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Starting my motion simulator

Discussion in 'DIY Motion Simulator Projects' started by mrbeginner, Apr 14, 2012.

  1. mrbeginner

    mrbeginner Active Member Gold Contributor

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    Hello to you all.

    I'm been watching this site many years and now i find the solution to my own project. The FernVeilleux zero gravity project is something what i like and i ask him to help me.
    First advise was that is better to open new topic so i can find help in problems and maybe project is finished in some day..

    I hope that the sim is ready in 12month but if not then its not :eek:

    First thing is to find air cylinder what is big enough to lift me, wheel&pedals and seat (100-120kg)

    In my garage i found 2 pcs ⌀20mm and 80mm stroke and one ⌀25mm and 100 stroke but is those too little?

    If they are too little then i go to local junkyard where i find many other parts to my projects.

    Peter
  2. bsft

    bsft

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    Probably send a PM to FernVeilleux and look at his thread would be a good start.
  3. FernVeilleux

    FernVeilleux New Member

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    Congratulation Peter,

    I will follow your project and help you on all aspect I can.

    Yes you are right these cylinders are too small, the 25mm will support only 35 Kg @ 100psi

    With 2 cylinders you can have 40 or 50 mm dia. but they both have to be the same diameter. As for stroke it can be up to 300-400 mm with a minimum of 150mm and they do not have to be the same since you will never use the full length. I will explain later and post schema.

    Fern
  4. FernVeilleux

    FernVeilleux New Member

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    One more thing,

    Wait until you see my schema before buying parts to make sure you understand what you must be looking for.

    Fern
  5. FernVeilleux

    FernVeilleux New Member

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    Hi Peter,

    Since it is what you asked, let's start with positionning arm. I will first explain what I did then what I would suggest.

    Sorry but if I try to draw in 3D, it will take forever.

    From the top drawing you see the pivot point is in front of my feet and when sliding to the side the movement is an arc.
    Top view 1.JPG
    It is exactly what I wanted. It involved making a positioning arm that was finally more work than expected. It has to clear the space in front for my feet, make sure that it was easy to get on the seat, was stiff enough, needed an attaching point, etc. Bending and making halves similar was a pain. The first one only had one tube and was not stiff enough for the job.
    AArm front.JPG AArm rear.JPG
    My suggestion instead is this :
    let's draw reference lines to the limits of movement on either side and draw new arms each side from the pivot to the reference lines behind the seat like this
    Proposed.JPG
    now let's cut the new arms at the intersections with front arc and we have this with their arcs.
    With new arms and arcs.JPG Proposed 2.JPG
    and when we move the seat to the right, we have a position that is almost the same as before, no one would feel a difference
    With new arms clean 1.JPG
    after cleaning up all the reference lines it is much easier to see
    With new arms clean 2.JPG
    On the side view we see that we have a very simple arm without bends, just 2 heims rod ends to a straight tube and support installed just below.
    Side view.JPG
    Now we see why it is best with 2 cylinders than one which would have to go under the seat with upper attach point lower than c.g.
    The support must NOT be attached to the arm but to the seat sub-frame close to c.g. and I recommend at an angle instead of vertical for efficiency on side to side movement. With my support it was not easy to make it work, because of weight shift I needed castors and anti-roll bar to make it what I wanted.
    Also note that now it needs a much shorter base than mine.

    So what is the first step ?
    Do like car designers do, they start with the passenger compartment. Why ? Because if they design the chassis and suspension first they migth find later there is not enough place for the driver's feet and they might have to redesign again. I had lots of clearance problems because I had most of the base done before I made the seat.

    Start with the seat frame. Find the seat you will use, define where the pedals, steering and shifter will be. Think what it will be like when you are going to race. Do you want to make it easy to take position in the seat or you want to make it like a F1 that takes 5 minutes with the help of mechanics. My new design will have only one tube for the pedals and it will not be centered but to the right and the steering will also move to the right, there will be nothing in front to make it very easy to board. Your frame should NOT have attach point for the actuators/motors, just the seat, pedals, steering and shifter. The keyboard does not need to be there. It will later be rubber mounted to a very simple sub-frame which will have the required attach points for the positioning arms, cylinders and actuators/motors. If you want to use tracks to make it adjustable for others it is OK. Finally make it light and if it is a little springy like mine is, it is OK, race cars are shaky. :yes:

    Once the seat frame is done, you will have to take measurement and find the c.g. point before doing a simple sub-frame. It's role is to join the seat to the base, allow to use rubber mount to protect the actuators/motor gears AND reposition the seat easily in case the balance is not right. Later after you figure the height your seat should be to make the actuators/motors efficient, it will be easier to define the specs your cylinders should have, at this point you will have about half of the work done. It will be time for electronics then and peripherals like where the keyboard should be, support for your monitor(s), etc.

