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Mendocino Motor Magnet Spacing

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  • #16
    Do you actually need the foam once you have the wire wound? You could fashion small clips attached to the wire to hold the cells.

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    • #17
      Darryl, it is quite dark below the armature, even in sunlight, so I don't think that is an issue, but sure something to try. A piece of black paper on the bottom, with a steady rotation would prove the thought. I will try it and let you know.

      On your magnetic suspension idea, sorry but you cannot levitate both vertical and horizontally at the same time, that is according to Earnshaw's theorem, Maxwell's equations prohibit this type of levitation. If you Google Earnshaw's theorem you will get all kinds of good reading material about why it can't be done. It sure would be neat, and I did cut a second set of matching end plates and tried it. It just will not work!

      I got some rubber cement this afternoon, will try it on a piece of foam tomorrow and see if the foam survives the experience.

      I did a lot of experimenting today, and have an even better and simpler working system. Have a bunch of pictures of the now finished project, will probably get them written up and on here sometime tomorrow. I think you will be pleased with the results that I got today, and it really looks nice to boot.

      Elf, that is a really neat idea, but I do see a lot of challenges you would need to overcome. The first would be a system to balance the finished armature. I would also think it would be difficult to hold the coils in place on the armature shaft, and how would you keep the bundles of wire in a permanent shape? It would really be different, give it some thought and see what kind of solutions you can come up with. Keep in mind it is number 30 wire so very small and flexible, 150 turns in each coil.

      More later,
      George
      My Web Site
      www.mrrace.com
      Builder & Test Pilot N73EX

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      • #18
        Today I really did a lot. I started by widening the end pair of magnets. Went from a center to center of 1.5 inches to 1.875. My idea was to bring the armature down closer to the end magnets as well as the base magnet. What a difference, almost immediately it started running, all by itself, in just the light in the shop. I got rid of the brass nuts (weights) on the both ends of the shaft and did a really fine balance of the armature. Made a new base with only one magnet, as the three were influencing the armature magnets to some degree. It immediately started running much smoother, and of course it sets deeper in the "Magnetic V" due to the wider spacing. Incidentally, after all the changes today, my armature weights a whole 2.5 ounces. After all the changes the armature sets just over .5 inches lower as well. The only thing left to finish is the gluing on of the photo cells. That will complete the build. The last thing I will add will be a list of materials that can be purchased to build a similar motor in your own shop. This is really a fun project! Anyone who sees it does not believe what they are seeing.

        Follows, a series of pictures of how the unit looks after doing a complete rebuild of the base frame work today.

        Here is how it looks running.

        Here is a full side view, and yes I did polish all the aluminum plate!

        Another side view, favoring the back end.
        The small holes you see in the foam are where I have pushed in #80 brass screws while balancing the armature.

        Here is a picture of the rear end rest. I machined it out of a piece of smoke lexan. It is bolted to the base with 2-56 screws in threaded holes.

        In the picture above, notice the way I am now holding the rotor magnets in place. As the shaft is .125 brass, the .125 milling tool stops are an ideal way to hold the magnets vertical and in place. The stops really press on hard, and will not move once in place. Just getting both end magnets to turn without a wobble is a giant step in getting the armature to run smoothly.
        Last edited by George_Race; 06-03-2012, 07:44 AM.
        My Web Site
        www.mrrace.com
        Builder & Test Pilot N73EX

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        • #19
          The next picture shows the "floating" end of the armature shaft. Note the tool stops holding the magnet in place.

          Here is a pictures of the front of the frame with pressed in magnets.

          Here is a picture of the rear of the frame, showing the end stop for the shaft.

          Here is a close up of the 1" X 3" .5VDC 250MA solar cell. Hopefully tomorrow I will have them all in place with some rubber cement, and the rubber bands will be gone for good.
          My Web Site
          www.mrrace.com
          Builder & Test Pilot N73EX

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          • #20
            And the last picture is of the bottom magnet that attracts the armature coil that drives the rotation. You are looking at the reflection of the armature in the base place. It really polished up very nicely.


            I did use my optical tachometer to check the speed today. Sitting under the shop ceiling lights it ticks over at about 215-220 RPM. I exposed it to blue sky this afternoon and was amazed when it consistently showed 2180-2190 RPM, and running very smoothly at that speed. For this unit, I believe that is the maximum speed it will achieve.

            For this to be a declared finished project, I will be adding a list of materials and links to the DXF files of the base unit and foam cutouts. I will also be writing up a list of dimensions for those that would like to have a starting point and do their own thing. I do think that my final dimensions are ideal, and will be very easy to duplicate. This is really a great running little motor!
            George
            My Web Site
            www.mrrace.com
            Builder & Test Pilot N73EX

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            • #21
              Nice work, George! I'm curious about the solar cells- are those amorphous? If so they must be some advanced version, since none that I have can put out that much current. I'm also intrigued by your good results with just the single base magnet. Maybe I was right about the solar cell working in current mode- with a single magnet there is probably less back emf, so the low voltage from the solar cells doesn't matter as much as to how fast the armature rotates.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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              • #22
                About the need for end plate:

                What if the ends of the shaft would have tiny magnets, with for example S poles pointing outwards and the end supports would have the same but pointing inwards, this would create an ever so small opposing forces that keep the shaft from touching anything.
                Amount of experience is in direct proportion to the value of broken equipment.

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                • #23
                  I made one of these repulsion-suspension things today, just to see. Mine is only magnets and supports- no solar cells, etc. I tried the dual sets of magnets- sure enough I couldn't make it work either. I also tried the end magnets to keep the shaft centered- couldn't get that to work either. Earnshaw comes out 2 to my 0.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #24
                    Solar Cell & End Support

                    The cells are actually rated at .55 VDC and .5 amps each. That does seem like a lot of current, but maybe that is why my concoction starts so easily and runs in very low light. I tried one of those HF LED flashlights, you know the ones they give away with a coupon, and it runs right along in a perfectly dark room.

                    Here is the link to information about the solar cells. Very good description of the type of cell down the page, toward the bottom.
                    http://www.ebay.com/itm/180803698979...84.m1439.l2649

                    And yes you are right, Earnshaw, got ti right! I tried several different configurations, and nothing seems to work. The one thing that I have not tried is putting 4 magnets in a square, facing each other in opposition, and then using 4 very small magnets on four sides of the spinning shaft, also in opposition to see if it will float. That is what I think that Jaakko is suggesting. But again, Earnshaw will probably win another one. I may mock that up just to prove it will not work.

                    Anyway, thanks for your comments, this has been a real fun thing to build and play with.
                    George
                    Last edited by George_Race; 06-04-2012, 08:16 AM.
                    My Web Site
                    www.mrrace.com
                    Builder & Test Pilot N73EX

                    Comment


                    • #25
                      Then there's the levitron:

                      http://www.levitron.com/


                      Some theorists had decided this was impossible not so long ago. There's a pretty juicy story of the guy who invented it, Roy Harrigen, and the guy who stole it and made money at it:

                      http://en.wikipedia.org/wiki/Levitron


                      In heaven, I will be able to levitate at will.

                      Finest regards,

                      doug

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