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2 DOF Simulator Design and Build

Discussion in 'DIY Motion Simulator Projects' started by Chris Chopping, Nov 13, 2020.

  1. Chris Chopping

    Chris Chopping New Member

    Joined:
    Jul 24, 2020
    Messages:
    9
    Occupation:
    Mechanical Engineer
    Location:
    Melbourne, Australia
    Balance:
    93Coins
    Ratings:
    +5 / 0 / -0
    My Motion Simulator:
    2DOF
    2 DOF

    Firstly, welcome to my 2 DOF design and manufacture. I will give an overview of my design and calculation along with any troubles I had on the way. I am still yet to use the rig as I have just got the motors and need to make shafts for them.

    Secondly, this build was during lockdown, so it has taken so much longer to receive parts or even ordering parts (up to 6 months even).

    Design:

    My first design idea was to build a rigid rig. This rig was to be f1 spec. F1 spec was to have myself in a seating position like an F1 driver with the legs up high and wheel close to my chest. Once I realised that this would be pretty easy to make, I decided to challenge myself and make a rig that can move. I decided that a 2 DOF rig would be best to start with as going to 3 DOF or even 6 DOF right off the bat would be too complicated.

    I used solidworks as my design platform (I am a mech engineer). I had a rigid wooden rig that was very simple I made a couple of years ago and knew the most important thing was the economics.
    So I measured myself up in a seating position that was comfortable with blocks of wood and pillows (pretty simplistic), all the angles and lengths were measured and chucked into CAD as a 2D drawing like so:

    [​IMG]

    I then moved to looking at what I currently had in terms of racing wheels and chairs etc as I wanted it to be as low price as possible. I had an old office chair and the G29 Logitech wheel and pedals.
    The chair was simplistically cadded, weighed along with the G29 setup. I then mated my body to the chair. What made this nice is that I didn’t have to put the chair at some weird angle to my body. The steering wheel I wanted facing flat towards me like a proper racing car (not like a truck wheel) and the pedals to either be facing completely flat or parallel to my feet. Therefore, the pedals would have to have at least two different positions.

    [​IMG]

    [​IMG]



    I then got to thinking about how to make it low in mass. I use just one middle steel tube as my support and from doing the numbers it was strong enough to take all that load. Everything was to be mounted to that tube. I used M6 bolts and nuts for all my connections as it is plenty strong enough to hold it all.

    [​IMG]

    After that I designed the base. The base needed to be strong to hold the motors and also not tip when the simulator was moving.

    [​IMG]

    I know that motors aren’t always super powerful so if I calculated the Centre of Gravity (COG) to be exactly over the universal joint then the only mass that the motors have to move is the inertia and any overhanging mass from angle changes.

    [​IMG]

    From CAD, the COG is very close to the centre of the UJ. I marked out extra holes in the top tube just in case it was wrong. Using this offset I could create a spreadsheet that calculates the RPM, torque

    etc that my motors will need from all of my parameters. I can share this if there is enough interest.

    [​IMG]

    I don’t own a lathe or mill so I would have to mark out all the measurements and drill them myself.
    TIP: If you’re using a 6mm bolt for instance and you are marking them out yourself, drill the hole to 6.5mm as your measuring tolerance will not be exact and nothing will line up.

    The steel I got from a supplier who cuts it all to your specs for a good price.
    [​IMG]

    I added extra holes for manoeuvrability for friends or myself if I gain a few kgs…

    [​IMG]

    I drilled all holes and welded the steering wheel base. Mind you this took a few days.

    I bolted the seat down and used a wooden board as my mount for the steering wheel. To reduce mass, I used an aluminium plate for the pedal mounting.

    The motors I chose which are from motion dynamics were sold out and therefore didn’t have access to them to create my motor shafts and mounting solutions (they supply a drawing but all info is not stated)., therefore I created what I thought might be the dimensions in CAD and then tacked the base together.

