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Cams instead of arm and rod

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Doon1, Dec 12, 2017.

  1. Doon1

    Doon1 Member

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    I was reading where Kermit Kong mentioned the non-linear function of the arm and rod setup for motion control. I was thinking about using a cam in place of the arm and rod. I've already drawn up the cam profile. Has anyone tried this?
  2. Alexey

    Alexey Well-Known Member

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    The cam would quickly deteriorate unless you harden the surfaces which wouldn't be a cheap exercise. Then there is how you would make it all rigid.
    By that time you may as well have made a linear actuator.

    Still curious to see your design however.
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  3. Doon1

    Doon1 Member

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    Here is the cam profile. It is directly proportional for a 2.5" throw. It can be scaled up as needed for a longer throw.

    Attached Files:

  4. Doon1

    Doon1 Member

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    The cam can be cut from 1" thick plastic to reduce noise. It would have to run on a wide bearing or a tube with bearings on each end to eliminate wear of the cam.
    Hah, I just found the drawing that I did years ago using 4 window motors and the gears from an Aerostar van. I still have the parts in my garage.

    Attached Files:

  5. Zed

    Zed VR Simming w/Reverb Gold Contributor

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    @Doon1 - I think Alexey is right about the wear issue but you might be able to modify a bit where it runs instead against a linear bearing of some sort - I think that’s what you mentioned. But it would also put you in the situation of needing to be loaded to have it keep contact. These things do pushing and pulling so you would need some way to have the pull work just as well. But if you load it hard to get good fidelity in the pull, then you stand to really increase power draw and motor requirements in the push. Not sure if that makes sense but I may not be understanding what you are saying.
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  6. Limongi

    Limongi Member

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    I have to agree with Zed that the motion is most certainly bidirectional for racing and it would feel bizzare not having it pull down as needed. You would feel a floating disconnected feeling imwhen you really want snappy change of direction.

    @Doon1 are you planning on flying or driving in your sim?
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  7. Doon1

    Doon1 Member

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    @Zed your right that there would be no pull down. Making sure that the cam stays loaded or use a return spring of some sort is a definite. The motors are pretty beefy but I have not been able to find the exact specs on them. I just realized that my power supplies are only 15 volt so if the motors are 24 volt I will have to re-think how I'm going to power them.
    @Limongi I'm a DCS and E:D junky so the rapid return wont be such a great issue yet I may want to do some driving in VR later on. So maintaining some sort of positive engagement may be necessary.
    Anyone know the specs of these motors?

    Attached Files:

  8. Hobbs77

    Hobbs77 Active Member

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    I think if you made the cam larger in size and be able to cut a slot for your bearings to run, you would have both push a pull. In other words, a slotted cam.
  9. RandomCoder

    RandomCoder Active Member Gold Contributor

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    @Doon1 the BK Precision is a good little PSU. For a previous work related project I once had to buy forty of them to install in a machine which applied a constant current across thermal switches to test their response. They ran continuously 5 days per week without fail.
  10. Doon1

    Doon1 Member

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    I thought about that but there would be too much play. I did a slotted cam for another project one time and it just didn't work out the way I intended.

    They are nice. I have 2 of them but probably won't be able to use them for this project. I used the motor brake to deadhead the motor and it maxed out the PS @ 15.3v/40a. Could be I won't need all of that power. we'll see.
    The motors are definitely 24v because there is a 24v/20a charger onboard the wheelchair. I think I will put a couple of 12v batteries in series and do a torque test tomorrow. I could even use batteries and a charger to run the chair probably. I have that charger and several HD truck batteries I can use.
    Last edited: Dec 12, 2017