OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk Wipac Magister Condenser Discharge Ignition System

Hi to All, this is the first thread, posted anonymously, in reply to Blumbly's photos of his SB Model 35 rotary....It is the first mention here of the mysterious "Magister".

Hi,
The mower you have is in fact a Scott Bonnar 35,Model 201 series 2.The the second series of the first rotary mower made by SB.The 3 wires you have are from the coil,they are joined via 3 x screw fittings that run to the secondry coil."Magister"then on the to spark plug.You will need a secondry coil,to run this mower,as for a spare,Ive only ever seen one intact...And I own it,I can supply you a picture if you like.they did make a few of these in a three series run,but it seems very few survived.Ive been told many times that they would over heat often,making them pretty much a failure.BUT mine runs fine,although I dont mow long grass so Ive not really tested it under load.At a guess going of the few numbers ive obtained they maybee made around 20,000 or so.Anyways I love this model and im currently restoring her now.Only missing a catcher,but i doubt id ever see one.

The Scott Bonnar Model 35 Rotary is fitted with the company's own engine, their Model 201 which was first produced at the end of 1957. Later engines used the Wipac Magister magneto. The company was proud of this engine which was powerful and quite successful. It was used on the Supercut reel mower occasionally and was the standard engine on the 20 inch Model 43 [pictured] which was used on bowling greens, but is rarely seen today. I think the Model 35 was the last time this engine was used. I have found the Model 201 to be excellent and a first pull starter on Model 43s. I've attached a little information about the engine.
Regards,
Grant.
[email][/email]

Wow thanks for that willingworker that is some very useful information on the engine.That's great if you have any more info on theses or any other Scott Bonnar rotary's I would be more than happy to hear from you.Thanks again.

Hi Grant and Blumbly, thanks Grant for posting the pic...you must have done a re-print of your excellent booklet...I just checked page 38 and have the Model 40 and the 430 Diplomat pictured.

I spoke to Charlie in Mildura the other day and he said you dropped in....do you know the model of the antique SB he has in his shed?
You have filled in a lot of blanks for Jeffery (blumbly) he has been searching for info on the SB rotaries for ages to no avail....can you please post anything you have on them....it would be fantastic for our archives.
Grant, once again thanks mate.

yes I agree.So far this information is like gold,but the more I can find the more I will learn.

Hi Jeffery, yes mate, Grant is a wealth of information on all things Scott Bonnar....it will be great for our archives to have good new pics to save in the SB history forum.

I just hope he can help me with the information I need to get this old girl going again.It just frustrates me that it's so hard not find the information I need.If it was a Victa I would already know.I guess that's 1 reason why I like Scott Bonnar rotary's but it frustrates me as well.

I cant contribute with any info but ......Very Nice!

Would be better if I could get the parts I need.Would restore it then.

Hi Jeffery, I did a little research on the Wipac "Magister Magneto"....it was used on a few British engines; including stationary engines by John Deere. It may be worth contacting the Old Lawnmower Club in England and make some inquiries....I think Ty is a member....they may be able to supply the maggy for you.

Thanks deejay,but didn't you tell me that the engine was made in Adelaide? So wouldn't they be different to the ones from England?

Well I decided that even tough I don't have everything I need to start the restore,that I had better do something with the engine before it does seize up.So I took it apart to see what sort of damage was done.I haven't as yet pulled the crankcase apart,but I will soon.The bearing I think are buggered.I did find some rust in the bore down the crankcase side.
Here are some pictures.






I will put some more pictures up after I have finished pulling it apart.

I'm sure I will be able to work something out with the ignition.

This is the first post by Plymouthbel that is in reply to the photos of his SB Model 47....it also mentions the Magister.


Being a rare one I will put it in storage for now until I can find more detail on it. I do have a feeling that magester thing is around the house somewhere and my son took it off so will have a look for that over the weekend. Any suggestions as to where to head now. I am getting nothing on the net anywhere for this one.

Let's hope you find the Magister coil and it's in working order. You also need the 3-lead wire that goes to it from the rest of the magneto, which is under the flywheel.

Beyond reading the thread I referred you to earlier, and perhaps sending a PM to bluegmhtmonaro, I think persisting with the internet is the most practical solution I can suggest.

Thanks mate and will let you know if I find it.

Hi again Plymouthbel, if you do find the 'Magister', could you please take some pics of it, particularly the inside, so as we can see how it functions....One of our members Blumbly is looking for one of these units to complete his restoration....so any info would be invaluable.
Thanks mate,

The idea of taking a Magister apart really worries me, Deejay. It appears to be made of something close to WW2 era bakelite, which is chemically unstable: if it is bakelite, it is likely to fall to pieces if it is disturbed. Also, I have the impression from things Mal has said that there are more non-functional Magisters than functional ones. If Plymouthbel has one and it happens to be in working order, that might change if it is dismantled.