    [​IMG]
    I made sure the UJ I ordered was very similar in length to the base bracket I had so I didn’t have to use any spacers. The brackets I used on the UJ are a turned piece of steel that is pressed into the UJ and 5mm steel plate that was drilled out. From calculations and simulation, this strong enough for my application.

    The mass of my top piece with everything mounted is 12kg and the bottom welded piece is 5kg. This makes it super easy to move around the house or to work on.


    I gave it a lick of paint.

    [​IMG][​IMG]


    I decided I needed a tv mount so I made a simple bolt in TV stand and painted it, this fits between the sim.

    [​IMG]

    I then moved to the electrical side of it. This is where my knowledge stops and lots of research had to be done. Thankyou to this site for helping me out.

    I designed a foldable aluminium box that could fit all of my components and can make the use of keeping everything housed and can move around as everything uses connectors.

    I cadded it all and created sketches to know the lengths of wires and also the connector sizes. [​IMG][​IMG]

    Initially I had planned to use 2 12V power supplies and 2 monster moto shields. After wiring it all up.. the magic smoke appeared and blew a monster moto… Turns out one of the positive terminals was hooked up to the negative power supply. Don’t do this…

    [​IMG]

    I am now just going to use a single 20A power supply with a single monster moto to learn and then upgrade later on once everything Is working.
    After wiring it all and using SMC3 utilities and reading how to use it, I have just turned the motors!

    I will update this thread as I get closer to using it along with my parameters and the final assembly.

    Happy to answer any questions!

    Attached Files:

  2. Ads Master

    Ads Master

    Balance:
    Coins
    Ratings:
    +0 / 0 / -0
  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
    Jul 13, 2014
    Messages:
    15,804
    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    115,446Coins
    Ratings:
    +9,228 / 46 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    Great to see the overview of your project.

    Unfortunately the images in your post do not display.
  4. Chris Chopping

    Chris Chopping New Member

    Joined:
    Jul 24, 2020
    Messages:
    9
    Occupation:
    Mechanical Engineer
    Location:
    Melbourne, Australia
    Balance:
    93Coins
    Ratings:
    +5 / 0 / -0
    My Motion Simulator:
    2DOF
    Post updated with non corrupted photos!

    2 DOF

    Firstly, welcome to my 2 DOF design and manufacture. I will give an overview of my design and calculation along with any troubles I had on the way. I am still yet to use the rig as I have just got the motors and need to make shafts for them.

    Secondly, this build was during lockdown, so it has taken so much longer to receive parts or even ordering parts (up to 6 months even).

    Design:

    My first design idea was to build a rigid rig. This rig was to be f1 spec. F1 spec was to have myself in a seating position like an F1 driver with the legs up high and wheel close to my chest. Once I realised that this would be pretty easy to make, I decided to challenge myself and make a rig that can move. I decided that a 2 DOF rig would be best to start with as going to 3 DOF or even 6 DOF right off the bat would be too complicated.

    I used solidworks as my design platform (I am a mech engineer). I had a rigid wooden rig that was very simple I made a couple of years ago and knew the most important thing was the economics.
    So I measured myself up in a seating position that was comfortable with blocks of wood and pillows (pretty simplistic), all the angles and lengths were measured and chucked into CAD as a 2D drawing like so:

    person.png
    I then moved to looking at what I currently had in terms of racing wheels and chairs etc as I wanted it to be as low price as possible. I had an old office chair and the G29 Logitech wheel and pedals.
    The chair was simplistically cadded, weighed along with the G29 setup. I then mated my body to the chair. What made this nice is that I didn’t have to put the chair at some weird angle to my body. The steering wheel I wanted facing flat towards me like a proper racing car (not like a truck wheel) and the pedals to either be facing completely flat or parallel to my feet. Therefore, the pedals would have to have at least two different positions.

    Top.png Pedals.png pedals 2.png

    I then got to thinking about how to make it low in mass. I use just one middle steel tube as my support and from doing the numbers it was strong enough to take all that load. Everything was to be mounted to that tube. I used M6 bolts and nuts for all my connections as it is plenty strong enough to hold it all.

    top assembled.png

    After that I designed the base. The base needed to be strong to hold the motors and also not tip when the simulator was moving. base.png


    I know that motors aren’t always super powerful so if I calculated the Centre of Gravity (COG) to be exactly over the universal joint then the only mass that the motors have to move is the inertia and any overhanging mass from angle changes.

