Nexus - 0303 - New Times Magazine-pages

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NEWSCIENCENEWSCIENCENEWSCIENCE RODIN COIL DESIGN Table 2: All tests at 1 kHz of 'vintage' GR 650-A L-bridge. Rodin-style coils con- by Bill Ramsay nected series-aiding. everal years ago I learned of Marko Winding Total Total Total Rodin‘s theoretical design for an | Form _____style _____wire ___turns _wraps__|,____Comments unusual coil. I got acopy of his | Yellow conv. 79 263 = sfaturns = 242 UH one layer book, Aerodynamics: The (Q .6) Dandelion Puff Principle—Point Energy | Yellow Rodin 79' 16 192 370 UH +53% Creation Physics’, and wound a few coils (8x2) (Q.1) based on his design. Only a few non-defin- | Biye conv. 122° 402 s/atums 480UH one + layer itive tests were run at the time. (Q.9) Recently I felt inspired to delve further | pi, Rodin 122° 22 264 780 UH +62.5% into the potentials of this design, and a (11x2) (Q L.5) , number of simple coils were made and sim- ple tests run. None of the coils so far winding consists of a number of turns laid wire in the usual way ought to yield the matches exactly the proportions Rodin — side by side around the outside, each con- highest L (inductance), since its field feels are necessary for the most profound necting segment crossing over the previous would be more concentrated than a Rodin results, but the coils do show some interest- _ ones as it passes through the centre. This is style where a good portion of the wire ing attributes and a few surprises suggest- necessary to ensure the outer turns progress _ would be ‘wasted’ going through the centre. ing more to come. Perhaps some of this in the same direction for each wrap to the Not so, as shown! (See Table 2.) will be of interest to others to find applica- _ left or right of each preceding wrap. Obviously the centre crossover region is tions. The hollow plastic forms are not very active! But how active? A half-inch diam- Most of the coils wound here so far use, rigid, so wires should be snug but not too eter by seven-inches-long ferrite rod placed as forms readily available, plastic 'rings' tight or they distort the form and loosen through the centre of the Rodin-style coils which are part of the Fisher-Price child's previous wraps. Some forms were split yielded 890 UH (Q 2.4) or +141% for the toy, "Rock-a-Stack". There are five differ- and stuffed with foam, which helps some. Yellow and 1,680 UH (Q 3.2) or +115% ent-sized and coloured forms in this set, Before winding, each form was prepared for the Blue one. As expected, this rod had priced at about US$4.00 at Walmarts. The by using a sharp knife to trim off the raised no effect on the conventionally wound approximate dimensions of these are listed lettering and to rough up the slick finish. ones. So, the centre region in Rodin-style in Table 1. Templates with the 10° segments were coils is quite active! But why? uscd to mark the outside with a felt-tipped pen. The segments thus formed were num- Figure 1 — — bered as to winding order. A B Cc WW) IW) I first wound the wire on a common — round pencil using this as a shuttle to pass [a7 | the wire through the centre. The known per-turn lengths were used to figure the amount of wire needed. Even with great care, the finished wind- In the Rodin design, two equal coils are ings were a bit loose, so household glue wound in the same direction of rotation, and/or tape was used to tidy these up. A with each wrap (12 wraps per turn) passing _ white fibreglass tape used is available from through the centre to connect with its 150° electric motor rewinding shops, which are separated neighbours. This results in 12 also a good source for the enamel wire. I wraps—semi-loops—with as many paid US$4.00 a pound, about 800 feet per crossover wires for cach of the two equal pound, for the #24 wire. Tape and glue turns. These centre crossover wires forma were used at the start and finish of each distinctive pattern Rodin calls “the magic winding. circle". The two equal windings are shifted Tests were run to see the first-order 10° from each other. (See Figure 1.) attributes and how these compared with I have a good stock of #24 enamel wire conventional winding methods. It seemed To try to help answer this, a coil with 24 so I used this throughout. Each completed logical to me that a toroid wound solid with separate 10-turn conventional windings, bunched at 10° intervals on a Yellow form, One One One was made. These separate windings were Table 1: Approx. dimensions in inches Form A B c D_ Rodin wrap Rodin turn conventional turn | first connected, every other one together Blue 48 225 3.9 11 5.563 66.75 3,896 (12 sets x 2), then each set connected Green 45 2.06 3.8 1.15. 292 63.5 3.802 series-aiding. This was done this way to Yellow 413 18 3.6 1.06 4.92 59 3.604 get the same groupings around the outside Orange 3.8 17 3.38 1.0 4.842 $4.5 3.375 as in Rodin-style windings. The L was Red 35 15 32 94 4.167 50 3.198 222 UH (Q 58). Next, these windings were connected RODIN COIL DESIGN by Bill Ramsay Total Bw 263 s/a turns conv. 16 (8x2) 402 +53% Rodin 19 192 122' s/a tums conv. Rodin 122° 264 +62.5% Figure 1 ¥ Sd 10 SRA ry y, i SAS QA SAN" , &®) EIN) One One One 52 ¢ NEXUS APRIL-MAY 1996