Gotta find it first guys

Is there a market in making reproductions? If so find me a non working one and the voltages and lets do it.

Grumpy, how do we know what it is made of, because other than Mal, none of us haven't seen one in the flesh, so to speak...it looks sturdy enough in this pic of Mals':

There is no information on this item available world-wide, and grumpy you know the time I have spent researching this mysterious little devil....they are very hard to find...until one becomes available (or can be fabricated) Jeffreys SB Model 35 resto is stalled.

Naturally, I do not suggest pulling it apart if it is going to damage the unit....but if it can, carefully, I, for one, would like to see inside it.

UPDATE: grumpy is correct; they are made of Bakelite and look very fragile....the internals are encapsulated in an epoxy resin...some black (so you cannot see inside)...some clear so you can at least see the components. They cannot be dismantled....Obviously a "repair by replacement" item, which may account for their rarity.

Hi again Plymouthbel, good thoughts there mate, but the trouble is we can't find one anywhere working or not working....there just not there to be had and I'm talking world wide.....anyone with one, would be attached to their restoration or perhaps stored in the shed...Mal's got 20 odd collectors looking for one for Jeffrey (blumbly) but, as yet, to no avail....
I don't know there would be a big market for them, apparently the were not that reliable....but it's a bit like the mascot on the radiator of a Rolls-Royce; just not the same if it is missing.

Hi all!
Great to see something different. Dad had one of these Scott Bonner engines in POP's old shed, I remember trying to start it but only got an occasional "bang / fluff" out of it. (probably just as well it was only held in the vice!!!) It went to land fill when he passed away.

Anyway I digress, has anyone checked out the National Library collection? I see they have Scott Bonner's from the 60's listed, i.e. brochures / catalogs (23pgs)Fly-mows etc.. Would be worth a look if someone lives close & photo copies some....

I do have a white Kirby tecumseh 2-Stroke air cowling with Scott Bonner on it, I can't help but wonder where / when & how that would fit in the Scott Bonner picture..

Hi All,

Just been having a look for some info on these coils. The only reference that I can find in publications is in a 1961 motorcycle magazine - there happens to be one for sale on eBay:

http://www.ebay.co.uk/itm/MOTOR-CYC...int-Special-Siba-Dynastart-/120826460728

May be worth a look.

Cheers,
Sir_Chook

Hi Sir Chook, yes mate, I have seen that publication during my research....but without knowing if was the same unit as fitted to the SB Model 35 and 47...we are at a loss. Unfortunately we can't see the pages they refer to.

Well I can't seem to stop drooling over it.If you do decide that seeing her off is what you want to do.I'll be here holding my hand up high.So high you'll see it every time you walk out your front and back door.

I've attached a photo of a WIPAC Magister magneto "Condenser Discharge Unit". This example has a clear plastic back and reveals perhaps a coil and a condenser.
Regards,
Grant.

Thanks for posting that Grant. It gives us quite a bit more to work with. There may be two capacitors in there, including a very small yellow one standing on its end in the upper right quadrant of the picture.

I think the next thing we need (other than a look at the alleged printed article in the vintage motorcycle magazine) is a circuit diagram for the full system. We know that three wires connect to the Magister unit, but we don't yet know where the ends of them go, and I at least haven't seen a picture of the magneto unit under the flywheel.

Hi Grant, mate you are a legend!! I've wanted to see what was inside one of these for ages....Now all we need is a circuit diagram to see how it works and the component values and voltages!

At least we now know that the brass strap on the front of the Magister (missing in your pic) may be some type of switch?...it seems to go to earth...maybe some early type of kill switch.

The following pics are of Jeffrey's Model 35 coil assembly....you can see the 3 wires from the magister.


I wish we could get our hands on a schematic.

That's another step at least, Deejay. Can we have a look under the cover of the points box?

Yes grumpy....my thoughts exactly....Hoping Jeffrey chimes in here and posts some pics.

Due to popular demand I have got those pictures everybody asked for.Hoping that I can find one and put my 35 back on the restoring table.





As you will see it's just a set of points under there.It seems all a little confusing to me not sure why they just didn't put it all under there.

Good stuff Jeffrey, thanks for the pics mate...we may figure out how it all actually works now...

I don't know why they just didn't do a bigger coil and then put the rest under the plate.I know I know it's just to make it harder for when it comes to me restoring it.That's why they did it that way.The mongrels.

Hi All,

I have managed to get a copy of the article from the State Library today. I will scan the article tomorrow. Is it possible to upload PDF's to the forum?

