I want to go through a bunch of machine bits and pieces with you so what better place to start..... Coils.
What is the coil core made from ? The core needs to be either iron or low carbon steel. there is actually very little difference between the two magnetically but from a cost point of view low carbon steel is the popular choice.
Technical : iron is just that... pure iron, mild steel or low carbon steel is an alloy of iron and carbon ( and some other bits and pieces in there for good measure ). Pure iron when heated becomes soft and workable, for example when blacksmiths heat and hammer to shape horseshoes. Add a small amount of carbon and it becomes stronger. Low carbon would be from say 0.05 to 0.25 % carbon content. No need to get much more complicated that that. The bolt hole to attach the core to the machine needs to be as shallow as you can get away with so that the core is solid and not hollow.
Why are there different height coils, some seem shorter than others ? To be honest, this is pretty much down to personal choice. I mostly build machines with shorty style one inch coils but the majority of machines out there use inch and a quarter coils.
Technical : Fact is that the shorter coils offer a lower centre of gravity on a machine which is why I make them that way, however, because the gap between the tip of the armature bar where your needle attaches and the vice clamp is slightly less you will need to set up your tips and grips differently and if you use fixed disposable tip grip combos then the machine will sit a little bit differently over your hand. Some prefer it but some it doesn’t suit. There is also a slight weight advantage with shorter coils obviously being lighter and the frame of the machine can be a bit smaller so the overall weight saving can be significant and make a difference.
What does it mean when they say 8 wrap coils or 10 wrap coils ? This actually refers to the amount of layers of wire over the coil cores. The technical term is actually layers but as we wrap the wire around the core I guess the name “wraps” has stuck.
Technical : However coils are wound, by hand or machine, the result is hopefully to get the wire onto the core nice and close together and tight to make it efficient. Starting at the bottom where the wire comes through the bottom coil washer, you wind to the top washer, that is then one wrap or layer. The wire turns back on itself as you turn the core and starts back on the next layer and so on until you have the desired amount. If you have an even amount of layers then it makes life easier to bring the tail end of the wire out through the bottom washer .
So what is the difference between the various sizes of coils and why the choice ? I am going to have to get technical for a bit on this but basically less wraps means less power so you could have a nice fast machine with 6 wraps that will be great for small lines but it just won’t work well pushing big needle groups for colour packing. Same as if you have a nice big set of 12 wraps on a machine, they will be far more suited to pushing bigger needles than small fine work. That’s the very short answer.
Technical : We need to get much more technical on this answer to have a fuller understanding of the differences. Let me start by comparing 6 and 12 wrap coils. Height of the coils doesn’t matter at this point. A 12 layer coil will, you would think, have twice as much wire on it as a 6 layer. well, it actually has a lot more than twice as much because what you have to bear in mind is that as you add each wrap/layer to the coil, it is getting thicker, so by layer six the coil is already quite wide. So when you add layer 7 it is going to take a lot more wire than when you added layer one and so on. So, when you put your voltage into your coils via power pack etc, it takes a lot longer to travel around a pair of 12 wrap coils than it would to wizz around a pair of nice tight 6 wraps. So, bearing this in mind, the 6 wraps will be faster coils and more suited to a small liner. It is also very easy to overload coils without knowing their limits, especially in these days of big bold lines and huge needles groupings. Personally I wind my coils with ten layers of wire. I find it to be a good happy medium between power and speed. 8 wraps are great but if driven hard may well heat up and 12 wraps will increase the weight of your machine. Obviously 12 or 14 wraps aren’t exclusively for shaders as many like a heavy liner and using the correct spring combination will do exactly what you want.
What is the wire that is used for making coils ? It is enamelled copper wire also called magnet wire . Same wire is found in coils and solenoids and transformers in loads of things in everyday use like telephones, computers, mobile phones etc.
Technical : As an extension of this very basic answer, magnet wire has it’s enamel coating to insulate it so as coils are wound the voltage has to travel all the way around the wire, if the wire wasn’t insulated with the coating then the voltage would just travel its quickest route and the wires would heat up and not charge the core as a magnet. In fact, if some of this coating comes off during the winding process you run the risk of the coil working but heating up and not being very efficient. The wire is available in many dimensions and is measured in either AWG ( American wire gauge ), SWG (standard wire gauge ) or just plain old metric measurements. Normal wire used is around the 24 to 26 gauge which is approx. 0.5mm diameter. All magnet wire measurements are quoted minus the coating which is approx. 0.03mm thick therefore a 0.50mm wire would actually measure 0.56mm diameter. Enough already.
Is there anything between the coil core and the coil wire ? Yes, the core is normally wrapped in kapton tape or the wire is wrapped around a plastic spool which then has the core pushed in to it.
