If you want the simplest and probably the most reliable ignition
 system
 get a two cycle two cylinder small outboard ignition system.
 Fires the same number of times and 180 degrees apart just like a
 2 rotor.
 As close as you will come to a A/C magneto.

 http://www.iboats.com/

 http://www.iboats.com/Johnson-Stators/dm/view_id.271367

 http://www.cdielectronics.com/
 Down load the complete catalog.

 Some of these stators are as low as $20 used.

 The high voltage coils supply 300 volts for a simple CD system
 and the other coils may supply enough 12 volt current for an EFI
 system.  No belts.  If the main electrical system or alternator
 fails the engine still runs.

 This stuff is mass produced in the millions and extremely reliable.

 Paul Lamar

 Some interesting stuff in that catalog. Some of us wouldn't know
 exactly
 what would comprise a complete system, as it looks like they are
 all parts
 of an upgrade for certain motors.
 Did you notice the EFI and ECU units in the catalog? They also
 note that
 these can be reprogrammed for "racing purposes".
 Would this be suitable for our purposes? Of course I don't think
 it would
 be
 a good idea to mention aircraft. One could say I'm making a
 marine rotary
 conversion.
 C. Smith


 Good idea Craig. A racing rotary boat motor :)

 All you need is a source of 300 volts, provided by the rotating
 magnet
 and stationary coil,  a 1 ufd 300 volt cap and a switch of
 some sort. An FET works fine and they are easy to use. Way back
 about 30
 years ago we discovered that a 50 cent CMOS CD4050 or a CD4049
 chip makes
 a great FET driver if most of the six gates in the chip are
 connected in
 parallel.

 Since that times 1000's of FET gate drivers have been  designed
 and built selling for as much as $6 each and so far I have not
 found one that works better than a CD4050.  Many of them require
 a regulated supply which lowers efficiency and cost more money
 and parts.


 I set up this simple CD circuit on the bench in half an hour with
 a 300
 volt DC power supply and it works great.  The FET is a IRF740.

 I am rapidly discovering it is all about the 300 volt power
 supply. You
 need a robust power supply that does not crap out when it is
 shorted to ground
 and that is where the charging coil in the outboard motor comes
 into play.

 Nothing could be simpler than a large magnet passing a coil to
 rapidly
 charge the 1 mfd cap.

 Paul Lamar
 --
 So now I have more questions. Does one of these 2 cyl systems
 have enough
 juice to fire both plugs at the same time?
 Can it be used for multi-spark, or would one need to stack 2 or
 more with
 abit of angular offset, then utilize your FET controller to
 switch the
 spark?
 Last, maybe a failsafe contactor to switch out multispark in the
 event of
 a malfunction of computer to revert to stone axe mode? Or am I
 making it
 overly complicated?
 C. Smith


 I think stacking two would be needed. The charging coils are
 available
 stand alone and very cheap. All we need do is find the curved
 magnets stand
 alone. Jeff can make the rotating magnet holder. The electronics
 are trivial
 as I just demonstrated.  Here is a picture of what the spark looks
 like. The picture is a bit out of focus but you can see the spark.


 Paul Lamar

 K&J Magnetics makes custom magnets, $150 minimum order. I
 wouldn't have
 a clue as to the dimensions or polarization, but
 I'll bet you do. Looks like a quote is free.
 http://www.kjmagnetics.com/custom.asp

 C. Smith


 One of my hangar neighbors fixes Mercury's. I can get the dims
 of one of those flywheels. Probably not for a week as I have
 to go to PA on biz next week.

 Paul Lamar

 Check out the last five magnets at the bottom of this page.
 http://www.kjmagnetics.com/products.asp?cat=168
 A the very least, it demonstrates it is doable.
 C. Smith

 Looks too small. We need something 3 inch radius
 or larger. Some of these big ones are high bucks.

 Paul Lamar

 Every Day Practical Electronics mag just published
 another article by my favorite world wide ignition
 engineer. Namely Australian John Clarke.
 www.epemag.com The subject was "Replacement Module for
 small petrol motors". Page 12

 Here are a couple of pictures of a used outboard motor flywheel
 I bought for $10 in an outboard engine repair shop. I wanted
 the magnets out of it.