Cheers,

Sir_Chook

The threads in the Manuals area are usually locked, and as far as I know PDFs cannot be loaded into other threads. I suggest you PM me and I will give you an email address, so you can send the PDF to me and I can upload it.

The answer to this question is yes you can....but there is a Mb limit....if the file is under 2MB you can upload it to a post, if the file is under that limit....Just use the "File Manager" in Post Options...Browse to the file; select it, and click "Add File"...wait till it loads....and then click "Done adding files" .....it will not preview, just click "Submit" and when the submitted post appears, there it will be.

This is the only diagram I have for the WIPAC Magister magneto.
Regards,
Grant.

I've attached some photos of a Scott Bonnar 155cc 2 stroke engine with the Magister magneto on a 20" Model 43 which I mow the front lawn with. The mower is from the 1960s.
Regards,
Grant.

Thanks for posting that Grant. It's the first time I've heard of a Magister ignition system that is actually in regular use. Nice mower restoration too. I don't recall ever seeing a Model 43 before.

Hi Grant, my thanks too for posting the pic...I have never laid eyes on one of these either....
It is of interest to note that this is the same engine and cowling as the Model 35 rotary; the only difference I can see is the air filter....they have even used the fuel tank strap up on the handles! This machine is also unusual in that it was only available in 20" cutting width and first released in 1960 and as a Model 43...was the forerunner of the ubiquitous Model 45.

Interesting also to note the this very large clutch and flywheel assembly on the 43 was not employed on the 45...SB reverted to the assembly found on the Model 33 also first released in 1960.

Hi All,

I have scanned the article and have attached it. Hopefully this helps to fill in some of the gaps in information about this interesting little magneto setup.

Cheers,

Sir_Chook

Thank you so much for the info, Sir Chook, we can hopefully know more about it and how it actually works...Well done mate! A very interesting article. Now all we need is the values and voltages.

Hi All, Thats an interesting little piece that coil and sorry to say I didnt locate it. It wouldnt be too hard to make a exact replica these days. As long as the right voltages come out and its identical on the outside job done. I just need a non working one to price it up. If there is enough people here interested I would take that on. Well done on the PDF Sir Chook.

Blumby you have done such a good job making me believe that this is a really rare collectable old mower,then you want to buy it

Here is a standard Kettering ignition circuit, as used in pretty much all spark ignition motor vehicles before electronic ignition took over:



Let's compare that with the Magister circuit:


In the Magister, the Feed Coil, Rectifier and Condenser do no more than create a DC voltage source for the coil. After that, the rest of the circuit is the same as the Kettering circuit, except there is no capacitor (condenser) across the points.

So, what advantage does the Magister have? It generates a DC supply that may be at a higher voltage than 12 Volts. However the Magister also has no capacitor across the points, and it only applies its DC voltage to the coil for an instant of time. The Kettering ignition system has that capacitor because it effectively converts the 12 Volt supply to 150 Volts at the moment the spark is developed. The Kettering system also magnetically "saturates" the iron core of the coil by maintaining current through the primary for a substantial period before the points open. When they open, the collapsing flux in the coil's iron core generates a "back EMF" of 150 Volts, and the coil turns the 150 Volts into perhaps 15,000 Volts. There is no saturation of the iron core with the Magister, and as a result the spark generated is of much shorter duration than with a Kettering system. Because of that it is a much lower energy spark - but it may have a very high intensity during its brief duration, depending on the DC voltage applied to the coil primary, and the coil's turns ratio.

The bottom line is that the Magister can fairly be described as a basic form of Capacitor Discharge Ignition system. CDI systems are notable for being able to fire fouled spark plugs. They are also notable for not being able to ignite lean mixtures, or mixtures diluted by exhaust gas due to poor scavenging, or deliberate Exhaust Gas Recirculation, due to the brief low-energy spark. Because port controlled 2 strokes usually have very poor scavenging at light load, I think it is unsurprising that the Magister system was not adopted by many engine manufacturers. However that does not mean that it was a crackpot idea: there was a lot of interest in CDI at about the time it was produced, and fouled spark plugs are a perennial problem with crankcase induction 2 strokes.

Hi Grumpy, Based on your description is there any point trying to make copies of the original or would it be better to hide a modern version in the same case? Got off the track of the original forum here but this is a very interesting little piece.

I don't think it is very practical to try to hide a standard modern CDI in such a small case, and in any case I think you'd have problems supplying it with smoothed 12 Volt power in sufficient quantity. You could reverse engineer the Magister itself - all that is required is experimenting with components, since the circuit is available.

