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Compact 2dof seatmover

Discussion in 'DIY Motion Simulator Projects' started by FargusFaustmeister, Mar 12, 2018.

  1. FargusFaustmeister

    FargusFaustmeister Member

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    Hello everyone. I've already introduced myself in the new member thread but I'll put a quick bio here as well. I am a mechanical engineering technologist and professional cheapo. I easily get obsessed about things that interest me and ooooh boy does motion sim VR racing interest me. Pursuant to my true calling as one who doesn't like to spend much money on things I intend to take a stab at designing a low-cost, true-linear motion sim. I have two main objectives with this build:

    1) Achieve lowest possible build cost to increase accessibility of multi DOF motion sim rigs.

    2) Use an iterative design process to enhance low-cost manufacturability.

    I believe that we should build on the shoulders of those who've gone before us so I intend to pull concepts from lots of other builds, but I also want to contribute to the community and hopefully add some [potentially disastrous] alternative designs to the quiver.

    I have decided to focus my effort on two axes to start: heave and sway. I want to build traction loss in eventually but for now I'm going to focus my efforts on these two axes of motion. I'll update this thread as I begin producing documentation for the project.

    Thanks for reading!

    /end of preamble.
  2. Ads Master

    Ads Master

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  3. FargusFaustmeister

    FargusFaustmeister Member

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    build a sim that follows a basic, proven design. So! With that spirit in mind...

    I checked my local used stuff website and found FIVE marine wiper motors for $30CAD. That's just about the sweetest deal I've ever seen since everything on the west coast of the GWN is so damn expensive compared to everywhere else.

    Two of the motors turned out to be sunroof jobbies so I haven't messed with them, but I inspected the other three and got some interesting specs.

    20180321_195149.jpg

    The two on the top are DOGA 319 series motors. The model is 3713 which I can't find information for, but they're 24V and seem to have on the order of 7Nm nominal torque and 50Nm starting torque. So that's really great! Amperage draw is probably on the order of 25A or so, so I'm guessing these are ~500W gear motors that chooch around 60Ripp'ems. Can't find much else on these so I'll have to do some testing to get values. Buddy who sold these to me said that one motor is good but the gears are toast, and the other gears are good but motor is pooched. So I'll have to investigate what's what but I only need two so here's hoping I can salvage the parts I need. The other motor is a B-Hepworth 50Nm dual speed wiper motor. Pretty scant on information here too so I'll have to look around.

    So that's that. $30 in to the game so far and now I'm looking for a drive shaft. I have lots and lots of research to do so don't expect anything too quick ;)
    Last edited: Mar 22, 2018
  4. FargusFaustmeister

    FargusFaustmeister Member

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    :cheers

    Found a BMW car seat for free on my local used-stuff site. Seller had it bolted to a coffee table to use as a gaming chair so it's gone from one quirky owner to another I suppose :p The seat is in VERY good condition, save the small delamination of the pleather. Apparently this is a common issue though, and since it is for a simulator I am not that fussed.

    BMWcarseat.jpg

    It has the mounting bracket and all of the adjustment functions work, so I'll have to do some clean sabotage to keep my users from shifting the COG.

    I also did some research today and decided to go with the Pololu Dual G2 High Voltage 24v14 driver because my motors are 24V and I only have to buy one of these :) I already have an Arduino Uno kicking around and I'm quite comfortable with it. I also like the idea of a single compact shield to minimize footprint and maximize cooling.

    Screen Shot 2018-04-04 at 8.12.52 PM.png

    I also have a slightly horrifying power situation going on in my house right now:

    20180404_201643.jpg

    Yup, those are 4 x 8000mAh LiPo batteries, 24V nominal (approximately); they can provide 24V @ 320A... so ~7600W... waaay more power than a couple linked server PSU's, quieter, and much more freaky. Luckily they're in very good shape, with no bloating or scratches lol. I got them for free, plus some others, a power supply and pretty nice balance charger from one of my friends. I'm juuuuuuust barely comfortable with them since they're in FireSafe bags but my plan is to get a second container to put them in and create some ventilation holes, then layer some charcoal filter material or something in case they go *POP*. I don't want black smoke filling my house if they burn.