Technical : Kapton tape is normally wrapped around the core, two or three layers of it. Also called polyimide tape , it withstands various extremes including vibration as well as heat up to about 260 degrees C and has silicone based adhesive. I prefer to use this method rather than a small plastic spool as you can make the coils slightly more powerful as the magnetic charge doesn’t need to pass through the plastic before it gets to the core. However, the spool obviously gives you more heat resistance and no chance of the wires coming into contact with the core so both ways have their advantages.
How are the coils connected together and connected to the machine ? When the coil wire is wound onto the core, it generally enters and exits the bottom washer. The entry wire is the one connected to the coil next to it and the other end is connected to the contact post.
Technical : Where the coils are connected together, the enamel has to be scraped off those bits of wire so that we get a good electrical connection prior to silver soldering the connection also. The rear coil is connected to the rear contact post and the front coil to the front contact post at the top of the machine where the contact screw is. Both of these connections are made using small solder tabs and again we would scrape off the enamel prior to actually soldering the wire and tab together.
But what about the capacitor ? The capacitor will either be within the coil circuit or wired individually. I prefer to wire mine separate from the coil circuit for ease of replacement.
Technical : The vast majority of machines have the capacitor within the coil circuit and it will be wired or fitted between the rear contact post and the front contact post. The problem with this is that should it fail then you have the headache of cutting it out and soldering in a new one whereas if it is wired individually then the replacement will be very straightforward requiring minimal effort and basic tools.
What does the capacitor actually do ? In a nutshell, the capacitor prevents your machine from having a big blue spark between the tip of the contact screw and the tip of the front spring when you run your machine.
Technical. This deserves a decent explanation. Yes the machine will run without a capacitor but it won’t be long before you have some bother ie. burnt out bits of spring and contact screw. Now some of you with older cars may remember the days of distributor caps with points and a condenser in them. Well basically a capacitor is in fact a condenser. Same thing. It is in the circuit to store excess charge momentarily and to prevent the charge from arcing across the gap between the front spring and the contact screw, much the same as they did with a set of points on a car. When your machine is running that fast, maybe say 100 to 130 hz or cps ( cycles per second) and with the gap being pretty small, the electricity can just jump right over the gap, by storing the charge momentarily this can be prevented, the charge is released as soon as the connection is re-made and then it all happens again......... up to say 130 times per second as mentioned. The capacitor rating is measured in microfarads or Uf and many builders use different sizes. Small sizes would typically be used for liners and larger ratings for shaders. I published some tests on capacitors and the differences they made a few years ago and the difference is nominal and as such it proved to me that the one size I use suits the coils I build exactly. It is pointless me going into the mathematical equations used to obtain exact rating required. To maximise the life of the capacitor it should be fitted the correct way around in the circuit, most are clearly marked for their flow direction.
There are so many ways to decorate coils, does it make a difference at all ? From the way that they actually run, generally no.
Technical : Not so much technical this one as common sense. The heat shrink you often see on coils serves a very good purpose by keeping them easy to clean and it is also replaceable . Many use plain black heat shrink and that’s fine, I use clear as I generally like to decorate the coils with banknotes or shiny stuff first then cover with heat shrink. The problems with coils covered in say string and stuff like that is that they can harbour lots of dirt and germs. OK, if you bag your machines then less so, but they can be very difficult to keep clean and if covered in varnish then very final and not easily recovered.
What about the coil washers, I often see different styles of those too ? Better looking doesn’t mean better working and in fact big thick washers can actually affect performance.
The vast majority of machine builders use either phenolic or fibre washers that are about 1.5mm thick. Sometimes you will see some fancy looking big thick washers on coils and I agree that some of them kinda look ok but check this out....
Technical : I am going to keep this short and straight to the point...... If you have thick washers say 3.5mm thick then that is 2mm per washer thicker than regular phenolic ones times that by two washers per core and that is 4mm of each core not covered in wire. Bearing in mind the wire is say 0.5mm thick then that is 8 turns of wire per layer missing, over 10 layer / wrap coil that is 80 turns of wire less in one coil. In a shorty one inch coil that is the equivalent of over 2 and a half wraps of wire so the big washers really can affect the performance of your coils.
What is it about coils with an extra half a wrap ?
They are completely pointless. don’t get mugged off into believing that half a wrap of loose wire actually does anything. for example, 9.5 wrap coils are in fact 9 wrap coils with the wire then wound around a bit on the way down to the lower washer where it exits. simple as that. it serves no purpose whatsoever and does not charge the coil at all, not even a tiny bit more, in fact it is a total waste because the builder is just being lazy by not completing the tenth wrap, and by doing the 10th wrap the coils would run cooler with less amperage required with more ohms resistance in the wire used. simple fact is that they just don’t know tech stuff otherwise they wouldn’t do it. It actually looks crappy too. Seems people like to copy the chinese, even use their frames and bits sometimes, dear me, that isn’t custom now is it ?
I hope you have found at least some of the information here of use, need any more then just get in touch.
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Coils Q. and A. .
Just to give you some tech. info on coils in a slightly different format. Hope you like it