If you have the behind-the-flywheel bits, which are difficult to make, the only requirement is to breadboard the parts that normally go in the round black module until they work. Just by spinning the flywheel, you'll find out what voltage is supplied by the feed coil. The diode was probably a feeble germanium item orginally, but an ordinary modern 1 Amp 1000 Volt silicon diode should be fine. The capacitor has to fit into the space ultimately, and this will determine its capacity, but you can find the required voltage rating by connecting your feed coil and diode to a high voltage-rating capacitor and measuring the steady-state voltage (typically 300 Volts for a CDI). That only leaves the ignition coil to fiddle with. Unfortunately tiny coils with a zillion turns on the secondary are a hassle to produce for experimenters, but once again, you would start off ignoring the size issue and testing to see what turns ratio is required (which depends in large part on what DC voltage you can develop on the capacitor). Many commercial CD units work with standard Kettering coils, which have a turns ratio of about 100:1 AFAIK. Once you know what works on the breadboard, you have to miniaturise, which requires ingenuity and cut-and-try techniques.

Interesting Grumpy. There is one for a rainy day and I do have all the parts mentioned in the shed right now for the bread board. Just need to unhook some of them from the Hydrogen Fuel Cell

Unfortunately, it does not explain the use of the brass strap fitting on the outside of the Magister unit....could it be a switch of some sort?

Why not ask willingworker (since he has one and mows the lawn with it regularly)? Incidentally, having this research split into two threads will be archivally unfortunate.

The brass strap on the Magister condenser discharge unit is an ignition switch, as you suspected.
Grant.

Thanks for that Grant....we now know how it all works...will see what we can do about the archive.....

Can you change the name from Scott Bonnar Query to something like Scott Bonner 19 Model 47 and Magister Coil??

Hi Plymouthbel, the problem is that the Magister issue lies across 2 threads, Blumbly's SB Model 35 and your SB Model 47. Both machines have the Magister in common.

What we have decided to do (which will make for a good archive) is to create a new thread using posts from both the previous topics for just the Magister discussion. This will be contained in an engine forum as it falls into that category, as an ignition system.

This will make it easier for anyone researching the Magister, as being buried in 2 different lawnmower threads would make it harder to find.

Hi to All, this thread is for discussion on the Wipac "Magister" condenser/capacitor discharge ignition system for 2 stroke engines. These units have been fitted to 2 Scott Bonnar rotary mowers that we know of; the SB Model 35 and Model 47.

Gleaning this information has not been easy, as worldwide very little seems to exist...but, with the help of our members, we now know how it works and have a circuit diagram of all components. Many thanks to all that have contributed to the archive.

Hi to All,
Well, we've finally come full circle...this thread was started by Jeffrey (Blumbly) referring to his Scott Bonnar Model 35 Rotary and his quest to find parts to complete his restoration; in particular, a Wipac "Magister".

Just recently, I was doing some SB research and talking to Grant (willingworker) in Adelaide and mentioned that I was anxious to find one of these mysterious little devils, for Jeffrey's Model 35 resto. Grant made some inquiries and found one for me. Many, many thanks to Grant!
It is missing the little brass strap and center brass screw, but the strap can easily fabricated from shim brass and the screw sourced easily as well.

It has made the journey to Wagga safely, and it is here to present to Jeffrey, when he heads this way, prior to his move north.
Now the quest begins to find a metal catcher for it!

Here's some pics....


A good result in the end!

That is excellent Deejay and willingworker, well done. A point of caution: be very careful finding a screw that actually fits that center thread. It might not only be Whitworth, which is interchangeable with UNC in all sizes except half inch (minor difference in thread angle, not usually necessary to worry about in low stress applications), but it could be BSF, or even BA, both of which are very rare these days. It seems unlikely to be either metric or one of the American threads, but anomalies do happen. The main point is that the right screw needs to be found, and it may well be something extremely unusual. Just finding a screw of the right diameter and screwing it in will simply ruin something rare, perhaps almost irreplaceable.

When the right screw is found, please post details here since it will be useful for the archive.

Thanks grumpy, yes mate, it is a great result.
More good news....the center hole in the middle of the "Magister" is not threaded...It is 3/16" in diameter and a clear hole right through. That makes it a bit easier.

Wow is all I can say I didn't think I would ever see one at all.Thanks to all who were involved,I can't thank you all enough.I do know that it will now be the first one to restore after the move.I don't know if we will be as lucky with finding the catcher.Maybe if I could get some details on one I maybe able to make one up.As far as the screws goes it screws into the side of the cowl.I have a glass jar full of old brass screws I'm sure I will have one that will do the trick.I will only need to find a piece of brass to make up the contact point.

