Magneto Magnetizer

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WARNING :

There are generally recognized hazards in every pursuit ofmachinery oper ation, cons truction and repai r. And in this projectyou will be exposed to the dangers of electricity as we ll . Thereis a possibility for fatal electrical shock, fire or other injuryand property damage when working with electrical current available

at ordinary household out let s. If you are not knowledgeab le andskilled in working with electricity you should find professionalhelp for that port ion of this pro ject. And you should check localelectrical codes and insurance underwriters rules before pluggingin a home built electrical devi ce . Bear in mind that the author isnot a scientist or engineer and that no amount of professionalengineering has been appli ed. This book is intended to describethe author's experience and discoveries for the benefit of othersinterested in a similar purs uit. While the intention is to presenta safe project, no attempt has been made to discover and reveal allhazards. You are entirely responsible for your own safety and thesafety of others who might come in contact with equipment you builda n d o p e r a t e .

FOREWORDThis is another offering in a series of HOW-TO manuals intended toprovide basic information to individuals working at home. Most ofthe information gathered for these projects is taken from out-of-print material and may be considered obsolete in the modern worldof high technology. However, our pursuits in the home shop areusually for pleasure rather than profit. And the efficiency andeconomy that might be possible with modern methods is not a vitalconsideration in a non-commercial project. We can be content tohave achieved our end by simple means since modern methods may verywell be beyond us technically, even if we could justify the cost.And it may even add to the personal satisfaction if we are able toachieve by simple means that which others can only stand in awe of.

It is a challenge and a pleasant adventure to research theseprojects, to build them and test them and finally to publish them.And it is never done single-handed. So here I offer thanks to themany friends and readers who offer suggestions and encouragement.And special thanks to two major contributors to this project:

Don Cokley, who worked dilligently on the researchand every detail in building the prototypes.

AND

Al Shepard, who did some of the machine work.


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CONTENTSMAGNETO DEVICES 2MAGNETISM 3INDUCTION 4MAGNETO TESTING 5OTHER MAGNETO DESIGNS 7BASIC REQUIREMENTS 8BUILDING THE MAGNETIZER 11MATERIAL LIST 11ASSEMBLE THE BASE 12ASSEMBLE THE CORE . . 17COIL DESIGN 17THE COIL FORMS 18THE COIL WINDER 22WINDING THE COILS 24INSTALL THE COILS 26THE POWER SUPPLY 30TESTING THE POWER SUPPLY 32

TESTING THE MAGNET 32OPERATING THE MAGNETIZER 33SPECIAL POLE SHAPES 35

ILLUSTRATIONSTHE BASE 13CORE LAYOUT 14CORE ASSEMBLY 15CORE AND BASE ASSEMBLY 16MAKING THE COIL TUBE 19NOTCHING COIL TUBE 20

ASSEMBLE COIL FORM 20COIL WINDER SIDE LAYOUT 21COIL WINDER ASSEMBLY 21COIL WINDER SPINDLE 22COIL WINDER DISCS AND HUBS 23COIL WINDER IN USE 25FINISHING THE COILS 25INSTALLING THE COILS 26INSTALL THE CHASSIS BOX 26ELECTRICAL COMPONENTS 28SCHEMATIC DIAGRAM 28PICTORIAL DIAGRAM 29SPECIAL POLE SHAPES 35


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INTRODUCTION

There are few mechanisms morefascinating than old internalcombustion engines. Andequally fascinating are theignition systems that enabledthem to run. While countlessthousands of the old engineshave been broken up and melteddown to be resurrected as moremodern machinery, it would seemthat they might easily have runforever had it not been forsome mysterious failure in theignition or fuel system. Infact today many of the relicsare being rescued from thescrap heap, and determinedpeople are restoring them torunning condition.

Fuel systems are generally easyto troubleshoot and restore bysimple cleaning and perhapsmaking a small part or two.Battery ignition systems, too,are straight forward, and anyable mechanic can determine bysimple tests whether the coiland condenser are good and ifthe points make and breakproperly. But if the engine isequipped with a magneto thechallenge becomes greater andit will be necessary to delve alittle deeper.

It is the purpose of this bookto reveal a few clues to aid insolving the mystery of thosevery cunning mechanisms. Andsince there is much more to amagneto than its magnets wewill spend a little bit of timediscussing some of its otherelements.

Like all mechanisms, a magnetois designed to do a specific

the best key toa non-functioning

job, andrestoringmechanism to normal operationis to fully understand what isnormal.

It would require a large bookindeed to describe and fullyillustrate the various types ofmagnetos. But I will have toleave that book for others topublish. The main intent hereis to detail construction ofthe equipment for restoring thevitality of the magnets. But afew broad and general tips willbe offered to guide those whoare completely in the darkabout magneto ignition devices.

In keeping with a very wiseadage: "IF IT AIN'T BROKE DON'TFIX IT", I urge you to developa careful series of diagnosticsteps before diving into theinner workings of the magneto.

In all of this discussion it isassumed that you are workingwith old engine magnetos thatwill seem rather complex. Andespecially if they are equippedwith "IMPULSE MECHANISMS" thatare designed to accelerate thespeed of the magneto rotor togain voltage. But they do notdiffer in principle with modernmagnetos as found on the usualengines of lawn mowers, gardentillers, etc.. However whileyou can buy just about anyrequired part for the modernmachine it is a very differentmatter with old equipment. Andso also is it difficult to findspecifications and service datafor old machines. So then itbecomes necessary to be verycautious and observant so that


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any part removed will not bedamaged and that it will bereinstalled properly withoutthe aid of a repair manual.

Even though the magnetizer isthe main offering in this bookit must be stressed that merelyrecharging the magnets willseldom restore a magneto toefficient operation. Howevermagnets do lose their magnetismfor various reasons and in thatevent it will be absolutelynecessary to re-magnetize them.

There is nothing at all new ororiginal in the design of themagnetizing device detailedlater in the book. In fact avery similar device was mostlikely used when your magnetowas originally manufactured.The only significant differencewould be the modern solid-statepower supply.

Since the pole pieces of themagnetizer are adjustable thedevice can be adapted to nearlyany ordinary magneto or magnet .Further, specially shaped poles

can be installed and adjustedto adapt to many other designsincluding flywheel magnets andbar magnets. And of course itcan be adapted for experimentaluse or for production of manypermanent magnets for a widevariety of purposes.

MAGNETO DEVICES

A magneto is not nearly asmysterious as some of the

"BLACK BOXES" found on modernmachinery and appliances. Thefiends who design this stuffwill put coils, capacitors,transistors, diodes, IC's,

thermistors, varistors andother such truck onto a multi-layered circuit board and fusethe whole thing into a glob ofplastic with wires sticking outat various points. Then theyconceal its true identity withcode numbers and letters thatwould stump agent 007, and thenproceed to design a replacementthat will obsolete the newestthing developed even before ithits the market. The thingsare designed to self-destructif you apply a test meter totry and figure out if they areany good. If you break themopen there will probably benothing recognizable inside.And if you brought one to thefeet of the Oracle at Delphi inthe hope of learning somethingabout it he would probablyshrug his shoulders and adviseyou to devote your time tosomething more worthwhile. Butyou can understand and repairengine magnetos.

