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2DOF Seatmover - a long way to go

Discussion in 'DIY Motion Simulator Projects' started by Knauba, Jan 10, 2017.

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  1. Knauba

    Knauba New Member

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    After reading a lot here already and looking through all the very nicely described and illustrated simulator builds, I said to myself: "How hard can it be?" and made an order last week:

    • 2x 24V DC Motor 40W 0-260U/min - 36,49 €
    • Pololu Dual VNH5019 - 46,94 €
    • Uno R3 ATmega328P Board ATmega16U2 - 8,99 €
    • HP DL380 G4 575W DPS-600PB B - 14,99 €
    • B10K 10K linear Potentiometer 5 Pack - 6,52 €

    Now the parts are arriving one by one and today I've got my motors. As I wanted to save money where I could, I looked around, to find a cheap one that is still capable of lifting my 70ish kg on my approximately 30-40 kg wooden seat construction (build not started yet). Here is what I wanted to give a try: 24V DC, 210 rpm (using 24V) 40 W, 30Nm

    Bildschirmfoto 2017-01-10 um 21.40.35.png


    As I read in multiple posts about short circuits concerning motors using the case as ground I opened one of them, to have a look inside. What a beauty :)

    Bildschirmfoto 2017-01-10 um 21.46.40.png

    The black cable is soldered directly to the coil without touching the case, so this should be fine without further tweaking:

    Bildschirmfoto 2017-01-10 um 21.51.28.png

    However, what I need to fiddle out now is, how to connect the rod. As the thread is only a M4, using this directly for the connection doesn't sound as a very good idea.

    Bildschirmfoto 2017-01-10 um 21.55.57.png

    so long...
  2. Ads Master

    Ads Master

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  3. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    Nice project!!

    sorry, but 40W motors will never give you 30Nm... your torque specs are probably not acurate saddly
    here some actual examples from https://simukit.com/ :
    - DC moteur 120W 24V 40rpm 25Nm
    - DC Moteur 350w 60 rpm 40Nm​

    If you look for rod connection, here are some ideas: :)
    742136crank2.jpg
    323500moyeublocageelastique14470pmod1ganter.jpg
    877779moyeudeserrageetmanivelleRacingMat.png

    yours
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  4. Knauba

    Knauba New Member

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    Thanks for your reply :)

    So the motors are most probably not strong enough, to give a good performance, right? I mean, as they are the ones I've got, I will give them a try anyways. And if they are completely useless, I can still modify my bbq with them

    However, according the rods connection, I thank you very much for the input. I was thinking the complete other way arroung, in somehow using the thread instead of the shaft.
  5. RacingMat

    RacingMat Well-Known Member Gold Contributor

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  6. Stealthelius

    Stealthelius Member

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    These are a very good motor @Knauba. I have one question for you. Are noisy the motors?
    I have a pairs of classic 12V wiper motors and they are too noisy.
  7. Knauba

    Knauba New Member

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    @Stealthelius as @RacingMat already pointed out, don't let the figures fool you ;). I haven't tested the motors yet. But I will try and post a video as soon as I did.
  8. Knauba

    Knauba New Member

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    Small update on the build and a quick question on the rod connection. It's really hard to find those adjustable bike cranks here in Germany. All cranks I've found have a fixed size... -_-

    That second picture you attached to your first post, @RacingMat, what exactly is this?

    Here is my U-Joint, it's from a Belarus MTS Fortschritt ZT.
    Bildschirmfoto 2017-01-13 um 21.23.54.png

    I also bought an old Recaro which I attached to it's wooden base.
    Bildschirmfoto 2017-01-13 um 21.24.19.png

    I'm thinking about using only the joint as the distance between the bottom base and the seat. This would give me enough room to additionally attach Roles underneath (my driving wheel is quite low). Although I'm a bit afraid to roll away, under heavy breaking. Has anyone experience with rolling seatmovers?
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    Last edited: Jan 14, 2017
  9. RacingMat

    RacingMat Well-Known Member Gold Contributor

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  10. Knauba

    Knauba New Member

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    According the U-Joint, I looked around quite some time to find one which I can use as is, as I don't have experience in welding nor a welder at my disposal. If someone is desperately looking for one, just PM me. They came in a pack of seven ;)

    Thanks for the explanation @RacingMat. I decided now to try and cut an external thread directly into the motor shaft. If this doesn't work out, I will go with a coupling and try to find someone for the welding.
  11. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    ok!
    but I would say that motor shafts have a surface treatment such as thermal tempering
    that would prevent you to thread it with standard tools

    keep us informed :)
  12. Knauba

    Knauba New Member

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    While waiting for the thread cutter box, and a thicker cable to connect my PSU, I attached the U-Joint.

    To find the balance point I followed the instructions here: https://www.xsimulator.net/communit...-of-gravity-to-balance-a-motion-simulator.55/ Afterwards I attached the Joint temporarily with wood screws to get a feeling of how well I hit the point.

    Bildschirmfoto 2017-01-16 um 22.18.31.png

    I moved the joint back just some mm for the final attachment, but it had a big impact on the overall balance.

