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My dumb noobie questions

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by MikeG, Nov 11, 2014.

  1. MikeG

    MikeG Member

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    Version 3 and more of my ramblings :p
    Really liking this one. Most likely change the pitch with levers to a belt drive mounted on the tuning fork, gets rid of the tie rods which, to me, are not very good. This gives me the ability to have 2 pots mounted so i can have one set up for the laid back F1 position and the other pot set for a more upright stance more suited to normal car and flight sim, just flick a switch to change. This version allows for a huge amount of yaw. It is also the most compact version except for a bit longer but the other advantages far outweigh that. Will need to get the shafts and bearing housings machined but that's a minor detail.
    Bugger i was planning a 2 or 3 DOF but now at 4 and traction loss will be 5 but it covers car and flight sims much better. :cool:


    [​IMG]

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  2. bsft

    bsft

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    RNR , rock n ride simulator
    having pivot above belly button would reduce it a bit, but thats where you would need more travel to overcome it
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  3. bsft

    bsft

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    129 deg yes, but we are not moving as much weight as what that frame will need to have.
    Motion will vary from person to person, but even 60:1 boxes can give nasty motion as well.
    I am still conernd about the idea of using 25:1 boxes, you need more 60:1 or even 100:1 to move yours and I think you are going to use it for race.
    Our race sims have a smaller degree of angle of tilt, maybe 8-11 deg. I guess you are looking at 25-30 angle or more.
    You may not quite get the jittery motion us seat mover boys get because I think you plan to use a larger range of travel with the motors.
    Did I make sense at all?
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  4. MikeG

    MikeG Member

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    bsft
    2.4:1 ratio with those motors would give about 50 degrees of motion with an input of 120 degrees. As it is I would most likely use 50 - 54 degrees for roll and about 40 for pitch with an offset of 20 degrees for the more upright setup.
    This thing won't have much weight. A carbon structure would weigh a lot less than steel and be stiffer, i will calculate the weight of it later. I know a composite construction engineer that has done a lot of work for the boat I am building, will see if he can plug the numbers into his F E A software and come up with some stresses.
    If i want less travel and more power i can always change the belt ratios so having 25: gearboxes shouldn't really matter. I could use 5:1 and only get 25 degrees total movement but i think, knowing me i would double up on motors, must be related to Tim the Tool Man - more power. :D
    Last edited: Dec 4, 2014
  5. bsft

    bsft

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    ok, carbon structure, thats good.
    My concern is the power of the motor needed. If your mate can, get him to work out the power needed to swing a person from full tilt forward to full tilt back and also from side to side.
    As said, your design is similar in concept to a rock n ride, but if you can change the design somehow so it will swing a person around without much effort , you will be fine.
    http://www.acesim.com/main.html this sim doesnt need motors at all and once it is balanced right, you can move it with your own weight easily.
    If you can get your concept frame to move as well without motors, you will make the job a lot easier.
    Unfortunately, I am no engineer so I dunno anymore on how to do most of this.
    If you have a friend whom can work it out, for sure have them help.
    Ah, just one question though, what belt ratios are you talking about?
    Dave.
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  6. MikeG

    MikeG Member

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    I wouldn't call him a mate, he has done the design and engineering on the masts for the boat, and a few other bits and pieces, he comes from an aeronautical engineering background. I have helped him with some electronics problems when he was constructing his filament winding machine. I have also come up with a few ideas for design of machines and construction methods that he has adopted. Now we seem to have quite long chats about our toys and stuff. Biggest problem he is in South Aus and I'm in W.A. so not real close in more ways than one. Called him this morning and he is off over seas on a consulting job for 2 weeks so it will have to wait.