Have villiersparts.com got these? They have alot of remanufatctored old coils, points and condensers. I know it's a bit late but may help other ppl out

Hi Michael, thanks for the input...the answer is no, they don't...I have checked all over the world...these are really like hens teeth....very rare! We were just very lucky to find one for Jeffrey.

I just looked up the wipac magister and it looks like old 2 stroke boat motors used them too. Hope this helps other ppl

Hi Michael, if you read the whole thread, you will see that a lot of people have been researching this mysterious "Magister" over quite a long period. We are aware that it was used on motorcycles, boats, stationary engines and of course Scott Bonnar rotary mowers. We now know how it works and have a schematic (circuit diagram) posted in this thread.
I am just waiting to give Jeffrey the one I have here.

This year I've bought two Scott Bonnar reel mowers on ebay, a Supercut and a Model 43, both with 155cc Scott Bonnar engines and both from the early 1960s. I need a couple of fuctioning Magister Capacitator Discharge Units for these mowers. I tried three old units and none were any good. A friend has the technical background and interest to attempt to build some units. I've attached a letter which adds a little to the great information obtained by a Forum member from Motor Cycle 1963. I've also attached photos of the mowers. I'll let you know how we go with this.
Regards
Grant

Hi Grant, I have merged your post with the original Wipac Magister Condenser Discharge Ignition System thread to keep the archive current and up to date.

Also, you will find the bulk of the well written post by grumpy (post 36972 Page 3 of this topic) has been quoted by your friend in the letter to you and posted above. It is great to see that the OutdoorKing forum is helping people by providing useful information, to help with their projects.

The sad part of Magister saga is that there are no values of the components contained inside this secretive beasty!
Hopefully grumpy might have some ideas for us.

Darryl,
Thanks for reopening the Magister thread. I read Grumpy's post quoted in Ron's letter and remember being impressed by the level of theoretical understanding. However, I didn't recognise that the quote in the letter had come from Grumpy's Outdoorking post. I'd apparently forgotten what the post actually told me! I've reread Grumpy's posts and see that he has given some advice about determining condenser and rectifier values. I would appreciate any further thoughts Grumpy may have on the Magister project.
Regards,
Grant

Hi Grant, it should be possible to duplicate the Magister fairly easily by experimenting a bit. I take it the objective is to come up with a device that has approximately the same component values and the same performance as the Magister, rather than trying to make it better than it was.

If we can duplicate the generator part of the Magister (the original "feed coil" inside the flywheel, and the flywheel itself) on a device driven by an electric motor, that will determine how much electrical energy we have available, and at what voltage. The rectifier that follows would be simply a silicon diode with a Peak Inverse Voltage rating of at least 1000 Volts and a current rating of say 1 amp (vastly more than is required). That kind of diode is readily available in the nearest electronic components shop for a few cents. A condenser (capacitor) is then required, and it must have a voltage rating high enough to withstand the voltage the feed coil supplies, whatever that turns out to be. I would guess that the voltage will most likely be in the vicinity of 300 Volts, but we will not know that accurately until the motorised device is available to carry out a test with an actual flywheel and feed coil. Because it is tricky to measure the voltage directly from the coil (it will be a series of very short pulses, relatively widely spaced), I suggest measuring the rectified voltage across the capacitor. The size of capacitor is not important at this initial stage, and 300 Volt capacitors are uncommon now that vacuum tubes (traditionally called "valves") have gone out of fashion, so it would be a matter of seeing what is available from the shops. I suspect two or three lower-voltage capacitors will have to be used in series.

When the experimental program reaches the point of telling us that voltage, it will be time to move on to the "real" test stage with a coil and spark plug connected to the capacitor. At that point, for early experiments it might be wise to use a very small high voltage DC power supply instead of the real feed coil, to guard against damaging a rare and relatively fragile item.

That is a short overview of the way I think this project could proceed. Of course I'm happy to discuss it in detail along the way.

As usual grumpy, a clear, concise and well written post mate. This will give Grant a plan of attack and the results will be invaluable for this archive. Well done mate.

Hello, are you going to make a coil to produce a certain voltage? (because they are not available)?

Magnetude of induced e.m.f. or voltage = number of turns x the change in flux divided by the change in time.

If you can come up with some values, to plug into this formula.
#Number of turns can be wound.
The flux produced by the magnet, I beleive it is horse shoe magnet embedded in the flywheel.
(Not sure of the amount in webers)
#Change in time? I guess if engine in rotating at 3000rpm, you could work that out.

Just looked up in text book, with just one diode that is called a single phase half wave rectifier.
As Grumpy said, it is choppy dc, diode blocks the negative half cycle of the ac waveform produced.

Voltage across the load coil,(primary coil) would be, 0.45 x ac Voltage produced by your supply coil.