    Bildschirmfoto 2017-01-16 um 22.18.44.png
  13. noorbeast

    noorbeast VR - The Next Generation SimTools 2.0 Beta Tester

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    That may be true of some but not all, the 25:1, 50:1 and 60:1 wormdrive gearboxes commonly used by DIY builders are not hardened.

    The gearboxes pictured have a hole in the end so it would be worth seeing if a thread can be cut by hand with a tap tool.
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  14. Knauba

    Knauba New Member

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    I'm done. I did not think that it could be that hard, but I finally did it.

    The hardest thing was really to fix that shaft in place, so it couldn't move in any direction while I was turning like a madman. Here is what worked best for me:

    image1.JPG

    Cutting a m12 thread before starting the m10 helped a lot. At least I found it a lot easier to cut the start with the bigger one.

    image2.JPG

    And the final result:
    image3.JPG

    The tools I used worked pretty good. What helped a lot, was the cutting oil I bought for half the price of the whole toolbox. But without that I wouldn't have made it.

    This is how it looks back in the motor. I will most probably use the tube connection for the potti.

    image4.JPG
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  15. Knauba

    Knauba New Member

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    I fixed the joint to the base today. This is how I would like to position the motors.

    IMG_1519.JPG
    I built a little podest for the U-Joint, but I'm not quite sure if the 16cm between the base and the seat in horizontal position is enough. Looks like I need to add some more height... -_-
  16. Knauba

    Knauba New Member

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    Hi guys,

    I'm a little stuck here and asking kindly for your support. After I finished my motormounts I see now, that the joints are a little too long. As you can see in the images, the levers are a little away from the 90 degree position. And also the offset is slightly different from lever to lever. Now my question: Do I need to raise the seat to have more room, or is the difference somehow compensated by the motorshield, or neglectable in later operation? I'm afraid, I already know the answer... -_-

    Btw. I can't lower the motors any more as otherwise the lever can't go in full 360 degree movement, that's why I added the bottom plate. I mean, if I would remove the bottom plate I have enough room for the right adjustment of the levers, but than I need to somehow restrict the movement between 210 and 330 degrees. Is this possible? Would this be recommendable?


    300px-Polar_graph_paper.svg.png

    Lever 1
    IMG_1546.JPG

    Lever 2:
    IMG_1555.JPG
  17. noorbeast

    noorbeast VR - The Next Generation SimTools 2.0 Beta Tester

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    It looks like your seat should be a little higher.

    Both levers should have the rose joints in the same orientation like this one, otherwise binding would be asn [​IMG] issue with one at 90 degrees to the other:
  18. Knauba

    Knauba New Member

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    Thanks for your answer @noorbeast. According the orientation I could go for a 180 degree switch on the second lever, as I have enough room to the right. But you are saying the 90 degree position is mandatory, yes?
  19. noorbeast

    noorbeast VR - The Next Generation SimTools 2.0 Beta Tester

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    I am saying that to prevent binding both rose joints need to be the same orientation.

    Effective torque delivery with a lever is at its maximum when at 90 degrees. Torque effectiveness falls off rapidly after about 40 degrees up or down. So it pays to have the same angle range up and down for a particular design. So while not mandatory it is sensible given your design to have the levers start at 90 degrees.
  20. Knauba

    Knauba New Member

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    Ok, I supose it's the wrong place for being lazy than I will disassemble and higher the seat. Thanks, @noorbeast.
  21. Knauba

    Knauba New Member

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    Now that all fits well, I started with the electronics. Using the great Ultrasonic PWM code from @RacingMat (thank you very much for sharing) found here: https://www.xsimulator.net/community/marketplace/ultrasonic-pwm-with-arduino.102/

    After testing that both pots are giving the right values using the arduino code found here: https://www.arduino.cc/en/Tutorial/AnalogReadSerial, I deployed the code from RacingMat onto the board and... YES, one motor was really doing what I expected... BUT, the other one did not a thing.

    I fiddled arround a bit, switching cables, potis, polarity and so on, which led me to the following really strange output, which I can't really explain:

    Leaving the motors out and just looking at the green and red lights of the pololu, while truning the potis:

    Scenario1:
    pot1 on A0: goes from red to green (motor would go forward and reverse like it should be) => works
    pot2 on A1: goes from black to green (motor only goes in one direction and stops) => works not

    Scenario2: (pots are both OK)
    pot1 on A1: works not
    pot2 on A0: works

    Scenario3: (maybe the cable/pin)
    pot1 on A0: works
    pot2 on A4: works not

    It's always the same picture for the not working part. It just won't go to reverse. I've also let the ground and 5v cables where they are on the potis and only switched the Pin cable. Anyone has an idea what this could be?

    Btw. I suppose the one motor, which does not to a thing, is broken. As when I connected the working motor on the not working channel it was at least going in one direction. The other one did not a thing on both channels... :(



    Changed pins for VNH:
    int inApin[2] = {
    2, 7}; // INA: Clockwise input
    int inBpin[2] = {
    4, 8}; // INB: Counter-clockwise input

    Changed pot pins:
    #define potL A0
    #define potR A1/A4

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