    When you say the seat shakers only have 8 -11 degrees of movement is this total or each side of the neutral position. This is why i was trying to find out typical angles before, this then becomes an easily comparable measure. Length of arms also depend on angles of movement of the motor shaft and the distance of the mounting point on the seat from the pivot point, gets a lot more complicated to compare rigs. If the typical shaker only has 10 degrees of movement then i will change my belt ratios to reflect that, i assumed it was a lot more and was aiming for about double.
    I would think power wise it should need substantially less than a seat shaker, for the same amount and speed of movement, as the pivot is a lot closer to the 3D CG. That last link shows how little power is needed when the cg is correct 3 dimensionally. At the moment i have no real idea as to where the CG would be when adding the wheel, pedals and seat, care to take a guess.

    The belt ratios i refer to are the gearing from the dc motor to the bearing shaft. I drew them as grey rectangles at the back end of the main bearing mounts. If I want a slower or reduced motion i can just change the pulleys to get anything i want, the ratios of the worm boxes becomes a little irrelevant although starting with a taller ratio makes it impossible to speed it up so 25:1 is probably ideal.
    Last edited: Dec 5, 2014
  7. bsft

    bsft

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    ok then, officially there is no "recommended" angle.
    You need to remember that simulation is a mind trick.
    small and or big angles can vary from ride to ride.
    motion profiles can have a big effect as well.
    I have seen and been linked videos of sims throwing right around, while it looks impressive, it may not actually reflect the true motion of the vehicle in game.
    Have a look at the commercial rides around.
    The force dynamics has a lot of travel and state it reflects realism in recreating motion.
    Dbox has very little travel, like 50mm total actuator travel, but new model dbox have more like 150mm.
    simx units , not sure how far the actuator travels, but they use about 10 ish deg total angle.
    Thats 5 deg from centre.
    Now, guys on site have varied builds from @BlazinH to @Pit to @Nick Moxley builds
    Blazinhs build has a lot of travel as he states it reflects more true to life simulation of g-forces.
    Pit on the other hand has smaller travel in a seat mover.
    Nick has seat mover with drift frame under it.
    Now the Rift is stepping into the picture, actual travel with such immersion can really effect things
    Ive had full frames as well in the past, but nothing really more than total 15 deg travel ( 7.5 deg from centre)
    I built a sim for a mate , full 2 DOF frame that does total 18 deg angle, 9 from centre, he wasnt happy till I did him a profile, big difference.
    If you can move your sim with a belt drive system, then go for it.
    Its hard to say whats a good and bad angle, people will state one thing from another.
    I do know that a group of kids playing dirt Showdown on my desk racer all in one, think its awesome, they can really feel like they are going over big jumps, even though the actual travel is not that much, maybe 6 deg from centre.
    Its all to do with immersion and good motion profile.
    If you can reduce the throw of your sim, do some tests to see what suits you.
    Dave.
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  8. MikeG

    MikeG Member

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    Wow a huge thanks for that bsft
    so it seems top end movement is 20 degrees total then, I was a little worried about the possibility of falling out of the thing with 54 total for roll :D
    Bottom end 10 total or even a bit less.
    I think you use the Motion Dynamics 200W motors. How many degrees of the output shaft do you use, that tells me the speed.
    That would give me enough to finalize the ratios.
    At this point in time I will aim for 20 total over 120 degrees of the shaft for all the axis.
    Sounds like a plan
  9. bsft

