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Wooden 2DOF wiper motion platform

Discussion in 'DIY Motion Simulator Projects' started by Hurjakuru, Feb 24, 2017.

  1. Hurjakuru

    Hurjakuru New Member

    Joined:
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    My Motion Simulator:
    2DOF, DC motor, Arduino
    Hello everyone!

    I've been lurking these forums for a while and finally got around to acquiring most of the parts i need to start the project. Before i do, i thought i'd ask for a bit of advice on a few things and bounce some ideas.

    Pictures attached are:
    1. the rig
    2. the platform its going to placed on + the parts that i have
    3. close up of PSU wires (question 2)

    First and foremost i'd like to mention that this is a(the) prototype build to see what works and what doesn't before i commit to metal. The main use for the rig will be rallying.

    For the general idea iam going with a U-joint from a driveshaft to balance the rig on and 2 motors in either front/back corners as it seems like a tried and true base solution.

    onto the issues/questions:
    1a. Iam a "bit" worried about the rig being too heavy for the wiper motors and was thinking about trying to ease the load on them by mounting springs(strenght to be determined) on the corners so when the rig moves they help the motors on pushing it back up to the neutral position. Does this make any sense? For example if i used a spring with a max resistance of 15kg and the motor had a weight of 20kg to push against, pushing against the spring the resistance would be somewhere between but lower than 20, yes? no?

    2. What should be the lever lenght used between the motor and the rig? the distance from the highest to the lowest point when turning the motor around(180 degrees) with the bit that connects the wipers to the motor is ~10cm. I lifted one of the corners of the rig by about that much and the amount of potential movement seems enough. Have i understood correctly that the amount of movement is only decided by that small bit connected to the motor axis while the connection between it and the rig only serves as a connection? Also the longer the bit connected to the motor axis= more power needed correct?

    3. I bought 2 DC server PSUs from a local computer hardware store: Dell PS-5361-1D1 with a max output of 360w. I read the tutorial how to modify a psu for this purpose but it seems to concern PSUs that have pin connectors. Mine have similar power cables to regular computer PSUs. Iam just guessing here but am i right in assuming that instead of soldering the pins i just have to cut the correct wires and solder them according to the instructions? I have included a picture of the cable bunches. They are labeled as P1 P2 P3. I'd be happy to take more detailed pictures if someone can help me identify the correct wires.

    4. I have 2 moto mosters, should i use one for both motors or one per motor? Iam leaning towards 1 per motor becouse of the planned upgrades but just to be sure.

    5. The motors are from 2 scrapped Nissan's, iam not a 100% sure if they are 100% identical since the specs have worn off but they are identical on the outside and from same sized cars of the same period. What can i expect to happen if they turn out be slightly different? I will upgrade the motors asap but they only cost me 10euros a piece so i thought i'd atleast try.

    Thats all for now, thank you all for this site and the resources it provides. Sorry if there are some overlap questions with the faqs and i hope i explained myself clearly enough. Thanks for the help in advance!

    Attached Files:

    Hurjakuru, Feb 24, 2017
    #1
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
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    My Motion Simulator:
    3DOF, DC motor, JRK
    1. Design and its inherent leverage plays a big part in determining what is needed to drive it motor wise. You have not said or posted a picture concerning what design you intend using. If you do a seat shaker design, where just the seat moves, with say shoulder mounts, then wiper motors will work If you plan on moving the full frame then I don't think wiper motors are likely enough.

    2. How the motors are placed is also dictated by design. Do a sketch of what you have in mind and post it here.

    3. Server PSUs need to be modified to work, I don't recall having seen that model but check here: https://www.xsimulator.net/communit...ver-power-supplies-as-cheap-powerful-psus.54/

    4. Use 1 MM per motor, like this: https://www.xsimulator.net/community/faq/monster-moto-shield-as-a-single-motor-driver.101/

    5. If the motors have different speeds it would make it difficult to tweak a motion profile.

    There is a FAQ section on Design Considerations that may be helpful: https://www.xsimulator.net/community/faq/design-considerations-resources.24/category
    noorbeast, Feb 25, 2017
    #2
  3. Hurjakuru

    Hurjakuru New Member

    Joined:
    Feb 5, 2017
    Messages:
    3
    Location:
    Finland
    Balance:
    177Coins
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    +0 / 0 / -0
    My Motion Simulator:
    2DOF, DC motor, Arduino
    Ah yeah sorry in my excitement i forgot the basic info. The idea is to move the full frame by balancing it(while in it) on the U-joint, thats why iam considering the springs on the corners to offset some of the weight. I made the sketch but it really is a sketch as iam about to head to bed. Thanks for the answers!

    Attached Files:

    Hurjakuru, Feb 25, 2017
    #3
  4. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
    Jul 13, 2014
    Messages:
    20,557
    Occupation:
    Innovative tech specialist for NGOs
    Location:
    St Helens, Tasmania, Australia
    Balance:
    145,160Coins
    Ratings:
    +10,780 / 52 / -2
    My Motion Simulator:
    3DOF, DC motor, JRK
    Spring assist can be helpful, I use it on my compact sim for heave, but the motors also have to work against it so in my view it only has limited useful applicability.

    Do you know the full mass of your rig, all peripherals plus yourself? You can do some calculations and guestimates but I think wiper motors will struggle: https://www.xsimulator.net/community/faq/calculating-basic-linear-speed-and-forces.89/

    Wiper motors are better suited to a shoulder mount seat shaker design, as the mass is normally just the seat itself and the user.
    noorbeast, Feb 25, 2017
    #4
  5. Hurjakuru

    Hurjakuru New Member

    Joined:
    Feb 5, 2017
    Messages:
    3
    Location:
    Finland
    Balance:
    177Coins
    Ratings:
    +0 / 0 / -0
    My Motion Simulator:
    2DOF, DC motor, Arduino
    No idea about the total mass, if i had to guess i'd place it somewhere around 160-170kg. I originally abandoned the idea of using wiper motors becouse i figured it would indeed be too heavy and decided to postpone until i could affford more powerful motors. But curiosity got the better of me so decided to try anyway. Worst case scenario i lose 20euros on the motors.

    Iam not sure i understand why the motors would have to work against the springs though? In my vision the weight of the rig would be capable on compressing the spring almost completely if it was attached to the U-joint and leaning towards it. The springs would be unloaded when the rig is level. So when the motors pull the rig down the front springs take on some of the weight and vice versa. I might be wrong, physics aren't really my thing.
    Hurjakuru, Feb 25, 2017
    #5