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Center of gravity discussion on 2 DOF platforms

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by tomkil192, Aug 14, 2015.

  1. tomkil192

    tomkil192 New Member

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    This is my first post so I would like to say Hello to everyone on this forum.

    I started fallow your projects about 2 months ago. Time to build my own one.

    So far i have had build RC servo temporary model, working perfect with sim and LFS.

    Great feeling to see it "alive". Now is time to build the platform and there is the question.


    Where should be centre of gravity point to simulate best Gforces.

    Im not talking about balancing the platform. Some of you probably seen Blue Tiger platform.

    They come out with different idea of bringing centre point up. Above the platform deck.

    In this case the physics are completely changing and you can feel it completely different corect me if im wrong.


    Could you tell me if any of you done it like that? I will send some pictures later on.

    Witch platform will simulate g forces more real?


    Thanks for reading


    Tom
  2. bsft

    bsft

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    generally its an immersion thing, a basic 2 DOF seat mover with a good profile and sitting behind a TV can give very good immersion feeling. You "think" you are under g-force.
    Remember, its a game, not a simulation teacher
    Ive had professional drivers on my seat movers and they say, even though its not like a real car, the immersion factor is there.
    • Agree Agree x 1
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  3. tomkil192

    tomkil192 New Member

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    my temporary special ms paint skils ....:sos platform.jpg
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  4. bsft

    bsft

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    the one on the right
  5. bsft

    bsft

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    however, having the motors connect higher up is better for leverage
    platform.jpg like I sketched on the one on the left
  6. tomkil192

    tomkil192 New Member

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    or use strong motors. for more compact design.

    When you siting in the normal car the 3d center of gravity is where the chassis is attached to the shocks (about stomach/chest height) and wherever the front and back balance is. am i right? should be this taken to the consideration when you build platform? unless you drive the lorry then the seat mover design works perfect.
    We have to try something different, most of people just copy projects. I havent seen anyone on this forum checking this factors. maybe im mad :)
    I should just copy and paste ;)

    btw. thanks for the respond Bsft
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  7. bsft

    bsft

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    Is this compact enough?
    2014-03-21 14.27.23.jpg 2014-03-21 16.43.58.jpg
    However, if you have a sketch of something in mind, post it up and we can discuss it.
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  8. tomkil192

    tomkil192 New Member

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    Woow. Great compact and simple design. I love it. Any youtube videos with it?
  9. bsft

    bsft

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  10. tomkil192

    tomkil192 New Member

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    Very good compact design. It would be nice to compare imersion feelings on your and different platforms.
  11. bsft

    bsft

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    I dont have comparisons written for every simulator I have built, but with a desk racer, surge is greater angle than sway, but a good profile adjust can make it seem the same.
    Here is another document I did a while ago between seat movers and full frames.
    Heres what I came up with, didnt record lap times. No frame made made me faster or slower, so times were about the same.


    Comparisons between simulators. Other people will of course differ with this comparison, so please add your thoughts.


    First things to consider, angle of actual swing of the frames and the profile written. Also, its a brain trick.

    If you want a big swinging frame, go hard, the biggest swing I have had is 14 deg total, but others have frames up to 25 deg. And thats for race, not just flight.

    Both frames use same motors and JRK control boards


    Seat mover with shoulder mounted motors.

    Generally ,a seat mover can give more precise motion detail as it has less over all weight to move than a full frame. However, too much movement can make it hard to hang onto the wheel or mash the juice pedal. And yes, the wheel and pedals are stationary, so proper placement to allow you being pulled away and pushed around has to be taken into consideration. But as said, it does give you the feeling of being moved around in a seat in a vehicle, even with a race seat to hold you in more. You tend to shift your body around to compensate for movement and also what your brain thinks you are moving like. You can still feel pitch and roll of track, but maybe a bit less as legs are still.

    Some SCN seat movers on videos have HEAPS of throw. It might look like fun, but can be too much and eventually make it tiring to drive the game.

    As mine is DIY and has 70mm travel of motor lever and at 600mm from the pivot , total angle is 6.5 degrees. Not much, but then again, too much may make it too hard. Other people will of course differ with this comparison.

