planes like my avatar , sail planes and other private aircraft. that said, WWII and other military aircraft and dog fights are fun. I know that loops and rolls and other aerobatic maneuvers will not be simulated well on the rig. If Simtools will allow for stroke assignment and adjustment, that would be awesome.

    I do intend to do some sim racing and other sim driving games and would dial the stoke lengths down for those.

    The 3DOF DIY SFX style 8020 rig would be very the way I would go. The rig would have 2 actuators in the back and 1 in the front. This would be a bit of an experiment as I have a lot of 15 series square 8020 and would have to stack them 3 high to get a 15x45 perimeter profile. I think it would work as the actuators are plenty powerful enough to handle the weight.

    I'll be following some of the other builds here to learn about different features, details and incorporate those that are appealing.:)

    I appreciate all of the knowledge and sharing on this site.
  13. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    Do you have a reason for choosing a 3 actuator SFX design over a traditional 3DOF, or other potential designs?
  14. Gary R Tree

    Gary R Tree New Member

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    I don't have a great reason for choosing a SFX design other than it is something I can build myself, learn about the technology and save some $. I would, of course, use the Thanos controller and longer shafts in the actuators. I some of the tools necessary to do this but do not have a lathe or CNC machine. I can cut aluminum materials on my saws. I have a drill press and can use that to make connections on the 8020 materials. I am able to source aluminum plate materials locally.

    I am very new to sim racing and am currently assembling a gaming computer, waiting for parts to become available, inventories to increase and prices to decrease. No hurry here as I use my Xbox and Switch in a wood rig entry-level wheels and pedals.

    I have a lot of room in a semi-finished basement to put a rig so I don't need to be concerned with a small footprint rig. TBH, I am interested in learning about the tech, 3D printing, design and maybe some programming. I have two grandsons who live nearby and would love to have a motion sim rig for them to experience. My son-in-law is a professional programmer for the University so he is more tech savy and should be able to help too,

    Eventually, I could see myself building a 6DOF system as a follow-up project. That would be a couple years down the road.

    So if there are other more gooder DIY 3DOF designs I should consider, please steer me in those directions.
  15. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    I am not criticizing your choice, just curious. The peg leg format of the SFX will give basic 3DOF and has detailed instruction, the latter is not as common with other DIY projects, so those generally need more research.

    Whatever your approach you can draw on the expertise and experience of others, for example if flight is your primary interest you may want to query @wannabeaflyer2's reasons for going from 4 to 3 peg leg actuators, and experience in getting it configure for flight: https://www.xsimulator.net/community/threads/flypt-mover.13464/page-65#post-200163
  16. Gary R Tree

    Gary R Tree New Member

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    Noorbeast,
    I did not mean to imply criticism. Frankly, I do not know much about motion rigs. An 8020 rig with linear actuators seems fairly simple to build. There seems to be a fair number of folks building them. I do not know how well they simulate the correct motions though or if there are more elegant solutions.

    I am open to suggestions and will definitely check out wannnabeflyer2 and the link.
    Thanks for sharing.
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  17. Guzz226

    Guzz226 New Member

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    Very very interesting thread and has really got me thinking about 3 acutator, not acutator for 3dof.

    In terms of the 4 acutator, leg up issue - has any tried 4 acutators but instead of the corners of the rig rectangle, positioning the 4 acutators on the respective axis?

    ie just like a 3 - so one acutator each side - but unlike a 3 where you place one at the front or rear, you position one at the front and rear.

    So unlike the common practice of positioning the acutators as "wheels" - they are more on the respective planes of movement you are seeking to reproduce?

    Hmmmmmm?????? Thoughts?
  18. Bryan Chan

    Bryan Chan How do you know it's good enough?

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    The fact remains that 4 points require more constraints to make a plane compared to 3 points. So moving the position of the 4 points doesn't make it easier to compute or the chances that one point will be out of plane.

    I am interested in Joe's point that there is no heave in racing sim. I understand that there is a lag between front tires and rear tires experiencing the same road feature so heave is not necessary for that. But on a track, there is a brief sensation of floating when your car get to a down slope with enough speed. The car's forward momentum causes that sensation as it reacts to the change in track angle. Is that not heave?

    I can appreciate that simulation of traction loss is not advanced enough to be an accurate motion feedback. I guess my question then would be is it good enough to make it a useful feedback? Can the driver properly convert what feedback is available back into useful control inputs? (i.e. countersteer)

    My take away from his post is that 3 out of the 6DOF is either not applicable in race sim or not good enough to be useful.