Coil Ignition Without A Battery

I have covered this elsewhere, but here's a condensed thread version I put together for another forum. It basically gives a better idea of how to do this yourself.

the only thing I would add is to make sure you use thick enough wire for your coil & I think the one I did here could have done with another 50 turns, but this generating set is having other problems, so apart from bench testing I have not used this method in anger, but it ran fine on the bench.

Anyway, here goes....

OK, so I've messed about with this for some time now & done a write up on another forum, but I feel it's time I shared my experiences over here as well, as this could be a valuable little trick for people with non-running engines due to magneto failure.

First of all, this is primarily for flywheel magneto engines, but could in theory be used for any rotating magnet magneto (IE: Wico A, Lucas SR1, Lucas RS1 etc etc).

This is not my idea, but was mentioned by another forum member &, having slightly more than a passing interest in all things electrical, I picked it up & worked with it. But, I'm nowhere near an electronics genius. I count myself as nothing more than an enthusiastic novice when it comes to this sort of stuff, having messed about with small circuits since childhood & becoming an electrician later in life.

Anyway, I will start the story here, with my Tarpen. I've had this engine since the age of about 6 or 7 & I did a full strip down & restoration last year. But at the last rally of the season the spark disappeared. I eventually found out it was due to the magneto coil. It had worked loose & the internal earth connection from the HT side had broken, so couldn't be repaired. A cheap BSA Bantam coil wouldn't fit & I couldn't afford to get it re-wound, so I decided to try a trick that was mentioned by a forum friend of mine.

Basically, what I have done is to use a motorcycle ignition coil. This is identical to the car type coils that many of us use to bring old engines back to life with the aid of a battery, but it's a 6v instead of 12v. But a 12v coil would work just as well for this purpose. Here's a couple of coils I had to work with, they are both off bikes, one is 12v the other is 6v....



Now, I don't want to have to cart a battery round with me everywhere, & I don't want to have to remember to recharge it every time I want to go to a rally. The Tarpen is a portable generating set, & I want it to remain portable.

So, it may be of interest to some of you to know that you don't need a battery to run these coils. All you need is a small kick of electricity to pass through the right terminals at the right time & that coil will give you an ample spark.

So, what do we have that can give us this "kick" of electricity just when we need it? Well, we did have a magneto, but that's no good. Or is it? Well, we still have the magnets, so all we need to do is have some copper wire, & those magnets can induce a small current again.

Basically (& I really am trying to keep this in as simple terms as possible, because believe me this really is a very simple exercise, you really don't need to know how it works, you just need to know that it does work) all we need to do is wind ourselves a small coil of wire around the old magneto coil centre (or any other coil centre which will fit), put it back in the mag, where the magnets can pass over it & give us that "kick" of electricity. Then simply connect it up to the car-type coil, connecting the other side to the points & condenser as usual, & we will have a spark again.

The simplest way to look at it is just think of this as a replacement for the battery you would normally use in this instance.

Here's what I did. I got some enamelled copper wire (sometimes called magnet wire, or winding wire), I wrapped a piece of card around the old coil centre, to protect the enamel on the copper wire from the sharp edges of the centre bar, then begun to wind myself a coil....



Now, you really need to keep this coil as neat as possible. I used a spacial winding tape, available on line, but ordinary insulation tape would do, even sellotape or masking tape would be fine. I made one layer of a coil, then applied a layer of tape over that. This isn't strictly necessary, but it is very helpful, as it keeps all your hard work together. Then you carry on with another layer of turns over the top of that. You obviously must keep turning in the same direction....



The best thing to do is count the number of turns on one layer, then use this number to estimate how many layers you are going to need. As a general rule, for a flywheel magneto, you will probably need about 250-300 turns to power a 12v coil. I ended up with around 150-200 turns on mine, which was enough to power a 6v coil, but really, with a 12v coil you'll probably need more like 250 at least.

A word of advice, you need to wrap the wire quite tightly to keep it neat & take up the least amount of room possible, so have some pieces of tape cut, ready to put on when you come to the end of that layer, as if you put it down it will unwind itself, which is very annoying. Also, this will make your hands ache, so be prepared to take a break, you can always put a bit of tape on half way across a layer, take a break, then take it off when you re-start.

When you have finished winding your coil, & covered the whole thing in tape, it is a good idea to solder, or crimp, some flexible cable tails to the ends. This winding wire is solid core, & as such it will work harden with movement or vibration & will eventually break (which is what happened to my coil in the first place), so connect some flex tails (any old flex will do) & wrap the whole thing in tape, obviously making sure your soldered joints don't touch each other & short out. This is what I did....