    I had a seat mover of 12.5 degrees at one stage, so with a good profile, it was nice, but a harsh profile and WHOA! Fun but hard to hang on.


    Full frame with motors mounted near feet

    Full frames allow you , wheel and pedals to move with you. You dont really get sensation of being pulled, pushed around from pedals and wheels. Obviously not as much as a seat mover, but still there. You tend to feel a bit more of the motion of roll and pitch , when your whole body is getting moved around, I find.

    Seat mover can lose this a bit, but not really much.

    Motors mounted at feet on the frame in question, may take away some of the finer vibration and motion that shoulder mount gives, but then again, shoulder mounting motors would return that finer detail due to higher leveage point. It may lessen a bit due to the fact that a full frame requires a bit more power to move. But hey, just change the profile and increase the motor power a bit more.

    Although, I must say, once again, a good profile can give the same sensation in motion, be it from a different spot. Feet or knees instead of shoulders.

    Full frame is about 8 deg total swing. May not sound like much considering 4 deg from centre, but again, throw a decent profile in it and you feel like you are moving a lot more.


    Summary

    After a while I get the same sort of feeling from both my frames, even though they are different in design.

    In your choice of motion sim build, It will come down to watching videos of other frames, opportunity to play on sims when they are around to do so. Taking a look at pics, seeing what takes your fancy. Heck, even a seat mover can be converted to full frame later, add the extra bit, move pivot, and off you go. 2 seat movers I have sold, the owners have since converted them to full frames, their choice of course. They enjoy both frames they tell me.

    I have played on a $40,000 VRX dbox with 3 screens, SimX seat movers , impressive rigs, but motion was lousy I though. Although others whom have such rigs wind it up and get great results. Mind you, I dont have that sort of money to get one.

    I have been through 10 different 2DOF designs, starting with joyrider design with about 9-10 deg total swing with screen on it. Good fun, but I found it a bit difficult to focus ona screen moving with you. But thats just me.

    Then I moved onto development of more compact designs, with motors under rear, at knees, out the side, shoulder mount, at feet. Still 2DOF. Screen static.

    So thats how I go here. Each frame design is a new learn to drive experience I find. Nothing makes me go faster I think. I am slow regardless.

    I may have missed something and please add your thoughts as well. Its always good to compare notes.
    • Informative Informative x 4
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  12. tomkil192

    tomkil192 New Member

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    Woow that is a good answer. I think i will start with your compact design. It seems to be the best so far. Then later i will build my option to compare.
    I will probably use wheelchair motors for start. Any experience with them? What kind of psu's you are using?

    Thanks for your reply
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  13. bsft

    bsft

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    I use golf trolley motors like this https://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html , there is probably an equivalent motor from a supplier in the UK. @AceOfSpies or @noorbeast might know of a supplier.
    PUSs I use LED power supplies, they are new, and very reliable, not 2nd hand like server PSUs, I run 12v 40 amps at least each motor. Also I use the pololu JRK 12v12, they run 30 amps continuous all day with 45 amp spikes, and yes, the power supplies handle the extra spike of power needed.
  14. Barry

    Barry Active Member

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    I went for the crab pot motors from canada. They were the only option for me to get decent motors without spending crazy money.
  15. tomkil192

    tomkil192 New Member

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    Thanks guys. I was doing research and worm gear motor wins. You can buy them in uk for about £70 each. But we went completely of the subject. I will build 2 temporary type of platforms with different centre of gravity point and compare
  16. Barry

    Barry Active Member

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  17. tomkil192

    tomkil192 New Member

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  18. dance77

    dance77 New Member

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    좋은 소식 ~~
  19. Dusko Dogandzic

    Dusko Dogandzic New Member

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    can anyone please explain are there any major difference in simulation effects and which is closer to reality for 2dof and how it relates to weights and center of gravity:

    a) connection points for motors to be on the back of the seat
    b) connection points for motors to be on in front of pedals

    I`m mostly interested if someone had a chance to test both setups and which one feels more realistic.