Magneto ignition systems areactually not greatly differentfrom battery systems so basic

troubleshooting is much thesame. It.would always be niceto have some sort of instrumentthat you could hook up thatwould tell you instantly wherethe trouble is and what torepair or replace. Such aremodern computerized systems.Or at least that is the claimof those who build them andfoist them upon us . A computerwould prove of little value indiagnosing magneto troubles.

But everything you need to knowcan be quickly learned by-simple tests. And when thesesimple tests indicate that allshould function if only the


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magnets are good you will havethe necessary equipment torecharge the magnets if youbuild the simple rechargerdescribed later. But bear inmind that magnet failure is notthe most common or likely causeof magneto failure. And, moreimportant, magnets should notbe casually removed or evercarelessly handled. In factyou can lose a significantamount of magnetic strength bysimply removing the magnetsimproperly. And reinstallingthem backwards can get you intosome very serious trouble.Dropping a magnet or strikingit with a hammer can alsoeffect its strength. Andexcessive heating, as with atorch, can completelydemagnetize the magnets. Thediscussion on basic trouble-shooting and repairs will begeneral and brief but you willget full details on buildingand using the magnetizer a bitlater. The best rule to followis to always leave the magnetsundisturbed until you havethoroughly considered every

other possible cause forfailure. -

A magneto is essentially agenerator used in conjunctionwith inductance and capacitanceto deliver an electrical sparkat the required instant tocause ignition in the enginecylinder. As the name implies,its source of energy is itsmagnet or magnets so that isthe proper place to begin the

discussion.

M A G N E T I S M

Magnetism is among the most

mysterious of the physicalphenomenon. While its actionscan be compared with those ofelectrical currents there aredistinct differences that havechallenged great minds forcenturies.

The first natural magnets aresaid to have been discovered inMagnesia, a small country inAsia Minor, around 600 B.C.,Thus they came to be called"Magnets". Knowing the originand date of discovery helps notin the least except that we canimpress people who did not knowthat already. And knowing theorigin of the name frees themind to look for more valuableinformation since we don't haveto wonder why it's calledmagnetism. A great deal hasbeen learned about magnetism inthe past centuries but muchremains to be discovered.

It is theorized that moleculesare aligned within the body ofmagnetized materials so thatthe attracting and repulsingforces of the electrons areconcentrated and polarized.Nothing can be gained from adiscussion of theory exceptthat we might finally agreethat one expression of theoryseems more plausible thanothers. But while little isknown or understood about whatmagnetism is and how it works,a great deal is known about itseffects. That knowledge isuseful in a study of magnetos.

Natural magnets are acrystalline form of iron oxidethat has come to be called"Magnetite". Very rich orethat yields high quality iron.


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Early sailors discovered thatan elongated piece of it hungfrom a cord or floating on ablock of wood in a pan of waterwould always orient itself withone end pointing north and theother south and thus the firstmagnetic compass was invented.They called it a "Lodestone",which means "Leading Stone".

Modern manufactured magnets aremany times stronger thannatural magnets and they aremade in an infinite variety ofshapes and sizes. Many otheruses have since been found formagnets and a large proportionare used in electrical and

electronic devices.Of particular interest to us isthe fact that when a magneticfield is cut by a conductor anelectrical current is induced.You can prove that yourself bywinding a small coil of about10 turns of insulated wire andconnecting its ends to a verysensitive milliamp meter. Thenpass a strong permanent magnetback and forth over the coil or

through its center and watchthe meter needle deflect. Thatis the phenomenon of INDUCTION,and what you have done is tofashion a simple generator.

And we are also interested inthe "POLARITY" of the magnet.I.E., one pole of a magnet willalign with the magnetic northpole of the earth and the otheraligns with the south pole ofthe earth. The magneticpolarity of the magnet has adirect relationship to theelectrical polarity of thecurrent it induces. (Positiveor negative) A physical law of

magnetism is that unlike polesattract and like poles repel.And the same law applies inelectricity and electronics.Understanding these laws isvital to an understanding ofinduction.

I N D U C T I O N

Just as an electrical currentis induced when a conductorcuts a magnetic field, so is amagnetic field induced eachtime an electrical currentpasses through a conductor.Generators and transformersfunction on these very basicprinciples. And a magneto is

really a generator to supply atransformer, or it incorporatesa transformer in its design.Actually the magneto is moreprecisely an alternator thatproduces an alternating currentat low voltage to be built upto a voltage high enough todischarge a spark. It is therapidly changing magnetic fieldthat induces the current. Andthe greater the number of turnsin the coil the higher the

voltage. So also, the fasterthe magneto spins, the higherthe voltage.

A typical magneto has a set offield magnets that charge thepole sections. The rotor iswound with a coil of wire thatrepresents the primary of atransformer. As it rotatesbetween the magnetized polepieces an alternating currentis induced. At precisely theright moment the contact pointsin the primary circuit open,which causes the magnetic fieldof the armature to collapserapidly, inducing the necessary


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high voltage in the secondarywinding to deliver the spark.

Given fully charged magnets,sound coils and condenser andproperly functioning contactpoints, a magneto will delivera hot, snappy blue spark ofsufficient length to jump thespark plug gap and fire theengine.

MAGNETO TESTING

As with any electrical ignitionsystem the logical first testis to determine whether a sparkof sufficient strength is beingdelivered. It is a simple

matter to remove the sparkplug, rest it on the cylinderhead and crank the engine. Ifyou see a bright, blue sparkand hear it snap it can beassumed that the magneto isfunctioning well. It remainsonly to assure that timing iscorrect and you can look toother causes for failure tostart. If, on the other hand,the spark is dim orange andbarely audible, if at all, youwill be justified in lookingmore deeply into the ignitionsystem. Naturally a weak ornon-existent spark indicates afailure in the magneto.

By far the most common problemwith magnetos is a faultycondenser or dirty contactpoints. Sometimes it is asimple matter to install areplacement condenser that isknown to be good and the

magneto is restored to perfectoperation. But some oldermagnetos have the condenserbuilt into the rotor and it canbe a major job to disassemble

it for replacement or to modifythe design so that an externalcondenser can be installed.

The logical first step is toclean the points and make surethat they are opening andclosing properly and that thereare no electrical shorts oropens. A simple ohm meter is apractical tool for these tests.Then crank the engine or spinthe magneto manually to see ifit will deliver a spark.

You can test a condenser withthe ohm meter if you isolate itfrom the rest of the circuit.The meter needle should jump

perceptibly and return to zerowhen the test prods are touchedto the condenser terminals.Then reverse the prods on theterminals and the needle shouldagain jump and return to zero.If the ohm meter needle doesnot jump when connected ineither polarity an opencondenser is indicated and itmust be replaced. If theneedle does not return to zeroin both directions it is anindication of a shorted orleaking condenser, which mustbe replaced.

It has been a common practiceto test a magneto by applyingbattery voltage to the contactpoints to test the coil and thecondenser. What the test mightprove is that the points, coilsand condenser are functioningand that the failure is in thegenerating or delivery system.

In fact failing magneto systemsare sometimes converted tobattery systems in this way.But while it may enable thetiming mechanism to deliver a


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spark and get the enginerunning it can also demagnetizethe magnets. The particulardesign of the magneto willdetermine whether such a testor emergency measure can besafely used. So bear in mindthat if you send an electricalcurrent through a coil that ispart of a magnetic circuit youmay cause a counter magneticfield that can damage themagnets.