 Also some more or less self explanatory Figures from the mag
article.

 Paul Lamar



 Could something like this be incorporated into the flex plate?
 Tracy's PSRU
 seems to have a lot of open area to route wiring out to the
 electronics.

 Joe Berki
 Limo EZ

 Certainly could fit in that area. Ideal for use with a carb.

 Paul Lamar


 Hi Paul,
 I took your advice and purchased an old 13b for tear down and
 familiarization purposes.  I also purchased Tracy's book and
 read it cover to cover 4 times (I learn a little more each time
 I read it).

 I want to start off sort of in Tracy's footsteps by using carbs.
 I have two Johnson / Evinrude 2 barrel carbs that I will
 fabricate onto an intake manifold, but I keep getting hung up on
 the ignition side.  I think the idea of using an outboard
 ignition system is the way to go for me.  I have electrical
 schematics for my 1973 Johnson that I can scan and send if it
 would help with this thread.  The main components would be
 stator, spark advance mechanism, power pack, flywheel with
 embedded magnets and coils.

 My only question is that on the Johnson, spark advance is
 controlled by the spark advance mechanism via a direct
 connection to the throttle.  Would we need to incorporate this
 into the design for a/c use or is there a different way of
 overcoming the spark advance problem?


 Franklin

 How much HP did the Johnson carbs develop?
 To work it should be around 200 to 250 HP.

 In other words what is the carb throat inside diameter?
 You will need about 3 square inches per carb.
 Do you plan to p-port?
 http://www.rotaryeng.net/fund-of-intake.html
 P-ports are worth it as the intake manifold becomes
 trivial to fabricate.

 Do you have access to a lathe?
 You will need it to make a rotating magnet holder for the
 front of the e-shaft. I have a fellow that can make
 that part for you if necessary.

 Yes by all means scan the Johnson electrical schematics.
 That will help when buying parts for the ignition.

 Don't worry about ignition advance. Just run the engine
 at 22 BTDC fixed. Aircraft engines like boat engines
 cruise at one RPM.

 Paul Lamar

 Paul,

 How about a dual ignition systems?  Assume coil-on-plugs design
 and that we would use a two stroke marine engine magneto and
 coils incorporated into the starter gear or torsion plate area
 of the housing.  Also assume we would have  capacitor driven
 ignition modules like the new solid state digital programmable
 MSD, 6AL-2.  Check them out.  Small and compact.  One for each
 rotor.

 First some givens about our rotary engines with the single
 leading plug:  The engine doesn't run very well on trailing
 plugs alone, as quite a lot of the fuel goes out the exhaust and
 is burned in the exhaust system.  Said another way, with a two
 rotor engine and a leading plug fouled, the exhaust system may
 well overheat, or the engine would run rough enough that we
 would want to shut it down after a short time.  That means the
 Achilles heel of the Mazda rotary is the leading plug.   As
 quite a few members have pointed out though, a spark plug is
 pretty basic technology.  Yes I agree  but I also can't count
 the number of times I have had them crap out on a  2 stroke oil
 burning engines.  Prudence would dictate changing them quite
 regularly since it is a critical point of failure or beg Mazda
 to cast us up some two bung leading plug housings.

 Conversely if the trailing plugs fail the engine power only
 reduces about 3% if that.  So with a good leading plug and a
 magneto system,  the engine would continue to operate just fine.
 BSFC will be a little off but we won't get our feet wet and the
 plane can continue on for many many hours.

 OK we can all agree that  a magneto is basic technology and
 very fail-safe.  The magneto fires when a magnet passes by
 coils set 180 degree  (20Bs would need three spaced at 120
 degrees) apart.   These coils could be wound to produce 300
 volts.  Timing can be fixed  for a cruise rpm.

 Now for the plus alpha.  The MSD ignition devices can be
 programed to fire the leading (and trailing) plugs many times
 and at moments when the magneto isn't doing that.   Each MSD
 power pack could  get its signal to prepare for  a firing
 sequence from the magneto or modified coil voltage pulse. Since
 the MSD devices have intelligence they can vary the timing with
 rpms. and other inputs received from sensors or even a
 MEGASQUIRT engine control board.