    COG.png

    From CAD, the COG is very close to the centre of the UJ. I marked out extra holes in the top tube just in case it was wrong. Using this offset I could create a spreadsheet that calculates the RPM, torque

    etc that my motors will need from all of my parameters. I can share this if there is enough interest.
    assembly.png


    I don’t own a lathe or mill so I would have to mark out all the measurements and drill them myself.
    TIP: If you’re using a 6mm bolt for instance and you are marking them out yourself, drill the hole to 6.5mm as your measuring tolerance will not be exact and nothing will line up.

    The steel I got from a supplier who cuts it all to your specs for a good price.
    steel.jpg

    I added extra holes for manoeuvrability for friends or myself if I gain a few kgs…
    build1.jpg


    I drilled all holes and welded the steering wheel base. Mind you this took a few days.

    I bolted the seat down and used a wooden board as my mount for the steering wheel. To reduce mass, I used an aluminium plate for the pedal mounting.

    The motors I chose which are from motion dynamics were sold out and therefore didn’t have access to them to create my motor shafts and mounting solutions (they supply a drawing but all info is not stated)., therefore I created what I thought might be the dimensions in CAD and then tacked the base together.
    base build.jpg

    I made sure the UJ I ordered was very similar in length to the base bracket I had so I didn’t have to use any spacers. The brackets I used on the UJ are a turned piece of steel that is pressed into the UJ and 5mm steel plate that was drilled out. From calculations and simulation, this strong enough for my application.

    The mass of my top piece with everything mounted is 12kg and the bottom welded piece is 5kg. This makes it super easy to move around the house or to work on.


    I gave it a lick of paint.

    Paint.jpg Paint1.jpg


    I decided I needed a tv mount so I made a simple bolt in TV stand and painted it, this fits between the sim.

    TV.jpg

    I then moved to the electrical side of it. This is where my knowledge stops and lots of research had to be done. Thankyou to this site for helping me out.

    I designed a foldable aluminium box that could fit all of my components and can make the use of keeping everything housed and can move around as everything uses connectors.
    Exbox2.png Ebox1.png
    I cadded it all and created sketches to know the lengths of wires and also the connector sizes.

    Initially I had planned to use 2 12V power supplies and 2 monster moto shields. After wiring it all up.. the magic smoke appeared and blew a monster moto… Turns out one of the positive terminals was hooked up to the negative power supply. Don’t do this…


    I am now just going to use a single 20A power supply with a single monster moto to learn and then upgrade later on once everything Is working.
    After wiring it all and using SMC3 utilities and reading how to use it, I have just turned the motors!

    I will update this thread as I get closer to using it along with my parameters and the final assembly.

    Happy to answer any questions!
    • Like Like x 2
  5. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
    Jul 13, 2014
    Messages:
    15,804
    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    115,446Coins
    Ratings:
    +9,228 / 46 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    What motors do you plan on using, as compact designs require plenty of torque?
  6. Chris Chopping

    Chris Chopping New Member

    Joined:
    Jul 24, 2020
    Messages:
    9
    Occupation:
    Mechanical Engineer
    Location:
    Melbourne, Australia
    Balance:
    93Coins
    Ratings:
    +5 / 0 / -0
    My Motion Simulator:
    2DOF
    Planning on using a 200W 20Nm worm drive motor. Rated to 17A
    Hopefully by my calculations that it is enough!
  7. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
    Jul 13, 2014
    Messages:
    15,804
    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    115,446Coins
    Ratings:
    +9,228 / 46 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    They can work for moderate loads, though use a very conservative lever CTC, as you want all the torque you can get.

