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Forum Index : Electronics : 1st post, so if I goof...
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| jimmj43 Newbie  Joined: 08/04/2008 Location: United StatesPosts: 3 |
Don't beat me up TOO badly, OK? The subject of my question is the DYI approach to winding your own stator windings. <--That in itself has loads of "how to" source material. But a few months ago (prior to a computer crash - lost bookmarks) I read a piece on (I think) Engadget or Gizmodo, where the author described a unique manner of winding coils to improve efficiency. Picture a paper clip - straightened except for a single arc, with the two straightened legs being approximately equal in length. With that picture in mind, let's say we need 100' of 18Ga wire, so we cut 100' to length, then double it to give us the loop - which we'll use to begin the winding. Being a fossil who suffers from CRS, I don't recall the exact advantage that approach to coil-winding promised. The second part of my question, still regarding DIY coil winding, relates to the cross-sectional shape of the winding. That is: Fat/round -vs- flat/skinny. This I ask after gutting a few old HDs and taking note of winding configuration of the disk wiper arms - VERY flat & VERY skinny, kind of resembling miniture spatulas. I'd like to offer a couple of hat-tips to this site and those who post here. I'm overwhelmed at the depth and breadth of the knowledge shared here, but also by the manner of clearly-understandable wording and phraseology. I just hope I can hold up my end and contribute meaningfully. Jim Fossil <--invented dirt |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I take it your talking about the axial flux type of alternators. With regards to the coil thickness, a flatter coil means the magnets can be set closer together, increasing the flux density within the coil, and therefore increasing the output voltage per turn of wire. However, a flatter coil pack means less space for coils, so less coils, and less volts. So I think its a balance between the number of turns and magnet spacing. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| jimmj43 Newbie Joined: 08/04/2008 Location: United StatesPosts: 3 |
I'm not even a little bit concerned about getting the magnets spaced too closely - I simply don't have enough of the hard-to-come-by little buggers. I intend to use the magnets out of scrapped HDs - more-or-less quarter-round in shape. I'm thinking in terms of 18 magnets with coils connected in a "Y". Am I correct in assuming that I want maximum magnet surface to travel across maximum coil surface - preferably allowing the magnet's flux to penetrate to the maximum depth of the coil? If so, then it seems to me the shape of the coil should approximate the shape of the magnet - more-or-less, correct? Here's a link to an image of one of the magnets I intend to use: http://img134.imageshack.us/img134/8325/hdmagnetvm4.jpg From furthest point to furthest point is ~ 1-11/16". I included a regular 5-stick pack of gum for perspective. And the orange bar is a pencil I had to place atop the magnet, then press down on the scanner lid to keep the scanner's lightbar from dragging the magnet back and forth. STRONG little magnet! I intend to mount the magnets with the outer circumference outward, so I'm assuming an oval shape(*) that approximates slightly less than the overall cross-sectional sweep of the magnet would be suitable. And I want maximum wire length exposed to maximum field strength, right? (*) Draw a straight line from one corner of the inside arc to the other, then draw a parallel line at the top of the outside arc. Let's say the distance between those 2 parallel lines is ~ 7/8". I have it in mind that my coils should be wound in a somewhat flattened oval shape ~ 5/8" wide and 1-1/2" long. Cross-section shape of the coil matters less than # of winds for voltage, and larger wire size will improve current capacity, so there's no need to flatten, or flat-wind the cross-section profile, right? At present, I intend to have a single disk with magnets attached, spinning over a single layer of coils. As I gather more magnets, I may consider adding a second spinning diskful of magnets and 'sandwich' the coil disk between the two. Which raises ANOTHER question! For the sake of this discussion, let's say I space the magnets 2" apart. If/when I add a second diskful of magnets, those should be configured identically, but offset from the first magnet disk so top and bottom magnets alternately travel across coils. I think I see a potential problem. If I PERMANENTLY mount the magnets on the first disk with magnet faces N-S-N-S, etc to the coils, then, it seems, if I replicate that magnet pattern on the second disk, I'd be hitting each coil twice in a row with N, followed by twice in a row with S. <--That's not good, is it? That still leaves unanswered that "unique", doubled-wire approach to coil-winding... Thanks, Gizmo. Jim Fossil <--invented dirt |
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WineGuy Newbie Joined: 16/04/2008 Location: United StatesPosts: 10 |
A couple of items here. 1) Hard drive magnets have a north and south pole on each face, so you will have to cut the magnet in half (1/8 moon shape) in order to get a single north on one side with a single south on the other side. 2)I'm sure you can find LOTS of similar information and designs here, but Hugh Piggott produced a 50 page document (2001) that describes what you are looking for in a "sandwitched" design. The link is http://www.scoraigwind.com/pmgbooklet/itpmg.pdf Sure wish I was smart instead of so darn cute! |
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| jimmj43 Newbie Joined: 08/04/2008 Location: United StatesPosts: 3 |
Hey! Thanks, Wine guy. 
The info on the HD magnets opens up what I believe is an opportunity to 'get inventive'! I happen to have a couple of sheets of tough fiberglass composite that's about 1/8" thick. If I can cut 2 semicircles, and fabricate a router pattern to make cutouts for the magnets in the 2 semicircles, then I can have a single magnet disk after epoxying the magnets in place. Then it'll be a matter of creating 2 stator winding mounts - 1 to collect "N" flux, the other to collect "S" flux, sandwiching the magnet rotor between the two. Thanks for that PDF link too. Duly saved. Jim Fossil <--invented dirt |
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