Project Logs

slip ring connectors

  1. donkey

    donkey VIP Member

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    donkey submitted a new Showcase Item:

    slip ring connectors

    Read more about this showcase item here...
     
    donkey, May 2, 2016
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  2. donkey

    Harald Kapp Moderator Moderator

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    A Google account is required to access these pages - I do not have one :confused:
     
    Harald Kapp, May 2, 2016
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  3. donkey

    donkey VIP Member

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    1.png 2.png
    ok figured out how to do the pic thingy...
    this is the internal rings, hole is place for wire to come through, need conductive ring on outside (am using copper pipe) they slot together (or will after some adjustment) now to make the housing
     
    donkey, May 2, 2016
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  4. donkey

    donkey VIP Member

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    have made the rar for an individual link... if you trust me just extract and use an STl viewer to see it.... when it's completed its going on thingiverse
     

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    donkey, May 2, 2016
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  5. donkey

    donkey VIP Member

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    am thinking I could use copper pipe for inner track and then a type of springed metal lug for outer track
     
    donkey, May 2, 2016
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  6. donkey

    Harald Kapp Moderator Moderator

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    The main issue I see is to get the surface of the outer track smooth, especially at the seam. A piece of copper tube for the outer track will not have that issue. It may not be easy to find a mathcing set of tubes, though.
     
    Harald Kapp, May 2, 2016
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  7. donkey

    donkey VIP Member

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    donkey, May 3, 2016
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  8. donkey

    donkey VIP Member

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    going to dodgy up a design to show the inner track it'll be posted soon
     
    donkey, May 3, 2016
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  9. donkey

    donkey VIP Member

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    for now here is a pic of those 8 innards joined together. the holes is where the wire comes out to connect to the outside conductor.
    I was just thinking of the hole through the middle and that could house not only the wires but a small solid bar for ground, that'll get me heaps of current if needed
     

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    donkey, May 3, 2016
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  10. donkey

    Fish4Fun So long, and Thanks for all the Fish! VIP Member

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    So is there a greater purpose for these slip rings? How much current are we trying to transfer? What rpm range is this designed for?

    Off the top of my head I am thinking there is an easier way to achieve your goal...for instance: pouring a piece of copper/brass tubing/pipe with a high strength resin (Alumilite?) then simply cutting "grooves" in the copper to isolate one ring from the next.....Obviously this process would be facilitated using a lathe, but if the desired final RPM is not too high then cutting with a dremel or hacksaw shouldn't be a problem....

    If the current is over a few amps AND/OR the rpm is above a few K then there will be a fair amount of heat...this might be problematic for 3D printed polymers.....a resin like Alumilite has a working temp of 250F, and is considerably stronger than most 3D printer polymers....

    If the rpm range is in the 3k to 20k range OR you plan on using bearings or bushings OR you simply want a very strong/robust/durable finished part, you might consider using a solid steel shaft through the center....select a standard size "Drill Rod" that approximates the OD of a "Standard PEX Pipe Size" (for example: 3/4in Pex has a nominal OD of 0.875in, so perhaps 0.5in to 0.75)....a piece of rubber carefully cut to slightly less than Pi * D of the steel shaft with a thickness of slightly greater than 1/2 * (PexOD - Shaft OD) ) ===> (Example 0.875 Pex OD - 0.625 Shaft OD = 0.250 --> 1/2 * 0.250 = 0.125in thick ..... readily available as "rubber gasket material")....Wrap the rubber around the steel shaft and take a "Pex Clamp Ring" (they are made of copper) ..... press it into place on the shaft with the rubber between it and the steel shaft...when all of the rings are in place, use a Pex Clamping tool to secure the rings permanently in place....

    This process will slightly distort the Pex Rings, so once they are all clamped you will want to turn the shaft using (ideally) a lathe, hand drill or perhaps simply mounted in whatever it is to be used for and use a file or sand paper to 1) "true" the rings with the shaft 2) remove the protective black oxide coating from the rings....

    A slight variation would be to cut ~1/4in strips of rubber long enough to extend longitudinally to ~0.100in beyond the outer two slip rings.....keep adding strips until all of the rings are "snug", then clamp/true as above....