    They will be back driven when up-powered, so take that into consideration with respect to the likes of pedal plate clearance to the floor.
  8. Chris Chopping

    Chris Chopping New Member

    Joined:
    Jul 24, 2020
    Messages:
    9
    Occupation:
    Mechanical Engineer
    Location:
    Melbourne, Australia
    Balance:
    93Coins
    Ratings:
    +5 / 0 / -0
    My Motion Simulator:
    2DOF
    Thanks for the tip noorbeast!
    Currently the motors will be underpowered due to the supply I’m using (this was just to get an understanding of the electrical side of things and didn’t want to blow anything up) but I will upgrade in due time.
    My lever is conservative as well which I’m hoping to attach all today and talk about
    • Like Like x 1
  9. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
    Jul 13, 2014
    Messages:
    15,804
    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    115,446Coins
    Ratings:
    +9,228 / 46 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    For future reference I use 200w motors with 60:1 wormdrives on my compact rig and they can't be back driven.

    Looking forward to your project updates :thumbs
  10. Chris Chopping

    Chris Chopping New Member

    Joined:
    Jul 24, 2020
    Messages:
    9
    Occupation:
    Mechanical Engineer
    Location:
    Melbourne, Australia
    Balance:
    93Coins
    Ratings:
    +5 / 0 / -0
    My Motion Simulator:
    2DOF
    Update:
    Attached the motor shaft today along with the arms. Found that the shaft was a little sloppy inside the motor so i decided to drill it out to a 5mm hole (was 4.3) and use a shoulder bolt. It has decreased the slop but there is still a slight movement which would be due to the shaft not being press fit. (upgrade for another day!) 124671399_1694599187384970_5252696999354357781_n.jpg
    124989487_2443769615927420_4627489797703146769_n.jpg

    Using the SMC3 tools, I calibrated it and had to swap motor 1's pot as it was moving in the wrong direction.
    Once i had done that i played with some values and finding after a certain period of time just using the Sin wave movement the motors die.
    My guess is because the MM is getting too hot and shutting down.

    Does anybody have any ideas on heatsinks and or fans that are suitable for this?

    Picture below of the setup! 125420976_657509131798724_582358405521066595_n.jpg
  11. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
    Jul 13, 2014
    Messages:
    15,804
    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    115,446Coins
    Ratings:
    +9,228 / 46 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    • Friendly Friendly x 1
  12. Chris Chopping

    Chris Chopping New Member

    Joined:
    Jul 24, 2020
    Messages:
    9
    Occupation:
    Mechanical Engineer
    Location:
    Melbourne, Australia
    Balance:
    93Coins
    Ratings:
    +5 / 0 / -0
    My Motion Simulator:
    2DOF
    Thanks mate!
    I’ve happened to stumble upon a broken inverter in the shed. Pulled it apart and will adapt the heat sink and a fan.
  13. Chris Chopping

    Chris Chopping New Member

    Joined:
    Jul 24, 2020
    Messages:
    9
    Occupation:
    Mechanical Engineer
    Location:
    Melbourne, Australia
    Balance:
    93Coins
    Ratings:
    +5 / 0 / -0
    My Motion Simulator:
    2DOF
    After a week of work, today i finally had time to play with the sim. Got it moving!
    buuut after 1 lap i hit a curb and bent the motor arms
    126321646_172444544583367_2566724162772639235_n.jpg .... Not great.
    I didnt factor in a curb load case into my simulations and due to the stress concentration that arises from threads it bent!
    I have now made a 10mm stainless steel rod with no thread with the correct measurements and welded the rod end straight to it.
  14. Chris Chopping

    Chris Chopping New Member

    Joined:
    Jul 24, 2020
    Messages:
    9
    Occupation:
    Mechanical Engineer
    Location:
    Melbourne, Australia
    Balance:
    93Coins
    Ratings:
    +5 / 0 / -0
    My Motion Simulator:
    2DOF
    Its now working again!
    It is about 30 degrees today and after 10 or so minutes the chips are overheating again. Even with the heatsink and fans attached to it. Maybe its worth getting an icepack somewhere in the cooling loop :p
    I have created a motion profile and is all setup ready to go! Video posted soon
    • Like Like x 1