View Full Version : CD Motor Winding For Thumbies -- The Classic 17 Turn

12-14-2005, 06:47 PM
For some time now the 26awg 17-turn has been a standard in the CDROM motor universe. It has only one purpose in life: to fly a 7oz or less 3D plane 2s with a GWS 8040 prop. Okay, you can run a 7060 for a bit more speed on some little pooch plane, or float a bigger "sport" model, or even go 3s with a 7x35. But that's all a bunch of hooie. It's an 8040 3D motor.

Warning: when I took these photos I was doing a 20mm stator, a vice I seldom indulge (but it was my test project at the time).

You should use the 22.7mm stator. It will deliver more power (at a small weight penalty) and be easier to work with. The best deal on a basic kit is the standard slofly kit at www.slofly.com (take a look at the other kits too. The Komodos deliver a heck of a wallop. If you're lazy just buy the Lens 22.7 20-turn. Great motor).

If you're gonna drop the big bucks for top-notch performance head on down to www.strongrcmotors.com and get a kit -- or even spring for the GBx setup. In either event, give the guy the extra bucks for the curved magnets. They're worth it. In for a penny, in for a pound.

Begin by marking your 'starter' teeth. I only mark two, since I'm going to cover the first position (to the left of the black dot) immediately. That's where I'll both start and end phase 1. Phase two will start on the black dot, and phase three on the red mess.

Start and end?

12-14-2005, 06:47 PM
The idea here is to waste a little wire making your first real tooth easier to start. Note I sort of wrap it backwards so it will be easy to unwrap. So make a few turns on the tooth you marked, count over three (which will be just to the right of the red mess on my stator) and start your actual wind. When you finish your first tooth, you can come back and unwrap this.

But we'll get to that.

12-14-2005, 06:48 PM
Neatly wind your first layer on the first tooth. You should be able to get 8 winds completely on both front and back (back is the direction the bearing tube faces). Wind firmly, but don't pull hard or yank. When you get around to the front at turn 8-1/2 you should basically run out of space and be forced to the second level. Stop at this point and smoosh the wires in flat to the stator (between the stator teeth; don't worry about front or back) with your favorite tool -- toothpick, carbon fiber flat stock, whatever.

12-14-2005, 06:49 PM
When you go around to the back again, loop the wire outside your eighth turn so it kind of overhangs the hammerhead. This will buy you enough space to get that 17th turn on when you get back down to the bottom of the tooth.

Note that the wires have been smooshed flat at this point.

12-14-2005, 06:50 PM
Do the same thing when you get back to the front. This one is a little bit trickier, but also just a little bit more important. You'll need the space on the front. So hook it on there and snug it down a little. It really will stay.

After you manage this, just keep on winding. Don't pull very snug at all -- you want a slightly (very slightly) loose wind so you can pop and snick the wires back toward the outside when they slip inward. Trust me, they will.

12-14-2005, 06:50 PM
Once you get back to the middle, the wire should just barely fit on the back side after your 17th turn. It's a good idea to do another smoosh at this point, getting the wires nice and flat against the sides of the stator.

Note that you never care what happens on the "back" of the stator. There's always plenty of room. While you're winding, you care what goes on between the teeth, but only while you're winding. Once the wire is in there, it just doesn't matter any more. But I like to keep all the mess on the rear of the stator, because the one place you do have to worry about in the end is the front. The wires will have to stay clear of the can.

Don't worry about that yet. I'm getting ahead of myself. At this point, you should see something like this:

12-14-2005, 06:51 PM
Once I've finished the first tooth, I go back and unwind my starter. Then I take the wire and jam it into the rear bearing hole to keep it out of the way.

Later, after I finish the entire phase (three teeth, the last being the tooth I originally used to anchor my wire), I tape the end to the bearing tube. This keeps all the floppy stuff out of the way while winding the next phase.

12-14-2005, 06:52 PM
When you start the next phase, you'll be confronted with winding a tooth next to one that's already full. You should find there's plenty of room to get the first layer on. When you get to turn 8-1/2 (as above) you'll want to do a little bit different smoosh.

Up until today, I used carbon flat stock to work this trick, but Jeff (galloping_gimp) turned me on to this slick move: use an old prop blade to get your center spacing. The entire problem is in the middle -- we'll have tons of room out at the hammerhead, but it's going to be a bit crowded near the hub. To open that up, cut off the end of a prop blade and slide it through the gap. It should go easily, and you should see plenty of room to slip the second layer on.

12-14-2005, 06:52 PM
After that, you just keep going. You might be worried that the third phase will be harder than the second, but I actually find it easier. During both of the first two phases, I'm concerned with making sure I leave enough room for the work I have to do later.

On the third phase, there is no work later. If you get the wire on, you're good to go.

When I get to the last half wind of the last tooth, I like to thread the wire under its own start. Otherwise it's just kind of dangling loose and doesn't necessarily even neatly finish the 17th turn. This may sound odd, but the pictures will help explain, and I guarantee when you get to that point you'll see what I mean.

First, I leave a lot of wire to make this operation easy:

12-14-2005, 06:53 PM
Then slip the wire under that same wire's start (on that tooth; not its original start...)

12-14-2005, 06:54 PM
Take it easy tightening the wire into place -- it's possible to kink it if you're not careful. When you're done, turn it out toward the edge. And that's about all there is to it.

12-14-2005, 06:55 PM
Here's about how it should look. You will want to smoosh down what you're looking at in this picture. These wires are trying very hard to make contact with the spinning can. Your job is to flatten them in to make sure they don't get the chance.

Now stick it on your shockie or slofly mini or whatever. It will do the job just fine, and you can start thinking about doing that 20-turn so you can go 3s with the 8040.

Dave North
December 2005

12-16-2005, 03:32 PM
Do-it-yourself motor (cd-rom & lrk) homepages, manuals/tutorials, checks and tests in the first message of this motor builders tips and tricks thread. The checks and tests may save you from frying your controller. Thread is active, bookmark it for future refence and subscribe to it:

12-16-2005, 07:23 PM
Thanks Ron!