    I'm going to put them into custom enclosures with hot-swappable power connectors and directed venting/cooling so they can be plugged installed and removed from the sim rig when I want to use them. Any opportunity to reduce the chance of fire while still being able to use these conveniently is one worth taking!

    So that's it for now. I am saving for a wedding so I simply can't afford to put any real capital towards this project, but for $30 I think I'm doing pretty well :D:cheers
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  5. MarkusB

    MarkusB Active Member Gold Contributor

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    My Motion Simulator:
    2DOF, 3DOF, DC motor, Arduino, Motion platform
    Well, maybe a server PSU does not give you 320 A, but at least it provides you with continuous power instead of just some minutes.
    8000 mAh means that the batteries provide 8 A (which is not really much for a motion simulator) for one hour. So if your motors need 20 A in average, you can enjoy your simulator for 24 minutes before charging. The 320 A you mentioned would be provided for 1.5 minutes.
  6. FargusFaustmeister

    FargusFaustmeister Member

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    That's a great point, but there are details I neglected to mention. I'm going to wire them in parallel to double their capacity, and at this pricepoint ($0.00) I'm happy to take a break every 45 minutes. Plus I figure I'll be using much less than 20A average so I'll have the benefit of batteries that can handle short spikes of extreme amperage demands. In the end (through personal experience and some guesswork) I figure I'll get more than an hour from a single charge and I have two sets so I should be good :)
  7. JonBakhol

    JonBakhol Member Gold Contributor

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    Ha @FargusFaustmeister ,

    Nice thread, I'm doing the same as you know.
    With the wipers, I think you are the luckiest guy indeed.
    Hope to see some nice pics and video soon. :)

    Ride on,
    Bakhol
  8. SeatTime

    SeatTime Well-Known Member

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    My Motion Simulator:
    AC motor, Arduino, Motion platform, 6DOF
    Nice - the price is right - especially as your getting married. Remember, its Her 'day'/wedding - most guys would not care, your just there to make her look good and pay for it :D. Good luck :thumbs.
  9. FargusFaustmeister

    FargusFaustmeister Member

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    I definitely scored when I found those wipers. They're dual speed/direction so I have to open the case and remove any advanced circuitry so the Driver I get can do all the control without anything in the way. Wedding is putting everything on hold so until I have the bills paid I won't be able to move forward on the more important components, but I may try to set up an Arduino to test SimTools outputs and understand the program. Thanks for following, I hope your build goes well too :)

    Hahaha "Happy Wife, Happy Life". I've heard that advice more times than I can count but it certainly has merit. I'm actually more involved in the planning etc. than any of my fiancé's friends' husbands were. I've been a bit of a prick at some points but you can't have everything without spending a TONNE more money so I was pretty much just the "brake man". I think we've come to a great plan though so we're both very excited. Thanks for the well wishes :)
  10. alexdixey

    alexdixey Member

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    My Motion Simulator:
    3DOF, DC motor, Arduino
    BMW seats. Best bang for the buck!!
    They last forever, Great ergonomics nice and durable upholstery.
    The junkyards are usually stocked with them with passenger side almost brand new!
    • Agree Agree x 1
  11. FargusFaustmeister

    FargusFaustmeister Member

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    This project, like so many others, has taken an interesting turn.

    I tore apart some old home-made speaker towers during a snowstorm in February and rebuilt them into a somewhat rigid mounting platform for a used G27 that I picked up for $130.