Some magnetos use brushes tocollect the current and thesecan fail. It is also possiblefor carbon from the wearingbrushes to collect and provide

a short circuit to ground,causing the magneto to fail.

Bearings can fail, causing therotor to drag on the polepieces and that will causemagneto failure. Magnetos areusually cunningly made anddisassembling can be tricky, soproceed slowly and cautiously.It may become necessary tocompletely disassemble amagneto to clean dirt, carbon

and oil, or to replace bearingsor other parts. That willrequire careful study, plentyof light and a clean bench top.In no case should you removethe magnets without firstputting a "Keeper" across theirpoles. A keeper is a bar ofiron or steel used to bridgethe gap between the poles ofthe magnet so that the magneticcircuit will remain intact. Avery substantial amount of

magnetism can be lost in only amoment so always be prepared torecharge your magnets if youhandle them improperly. Andyou should avoid removing the

magnets if at all possible. Ifthe magnets must be removed tocomplete disassembly they mustbe carefully marked to bereturned to their originalpolarity. The magnets are alsoeffected by shock so you mustnot pound on them or drop them.

Some magnetos have both theprimary and secondary windingson the rotor, while others haveonly the primary winding on therotor with the secondary on aseparate laminated core. Stillothers will have both primaryand secondary on a separatecore and the rotor will providethe magnetic field.

Coils fail through open orshort circuited windings andthey can be tested with the ohmmeter.

More difficult and uncertain todetermine is whether or not thesecondary coil insulation isleaking. Lacking specializedequipment a leaking coil isdiagnosed only by elimination.That means when you have made

certain that everything else isOK the problem can only be aleaking coil.

It is rarely possible torestore a leaking coil bybaking it for a couple hours at225 degrees F. to drive out themoisture. But if you arecertain the coil is leakingnothing is lost by trying. Youare going to need permissionfrom the lady of the house to

do that , and you are probablygoing to get into big troubleanyway if you make some smokeor smell. If baking out themoisture restores the coil you


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the condition of the magnetsand how to test them.

should soak it in thin varnishto seal it.

When testing coils with the ohmmeter make certain that theyare isolated so that you don'tget a false reading from afaulty condenser or shorting ordirty points. Also check for"carbon tracking", which is atiny high resistance path toground due to a dirt or carbonfilled crack in insulation.

Some magnetos have a "SafetyGap", which is designed todischarge the spark to groundsafely if the high tensionwiring or spark plug fails.The idea is that voltage couldbecome high enough to pierceinsulation in the secondarywinding if it does not find asafe path to ground through thespark plug. The safety gapwill be somewhat wider than thenormal spark plug gap so thatit won't interfere with normalignition. But it will be closeenough so that if the sparkplug gap widens too much or thespark plug wire is removed the

spark will jump the safety gapand preserve the insulation ofthe secondary coil. It ispossible for the safety gap tobecome shorted so that sparkwill not be delivered eventhough the magneto actually isfunctioning. And if you removethe spark plug wire and crankthe engine to test for sparkyou may not see a spark at thewire because it is dischargingat the safety gap out of view.

By now it must be apparent thatmagneto troubleshooting is verylittle different than trouble-shooting battery systems. Theonly other element of doubt is

The only practical magnetomagnet test I've ever known ofis that "A good magnet willlift 20 pounds of iron.". Itis a simple matter to attach aplate of mild steel to a springscale and observe the scalereading then the magnet pullsfree of the plate. Of coursethere are modern devices thatwill measure field strength andevaluate magnets in technicalterms. But by far the mostcommon practice in commercialmagnet testing continues to becomparing the "pull" or fieldstrength in some sort ofmechanical testing fixture.Without very expensive andsophisticated equipment magnettesting for most of us willremain a matter of acquiredjudgement. It will generallybe impractical to remove themagnets to determine if theywill lift 20 pounds. But afterhandling a number of normallyfunctioning magnetos you willlearn to judge the amount ofmagnetic "drag" you feel whilerotating by hand. Of coursethe impulse mechanism caninterfere with manual turningso partial disassembly will berequired for some testing.

OTHER MAGNETO DESIGNS

The types of magnetos we havediscussed up to this point areall "High Tension" magnetosthat deliver a high voltage

spark through a rotatingmechanism. There are alsoreciprocating magnetos oroscillating magnetos thataccomplish the same thing by


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different mechanisms. Andthere are "Low Tension"magnetos that deliver a sparkby breaking the primary circuitinside the cylinder. Thecommon element in all of themis the magnet, and if it isdetermined that the magnetshave failed the next step is tobuild a magnetizer.

BASIC REQUIREMENTS

As intricate as magnetos mayseem, a magnetizer is about assimple a device as can beimagined. A hefty steel corewith appropriate pole pieces, apair of coils and a simpledirect current power supplywith a convenient switchingarrangement is all that isrequired. Cost is not at allprohibitive and everythingneeded is generally available.But while only ordinary basicmechanical ability is required,at least a portion of the workshould be machined for bestresults. Namely, the heavycylindrical cores should befaced off to true flatness and

uniform length in a lathe. Andthe slots in the pole piecesshould be milled or cut with ametal cutting band saw.Additionally, if speciallyshaped pole pieces will berequired they will surely haveto be made with a lathe ormilling machine.

While most of what you needwill be available locally youmay not be able to buy magnet

wire. Some local motorrewinding shops may sell youmagnet wire if they arepersuaded that you are notgoing to compete with them in

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the motor winding business. Ifyou have an amount of magnetwire available from a largetransformer or other salvageitem study all of the designconsiderations text beforeproceeding. But if you don'tfind what you need locally forless than $3.00 per pound youcan order it. What you need istwo 6 pound spools of 18 gaugeenameled copper magnet wire.It is available from:

CONDUCTORS UNLIMITEDPO BOX 2 82LYONS, IL 60534-0282.

Write or phone 708 447-2666.

The cost varies from day to daydue to fluctuations in thecopper market so it is notpossible to quote an accuratecost here. But ConductorsUnlimited will quote you thecurrent price plus shipping andhandling and tell you how toenter your order. A reasonablesource for magnet wire is vitalto a project like this and Iwould not have dared to publishthis manual unless I was ableto name such a source.

DESIGN CONSIDERATIONS

This device is nothing more orless than an electro-magnetwith specially designed polepieces to make it adaptable tovarious sizes and shapes ofmagneto magnets. The basicconsideration was to make itpowerful enough to saturate its

own steel core with magnetism,which ensures that it willsaturate any other magneticmaterial of cross sectionalarea in the same size range.


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Once its size was determinedthe next consideration was tokeep construction methods assimple as possible. And alsoto specify materials that arecommonly available even thoughbetter materials might be inexistence but difficult forindividuals to obtain. Thuscommon cold-rolled steel isspecified for the core andpoles even though better alloysexist. And the chassis is madeof wood instead of steel for noother reason than ease andsimplicity.

There are empirical formulasthat make it possible to designsuch a device very precisely inregard to many factors. Andthere is a very broad andcomprehensive scientificlanguage to express the manyfactors in measurable andcomparable terms. But sincethis device is more than twiceas powerful as it needs to befor its intended purpose, allformulas except for ohms lawwere disregarded.