    I explained what I did and what I think is a better, simpler design. You choose what you like best and if you like fancy or flashy panels with stickers and everything you can still add them later if you will. ;D

    In a next post I will explain my view about attach points.

    Fern
  6. mrbeginner

    mrbeginner Active Member Gold Contributor

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    Hello!

    That looks nice, but one thing i'm not so sure. because if those arm's going to back and the seat move side to side.
    then the seat move front to back 2-3cm is that problem?

    Untitled.jpg
  7. FernVeilleux

    FernVeilleux New Member

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    Hi Peter

    The limit is the misalignment the rod ends can take which is about 20 degrees. At 20° with an arm of 480mm, the travel side to side is 166.702mm and the front to back is 1.587mm
    Arm movement.jpg
    Fern
  8. mrbeginner

    mrbeginner Active Member Gold Contributor

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    Ok! Then that's look good to my project. Now i just go to garage and make the seat frame. Maybe not today but soon. I send pictures when i begin.
  9. FernVeilleux

    FernVeilleux New Member

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    Hi Peter,

    Here some ideas for a seat frame Seat frame.jpg
    Best is starting with the main tube, decide the length and metal thickness, add seat brackets and maybe reinforcement, then the pedals and shifter.
    Tack weld only and weld completely just before painting when you are sure it is right

    Fern
  10. mrbeginner

    mrbeginner Active Member Gold Contributor

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    Hi!

    I've been thinking same way and this what i start to do. versio 1.jpg
    I use 25*25 and 30*30 1,5mm thick steel pipe. I put hinge and little locking device on the wheel table and the pedals are adjustable front to back.
  11. FernVeilleux

    FernVeilleux New Member

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    Hi Peter,

    Nice design.
    See if you can remove those seat brackets, they could raise the seat to high when finished. You will want the pushrod to be as long as possible for they stay vertical on sway, I know they will not but you want a minimum of lean for efficiency.

    You are doing fine, keep on

    Fern
  12. mrbeginner

    mrbeginner Active Member Gold Contributor

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    Hi to you all!

    First raw seat version is ready. 2012-05-01-320.jpg
    I remember the first good rule of making things KISS (keep it simple stupid) 2012-05-01-321.jpg Now i have easy access on the chair and enough adjust for wheel. 2012-05-01-322.jpg Now i can attach this frame easy in sim. I just make clamps what i mount on those side tubes. Next i just have to do little finishing smilie_schweissen (1).gif .
  13. bsft

    bsft

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    Thats a nice design there, it will be interesting to see how the frame flexes as you do not have a brace on the left hand side though, but still, great job there!
  14. mrbeginner

    mrbeginner Active Member Gold Contributor

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    Hi!

    I was thinking the bracket and this is what come in my mind

    bracket1.jpg

    It's bolt on the seat frame and can be moved if it not right place.
    Maybe i connect brackets to each other so they can be moved with some kind of trapezoidal screw

    bracket2.jpg

    If you have any ideas then it's better to tell. Because afterward you can say i told you so if i do wrong movement :5+5:

    Peter
  15. bsft

    bsft

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    Never a told you so, just all part of the fun of home sim building!
    :thbup:
  16. FernVeilleux

    FernVeilleux New Member

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    Next step

    Well done Peter, it looks good to me.

    Sure it will flex and it is OK! Mine flexes and I never had a bad feeling about it. Having 2 tubes to the right is not much different than 2 on opposite sides.

    I guess you took place on the seat and tested for stiffness by pushing with your legs not only with your feet. When fully welded it will be stiffer but you should not do it now, you might have something to correct.