BTW, all these pictures, & more, are in a dedicated photobucket album, which can be found here....

[URL="http://s682.beta.photobucket.com/user/nutgone_matt/library/Magneto%20Ignition%20Experiments"]http://s682.beta.photobucket.com/user/nutgone_matt/library/Magneto%20Ignition%20Experiments[/URL]

Now, a quick word about wire. The wire size for your coil is pretty unimportant. I think I used wire size 20SWG (Standard Wire Gauge), which translates to 19AWG (American Wire Gauge), & is about 1mm in diameter, but you could go smaller. I would personally recommend something in the size range of 19-24SWG which is 18-23AWG (or 1.01-0.56mm diameter, or 0.81-0.24mmsq cross section). You don't want to go too big, as it will take up too much room, & you don't want to go too small as it's very difficult to work with very thin wire.

Once you've built your coil you need to know where to connect it. Now don't think about this too hard. Basically, all this coil is doing is replacing the battery you would have used, so one end goes to the chassis of the machine, as an earth. The other side goes to the + (positive) connection on the coil, otherwise known as +ve, supply, battery, or something else.

There you go, simple really. Now, you need a wire from your points & condenser to the other small terminal on the coil (usually marked -, or neg, or something else). Your points should still be in the same place they were before, just put a ring terminal on a piece of flexible wire, put it either on the points terminal, or on the condenser terminal, which ever one has the easiest terminal. If necessary you can solder this wire on, just make sure all these wires are long enough.

Now you will need to hide the coil somewhere & put a piece of HT lead from it to the spark plug. Then route your wires. You may want to take the earth wire out with the others & earth it out there somewhere, or you can earth it inside the magneto somewhere, as long as everything is earthed, it doesn't matter.

Now, there is a possibility that your hand made coil may work better wired one way round than the other, but usually it makes no difference. The best thing to do is leave the wires long enough to go to either the coil positive or the earth point, try them either way round & see if you have a better or worse spark (I like to use the beginning of the coil as my earth, but that's just me).

Now just find some way of clamping down your car-type ignition coil, do all your connections up nice & tight, connect up your spark plug & give it a spin.

Here's a few more pics of what I did....







As you can see, it's all hidden from this side, so no one's the wiser....



I will post something up next about my experiments with a Lucas SR1, rotating magnet magneto. I had a little play about with this method & got some good results. But first I need to have some lunch & do some more in the workshop.

Any questions or comments, by all means ask. If you want to PM me about this then feel free. If there are any more knowledgeable people out there who would like to make up some sort of easy-to-follow diagram, then go right ahead.

This could be a really good way fo saving engines from the scrap yard, especially with Villiers engines, as they are notorious for the magneto coils rotting. So go on, get that old Villiers Mk10 out & give it a go! A few yards of enamelled copper winding wire & you'll never need to cart that battery round with you again!

I'm glad someone knows what there talking about.

Great work Nuts and thanks for giving up your time to help others understand and what to do if they want to convert there own engine.

Stu.

Hi All
What an excellent little how to. Good to know this work's
Andrew

Excellent work Matt. Have just disassembled my MK10 Villiers and indeed the magneto coil is goosed. Looks like a trip to Maplin later today. Thanks again.

Well I will soon be winding full-blown magneto coils, so shouldn't have to do this little trick again. Hopefully I will be offering re-wind services to engine enthusiasts within the next 12 months, depending on how other things go in my life (could be sooner).

I will keep this forum updated with progress & will be talking to admin about possibly offering discounts to active members of this forum (& only this forum). See how it goes.

Still, with a coil winder now at my disposal, I can see a few different ignition experiments coming on.......

Hi Matt,
Stripped the magneto and wound new primary using 22 gauge enameled copper wire (£8 from Maplin) Connected one end internally to body and took other end out through old bakelite HT connector. Wired to 12 volt ignition coil from autojumble (£3) and fitted new HT lead and plug. Turned it over and got an excellent spark. Drop of petrol in the carb' and she fired up first time.
I now have a running Villiers MK10 for less than £15 spent on ignition

Brilliant 'how to' Thanks again.

Great stuff.

Hi All,

Thought I would throw my two penny worth at this.

I used to wind ignition coils many years ago and I still have most of the equipment (Douglas No. 6 automatic coil winders, vacuum tank etc, etc etc.) so I am going to offer my services here.

I can wind most fixed i.e. non rotating coils for €32.00 plus postage. Rotating coil armatures do cost more because they are a pain in the bum to do.