    Yet another variation (if rubber is difficult to source, OR you need a size not available in Pex Rings) is to wrap nylon thread/string/rope down a steel shaft (again, extend longitudinally to ~0.100in beyond the outer two slip rings) ...

    if for instance you wanted to use a 1/2in Shaft and 1in OD brass tube for your slip rings, you could wrap several layers of nylon thread until the slip rings were a "snug fit" over the layers of thread....press the slip rings into place and add another layer of thread between the slip rings....then mix some relatively slow drying resin (epoxies are good in working environments up to ~150F....some urethane resins up to ~250F and some polyester resins up to ~350F) and coat the thread with the resin...

    You will need to slowly turn the shaft as the resin cures and if the thread layers are thick you will need to continue to add resin between the slip rings as it "soaks into" the lower layers.....The advantage to using thread/resin is that (with careful wrapping techniques) the concentricity of the rings with the shaft will be extremely close.....

    **Note: if you are going to wrap more than 2 layers you should consider putting resin on each layer as you go....choose a resin with a working time that is longer than you anticipate it will take to wrap all of the layers....and mix it after the first layer is complete... putting a very thin layer of resin on each layer as you go...this will ensure the filler is uniformly whetted and give the best possible mechanical properties....

    Of course it is possible to use "standard" filler materials like fiberglass mat/cloth, kevlar, carbon fiber etc, etc, BUT maintaining concentricity w/o post processing (ie turning the hardened composite in a lathe prior to adding the rings and the final resin/filler) requires a great deal of skill and typically specially designed molds....The "thread process" (including String and/or Rope) is actually much easier to accomplish for short runs or limited DIY tooling.....

    For instructions on how to "wrap thread" do a search on "fishing rod guide wrapping".....it takes a bit of practice, but once you are familiar with the wrapping process, wrapping a 1m length of shaft shouldn't take more than a minute or two per layer assuming a "power wrapper" (most "power wrappers" are just old sewing machine motors with some kind of adapter to attach the work to the motor shaft....) or 10 to 20 minutes if "turning by hand".... The number of "turns" per layer is a function of the thread/string/rope diameter.....

    NOTE: For Multiple Layers it is imperative that the diameter of the thread/string/rope remain constant OR INCREASE on each subsequent layer...attempting to use "smaller thread" on top of a "larger thread" is 1) Very difficult to do 2) Will ALWAYS produce "gaps" which in-turn will almost certainly cause a decrease in concentricity.

    Just off the top of my head....the above mentioned methods seem more robust, faster and easier 3D printing....but, again, I don't know what the ultimate purpose of the "multiple slip ring" project is....

    Good Luck!

    Fish
     
    Fish4Fun, Aug 4, 2016
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  11. donkey

    Harald Kapp Moderator Moderator

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    @Fish4Fun : I don't think donkey is after a simple solution. He's the proud owner of a 3D printer looking for something to build (possibly to justify the cost of the printer to his wife ;)?).
     
    Harald Kapp, Aug 5, 2016
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  12. donkey

    Fish4Fun So long, and Thanks for all the Fish! VIP Member

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    @Harald Kapp.....

    Fair enough.....

    @donkey

    Ignore my previous post and carry-on!

    Good Luck!

    Fish
     
    Fish4Fun, Aug 6, 2016
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  13. donkey

    Steve Peart

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    I attempted to create a 3d printable slip ring as well using TinkerCad and a 3d printer at my library. I moved before I could print it and test though. My plan was to wrap the inner rings with copper tape and the outer "brushes" which were actually made to be circular to avoid a scratching of the inner rings would have the tape as well and maintain stability by having 4 points of contact to the inner ring. My application was really not meant for speed, but as a simple low-rpm robotics slip ring, that had as many connections as possible, not just one wire. If you want I can try to rustle up my design and send it to you. Was just messing around with it, not sure how effective the design would end up being.
     
    Steve Peart, Nov 9, 2016
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  14. donkey

    donkey VIP Member

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    steve feel free to throw me a link, My bp and I might find a use for it, if ya want we could possibly organise getting one to you if its not too much of a cost our end
     
    donkey, Nov 11, 2016
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  15. donkey

    Steve Peart

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    OBJ File: slip_ring.obj
    STL File: slip_ring.stl

    Let me know what you think, it was a first thought sort of idea since I was sick of waiting 4 weeks to get slip rings from china.
     
    Steve Peart, Nov 12, 2016
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