Saving Old Seagulls

Have to admit to being short of a few grey cells in the electrical dept ...basic spanner wielding is enough of a challenge

Finally got all the bits of a lovely 1957 SJP together plugs, points all clean and gapped, new HT lead and old style cap
Job's a good 'un ?????...... NO !!!! ....
No joy at all, even spun up on the drill

lengthy instructional lecture from 40tpi on the uses of my ohm meter (thanks Peter) and despite a spark, albeit weak NOTHING
while chatting to said electrical wizard (what the hell is an open circuit ??) I tried out 4 other coils

NONE of them gave a reading on the meter, despite me jabbing with the probes like a crazed squaddie on bayonet training
BUT my 2 assembled power heads 1 x SD and 1x OP give a great spark

I asked George, the nice man at Villiers, and got this back ....

TEST FOR CIRCUIT BETWEEN HT & LT, WITH CONDENSOR DEWIRED U MUST DO,
MOST OLD VILLIERS COILS R NOW DEAD OR DYING, EXTERNAL LOOKS MEAN NOTHING,

HT? LT? where the hell is the condenser? ..sort of need to know that in order to dewire it
what ohms resistance is one looking for ??

call me a cheapskate if you will, but 5 seemingly dead coils @ £50-00 each is a bit of a gulp ...or is it the mysterious condenser

Hi,
depending on the make-up of some of the coils you cannot test them with a DVM. There are a few threads about the safety air gap in the electric string in some coils. This makes it impossible to check. If you have a spark that will wobble your arm then it's not electrical.
Condenser is a word used to describe a capacitor located under the points box. Again, If you have a spark that will wobble your arm then it's not electrical.
HT is the sparking side of the coil, the big volts, LT is the bit of electric made by the magnets in the flywheel that the coil uses to make the HT bit, IE the small ones.
Try injecting fuel into the crank case with a bit of drug taking kit, and neat oil into the sparkplug hole. I have had problems before with dry bushes preventing the suck, blow, bang thing hapening due to leaking bushes and dry piston rings.
regards
Phil

What we need to do is rewind our own coils.

Peter needs to get his thinking cap on, Coil winding cant be that hard. Only a few miles of hair thin wire and a bit of shellac.

H-A

oh and open cct means not connected
Phil

Remembered watching this thinking it could be useful.

http://www.youtube.com/watch?v=KT8rk5QWgS0

Now I see why the Primary coil is not normally a problem. This one is good, but had a dud Secondary coil.





Got it apart by soaking in meths, cut off loads of 3.5 thou copper wire.

Anyone got a coil winding machine and some wire

The Secondary wire must connect to the core, from what I can see there is no obvious way it can be fitted after the Primary coil has been wound.
There is a hole in the end insulator but I can not see how the wire would attach ( anyone got an idea).

The Primary is separated from the Secondary coil by some cotton tape soaked in glue type goo.

The pick up is soldered to a band of windings about 3mm wide, when the soldering takes place the rest of the coil is protected by a mica patch.

I do remember seeing an article about coil winding using a lathe, the only problem that I now have is how many windings will I need to put on.

Is there a formula for working out how many turns would be needed, or is it the more the merrier.

H-A

Horsley-Anarak wrote:
........Only a few miles of hair thin wire and a bit of shellac.

H-A

There is no easy answer........... and selling my old AVO motorised automatic coil winder some years ago, before becoming interested in magnetos, was clearly foolish with 20/20 hindsight.....

However moving swiftly on........a little refinement to my after lunch Cholesey SWAG :

A 4,000 Ohm secondary wound from 40 SWG enamelled copper wire at 1.48 Ohm/metre requires 2927 yards (1.66miles) of wire. (Apologies for the mixed units , my ancient BICC wire charts are not easily to hand and that's data off Google) Pause for a moment and then turn that length into number of turns by assuming a wet finger average winding diameter of an inch....gives around 33,500 turns

Factor the above up or down by changing wire gauge or required dc resistance.. but it doesn't get any easier. The basic problem is not the number of turns, a few hundred either way won't matter. The first problem is winding wire of this diameter ( 4 thou) close wound (at a single diameter) in repeated layers without it "pile" winding. And then doing it at any speed with wire that has a breaking strain measured in ounces/tens of grams.