Once the main core size wasdetermined the next step was todesign the coils. Since thestrength of an electro-magnetis determined by the number ofturns in the coils and theamount of current flowingthrough the coils, there are anearly infinite range ofpossible choices. For examplea coil of 100 turns at 60 ampsinduces the same magnetic forceas a coil of 600 turns at 10

amps. Neither the current orthe number of turns alonedetermines the strength, butrather the product of currentand turns. That is expressed

simply as AMPERE TURNS. Bothcoils described above have thesame effect even though theyare physically much different.Both deliver a magnetic forceof 6000 ampere turns and wouldbe equally as effective inidentical applications. Butboth require vastly differentelectrical power supplies, andthe size of wire required isvery different.

While many magnet rechargershave been built using heavycoils drawing high current frombatteries, that design concepthas more than one drawback.Most serious is the danger ofexplosion of the battery byigniting the very dangeroushydrogen gas that is liberatedfrom the rapidly dischargingbattery. For that reason thebattery must be a substantialdistance from the point of use.And even that does not fullyguarantee that ignition won'toccur from causes other thanarcing at the switch. The veryhigh current also generatesconsiderable heat in coils,

wiring and switches, whichposes a burn hazard. And justas important, heavy cables andswitching must be used and thattends to be quite costly.

A maximum current of 10 ampswas selected for this designbecause that permits the use ofeasily available and low costelectrical components. It alsoenables the use of standardhousehold line current and the

use of a solid state D.C. powersupply that is much cheaper andmore reliable than batterypower, and safer as well.

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18 gauge magnet wire wasselected for the coils becauseit will safely carry the 10ampere current without anydangerous heating. And it isflexible enough to make coilwinding easy while strong

enough so that there is noundue danger of breaking.

Given a coil form diameter of 21/8", more or less, and a formlength of 4", six pounds of 18gauge magnet wire will give 16to 18 layers of turns at about95 turns per layer. That willmean a total of from 1600 to1800 turns on each coil. Thetotal number of turns can varysignificantly, depending uponhow neatly the turns are laidon. There is no need to countturns or to take any steps toensure that the coils areexactly equal in turns. Butwind them as neatly andcompactly as you can forfirmness and easy finishing.

The D.C. resistance of 18 ga.magnet wire is 1.2721 ohms perpound so the resistance of eachsix pound coil is 7.63 ohms.The coils are connected inseries so the nominal circuitresistance is 15.26 ohms. Ohmslaw declares that the currentin a D.C circuit is equal tothe voltage divided by theresistance so 115 volts dividedby 15.26 ohms gives a currentof 7.54 amps. In fact an ampmeter in series with the coilson the initial test read justslightly under 7.5 amps so we

can be satisfied that it workswell within the design limits.

A total of 1600 turns at 7.5amps gives a magnemotive force

(mmf) of 12,000 ampere turns.(1600 x 7.5 = 12,000) Thetechnical term for units of mmfis the "Gilbert". Simplymultiply 12000 ampere turns by1.26 and you have 15,120Gilberts. In this application

I'm unable to tell you of whatuse that information is, exceptthat, again, you might impresspeople who don't happen to knowthat. And it will satisfy anyscientific types that you havemore than twice the requiredmagnetic power to saturate anyordinary magneto magnet youmight apply to the poles ofthis magnetizer.

Since no voltage droppingtransformer is in the circuitwe are applying the full 115volts of A.C. to the full wavebridge rectifier. The outputof the rectifier is a nominal115 volts pulsating D.C. to befiltered by the 100 mfdcapacitor for a reasonablysmooth direct current supply tothe coils.

A momentary switch, either pushbutton or spring return lever,rated at 10 amps or more closesthe circuit to energize themagnets. If you connect an ampmeter in series with the coilsyou will see the current climbto a peak of around 7.5 amps inless than 5 seconds. When thecurrent peaks the magnetic coreis fully saturated and nothingis gained by additional time.In any case an on time of 5seconds will be adequate so

there is no serious need for anamp meter in the circuit.However there is no reason forleaving it out if you happen tohave one on hand.

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Of course the unit will work aswell without the pilot light.But the practical purpose forthe pilot light is to let youknow if the switch ever failsin the closed position.

WARNING!

The three wire grounded supplycord and plug is specified foryour safety. The steel coreand chassis box must beconnected together and toground in the event that thecoils or any other electricalcomponent fails. Such failuresdo happen without warning orany indication, and thisequipment is capable ofdelivering a DEADLY ELECTRICALSHOCK. And bear in mind thatno protection is gained byusing the three wired groundedcord and plug if it is notplugged into a properlygrounded outlet. Seekprofessional help if you haveany doubts about your owncompetence. Bear in mind alsothat you may be subject tolocal codes or fire insuranceunderwriters rules so make sureyou are in compliance

BUILDING THE MAGNETIZER

Before you buy your wire orother materials make sure thatyou have the capability toprepare the heavy metal coresand pole pieces. Other aspectsof the project are quite simpleand direct but the ends of thecore pieces must be truly flat

and they must be of uniformlength. That can pose a greatchallenge if you don't havemachining capability. Whileit is conceivable that you

could do the work with hacksawand file it would requireseveral hours of tedious workand you would have to be a verydetermined individual. Thebetter plan is to get a friendor local machine shop to face

off the core pieces to trulyflat and equal length and tomill the slots in the polepieces. Another idea is toenroll in a local vocationalschool class to gain access totheir equipment. But of courseif you do that you shouldcomplete the entire period ofenrollment in order to takefull advantage of the course,which is certain to benefit youin many ways.

MATERIAL LIST

BASE

1 .2 .4 .

CORE

1 .22 .4 .1 .

3/4" plywood, 10" X 12"3/4" X 1 1/2 wood, 9"#8 X 1 1/2" screws

1" X 4" X 10" C.R. Steel1" X 4" X 3" C. R. Steel2" dia. X 6" C. R. Steel3/8" X 1 1/2" Cap Screws1/4" X 2" Carriage Bolt

COIL WINDER

1 2" X 6" X 18"2 . 3/4" Plywood, 6" X 18"2 . 5" dia. Plywood Discs1 . 5/16" dia. Rod, 9 1/2"5 . 5/16" Hex Nuts6 . 5/16" S.A.E. Washers

2 . 2" X 3/8" O.D. Copper Tube1 . 1/8" X 3/4" X 4" Strap1 . 1/8" X 3/4" X 3" Strap8 . # 8 X 1 1/2" screws2 . 3/4" Plywood, 2" X 2"

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COILS

2121

6 LB. spools, 18 ga. wireroll plastic elec. tape,sheets of poster cardsmall white glue

ELECTRICAL

1 . 5" X 4" X 3" Chassis Box1 . 25 Amp, 200 V. Rectifier1 . 100 mfd, 200 V. Capacitor1 . 10 Amp Fuse holder & Fuse1 . 3 lug terminal strip1 . 115 V. pilot lamp1 . 15 amp switch1 . 3 wire cord and plug

ASSEMBLE THE BASE

The base is simply a 3/4"plywood rectangle with common 1X 2 cleats screwed to theunderside to provide fingerclearance when you want to movethe unit about. Two 3/4" holesare drilled through the boardto accept the heads of the corebolts. And a single 1/4" holeis drilled to accept the 1/4" X2" carriage bolt that willfasten the core to the base.One or two coats of varnish orpaint will preserve the baseand enhance its appearance.See figure 1

