Pictured above Scott's winding with two strands of wire. This is necessary for 12 Volt machines.
The magnet wire you need depends on the voltage of your system. Roughly speaking, every time we go up 3 sizes in magnet wire then the wire has half the cross sectional area. The voltage of the machine is directly related to the number of turns in the coils. If we double the number of turns, then we double the voltage. No matter what the voltage of the machine, the coil size and weight needs to remain about the same. 12 Volt machines require very thick wire, so thick that it makes sense to wind with two strands in hand. (so for 12V machines we need two spools of wire and we're handling two strands as if they were one)
- For 12 Volt machines you need to wind with two strands of #14 gage wire in hand and each coil should have 36 turns.
- For 24 Volt machines wind with 1 strand of #14 gage wire and each coil should have 70 turns.
- For 48 Volt machines wind with 1 strand of #17 gage wire and each coil should have 140 turns.
If you follow the guidelines above, and the coil winder is made according to the plan then the coils should fit nicely in their alloted space, and the whole stator should require about 6 pounds of wire. If the rest of the alternator is assembled properly then the machine should start charging batteries at about 140 rpm which is nice for a 10' diameter blade.
Start by creating some kind of fixture to hold the spool of magnet wire. I usually use a vice with a piece of threaded rod, or a wooden dowel sticking up to put the spool. Clamp it to the work bench securely.
You'll need a pair of side cutters (to cut the wire), a pair of needle nosed pliers (to bend the wire) and some electrical tape. If the coil winder has a wing nut holding it together then you can use your fingers to take it apart. Otherwise you'll need a 1/2 wrench. When you bolt the front on the coil winder finger tight is fine, but after all the wire is wound on the spool the nut will be tight so - if you dont have a wing nut, you'll need a wrench to get it apart.
Drop the wire in the slot of the coil winder and bend the end around the nut. (A wing nut helps here too..) This will hold the wire from slipping when you wind the coil.
Hold the wire tightly in one hand (keep tension on it) while turning the crank with the other hand. Be careful to keep constant tension on the wire and try to turn the coil winder at a constant speed. I notice lots of folks tend to turn it faster on the down stroke and slower on the upstroke - this will usually result in a lop-sided coil (one side of the coil wider than the other). It's important to keep constant speed and consistant tension. Try to wind the wire in neatly but don't obsess over perfection. I've seen some folks take over an hour to wind a coil trying to pile the wire in perfectly. It should take no more than a minute or two to wind a coil.
Once you've got the correct number of turns, pull the lead out of the slot and twist the two ends together (1/2 twist - just enough to hold them together). Don't twist more than you need because later you'll undo this and it's nice not to bend up the wire more than necessary. Grab the wire between the spool and the coil with one hand, and clip it so that there's about 10" of wire out of the coil. (both leads coming from the coil should be about 10" long) Take the loose end that's coming from the spool, put it on the workbench and set something on it (the side cutters are handy since they're probably still in your hand) so that the wire on the spool doesn't unravel.
The coil should pretty much fall off the end if you just turn it over. Do it carefully so the coil doesn't fall apart.
We refer the longest sides of the coil as the 'legs'. Tape the legs of the coils with a couple wraps of electrical tape to hold things together. One coil is finished.
Check your coils, they should fit in the stator mold as shown in the picture. It's OK if they're a bit smaller we used #16 gage wire in the coil pictured. If you use #17 wire as called for, they'll be a bit smaller. Remember the stator mold has 9 radial lines that tell us the maximum width of the coil, and it has two circles (8" and 12" diameter) that show us the path of the magnets. When checking the size of the coil center the hole in the coils center over the 8" and 12" circles. In that position the coil must fit in between two of the radial lines.
If the first coil fits well, then wind 8 more like it. In the picture we've put all 9 finished coils in the mold, you can see how they're almost a perfect fit. Again - you might have them come out slightly smaller than those pictured which is fine.
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