Adjacent turn insulation is not a problem; we are talking fractional volts/turn. Layer to layer to layer however most certainly is! A good figure to keep in mind here is that the breakdown voltage of air at sea level is around 26kV/inch. ( Reduce substantially for Seagulls elevated to Alaskan mountain ponds....)

I have no idea what the actual wire gauge is on our Villiers Mk1 magnetos. If anybody has cut one open I'd very much appreciate learning the wire gauges/ diameters on the primary and secondary and how the windings were organised and insulated so we can refine a design solution.

I'm sure there would be a tremendous sense of achievement in rewinding a magneto from scratch but it may simply not be worth it. The 40 SWG solution above takes approximately 300gms of copper wire which lists at around 8 GBP plus carriage on the first Google hit. Add "shellac", mylar/ptfe/fish paper or equivalent, scrappage/screw ups/birds nests and no account of personal time and you may start to think that the published rewind prices may not be unreasonable........

Then again I'm not anything if a parsimonious Tyke so I'll give it a go sometime! But I doubt I'll be offering a rewind service!

Peter

ps. We happily repeat information on this forum to help out but I do wish we could leave behind the notion that Seagull Villiers or WIPAC magnetos have an internal spark gap, safety related , spark enhancing or otherwise. They don't!

That will teach me to type faster Allan.....! Your post went up whilst I slowly flat fingered it...! If you've measured 3.5 thou then we are close at 40SWG.

Good pics . Will re-calc. How many turns on the primary please? Wire diameter?

Peter

ahh ...yes ...well...ummmm
sort of gald I asked ...I think

slowly spinning up a coil in grubby fingers, wire thinner that 2oz fishing filament, and about as frustrating while viewing back issues of Coronation St ...back to when Ena Sharles was still in it

...nope pay George his wonga ...he deserves it ...not worth the aggro

Horsley-Anarak wrote: ..................
some wire ..................

The Primary is separated from the Secondary coil by some cotton tape soaked in glue type goo..................

The pick up is soldered to a band of windings about 3mm wide, when the soldering takes place the rest of the coil is protected by a mica patch...........

Quite exciting.... read and re-read....great post mortem

Wire availability will probably not be a problem.............

Primary wire looks like single or possibly double cotton covered wire impregnated with varnish rather than single enamelled. Probably paper insulation underneath insulating iron core? An estimate of the diameter of the core plus primary and same plus thickness of cotton tape plus goo would be useful.

Any evidence of insulation, other than varnish impregnation, between successive layers of the secondary?

Secondary termination with a "3mm wide band of winding forming the solder point" sounds great mechanically but is puzzling electrically since this equates to a massive shorted turn to the primary flux .... a total no-no. A typical transformer stress relief connection is sometimes made by winding a non shorting strip of metal around the core insulated from itself with a layer of paper or other insulator and then fastening the thin copper transformer wire and the external connection to this strip. (Similar technique to adding a non shorting copper Faraday shielding to outside of a transformer bobbin core).

Use of mica in this vintage is predictable ....good insulator and also heat resistant. Unusual to see it bent round a tubular shape however...........

With no mention of secondary layer to layer insulation I may have to admit a serious error in assuming it was strict close pitch/ layer wound. It may well have been semi scramble wound rather than strict layers..... any evidence when stripping? If so winding accuracy becomes much less demanding. ( It might also imply a potential failure mode)

Pretty sophisticated core winding calculators ( toroidal and conventional split core) can be downloaded from the web from quite a few of the ferrite and iron powder core manufacturers however we don't need most of the features. We can start our basic calculations from a knowledge of the typical production secondary resistance and the original wire gauge Villiers used.