ASSEMBLE THE CORE

The material for the core andpoles is common cold-rolledsteel. 2" round and 1" X 4"stock is very heavy so youshould buy it locally if at allpossible to avoid shippingcosts. Shop around and buy"Drops" if available becausesome suppliers charge veryexorbitant fees for cutting.It is possible to pay more for

the cutting than for the steelitself so be forewarned. Mailorder suppliers who charge onlyreasonable cutting fees are, inalphabetical order:

Blue Ridge Machinery & Tool

2806 Putnam Ave.Hurricane WV 255261-800-872-6500

Campbell Tools Co.2100 Selma Rd.Springfield, Ohio 455051-513-322-8562

Cardinal EngineeringRR 1, Box 163Cameron, IL 614231-309-342-7474

Power Model Supply13260 Summit Dr.DeSoto, M0 63020314-586-6466

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The dimensions suggested forthe core pieces are notcritical so you may be able towork with materials of neardimension on hand. For exampleThe cylindrical pieces could be1 1/2" or 1 3/4". And the flat

stock could be 3/4" thickinstead of 1". Hot rolledsteel could be used for thecylindrical pieces since theends must be faced off ormilled anyway. But if hotrolled steel is used for theflat pieces the scale shouldmilled, filed or scraped off toprovide good contact with theends of the cylindrical pieces.Any scale, rust or dirt betweenthe core pieces introduces

"reluctance" in the magneticcircuit and that reduces themagnetic flux at the poles.The first, and surely the mostchallenging, task is to faceoff the cylindrical cores trulyflat and to identical length.

The flatness is very importantbecause even a small air gapwhere the parts of the magneticcore meet will introducereluctance with the same effectas dirt or scale. And bothcores must be the same length

so that the surface of bothpoles will be on the same planeto ensure full contact with themagnets to be charged.

In addition to facing off ormilling the ends, drill a21/64" hole about 1" deep inboth ends of both pieces andtap them 3/8"-16. The usualtap drill size for 3/8"-16 is5/16". But tapping a hole l"deep puts a very considerable

strain on the tap, while theoversized hole eases the taskand much reduces the risk ofbreaking the tap. There willbe no great strain on thethreads so the shallowerthreads will be strong enough.

Figure 2

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Figure 3

The next operation is to drilltwo 3/8" holes and one 5/16"hole through the 10" long bar.This work should be done with adrill press to ensure that theholes will be truly perpendic-ular. And the best procedureis to drill three 3/16" holeson the locations on the centerline as indicated in figure 2,enlarge all three to 5/16" and

finally enlarge the outer twoholes to 3/8". This "step-drilling" procedure ensuresthat the holes remain closer tothe layout dimensions and it

reduces the amount ofneeded to do the work.

power

With both cylindrical coresprepared and the base bardrilled you can begin theassembly. Bolt the cylindricalpieces to the bar with 3/8"-16X 1 1/2" cap screws as shown infigure 3. The heads of the3/8" bolts will fit in the 3/4"

holes drilled in the base boardso that you can bolt the entireassembly to the base with a1/4" X 2" carriage bolt asshown in figure 4.

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Figur e 4

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The pole pieces that willactually contact the magnets tobe charged may be made in avariety of shapes. But thesimple ones shown in figure 4will serve in the majority ofapplications.

Two alternate methods formaking the pole pieces areshown in figure 4. Notice thatthe one on the left has a 3/8"slot milled on the center line.And the one on the right has aslot sawed from the edge, whichis one answer if you don't haveaccess to a milling machine. Ametal cutting band saw will cutthe slot with relative easecompared to a hand hacksaw.Yet another way would be todrill a row of holes on thecenter line to provide a meansof adjusting the space betweenthe poles. And yet anotheridea would be to make a varietyof pole pieces or to customprepare them for each job. Alarge flat washer is used witha 3/8"-16 X 1 1/2" cap screw tosecure the pole pieces to thecylindrical cores.

The illustrated pole pieces are1" X 3" X 4" cold rolled steel.If you work with magnets ofirregular shape you can makeauxiliary pieces that willadapt the poles to the magnets.They do not necessarily have tobe bolted in place. But youmust provide a maximum contactsurface so that the crosssectional area of the magneticcircuit is not significantly

reduced. The safe rule ofthumb is that nowhere in themagnetic circuit should thecross sectional area be lessthan the cross sectional area

of the magnet you are workingwith. However satisfactoryresults can be had witharrangements less than perfect.

C O I L D E S I G N

The coils required for thisunit are simple solenoid coils.That means that they are simplywound on a spool without anyparticular need for countingthe turns or laying them inwith great precision. It doesmake sense, though, to preparespools for them so that you caneasily slip them in place. Andin the event that they ever getdamaged in use it will be asimple matter to remove themfor repair or replacement. Thesimple coil winder that is tobe described later will makethe job much easier and it willsave more time and labor thanis consumed in its making.

Earlier, in the section ondesign considerations, wediscussed wire size and thecharacteristics of the coils.In the event that you decide touse a different size wire keepthe basic characteristics ofthe suggested coils in mind.When you change the wire sizethe amount of resistance alsochanges and so also the totalcurrent. Remember that it isthe product of the current andturns that determines the powerof the magnetic flux. A coilof heavier wire will pass ahigher current and, Conversely,a coil of lighter wire will

pass less current.Your main consideration must beto use enough wire so that theresistance will limit the

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current to a safe level forthat size wire at the availablevoltage. Even though power isapplied to the coils verybriefly they should be designedto carry the current for longerperiods of time. A safety

ground is an absolute must.And keep in mind that the fuseis sized to protect the wire inthe event of a short circuit.In no event should the fuse belarger than the capacity of thewire to carry a continuouscurrent. If you elect to useheavier wire at lower voltageand higher current rememberthat considerable heat may begenerated. And if you decideto use a battery power supply

be sure to use a switch heavyenough to carry the highcurrent. And be sure to usecables long enough to isolatethe sparking of the switch fromthe battery to avoid explosion,and heavy enough to avoidexcessive heating.

T H E C O I L F O R M S

Initially it might seem thatyou could simply wrap the coreswith an insulating material andwind the coils directly onthem. In reality that would bedifficult if not altogetherimpractical. It is a simplematter to make a pair of sturdyforms to simplify the job.

While some may be fortunateenough to find a paper mailingtube of the right size to slipeasily over the cores, mostwill have to make the tube.Ordinary poster card as foundin local variety stores is acheap and handy material formaking the forms. It comes in

a 24" X 36" size and two sheetswill be enough.

The tube must be an easy fitover the core and it must besturdy enough to retain itscircular shape during the

winding operation. Threethicknesses of poster card isadequate unless you elect touse heavy wire for the coils.Then it may require four ormore thicknesses of card.

A cylindrical form is requiredto make the tubes. I used alength of automobile exhausttubing of the same outsidediameter as my cores. Thelocal muffler shop cheerfullylet me pick some out of theirdumpster at no charge since thepieces were too short for usein their work. I wrapped theexhaust tube with three layersof plastic from a plasticshopping bag so that the gluewould not bond the poster cardto the form and so that itwould be slightly larger thanthe core for an easy slip fit.

Then cut the poster card into2" wide strips and wrap thefirst strip, spirally aroundthe form as shown in figure 5.Fasten both ends with maskingtape .

It will be a good idea toprepare a dozen or so shortpieces of masking tape andstick them in a handy place tobe ready for the followingoperations.