    Have you figure where the CG is yet ? If you need help on this these links will explain how to do it
    http://www.wikihow.com/Calculate-Center-of-Gravity
    http://en.wikipedia.org/wiki/Center_of_mass

    However, there is no rush to find it until you are ready to attach it to the sub-frame. Between the seat frame and the sub-frame you could optionally use sliders if you often let friends use it. I would recommend using rubber isolators if you use motors with plastic gears.

    This post is supposed to be about attach points.

    Years ago someone wrote a book with this title : A WEAK CONCEPT BROUGHT TO PERFECTION
    That book was about the Porsche 911. Weak concept because of it's configuration with the motor in overhang and the spin effect force that results. However Porsche managed to make it one of the great cars of all time. The 911 is not the only weak concept that had a great success, Microsoft Windows also has a great success mainly due to it's aggressive marketing.

    I will show another weak concept I hope you will avoid.
    This drawing shows a gate and the arrow the force someone is applying to open it. Clearly it is not efficient and a loss of energy. Not efficient.JPG
    This other drawing shows another way that everyone will agree is the most efficient. Efficient.JPG

    If we just rotate the first drawing 80° it becomes the drawing of what some builders do Seat1.JPG Seat2.JPG If it is not efficient for a gate could it be for a sim ? It does not mean that it will not work, simply that it is a waste of efforts/energy not matter the angle at the bottom or the distance between mounting points at the bottom, what is efficient is the angle the force is applied in relation with the rotation point and that should be as close as possible to 90°. The next drawings all show efficient ways Seat3.JPG Seat4.JPG Seat5.JPG Seat6.JPG

    In deciding the positions of pivot and push rod points do not forget that all the movements could cause some binding of the push rods. The limits are always the maximum misalignment the rod ends can take that is 20° for most of them. Would it be a good idea to have the ones that can take 27° ? I'd say not for a race sim and 27° would not be enough for a flight sim.
    You may think that 20° is not much since it means 10° in each direction. If you download pictures of racing or passenger cars and study the lean angle they attain you will find that 8° is about the maximum. In all your calculations you should stay within 9½°.
    The distance between pivot and rod point is dependent of the power of your motor/actuator. On my sim, the distance between rods R/L is 40cm and F/R is 56cm.

    These drawings show different view you have to consider.
    Seat7.JPG Seat8.JPG Seat9.JPG Front1.JPG Front2.JPG Front3.JPG RearI.JPG RearI1.JPG RearO2.JPG
    You will spend some time at drawings before returning to your garage.
    Keep in mind the 20° rule.
    Good luck and KISS

    Fern
  17. mrbeginner

    mrbeginner Active Member Gold Contributor

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    Hi!

    So if i understand correct those pictures, it's better connect pushrods and aircylinder in same place near CG? Then those cylinders don't affect anything else than seat heigh.

    Peter
  18. floriske.nl

    floriske.nl Member

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    I'm very curious about this project. Especially since Fern is helping you out.

    Looking good so far!
  19. FernVeilleux

    FernVeilleux New Member

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    Hi Peter,

    Pushrods must attach at some points in relation with the rotation of the seat in a way to avoid binding and air cylinders only support the seat and will follow the motors. Close to CG is preferable for the motors/support but I think if it is right on that it could make a strange feeling on braking/acceleration and lateral movement, no change in vertical movement. I think it is best to have the rotation point a little below CG maybe100-150mm. I calculated the CG on my rig is about at my belt buckle.

    You understand that the supports also must attach to the sub-frame. I did not write everything because I thought there was enough stuff to think about with what I wrote. It is in fact quite simple but we must not overlook anything or we could have to do corrections that are not easy (waste of energy and money, and maybe wife unhappy with waste of money).

    I will make a few more drawings of possible ways of supporting the seat and this information is needed before you build the sub-frame. It will give you a much clearer view of your finished sim.
    I hope I can do it this week but you do not have to just wait for this, now is also the time to find your motors/actuators if you do not already have them.

    I will take pictures of some I have and post things to consider before you select anything. A day or 2 I need for this.

    Fernand
  20. mrbeginner

    mrbeginner Active Member Gold Contributor

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    Hello!

    Those brackets what i was thinking, are one part of sub-frame. I was thinking that all connections meaning motors, cylinders, pushrods and stabilizer bar are connect those brackets. This way i have one point where to start subframe and it's easy to lock subframe. Not so easy to explain but i try to draw it this evening if family let me...