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Old Mar 15, 2002, 04:59 PM
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Dave Wulff's Avatar
USA, FL, Fort Lauderdale
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Actuator coil winding method

Most of this coil winding method was explained to me by Phil, I only added the polypropylene materials to get away from the usual white glue/soap mixture and the lengthy soaking to get everything apart. Here goes. The sides of the fixture are 1/2" circles cut from a plastic coffee can lid (polypropylene). I sharpened a 1/2" pc. of brass tubing to use as a cutter. Then I sharpened a 1/8" brass tube to cut the center hole. Put a large wheel collar in the middle of a 3" pc. of 1/8" wood dowel, then slide one of the discs on. When the discs are cut with the brass tubing it gives a rounded edge on the side you cut from, this rounded edge should face toward the inside of the coil. Get some 5-mil plastic sheeting, like a painter’s drop cloth but the real heavy-duty stuff. This is also polypropylene. With a sharp blade and a straightedge, slice off a length 3/16" wide. It is important not to have any taper on this, and that the cut be clean and sharp. Cut a pc. of this strip to 4 1/2" long. Wrap the strip around the dowel, up tight next to the disc. At first the strip will want to rotate on the dowel, but about half way through the wrap it will grab hold and allow you to pull it all snug. Hold the end of the strip and put on the other disc, rounded edge in, and push it up tight against the wrap. Fasten with a wheel collar. The pressure from the discs will keep the wrap from unraveling until you can get a couple of turns of wire on it. I mount the dowel in a cordless drill that turns about 400 rpm. Set your wire up so that it will unroll easily. I mounted mine on a spool and hung it in an old tape dispenser. Take a few inches of wire and wrap it around the dowel, between the fixture and the drill chuck. Then loop the wire up and over the disc and take a few turns on the core. Make sure to leave some loose wire as you go over the disc, as the winding process will tighten this area up a bit and break the wire if you don’t leave some slack. Mix up some five minute epoxy and, using a small pc. of balsa, put a little on the core. Gently begin winding, stopping occasionally to add or redistribute the epoxy. When the coil is the size you want, make sure it has a lite coat of epoxy on the surface. On this fixture, 1000 turns of #44 wire give me about 190 ohms. Clean off as much epoxy from the sides of the discs as possible, otherwise your coil will have an epoxy rim around the edges that will need to be trimmed off. Leave another six inches of wire loose at the end of the wind. This combination will give you a 3/16" wide coil, with a 3/16" inside hole for the magnet. By varying the width and length of the wrap, you can control the finished dimensions of the coil. If you can’t find 5 mil sheet you can use a longer pc. of thinner material to get the same core diameter, but the thinner material will be harder to work with. The key is that polypropylene damn near repels epoxy. When dry, about an hour, remove the collars and slide the discs off. Slide out the dowel, but leave the wrap. Now take a good pair of tweezers, find the inside end of the wrap, and slowly uncoil it to pull it out. The wrap and discs can be used over again, just be careful not to scratch them, that would give the epoxy a place to grab on to.

Dave W
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Last edited by Dave Wulff; Mar 17, 2002 at 07:42 AM.
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Old Mar 15, 2002, 06:52 PM
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Fort Wayne IN USA
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Dow, thanks for posting the info, I'll try it. Bill
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Old Mar 15, 2002, 08:37 PM
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Thousand Oaks, Ca
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THANKS to Dow

Thanks you Dow for sharing the winging method. Will try it soon!!!
Chuck
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Old Mar 16, 2002, 04:19 AM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
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To save even more time make a three piece former consisting of two side cheeks and a central hub. These can be simply bolted together and stuck into your drill or screwed into an adapter on a geared motor. I use the latter as it can be mounted to a board along with the reel holder. The one in the picture isn't polypropylene (yet) but releases without soaking as I use commercial pva release agent.

I would recomend 1 hour epoxy as 5 min can get a bit stiff by the end of the coil and hard to remov the excess, but it's a matter of experimentation. I bake my coils in the oven at 75C for 5min which sets them hard so no reduction in speed.

Add a magnet to the head of your winder and a reed switch wired to the equals button of a calculator. Type 0+1 and every time the reed switch is energised one will be added to the calculation keeping track of your turns.

better wind this up

Graham
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Old Mar 16, 2002, 06:55 AM
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USA, FL, Fort Lauderdale
Joined Feb 2002
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Graham

My fixture looks the same as yours, except that the spacer is made from the strip of polypropylene wound on the dowel. I used the dowel/wheel collars instead of a machine screw, as the threads would dig into the softer material, making it tough to slide out. I was looking for a method where the core could be collapsed after the side discs were removed, so that no release agent would be necessary. This, combined with using polypropylene, allows the fixture to literally fall apart as it is disassembled. If a longer machine screw, that had the proper length smooth sholder could be found, that would eliminate the wheel collars. Your reed switch/magnet/calculator counter idea is great. I have an optical counter at my business, but it costs about $300 so I didn't mention it, as it is not absolutely necessary. However counting the turns gives a very predictable ohm value. Using one hour epoxy is also a better idea as the extra working time takes the pressure off if things don't go smoothly.