When the first strip is securedto the exhaust tubing wrap thesecond strip over the first.

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Figure 5

spirally in the oppositedirection, and secure it at theends with masking tape.

Now make a small squeegee of apiece of stiff cardboard.Release one end of the secondstrip and let it unwind forabout half the distance of theform. Apply white carpentersglue to the first strip andspread it evenly around withthe cardboard squeegee. Thenimmediately rewind the secondstrip over the glue and secureit at the end with maskingtape. Then release the otherend of the second strip and letit unwind to the area where ithas been glued. Apply theglue, spread it with the

squeegee and rewind and tapeit. This operation is done intwo steps because the gluetends to set rather quickly soit would not remain open longenough to wrap the entiresecond strip over the first.

Apply the third and anysubsequent strips in the samemanner, with each being wrappedin an opposite spiral. Theresult is a neat cylindricalform several inches longer thanrequired. The first one can beslipped off the exhaust tubesoon after it is finished andthe second one made on the sametube. When both have had abouta half hour to dry they can besquared and cut to 5" length.

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Figure 6

Figure 7

Next cut notches 1/2" deep andspaced about 3/8" on each endof both tubes as shown infigure 6. Set them aside while

you prepare the ends of theforms. Now cut twelve 5"diameter discs with holes inthe center to slip easily over

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the cardboard cylinders. Gluethe discs together in sets ofthree each to make four endsfor the forms. Complete theforms by bending over the tabsand gluing them to the discs asshown in figure 7.

While the white carpenter's

glue sets up rather quickly ittakes a day for it to reachfull strength. So set theforms aside while you assemblethe coil winder. Of course youwill make certain that theforms slip easily over the

cylindrical magnet cores beforeyou proceed.

Figure 8

Figure 9

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THE COIL WINDER

Certainly the coils can bewound on the metal lathe if youhave one, but for those whodon't have such a luxury ameans must be had for firmly

supporting the coils whilewinding them, and also forsupporting the supply spools.There is a substantial amountof wire involved here and youcan easily get into a very badtangle if you don't anticipatewhat can happen in advance. Itwon't take long to assemble thewinder. And you may even findit worthwhile even if you havea lathe.

The frame of the winder is asimple wooden trough as seen infigure 9. The sides of theframe are 3/4" plywood, 5 1/2"X 18", with two slots formed bydrilling 3/8" holes 1" belowthe edge and cutting the slotsfrom the edge to the holes asseen in figure 8. Fasten the

sides to an 18" length ofcommon 2 X 6 lumber with screwsor nails to complete the frame.

One pair of slots will be used

to accommodate a shaft tosupport the supply spool andthe other will accommodate thespindle that will be used towind the coil. So the nextorder of business is to makethe spindle and crank.

Two bearings are made bysoldering flat washers to theends of 2" lengths of 3/8"copper tubing. Ream the endsof the tubing after cutting so

that it will slip easily overthe 5/16" spindle. A 4" lengthof 1/16" X 3/4" strap isdrilled 5/16" at each end toform the crank. Cut the headfrom a 5/16" X 2 1/2" bolt andfasten it to one end of thecrank with 2 nuts. Fasten theother end of the crank to the

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10" length of 5/16" threadedrod used for the spindle with 2nuts and assemble the wholeunit as shown in figure 10.

Cut a pair of 5" diameter discsfrom 1/4" plywood. Drill 5/16"

holes in the center of thediscs and fasten hubs to thediscs to fit the insidediameter of the coil forms. Ifyou have a lathe you can turnhubs from 3/4" plywood to aneasy fit inside the forms. Ifyou don't have a lathe it iseasier to make square hubs witha diagonal measurement to givea snug fit in the forms. For a2" diameter the square hubswill measure about 1 7/16"square. Or you could make them1 1/2" square and trim off thecorners until they fit insidethe forms without distortingthem. The discs and hubssupport the form during thewinding. See Figure 11.

Drill a 3/16" hole near eachend of a 1/16" X 3/4" strap andcenter it over the slot wherethe crank end of the spindlewill be. Drill pilot holesinto the edge of the wood toscrew the strap in place. Cut

a block of wood to fit the slotand long enough to bear againstthe spindle bearing when thestrap is tightened against it.This strap and block will holdthe spindle in place while youturn the crank and it will alsoenable you to quickly and veryeasily lift the spindle whenwinding is finished. It alsoprovides an adjustable frictionbrake that you will appreciatewhen the winding work begins.

Note that the winder isuniversal in that it can beoperated either right or lefthanded. In use the supplyspool is mounted on a 3/8" rodthat rests in one pair of

Figure 11

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slots. The coil form ismounted on the crank spindlewith about 6" of the wirepushed through a small hole inthe end of the form at thestarting position. Then yousimply apply moderate tensionwith one hand as you turn thecrank with the other to lay inthe turns. Refer to figure 12.

W I N D I N G T H E C O I L S

Have a few short lengths ofmasking tape stuck in a handyplace near by in case you needto stop winding for any reason.According to Murphy's law youwill surely get a phone call ora visit. or the prunes you hadfor breakfast will work todayor something

With patience it is possible tolay the turns in snugly, layerby layer. But do not becomeupset if things go awry after atime. In fact you could simply"scramble wind" the coils andthey would work as well. Theimportant thing is the numberof turns all in the same

direction. But keep them asneat as you can so that it willbe easy to finish them offnicely. And take special careto avoid kinks and curls.Modern magnet wire has a verydurable insulating film thatwill tolerate some mildabrasion. But take care not todamage the insulation, forexample by allowing it toscrape on a finger ring orother cutting or scraping edge.

Assuming that you begin withtwo 6 pound spools of # 18wire, simply continue windinguntil all 6 pounds are on theform. There is no need to

count turns because whenproperly connected the magneticfields of both coils will addto the same total even if theyare significantly different innumber of turns. And if theyare both wound with the sameweight volume of wire they willnot be significantly differentin number of turns. Wind allbut the final 6" of wire ontothe form. Manipulate thewinding so that the final turnis on the same end of the formas the starting turn. Tape thefinal turn securely. Make bothcoils with the start and finishon the same end.

The coil will finish up atsomething near 4" in diameter.With the final turn securelytaped in place, remove the coilfrom the spindle. Punch asmall hole through the end discof the form and draw thefinishing lead through thehole. Now cut a strip ofposter card to fit between thediscs of the form and wrap itaround the finished coil andsecure it with masking tape.Then cut notches around theedge of the end discs so thatthe excess can be folded over.With the resulting tabs foldedover, wrap the entire outsideof the coil with plasticelectrical tape. Figure 13.

While you could connect thecoils together and into thecircuit using the magnet wireleads it will be much better touse stranded insulated wire.

You may lose track of whichlead is which when the coilsare finished so they should beidentified either with a tag orby using a different color lead

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Figure 12

Figure 13

for start and finish. Avoidthe error of tagging one lead"S" for START and the other " S"

for STOP. (I jest!)Cut two 4" diameter discs ofposter card with holes in thecenter for an easy fit over the

cores These will cover thesplices where you attach thestranded leads. Shorten the

magnet wire leads to aconvenient length and scrapeabout 1/2" of each lead cleanof its insulating coating.Splice 18 ga. stranded

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Figure 14

insulated leads about 10" longand apply solder to the splice.Then cover the splice withelectrical tape or apply heat-

shrink tubing. Finally, laythe splices well separatedagainst the end of the coilforms and glue the poster carddiscs over the splices.