My coils are wound with G2 wire and interleaved with craft transformer paper 2 thou thick. All coils are vacuum impregnated with an epoxy varnish and finished with several coats of a solvent varnish. They are also serial numbered.

The big draw back to all this is that I live in the west of Ireland, County Roscommon to be exact, and payment must be in euros.

I will also soon be able to re-magnetize most magnetos as I am restoring my magnetizer that I built from the Lucas spec and runs at 400-500 volt dc.

I have set up a facebook page in the last couple of weeks where I have put up some pictures of my set up so far.
My facebook page is Coil winding Services Ireland.
I hope that I can be a cost effective help to engine restorers.
Thanks
Simon

That's more like it!
Finally someone doing these things at a price aimed at the engine enthusiast.
I was hoping to do non-rotating coils for around the £40 mark, but am still not tooled up yet.

I will make sure to come & look at your facebook page. Best of luck to you. (you may not find other magneto specialists so encouraging, I've found a few at least to be quite rude & certainly less than encouraging to me, fortunately though my local guy has actually been very helpful, he is very successful & as such has a 15 month backlog & is happy for me to take some of the strain).

Hi Simon,
Don't have (and won't have ) a facebook account. Any other contact point?

Hi Matt,
Are you any further on yet?

[quote="Woodsman"
Hi Matt,
Are you any further on yet?[/quote]

Not yet, my treatment is taking its toll at the moment, so I don't have many useful hours in each day, & I've got so many other projects I need finished & out of the way to make room for this venture. I've almost sorted my workshop heating though, I've designed & built a sealed system, blown-air heating based on a rocket-mass heater, but which runs off wood pellets. That's taken longer to get the teething troubles ironed out than I expected, but I need a warm space to work in, or I'll just end up making myself even more ill.

I will make an announcement when I'm up & running. I've found a very well respected local magneto rebuilding company that are happy to help me out (they have a 15 month plus waiting list so are happy for someone to take some of the strain & they are also happy for me to take stationary engine customers as they are more interested in vintage car & motorbike people). They are going to advise me on procedures & the various different materials used in the process.

Once I get some space sorted & some form of coil holder made up for my winder, it won't be long. Just got a couple of engines to finish off first.

Hi Matt,
Not up to speed with your illness/treatment (not a forum topic I guess) but best wishes for a speedy recovery.
A self built rocket-mass heater - top man! I'd be satisfied with a little pot bellied stove to get rid of all the waste from my workworking projects.

PS Love the automatic similar topics !

I thought I would resurrect this thread as I found myself with defunct coils on both my Villiers MK12 and MK15. Coils are available but are around £65, so having read nutgones excellent guide several times and having a 12V coil to hand I thought I would give it a try.

The world's ugliest 12V coil:


I bought my winding wire on Ebay, I got 125G of 1mm diameter. Now at this point I had no idea whether that would be enough, even if I knew what 125G was in length I didn't know what length I needed...

First job was to 'dismantle' one of the old coils, this is the MK12 one:


I was planning to glue some plastic discs onto the core but the old ends stayed on, saving me a job:


I found gaffer tape was just the right width, so with some pieces cut ready I started winding:


I found with the first couple of layers I could wind a few turns on and then push them up to the previous turns, after that I had to wind them tightly:


Getting there:



I found I could get around 37 turns on each layer and ended up with 8 layers, so around 296 turns. I used the last few turns to take the 'tail' to opposite end of the coil to the start:


Final taping:


I then soldered and heat shrinked two leads on:


Having sorted out the best routing of the wires I crimped a ring terminal on to earth onto one of the backplate mounting studs:


I extended the points wire and ran it out through the redundant HT lead ferrule:


The coil wire I ran through the insulating bush where the stop blade had been, unfortunately the bush didn't stay in place:


I was then a case of refitting the backplate, resetting the points and refitting the flywheel ect. (I had marked the flywheel with the engine at TDC so didn't have to faf about retiming it).

I mounted the coil temporarily and put a switch in the '+' side:


So, the million dollar question... did it work?

YES!


The end result, with the coating sanded off the coil and the top painted. Due to the length of the wires I ended up with the switch in the points side but I don't think it makes any difference:


So there we are, for less than a tenner for the wire and a couple of days tinkering time I have a running engine, for my MK12 I was thinking of trying one of these 6V coils:
https://www.ebay.co.uk/itm/194220804382

Nice one! Good to bump up Nut's post.

Tried it successfully on my first engine (MK10) and it's still there. I keep considering replacing it a cheap Taiwanese coil, which I have done in the past, but haven't got round to it.