    bsft

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    The 200 watt motors may do it with the right gearbox. Again, start with 25:1 and if it struggles, move up to 60:1 boxes.
    Yes I use the motion dynamics motors, but remember, mines a seat mover, not a full frame.
    I am not sure of actual degree of travel of the arm. I use 50mm of travel I think on desk racers, with a 40mm CTC lever. As I use JRKS, I can adjust the power and speed and PID of the motors with ease to suit it all.
    With the desk racer, because the pivot is so close to the motors, like 250mm from centre on sides and 180mm from the pivot back, I have more surge than sway, 7 deg total sway and 17 deg surge.
    on the other hand, my old foot motor frame had more sway than surge.
    700mm from pivot to motors, but spread only 225mm each side. 7 deg surge 18 deg sway, 45 mm CTC lever.
    A good profile fix sorted that out so its even.
    I think its about 200-250mm per second loaded. I can slow it or make it faster if needed. In my case, I chose a mid range setting to suit myself and others playing them, as they are hire sims.
    My personal ride uses re-modded brick spreader actuators, so they dont really matter here.
    to be honest, I prefer the motion of DC motors, but the actuators were a gift and I have spent a LOT of time getting them setup so its another learning curve for me. That and I have plans for them later on another project, so eventually I will convert that ride to DC motors again.
    I just remembered, I have a mate whom has a 2 DOF that is on 1/2 moon style rollers, he insists that 30 deg total swing is needed for more simulation, but thats what he likes. And thats for racing.
    No he hasnt featured it here.
    Am I making sense here, or am I going off on tangents?
    Dave.
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  10. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    Despite the intended carbon structure I would suggest going with the 50:1 or 60:1 gearboxes, as I found the additional weight of hefty controls made a significant difference and was more than the 25:1 could handle.
  11. MikeG

    MikeG Member

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    sorry a bit late to reply, was playing F1 2013 and then we watched a movie. Happy wife happy life :cool:

    bsft
    Certainly not going off on tangents, lots more data points for me to base my guess on.

    A 150 rpm 25:1 box with 50mm of travel and 40mm CTC lever will move over about 80 degrees in .1 sec so top speed would be around 500mm/sec and you run it at a lower speed so i could probably use a bit more angle, back to 120 degrees this would be a time of .13 sec. I will set that as a data point.

    Now to angles of rotation -
    54 degrees of roll seems huge for a racing sim but not too sure about a flight sim, need more research, maybe 30 total. I think i may need a bit more than a seat shaker as i have reduced head movement with the shift in CG, huge assumption here :D.
    Was aiming for 40 degrees of pitch and the belt system would allow me to electrically move the center to a bit more upright for air and car syms, love that feature. Maybe reduce this to 30 total again plus 10 degrees of shift.
    120 degrees of motor to 30 for the victim gives a belt ratio of 4:1. Hopefully the angular velocity will come out similar to your usual settings. If i have stuffed up then i get to buy 2 more pulleys :oops:
    Would build it ready to take the yaw axis and set pulleys based on the result of the other 2 but probably the same. Really need yaw for landing approaches in cross wind.
    Surge could be 2 pulleys and a belt. Use the same times and motor angles with pulley sized for 300mm of movement. Too much?
    Traction loss comes later, brain tired :confused:.

    bsft and beast
    Will go for the 25:1 boxes as it is easy to change gearing to a higher value which would trade off motion or speed and give more torque if i need to. Starting with 50 or higher ratios i can't go back the other way without replacing the boxes.
    I am convinced that the higher CG will reduce the power needed to keep to my numbers but then i have been known to stuff up occasionally and i can always add more power if I have to.
    Last edited: Dec 5, 2014
  12. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    I also started with 25:1 and a light aluminium build but found the weight of Fanatec controllers was too much for the motors without the person in the rig for counterbalance.

    It is easy enough to change the gearboxes, though there are some slight design differences that meant I also had to redo my pot attachments and mounts.

    Do experiment and push the boundaries @MikeG, we all benefit from finding out what does and does work in practice, along with the inevitable design decisions and compromises along the way.
  13. MikeG

    MikeG Member

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    beast
    I think the design challenge is a big part of the fun for me. Just have to build it and see how wrong i got it :D. Got to push the boundaries as you say. Yes changing boxes isn't hard but a new pinion pulley is a lot cheaper.