INSTALL THE COILS

Slip the finished coils ontothe cores with the leads at the

bottom and facing towards therear as in figure 14.

Shorten the 2 finish leads to aconvenient length, strip the

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Figure 15

ends and join them with a"Wire nut" as shown in figure14.

Pass the 2 start leads betweenthe coils towards the front sothat they will be available to

connect to the power supply.

Now you can fasten the chassisbox to the base as shown infigure 15. A 1/2" hole isdrilled in the chassis box toaccept the leads from the coil

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FIGURE 16

FIGURE 17

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FIGURE 18

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and the ground wire, and arubber grommet is used in thehole to protect the insulationof the wires. Pass the coilleads and the ground wirethrough the grommet.

THE POWER SUPPLY

WARNING: DEADLYELECTRICAL SHOCKHAZARD!

A schematic wiring diagram isshown in figure 17. And apictorial diagram is shown infigure 18. The power supply isextremely simple and nodifficulty will be had infinding the components andassembling them if you areexperienced in working withelectricity and electronics.If you are not experienced itmay be best to ask help fromsomeone who is. There aresimple rules, both for safetyand technical reasons, whenworking with electricity.

The first and most importantrule is that if you allow anypart of your person to become apart of an electrical circuityou can get a very painfulelectrical shock, and the shockcan be FATAL. Common elementsof your home or shop that youmay not suspect can be a partof the electrical supplycircuit. These elementsinclude the plumbing or heatingpipes and any metal article orappliance that is connected tothe electrical supply or that

is in good contact with theearth. In fact the earthitself is a part of theelectrical power supply, and itconducts electricity very well

when wet or even damp. Thatmeans that a wet or damp floorcan complete an electricalcircuit so remember thatELECTRICITY AND WATER DON'TMIX.

It is customary to usedifferent colored insulation onwiring, and those colors havespecific meaning. In ACdevices the white wire (WT.) iscalled the "neutral" wire andthere should be no voltagebetween it and ground. Theblack wire (BLK.) is called the"hot" wire and there will beline voltage between it andground. The green wire (GRN)is the safety ground. There isno voltage between it andground and it is connected tometallic parts, cabinets, etc.so that any accidental shortcircuit will deliver itscurrent safely to groundinstead of through the body ofany person in contact at themoment of the short circuit.Other colored wires may be usedin more complex circuits foridentification to make circuittracing and troubleshootingeasier. In DC circuits wirecolors may indicate polarity.Red wires are of positivepolarity and black wires arenegative polarity. Other colorcodings are used but there isno need to consider them inthis project.

Figure 16 illustrates threecomponents that you may not befamiliar with. If they are not

properly used serious problemscan arise .

The rectifier is called a "fullwave bridge". It is comprised

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of four diodes arrangedinternally to convert thealternating current of thestandard outlet to directcurrent for the coils. Thewhole is imbedded in a casethat measures 1 1/8" square and

about 1/2" tall. It has a holein the center that is used tomount it to the base with ascrew that also mounts thechassis box. A 25 amp 200 voltbridge is specified because itis commonly available at localelectronic supply houses.Actually any bridge rated above8 amps and 115 volts can beused as well. The terminalswill be clearly identified aseither AC or + or -. ACmeaning alternating current, +meaning positive DC andmeaning negative DC. The ACterminals will be diagonallyopposite, as are the DCterminals. Connections to thebridge rectifier are to be madewith "spade" terminals crimpedto the leads.

The electrolytic capacitor isalso "polarized" and the bodywill be marked to indicatewhich wire is positive andwhich is negative. As with therectifier, the polarity isimportant and these componentsmust be connected properly.

The terminal strip is comprisedof three solder lugs mounted onan insulating bar to keep themseparate. Note that one lug isalso the mounting lug and itmakes electrical contact with

the chassis box. The groundwire in the line cord is greenand it is fitted with aterminal to be screwed to thebase with the same screw that

mounts the terminal strip. Andthe ground wire from the magnetcore is soldered to that samegrounded lug on the terminalstrip. The other two lugs onthe strip are insulated fromground and from each other so

they provide connecting pointsfor the polarized leads in thecircuit, including the leads ofthe filter capacitor.

Connections in the circuit thatare not made with spadeterminals or screw terminalsare to be soldered with rosincore solder. DO NOT USE ACIDCORE SOLDER FOR ANY ELECTRICALWORK, EVER!

Note in the schematic diagramin figure 17 that the fuse andswitch are connected in serieswith the black AC wire. Thewhite wire in an AC circuit isnever broken with a switch orfuse. Remember that the whitewire is neutral and has novoltage potential to ground.So if the white wire is brokenwith a switch or fuse the blackwire remains live and any openin the white wire will also belive .

Leads from components in thechassis box cover to those inthe base should be long enoughso that the cover can beremoved easily and laid upsidedown beside the base. None ofthe leads should be less than18 ga..

CAUTION!

The electrolytic capacitorbecomes charged when voltage isapplied to it and it can retainthat charge for long periods of

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time unless it is dischargedwhen the current is shut off.If charged and left with opencircuit it can deliver a verypainful and dangerous shock.In this power supply circuitthe capacitor will normally be

discharged when the power isoff because the coils arealways in the circuit toprovide a discharge path. Whenworking on the power supplycircuit it is sound practice toshort the capacitor terminalstogether after the power isshut off before touching anywiring.

T E S T I N G T H E P O W E R

S U P P L Y

To those who are familiar withelectrical or electronicsprojects the term "Smoke Test"is well understood. Of coursethat means that when you plugit in there should be no flashof fire or puff of smoke. Andthere usually will not be anyfire or smoke. But componentscan be faulty and you can makeerrors in assembly so everyreasonable test should be madeto ensure that all is sound andsafe .

A practical safety test is totouch one lead of the ACvoltmeter to a good ground,such as a water pipe, and theother lead is touched to thechassis box and the magnetcore. A voltage reading in anyamount indicates that there isa shorted or leaking component

and it is not safe. Thereshould be absolutely no voltagepotential between the metallicparts and ground.

Having proved that it is safeto touch the unit when pluggedin, try the same test whileclosing the switch with aninsulating material. Againthere should be no voltagereading between the metallic

parts and ground. And if thepilot light glows when youclose the switch you are .assured that you are at leastdelivering AC voltage to thecircuit. The remainder ofelectrical tests must now bemade inside the chassis box.

Unplug the unit before removingthe chassis box cover. Invertthe cover beside the base toexpose all of the componentsand wiring. An assistant maybe required to close the switchas you apply the volt meterleads to the terminals.

With the meter switched to DCfunction, test to see if DCvoltage is supplied to theterminal strip when the switchis closed. If you get a DCreading near line potential nofurther tests will be needed.Assuming that the coils areproperly connected in thecircuit the unit will function.It remains only to test themagnet.

TESTING THE MAGNET

The poles of the magnet aremeant to be opposite. That isone will be north and the othersouth. An ordinary compass isall you need to determine which

is which.A fundamental rule of magnetismis that like poles repel andunlike poles attract. So a

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preliminary test will be toplace a bar of iron or steelacross the poles of the magnetand close the switch for amoment. It should becomefirmly attached and it willtake considerable force toremove it.