Dave W.
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Old Mar 16, 2002, 07:14 AM
Sticky Shepherd
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Oxford/England
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If I can get some polyproplene rod then hopefully my fixture won't require any release agent either or perhaps just wax polish. I have just never been very good a wrapping things neatly.

I also find a baked coil is more resistant to core removal and have had no problems since starting.

As it happens I'm moving to an optical counter as there are less problems with bounce, a basic emmiter detector pair with amplifed output is cheap ~$5 ? and I'll feed this in to the parallel port of my pc. Why? Because I just added a stepper motor driven traverse to my coil winder. Next step might be hot air bonding and auto eject

Graham
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Old Mar 16, 2002, 07:45 AM
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Graham

5 mil poly is pretty hefty stuff. As the side disc is already in place, it is really not difficult to wind the core. The poly rod might just slip out, particularly if you could turn a bit of draft on it (then remember which direction to pull it). The problem is that poly dosen't machine very well, sort of like trying to work with chewing gum. The finished surface would need to be polished smooth as a baby's butt. I still like the idea of the wrapped core, as it collapses as it unwinds, taking all of the outward pressure off of the coil. The last turn, next to the wire, just falls away.
More details on your winding machine, if you please.

Dave W.
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Old Mar 16, 2002, 09:56 PM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
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Quote:
Originally posted by dow
More details on your winding machine, if you please.
Its a pretty low tech affair in some ways. I have a base board on to which everything mounts. The motor is just a geared 12v one that runs at about 300/400rpm. On the end of this is a super simple brass adapter. Basically a lump of brass with threaded hole in the end held onto the shaft with a grub screw. The coil fixture shown above screws into the end. A magnet is also glued onto the adapter for the counting method mentioned above. I also have a simple wire clip, a piece of bluetack. The wire I buy is on fairly small reels so I use a glorified "pencil method" I have a dowel that passes through two bearings with the spool mounted on the dowel. Two cone shaped pieces of balsa keep the spool centralized on the axis of the dowel. To provide tension and to stop the spool over spinning I have a metal rod pressing against the axle tensioned with an elastic band. The wire guiding is done by a small tube that moves back and forth. This is on the end of a salvaged micrometer which is driven by a stepper motor. The software causes the stepper motor to rotate a given number of steps each time a revolution is completed and causes the guide tube to traverse back and forth. It works pretty well but there is far too much play and too many differences between my coil formers for "perfect wound" coils.


I can recomend setting up winders on a board even if it is a simple hand winder, it makes the whole process easier.

Graham
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Old Mar 17, 2002, 07:40 AM
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Graham

Sounds impressive, but a bit too much work unless you were going into production. Eventually I can see myself winding 20 or 30 coils for my own use, plus a few for friends. My simple rig will do that nicely. My reason to post this method is that building the electronics like the DU system is out of reach for most all of us. However, actuator coil winding is not. The money saved on pre-made coils could be better spent on extra recievers. Personally, I can see myself with half a dozen or so of my favorite planes (SE5, DVII, JN5, etc.). If they all had coils, swapping recievers would give you two or three ready to fly at any one time. BTW, I think the title for the post is a bit fuzzy. I will try to change it to "Actuator coil winding method" if I can.

Dave W.
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Old Mar 18, 2002, 06:40 PM
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Idaho
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Another coil winder

The pic shows a coil winder I made up from mostly scrap bin parts. I turned a polished aluminum winding bobbin with separate endplates. The 5:1 gearset is from one of the kids old toys. The $3 calculator is mounted so a trip ear on the primary shaft presses the "=" each revolution. The polished aluminum works fine with just Johnson's paste wax for a release agent. I haven't run down any bulk magnet wire But I found that a cheap electric quartz clockworks has enough ~#40 AWG to make up 3 DU-dimension coils, 550 turns gives 50 ohms. I bought 4 clocks (Ingraham) at Shopco for $2.99 each on sale so that's enough for a dozen coils. Incidentally, each clockworks has four sets of gears that are keepers for small gearboxes. Be sure to color code the gears when the clockworks is disassembled because there are at least three different moduli involved and they are hard to tell apart.
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Old Mar 18, 2002, 10:03 PM
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Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
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Carl, very nice. That was quick work if the DU system was your first venture into actuators and now you are making your own.
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