Use of a lathe to wind coils is just the same as cutting a thread with change wheels and a lead screw and this is very much the technique used in commercial coil winders. Solenoid coil winders however have accurate auto reverse facilities and infinitely variable pitch control. (Variation on the rubber variomatic gearbox drive technique) More importantly they have quite sophisticated tension controllers for wire feeding. From recollection the smallest feed pitch on an ML7/S7 is around 8 thou?

The "chassis side" connection of the secondary might actually be to the hot end of the primary rather than down to the core itself. Electrically this makes it an auto transformer and actually jacks up the EHT by the few volts already in the primary. No real benefit or real consequence electrically but may be far more convenient mechanically in production.


Peter

40TPI wrote: ,............The "chassis side" connection of the secondary might actually be to the hot end of the primary rather than down to the core itself. Electrically this makes it an auto transformer and actually jacks up the EHT by the few volts already in the primary. No real benefit or real consequence electrically but may be far more convenient mechanically in production.

It is futile to attempt to measure the very small primary resistance in series with the secondary with a simple hand held DVM and hope to accurately see the difference when simply measuring the secondary in isolation. Just done the equivalent of a 4 wire resistance measurement on two good Villiers magneto plates to find the primary resistance and confirm that it is indeed an autotransformer configuration. Measured the indicated resistance of each secondary; 3.250k Ohm and 2.680k Ohm. Forced an accurately measured voltage in the region of 10V dc ( 10.0190 V) through the secondary with the current returning through the plate. The primary points connections showed 0.000932 and 0.001168 V respectively. To a good approximation this gives primary resistances of 0.302 and 0.312 Ohms respectively. The presence of the voltage also shows it is an auto transformer configuration; the earth end of the secondary is connected to the points connection on the periphery of the coil former and not to the iron core.

The difference in the secondary resistances seem far far larger than one would expect from a reasonably precision wound item. The difference implies quite a bulk of wire if the same gauge has been used on both coils..... I'm seriously starting to think that these coils have just been semi scramble wound as neat as possible until the former was filled and then the outer outer sleeve fitted with a dollop of shellac as it closed........ Then solder dropped through the hole in the side button to make the EHT contact.

Still can't find the BICC wire data booklet but have found a couple of kg of wire around the 36 SWG size. A little too big I think. The workshop search continues....

Peter

Have just put a mk 1 villiers (the longer SD, Marston type) coil in some meths.

I will take it apart with more care and try to count the layers of windings and inter winding insulation.

Also I will look more carefully at the pick up point and start of the secondary coil.

Peter I think you are correct in saying that the secondary starts from the hot end of the primary, there is a solder blob on the first one that i took apart.

The meths is dissolving the varnish/shellac goo well and shows the fabric insulation.
It will be a bit like unravelling the Turin Shroud

Will take pictures.

At least Neal has loads of duff ones if we need more to look at

Like any other part of a seagull, if it has been made once it can be made again.

H-A

The correct method is to have your coil and condensor tested on a proper testing unit , these simulate RPMs for breakdown , however even a proper tester cannot simulate heat build up and the asscociated breakdown of components.
At the end of the day , after all the hassle surely it is cheaper in the long run to buy a new one.
Villiers coils were a truly hideous piece of electrical engineering , they're only saviour being that on a Seagull they were kept cooler , and in general gave a bit more reliability , however on the application they were designed for (much hotter running air cooled industrial engines) they were to say the very least ......... a disaster.

Andy .

"At the end of the day , after all the hassle surely it is cheaper in the long run to buy a new one."

Which one would i buy, Mariner or Yamaha possibly a Mercury

Seagulls are a truly hideous piece of engineering ( we all know that).

I think that you might be missing the point twostrokenut.

If all I wanted to do was move a boat on water, I would not even think of using a rubbish 70 year old Seagull.

H-A