When you remove the bar it willquickly lose most of itsmagnetism and so will the polesof the magnetizer. But anamount of residual magnetismwill remain and that is enoughfor the compass test.

Simply bring the compass neareither pole and note thecompass reading. If it isindicating north you are closeto the south pole of themagnet. And of course if itindicates south you are closeto the north pole. Once youhave identified the poles markthem by some permanent means.Now you are ready to use yourmagnetizer.

OPERATING THE MAGNETIZER

CAUTION!

Magneto impulse mechanisms canbe made inoperable if theirparts become magnetized. It isnecessary to remove thosemechanisms before re-chargingthe magnets on the magneto.

The actual application willdiffer from job to job. Inmost cases it will be best to

magnetize the assembledmagneto, and in some cases thatwill be the only practical waybecause it would be toodifficult to devise a keeper so

that magnets could be removed.You must determine the polarityof the magneto magnets and thecompass will serve very wellfor that purpose. Rememberthat the poles of the magnetomagnets are applied to OPPOSITEpoles of the magnetizer. Northto south and south to north.You must avoid reversing thepolarity of your magnets. Ifthe magnets or the magneto issuspended from a strong cord,free to turn, and allowed toapproach the magnetizer slowlywhen the current is on it willorient itself properly.

In some cases the magnets willbe covered with a brass shieldand that must be removed beforere-charging the magnets. Anynon-magnetic material in themagnetic circuit increasesreluctance, which reduces themagnetic flux.

The main requirement is thatthe pole surfaces of themagneto magnet must be in verygood contact with the poles ofthe magnetizer. That is

usually not a problem withmagnetos that use horse shoeshaped magnets. However it isnot always possible to achievefull contact so compromisesmust be made to pass thegreatest magnetic flux possiblethrough the magnetos magneticcircuit.

When magnets are removed forre-charging they must bereturned to the same original

position. Although reversingpolarity entirely may notnecessarily reduce performance,all of the magnets must beoriented in the same way or

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performance will be lost. Soit is always safest to ensurere-installing in the originalposition.

It is absolutely necessary touse keepers when magnets areremoved from the magneto forre-charging. Even if it takesonly moments to transfer themagnets from the magnetizer tothe magneto a very substantialamount of magnetism will belost. The keeper can be a barof iron or mild steel of anyshape so long as it closes themagnetic circuit. Of coursethe keeper is removed duringcharging. But it must be inplace before the magnet isremoved from the charger.

If magnets are removed from themagneto even momentarily theywill need to be re-charged.

Although the magnetic fluxreaches a peak in themagnetizer in 5 seconds or lessthere may be some benefit inholding the current for as longas 30 seconds. There have beenclaims in old manuals thatadditional time was beneficial.So also was it claimed thatrapping the magnet with a brasshammer was beneficial. Andsome claimed that rocking themagnet back and forth on themagnetizer poles would make itstronger.

Magnetos with two-pole rotatingmagnets may require removingthe rotor and charging it

between the magnetizer poles.And a special keeper made likea tuning fork is used totransfer the rotor back to themagneto and re-install it

between the poles to retainmaximum magnet ism. It may alsobe practical to remove the coilwith its core so that the rotorcan be re-charged in pla ce. Ifthe coil and core are notremoved the magnetic flux will

travel through the coil coreinstead of the rotor and norecharg ing will occur. You maywant to slip steel shimsbetween the rotor and poles toreduce reluctance.

Type E.K. Wico magnetos have aset of bar magnets instead ofhorse shoe magnets. This is anoscillating magneto and theelectricity is generated as themagnet makes and breaks contactwith the laminated core of thetransf ormers . They can be re-charged without removing themagnets .

1. Remove outer sheet brasshousing.

2. Wedge the armature openwith wooden shims 1/16"thick.

3. Place the magnet end ofthe magneto on the polesof the magnetizer in theproper orientation.

4. Close the magnetize rswitch for 20 to 30seconds and tap themagnets lightly with abrass hammer.

5. Remove the wooden wed ges.

6. Remove the magneto fromthe charger and re-installthe brass housing.

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fIGURE 19

S P E C I A L P O L E S H A P E S

While most magnetos that havehorse shoe magnets or barmagnets can be recharged withthe simple rectangular polepieces, some unusual designsand those with the magnetsimbedded in the flywheel will

require auxiliary pole pieces.These include outboard motorsand the many small engines withflywheel magnetos. Dimensionswill have to be worked out as

needs occur. But a view ofseveral basic shapes in figure19 will show how to design yourspecial pole pieces.

These sketches point out thebasic principles so that themagnets mounted in inside oroutside diameters can be dealt

with as the need arises. Theobject is to make good contactwith the poles of the magnetwhile maintaining isolation ofthe poles.

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The idea is to use theseauxiliary pole pieces alongwith the universal rectangularpoles as adapters. And theymay or may not have to bebolted or doweled to theuniversal poles.

Obviously machining capabilityis required to make them. Andany grade of mild steel stockwill be acceptable.

While the magnetizer detailedhere is adequate for re-charging magnets made ofhardened alloy steel, ascommonly used in magnetos ofolder manufacture, It may notbe adequate for modern maenets.

such as those called "ALNICO".These modern, powerful magnetsare originally charged with"IMPULSE MAGNETIZERS" usingspecial power supplies equippedwith capacitors and electronictriggering circuits that send agreat surge of current throughthe coils. It is certainlypractical for individuals tobuild such equipment andinformation has been publishedin engineering manuals. Butthese modern magnets are sostable and so resistive ofordinary demagnetizing forcesthat it does not seem at allworthwhile to research thatprocess so I can't tell you howto build it .

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How to Build a Magneto Magnetizer

Scientific phenomena include fascinating mysteries in suchfields as electricity, electronics, chemistry, and so on. These areasof scientific study have been extensively explored over the yearsand many of the mysteries have been solved. Although the phenom-enon of magnetism has been explored in great depth, it still remainsvery much a mystery.

Magnetism is absolutely vital in modern technology. We knowhow it acts. We can create magnetism in materials that were notformerly magnetized. We can use magnetism in countless devices andmechanisms. But when pressed for a clear definition of exactly whatmagnetism is and why it acts the way it does, we can only offer

theories and analogies that compare magnetism to electrical andelectronic principles that are better understood. Like gravity, mag-netism remains mostly a mystery. Although we can't diagram it orillustrate it in a definitive way, we can put it to work and use it.

If you have a particular interest in magnets, you can build thissimple device to create new magnets and recharge weak ones. Al-though specifically designed to recharge magnets used in enginemagnetos, this device can be used for producing or restoring mag-nets in a great variety of shapes and sizes so long as they aremade of alloy steels.

A limitation of the magnetizer described here is that it will most

likely not be adequate for charging the ALNICO magnets found inmodern equipment. Such magnets require far greater magnetizing forcethan can be generated with the type of power supply described. Nev-ertheless, this magnetizer can be of great use to the restorer and ofgreat interest to the experimenter.

This is a relatively simple device. Only ordinary mechanical skillsare required to build it. The metal core is of very heavy steel,however, and some machining operations will surely be required.While it would at first appear that the machining might be accom-plished with a hacksaw and a file, all but the most dedicated builderwill surely resort to a lathe or milling machine.

Once built, you'll realize that this magnetizer is worth manytimes the cost of building it.

Magneto Magnetizer

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