Mark, the coils, though rare, are not nearly as rare as working Magister modules. I suspect Grant will be able to put his hands on a coil to find out its characteristics experimentally - but they are too rare to risk damaging by putting one into an experimental ignition circuit. By connecting the coil only to a diode and a fairly small high voltage capacitor, we can learn what its output voltage is. Later, Grant might be able to physically measure a coil. When we know the dimensions of the wire winding (outside dimensions less core size) and the wire diameter, we can estimate the number of turns so that new coils could be wound. Then a new coil with the same characteristics as an original one, could be used in the actual ignition circuit. This minimises the risk of damaging rare items.

Of course once a working ignition system has been produced and tested, so we know it isn't a coil-killer, it might be feasible to run it from an original coil instead of a reproduction one. The aim here is to duplicate the Magister as far as possible rather than parallel-engineer an equivalent item. Unfortunately there isn't all that much chance of making a physically-accurate reproduction of the module itself, because it is assembled in a specially-designed chunk of Bakelite and encapsulated in epoxy. I suspect we can fairly easily produce a device that performs like a Magister but is actually built in a small tin box rather than a Bakelite housing that looks like a WW2 earphone. Once that is accomplished and the design information posted, somebody may or may not start turning up pieces of Bakelite and trying to make a real one - or a whole batch of real ones, to get a lot of Magister-equipped engines back into operation.

Thanks for your technical input which will help us refine the job. Ron made up the trial Capacitor Discharge Unit shown in the photos using items from his shed. The engine pictured runs well with the unit and ticks over very slowly when idling. However, the spark is not impressive.
You can identify the main items: the coil is from I think a Suffolk 4 stroke with 3 leads from the coil, the condenser [capacitor] is a .22uf normally used in small engines and also a diode [rectifier].
These 3 items are wired up as in the diagram and connected to the original 3 leads coming from the flywheel unit: feed coil, points and earth.
The next step is to assemble a tidy looking unit contained in a plastic box.

Thanks for that progress report, Grant. So you are using the original Magister feed coil? Can you measure and report the voltage across the condenser when the engine is running? Is the 0.22 microfarad condenser a standard Kettering ignition condenser?

Ron's Capacitor Discharge Induction set-up uses the original Magister feed coil and points, and the condenser we used in the external unit is a standard Kettering type. It would be interesting to see a voltage measure across the condenser and I'll see what I can get. Presumably the high voltage pulse through the coil is "stored" in the condenser and this part should be critical for the unit to work effectively and to last. Regarding the high apparent failure rate of the external units, it is possibile that in miniaturising the original unit, the coil itself was too small or fragile for the job.
Regards,
Grant.

G'day Grant,
looking at your ignition diagram, the capacitor would have to be polarised, i.e. have a positive terminal, as it is applied to rectified dc voltage.

I will let you know, this the first time I have been exposed to this set up with a feed coil.

The normal mower set up, the capacitior is applied to ac voltage, so would not be a polarised type.

Just something I noticed.

It will not be an electrolytic capacitor Mark. The Magister is a sort of el cheapo Capacitive Discharge Ignition - the capacitor is the hardest working component in the system, and it experiences wild voltage swings and high currents during each spark event. It may or may not actually have reverse voltage applied, but it covers a wide voltage range. Normally the capacitor is an encapsulated plastic type.

Note also that CDI capacitors typically run at 300 Volts, and very small 300 V electrolytic capacitors are not a common component. This is not the reason electrolytics aren't used (they are filtering capacitors, unsuited to complete discharge and recharge 400 times per second, in the case of a CDI on a V8 at 6,000 rpm) but it would be a problem even if this type of capacitor were otherwise suitable.

Hi to all,
Well yesterday, a milestone was reached when the Wipac Magister was finally handed over to Blumbly for his Model 35 Scott Bonnar rotary. Jeffrey came over to Enoggera in Brisbane to collect it and finally meet in person.
This has been a good adventure for us all, first finding one, (many thanks to Grant (willing worker) )and then get it to Wagga and thence to Brisbane.
to Jeffrey, now on to the restore mate!

G'day folks,
Substantial new info located, so I'll reopen this thread to add it.

The notion to look in patent literature, for info on this system, occurred to me recently. It seemed to me, that it was innovative enough that it might have been worth patenting.
And it had been...

So this looks like the right thread for this information. The diagrams and info supplied by previous posters here has been invaluable, in selecting the most relevant patents.



This is the circuit diagram from US Patent 3037148, class 'Ignition Systems for Internal Combustion Engines', filed 28 Dec 1959, granted May 1962.
Invented by George Gayler, and assigned to Wipac Development Ltd.