    Did a bit of working out weights and the main curved beam with the U shaped fork to the seat should be about 4Kg . Each bearing housing shaft and bearings about 2.5Kg each then motors at 2.7Kg each. Maybe about 4 kg for the linear bearings and tracks for surge. It all adds up but only the U shaped fork to the seat is part of the equation for pitch and roll. The rest only affects the yaw, surge and traction loss.
  14. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    Nice and light design @MikeG. Do also factor in the weight plus design leverage of controllers, that made a much bigger difference than I had anticipated in my build.
  15. MikeG

    MikeG Member

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    i have the controllers in the back of my mind but most likely will set it all up after i make the seat and find the balance point. Have a few tasks on the go with the boat and then off on holls. When i get back i then have the boat and CNC to get stuck into. The seat will get snuck in between the others then after the CNC i can start on the frame. WIll do some drawings to give to the machinist so i have the shafts and bearing holders for when i get started.

    Not enough hours in the day sometimes.
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  16. MikeG

    MikeG Member

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    Another q if i may.
    Been trying to decide on seat construction, angles of the different sections. While doing this I wondered what a comercial seat weighs. Checked the net for some proper racing seats and come up with about 5Kg. Many of the sims i see here seem to have some pretty comfy looking seats that to my eye must be quite heavy. Any idea what these seats typically weigh. My target weight is set by the racing seats so under 5Kg but am curious what people tend to use.
  17. BlazinH

    BlazinH Well-Known Member

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    Yes, this is how I felt about it initially @bsft. My rig was originally designed as a flight simulator so I wanted as much travel as possible in all axis. But then I converted it to a racing rig and made it faster than it was. I liked this for awhile but then started disliking more the feeling of rotation and the transitional time taken to move from one side to the other when using a lot of travel, especially in the rigs roll axis where I am using sway on it. So, I use much less travel now in the pitch and roll axis but still like a lot in heave since its axis is not effected by rotational forces. However, I use less heave now too on my newest rig because it no longer moves the monitor with it. If you don't know or haven't already figured it out @MikeG, my rig is a 3dof with heave.
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    Last edited: Dec 6, 2014
  18. MikeG

    MikeG Member

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    BlazinH
    Good to have your input. You have tried the big movement but slow then changed to smaller and faster. Having tried a few different ranges and speeds what would your ideal speed and angles be now for a flight sim and a racing sim, purely from an ideal perspective and ignoring practical issues.
    Have you ever measured or calculated your new angles of movement and/or speeds and what the old ones were. If i can get a range for movement and speed i can probably calculate the power needed to achieve it.

    Heave is very interesting to me as well as I haven't seen a lot of data on that either. I think it was seat time that had about 50mm of total movement. Any ideas of what you have now and what your ideal would be. I will be having the monitor move with the seat so that will affect your ideal from the sound of it, probably an oculus from what i have read of the latest version. Heave has been in the back of my mind but i hadn't had many ideas for an elegant way to achieve it in the designs i have been sketching. I was asleep just now and woke up with one that i quite like but need to do some more work on implementing it. I was trying to avoid the bash in the bum like seat time made as i want to play with the RC servos that someone did, sorry to them i have forgotten who it was :blush.

    I hope people don't mind me questioning too much but the more data i can assemble the better choices i think i can make so i thank all for their participation. :thumbs I do promise to stop analyzing at some stage and start slopping some epoxy.
  19. bsft

    bsft

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    baja buggy seats about 3KG I think
    I use a racingseat, bought cheap , weight 9kg.
    dimage.jpg
  20. MikeG

    MikeG Member

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    9Kg is not bad. They look a lot heavier than that.
    searched for the baja seats and i think 3kg is unpadded.
    Thanks for that. I can't use a commercial seat as it needs the reinforcements designed to carry the pitch pivots, but i was curious. Target at 5KG still then.

    Just worked out the power for the heave axis and that gets a lot harder. To lift 100Kg 50mm in .15 seconds requires 327W but that is after inefficiencies. Worm boxes are terribly inefficient, I would need about 25rpm so just guessing probably 5 to 600W before losses :( Maybe not bother. I know people here overdrive the motors but that maybe a bit too far to hope for.