    [​IMG]

    It was pretty loosy-goosy and had a tendency to get away from you while you were stomping the brake or clutch, but the experience was still amazing. Sim racing went from being impossible and sickening to only slightly impossible, but still sickening ;) I played for a few more weeks, sporadically, but always turned off by the rig slipping forward. Queue the modified plan:

    Designing and building a motion sim rig was too much for me to bother with for a first iteration; I decided that a static rig that could be upgraded with bass transducers would be good enough to simply get going. My 8020 quote came back as being $1000 or so, so I decided to do switch to "rough it up on the fly" mode. A sketch and an email later and my uncle and I were cutting up 1.25" x 0.25" steel tube.

    20190404_181514.jpg

    I had a couple of measurement boo-boos and made my overall width the C-C distance for the mounting holes of my seat, so I ground out the welds and started again another day. Got it all welded, then painted with some rust-inhibiting flat black spraypaint, then took it home to assemble:

    20190417_125958.jpg
    20190417_132248.jpg 20190417_162023.jpg

    I learned that sheet metal screws are tough to get through 1/4" steel, but luckily had a HSS bit hanging around. Got the steering crossbar installed, glued on some planks from the "first sim rig" and screwed the pedals on to them (and almost superglued my fingers to some cardboard, and then together, a few times) and ended up with this:

    20190419_124448.jpg

    It's rough; the steering assembly is clamped to the frame because I didn't want to drill anymore holes, and the seat is secured with through two of the frame levelling feet bolts and a single sheet metal screw, but I don't care; I LOVE IT. I'm able to sit semi-comfortably for an hour or two at a time doing 25 minute practice laps of the beginner series of PC2 and SO SO SO enjoying the rigidity of my components. The steering wheel doesn't slip away, the pedals are solid, and my seat can be adjusted depending on the car I'm in.

    The biggest advantage is that I can rule out rig-slippage and woobly-goobly from my sharty racing technique and focus on WHY I keep going wide in the corners (I brake early and turn late, currently working on that). I am truly loving the experience of sim racing now, and I'm slowly becoming better ;) I've worked up to 55% AI skill and moderate aggression to try and balance being a beginner and building confidence with pressure to perform consistently and improve to get away from the pack. I'm still winning by 7-10+ seconds so I have some more tweaking to do, but I'm happy to keep doing dozens of laps in the pursuit of the feeling of negative deltas.

    So where to from here? I've been reading and re-reading Grigory's 6DOF build and am settling myself into the long term planning phase for my own setup. I race in VR exclusively so making the rig extremely light and designing with a VERY short throw (probably less than 80mm of linear travel) I should be able to achieve a pretty serious Gough-Stewart style rig with mid-power actuators. Or not, who knows? ;)

    This concludes my "2DoF Seatmover" thread. Thanks for reading!

    Attached Files:

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  12. yellofella

    yellofella Member

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    Hi fargus, your sim looks like my first sim nearly 10 years ago. the first things I did was to make sure everything was tight and brace any frame wobbles I had so I felt confident nothing was going to move or come loose. I bolted my g27 steering wheel to the frame instead of using the plastic clamps and bolted down the pedals but pitched the back up so they sat at about 20 degrees bringing the pedels more vertical at rest position. I would also recommend upgrading the brake pedal to a g27 load cell conversion and directly plugging the pedals into your pc and not via the steering wheel. you could do this 2 ways.
    The first easy way is to use a leo bodnar g27 pedal cable (Logitech® G25/G27/G29/G920/DFGT/DFP or Generic Pedals Adapter so you will have a load cell brake with improved 10 bit resolution.
    The second is to buy a leo bodnar BU0836-LC Load Cell Joystick Controller and wire all pedals into it then you would have 12 bit resolution on all 3 pedals. This is the way I would go as ive got a very expensive set of tilton 600 pedals that use this controller.
    better precision pedels will help bring lap times down and keep them more consistent
    I would also recommend using a power supply if you are thinking of a 2 dof as you will soon find you need more power. I used 2 car batteries in parallel when I started but got bugged keep having to charge them all the time and they only lasted about 90 mins then you could feel the motors struggling under breaking so invested in a 480w led power supply for about £25 and well worth it.
    good luck with the build