The major components here are :
11. Flywheel
12. Feed Coil stator
13. Flywheel magnet
14. Feed Coil ~ 4-5,000 turns
15. Rectifier diode
16. Condenser/capacitor, 0.2 microfarad
17. Primary winding of 18
18. Voltage transformer coil, 70:1 turns ratio
19. Contact points
20. Points cam
21. Spark plug
22. Secondary winding of 18

The three Magister module low tension wires are connections from the feed coil 14 [to rectifier 15], points 19 [to the primary of the transformer coil 17], and chassis earth. This isn't shown very clearly in the circuit diagram as drawn, though. The next patent listed here, 3175122, does a better job of showing 'modular' construction.

Note that the transformer coil shown here is wired a bit differently ['autotransformer' configuration] to the production Magister in grumpy's earlier post, but the patent covers both variants. Production 'Magister' ignitions would very likely have differed a bit in construction detail from the patent examples; these aren't rigid specs. Production units would have been optimised for the mass production processes in use, and the situation they were to be used in.

The essential bits from this patent, summarised:

Operation: The capacitor is charged with the contact points open. When the points close, the capacitor discharges through the primary winding of the transformer coil, inducing a high voltage in the secondary winding and causing a discharge across the electrode gap of the spark plug.

The Feed Coil - details for two examples are given:
Type 1 was 5,000 turns of 36SWG aluminium wire. This generated increasing voltage to a peak of 250V at 2,000rpm, then declining to 225V at 3,000rpm.

Type 2 was 4,000 turns of 34SWG copper wire. This also generated 250V at 2,000rpm, but then kept on increasing, to 325V at 3,000rpm.

The transformer coil - specification of 70:1 turns ratio, and inductance of 20 microhenries measured across the primary winding.

---------------------------

Gayler, and a Reginald Penn as coinventor, filed another patent in this class on the same date, which covers operation of this ignition circuit, and several variants of it, from any AC current source; US Patent 3175122, granted March 1965. The low voltage alternator variants had two transformer coils.

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The construction of the transformer coil is most probably along the lines of yet another patent, also filed on 28th Dec 1959, but not granted until August 1965. Inventor was Reginald Penn, US Patent 3202950, class 'Step-Up Voltage Transformer having High Tension Lead'.

This describes a very compact cylindrical transformer, wound on an insulating tubular former with a ferrite core, and the primary winding wound over the secondary.

In the patent, the 'working example' dimensions of the former tube are given as 0.75" long, 0.13" ID, 0.15" OD. Over this is wound the 47SWG enamelled copper wire secondary; described as one layer of three turns plus 15 layers of 193 turns, with paper insulation between layers. Then the primary winding, of 33 turns of 36SWG wire. This gives a turns ratio of ~88:1.
Again this was a 'concept' example, and not necessarily exactly the same as the production units. But it does look a very good match dimensionally for the known Magister examples.

There was also an article titled 'Magister Ignition system' in the UK 'Automobile Engineer' journal, vol 51 p240 (1961), if anyone can find that one.

Perfect....Thank you gadge,provided the trans coil is obtainable this should be fairly easy.
I dont need to make the feed coil since its already there and looks to be example 2 since mine is copper.
Ill show this to my boy and see what he thinks...if the coil is small enough i may even be able to reuse the original casing and reseal it

Thankyou for your efforts...Outstanding!

Hi all,

I'm not up with the theory on the Magister system or, indeed, that thing 'electricity'.
I'm glad there appears to be a possible solution for failing or failed units.

From a historical point of view, this is one of the curiosities.
I would particularly like to thank Moderator Gadge for that extraordinary research
and summary of the issues, and I hope Blue finds a suitable solution.

All very commendable.
---------------------------------------
JACK.

Thanks Gadge, that has validated the interpretation we had of the Magister (that it is simply a crude capacitive discharge ignition system, with a very small charge capacity and therefore a very small capacitor). More importantly, it has confirmed that it uses a typical charge voltage (about 300 Volts) and has given component values and coil-winding data. There seems no obstacle now to anyone with sufficient enthusiasm, repairing or restoring Magister systems.

I'm a bit doubtful about the wisdom of having used aluminium wire on the first version of the feed coil, partly because it is about three times the bulk of copper for the same conductivity level, and partly because unless it is high purity, it is difficult to protect from corrosion over the long term. However from the restorer's point of view, if the feed coil armature has room for aluminium (as, it seems, it must), there should be scads of room to rewind it in copper.

Personally I'd still like to know more about the physical layout of the encapsulated parts in that bakelite "earphone" housing. It will also be interesting to see whether people find convenient ways to remove the epoxy or whateve that potting material is, without damaging the earphone housing.