    My primary focus is on RBR and dirt rally

    here is a plan for my rig so u have better understanding of what i intend to do.
    [​IMG]
  20. bsft

    bsft

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    @Dusko Dogandzic , Connections where the motors go does not affect centre of gravity. However, if you plan to have the screen moving with the sim , 50:1 or 60:1 boxed 200 watt 12v motors, and shouder mount at rear. Nothing else. Do not add under the sim as your planned design is very top heavy.

    Just for reference of seat move and full frame, heres something I did a while ago
    Heres what I came up with, didnt record lap times. No frame made made me faster or slower, so times were about the same.


    Comparisons between simulators. Other people will of course differ with this comparison, so please add your thoughts.


    First things to consider, angle of actual swing of the frames and the profile written. Also, its a brain trick.

    If you want a big swinging frame, go hard, the biggest swing I have had is 14 deg total, but others have frames up to 25 deg. And thats for race, not just flight.

    Both frames use same motors and JRK control boards


    Seat mover with shoulder mounted motors.

    Generally, a seat mover can give more precise motion detail as it has less over all weight to move than a full frame. However, too much movement can make it hard to hang onto the wheel or mash the juice pedal. And yes, the wheel and pedals are stationary, so proper placement to allow you being pulled away and pushed around has to be taken into consideration. But as said, it does give you the feeling of being moved around in a seat in a vehicle, even with a race seat to hold you in more. You tend to shift your body around to compensate for movement and also what your brain thinks you are moving like. You can still feel pitch and roll of track, but maybe a bit less as legs are still.

    Some SCN seat movers on videos have HEAPS of throw. It might look like fun, but can be too much and eventually make it tiring to drive the game.

    As mine is DIY and has 70mm travel of motor lever and at 600mm from the pivot , total angle is 6.5 degrees. Not much, but then again, too much may make it too hard. Other people will of course differ with this comparison.

    I had a seat mover of 12.5 degrees at one stage, so with a good profile, it was nice, but a harsh profile and WHOA! Fun but hard to hang on.


    Full frame with motors mounted near feet

    Full frames allow you , wheel and pedals to move with you. You dont really get sensation of being pulled, pushed around from pedals and wheels. Obviously not as much as a seat mover, but still there. You tend to feel a bit more of the motion of roll and pitch , when your whole body is getting moved around, I find.

    Seat mover can lose this a bit, but not really much.

    Motors mounted at feet on the frame in question, may take away some of the finer vibration and motion that shoulder mount gives, but then again, shoulder mounting motors would return that finer detail due to higher leveage point. It may lessen a bit due to the fact that a full frame requires a bit more power to move. But hey, just change the profile and increase the motor power a bit more.

    Although, I must say, once again, a good profile can give the same sensation in motion, be it from a different spot. Feet or knees instead of shoulders.

    Full frame is about 8 deg total swing. May not sound like much considering 4 deg from centre, but again, throw a decent profile in it and you feel like you are moving a lot more.


    Summary

    After a while I get the same sort of feeling from both my frames, even though they are different in design.

    In your choice of motion sim build, It will come down to watching videos of other frames, opportunity to play on sims when they are around to do so. Taking a look at pics, seeing what takes your fancy. Heck, even a seat mover can be converted to full frame later, add the extra bit, move pivot, and off you go. 2 seat movers I have sold, the owners have since converted them to full frames, their choice of course. They enjoy both frames they tell me.

    I have played on dbox, and scn simulators and the motion is set tame. Although others whom have such rigs wind it up and get great results. Mind you, I dont have that sort of money to get one.

    I have been through 14 different 2DOF designs, starting with joyrider design with about 9-10 deg total swing with screen on it. Good fun, but I found it a bit difficult to focus on a screen moving with you. But thats just me.

    I had 2 hire sims based on the Desk Racer for a while and over 100 players though they were immersive.

    8 professional drivers have played on those simulators as well, and they admit, its not real, but the immersion of being in game is.

    Then I moved onto development of more compact designs, with motors under rear, at knees, out the side, shoulder mount, at feet. Still 2DOF. Screen static.

    So thats how I go here. Each frame design is a new learn to drive experience I find. Nothing makes me go faster I think. I am slow regardless.

    I may have missed something and please add your thoughts as well. Its always good to compare notes.
    • Like Like x 1
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