Yes its epoxy resin and I heated the unit to get the components out. Casing is fine and ok to reuse,the components are not. My initial thought was an epoxy covering,unfortunately the Whole system is filled. The wires,switch contact and HT screw go in,then the components are fitted and soldered,then the whole unit is flooded with resin.
I can see no way possible for failure due to moisture as initially thought. Instead id be more inclined to say it was due to possible overheating.

anyways im gonna give it a go....Not a job id recomend as far as redoing the original,but ill try anything. I think the manufacture of a new unit by restorers may be a better proposition and could be integrated into the system neatly....

Complete system in the flesh.....sealed unit has been stripped of components.
So it can be done...what remains to be seen,is whether the parts can be sourced and then fitted to its original housing. I am however optimistic it can be done.

Nice pictures, Blue. If you test the original components, you should easily find which ones work and which ones don't. The most likely component to fail, is the capacitor (condenser). I'm guessing that you will put it back together with some more convenient type of protective material than the original - maybe some RTV silicone adhesive?

Yes possibly,but I do have easy flow epoxy and might is it just to secure the parts as silastic will be more destructive to the unit if removal is necessary. Ill make a cover plate and seal that.
Agreed on the Condenser/capacitor Grumps as it had a weak spark before I stripped It.
did everything to boost it...new lead points checked and rechecked and all connectiins redone....but barely any change.

One thing im curious about is the switch and BM strip. I always assumed it eas a cut out and closed on overheating....but in a prior post it says its a switch,which on dismantking proves this...BUT... I only got spark when the strip was not touching the switch contact.

Anyways lets see what happens as we go along

Thanks Again Gadge and Grumps for your help and input

Cheers

I think that is an ordinary kill switch, Blue. Hence it shorts out the ignition system when it makes contact. Grant (willingworker) was still running a Magister on his usual mower a few months ago, and using that copper strip as the kill switch, as he had always done.

You might try checking continuity and earth leakage of the transformer (HT coil). Use a megger for the earth leakage - they test at around 300 Volts, which is much lower than the service voltage, but makes more sense than using an ordinary DMM as a test on a High Tension coil.

Yes mate that was my understanding either a kill switch or overheating strip like a bi metal strip....But it was actually willing worker in a prior thread who said it was an ignition switch. So I took that to mean the strip was permantly contacted and opened if the thing overheated.... But both mine do not make contact which I knew was how it worked.....All good,pays to just make sure...

I would think that the transformer coil would be the difficult component to replace. Mainly due to its small size; its electrical characteristics aren't too unusual.

It may be possible to get a transformer coil rewound by a magneto repair specialist, but I wouldn't expect that to be cheap. There are only a few of these specialists about, and some also rewind other very small coils, such as the pulse generator and trigger units used in more modern motorcycle ignitions.

As grumpy says, the capacitors of that era were very failure-prone, but it's easy to find a far superior modern equivalent. Same for the rectifier diode, and I'm a bit suspicious about the reliability of the original type. If it is indeed a selenium type [as stated in that 'The Motor Cycle' article earlier in this thread], those weren't known for their durability.

I would be very surprised if that cutout switch is a bimetallic strip - plain hard brass would be much more likely.

Agreed Gadge...Ive found a few equivalent caps and diodes. But yeah the coil may be the hard bit,but ive an electrical engineer mate who designs lighting alarm and power systems,so ive got a foot in the door for parts....Yes the strip is plain brass and doesnt give like a bms...

Anyways im happy to give it a go,if all fails then ive got my spare on a runner but didnt want to swap it over to my display 35 as it will be wasted.

Hi all,

I've just posted some Supa-Swift info. in the History Forums.
I have a question ...

The Villiers Torque-Major Deluxe 140 engine used a Magister ignition with cut-out switch.
I was wondering whether this is of any help here?

Link to Supa-Swift HERE.
Link to Villiers 140 HERE.

All very interesting.
------------------------------------
JACK.

Gadge has obtained a Turner serviceman's instruction sheet for testing the Magister unit. Here is a scan of it:



Thanks Gadge, that gives us some information on the components themselves.

I should say that heat is the only practicable means of 'depotting', given that the potting compound is known [from 'The Motor Cycle' article above] to be an early Araldite epoxy.

There are only one or two solvents that will work on cured epoxy resins, and they are nasty enough to require a fume cupboard. Even then, it takes some time. Not sure if they'd affect the phenol-formaldehyde resin [Bakelite] casing as well, either.

For re-potting, there are any number of different non-corrosive 'electronic potting compounds' available these days. Check the RS Components or Element14 websites for examples.

I feel that there has been adequate time for comment since the last post here, so I'm locking this thread once more.

As always, it can be re-opened by requesting a Moderator to do so.