 The question is,  How do we isolate the MSD power from the
 magneto power because they are both hooked up to the same coil?
 Diodes are the easy answer but I wonder if that is a robust
 solution?  In the scenario above  power unit could be charging
 the leading plug coil.

 A FET switch  might be an answer but the fail safe would have
 to allow the magneto to continue firing the leading plug coil

 FETs on the two MSD outputs to the leading and trailing plugs
 would allow split timing if necessary at the higher rpms.  For
 instance the magneto fires the first burst on the leading plug,
 followed immediately by two stronger pulses from the MSD
 Capacitor while perhaps a third pulse from the MSD is directed
 only to the trailing plug.

 Your thoughts?

 Doug in Japan

 I think you are making a mountain out of a mole hill here Doug.
 A phenomena call sag happens when the plugs get to be about 50
hours
 old or so. Minor loss of power.

 The solution is put in new plugs on a regular basis. The plugs
catch
 hell in a rotary as they spark twice as often as a 4 cycle piston
 engine. The same as a two stroke. Now this has been reported with
 inductive type ignition only but as far as I know nobody is using
 a CD
 system in a flying aircraft. CD systems have a proven track record
 of making plugs last longer in piston engines.

 No telling what the CD spark plug life would be in a rotary
until we
 get some good data. The MSD ignition apparently only fires more
than
 once up to some RPM which I know not. I have talked to their
 engineers
 about it and they don't seem to understand the rotary so they
cannot
 give me a good answer. One MSD system per plug would give a lot of
 redundancy.

 We don't have any data running on trailing plugs
 alone for a period of time so it is hard to say what will happen.
 Ignition failures of any kind are rather rare with the possible
 exception of 2nd gen igniter ballast resistors which can be traced
 to continuous high RPM use. The wattage rating of these resistors
 must be increased.

 Tracy also had problems with early Corvette
 coils over heating but I suspect that was caused by excessive
 dwell and the fact they were being triggered twice as often.

 One unknown is the charging coil in an outboard motor may not be
 able to charge more than one capacitor at a time so the outboard
 type ignition system may require two magnets, two capacitors and
 two charging coils per rotor for firing both leading and trailing
 coils. Some experiments need to be made to check and see if this
 is true.

 You will also need outboard type CD coils as RX8 or Corvette
 coils per plug  will not work with CD systems.

 The thing about 2 cycle outboard coils is they are designed
 to run at high RPM and CD systems are actually easier on coils.
 They become mere pulse transformers and not a device to
 store energy. In that case they should be far more reliable

 Paul Lamar

 Hello Paul,

 Attached please find the wiring diagram for a 1977 V4 2 cycle 85
 HP outboard.  I do believe the stator and circuitry is more
 complex than the application we are looking for due in part that
 it is working 4 cylinders instead of two.  If perhaps someone
 had a wiring diagram of a 2 cylinder 2cycle outboard it would be
 even better.

 With regards to the throat diameter of the carbs I was
 considering, I was going to use Tracy's estimate of 1 square
 inch per 50 horsepower.  Is that in the ball park or should I go
 larger?  I have not thought about a P-Port yet as I'm still
 learning and the thought of taking a grinder to the engine is,
 at this point, beyond my ability.



 Regards,
 FranklinHello Paul,

 Attached please find the wiring diagram for a 1977 V4 2 cycle 85
 HP outboard.  I do believe the stator and circuitry is more
 complex than the application we are looking for due in part that
 it is working 4 cylinders instead of two.  If perhaps someone
 had a wiring diagram of a 2 cylinder 2cycle outboard it would be
 even better.

 With regards to the throat diameter of the carbs I was
 considering, I was going to use Tracy's estimate of 1 square
 inch per 50 horsepower.  Is that in the ball park or should I go
 larger?  I have not thought about a P-Port yet as I'm still
 learning and the thought of taking a grinder to the engine is,
 at this point, beyond my ability.


 Regards,
 Franklin


 Nothing was attached Franklin. Try again.

 1 square inch is on the small side for 50 HP. 1 square inch
 is more like 45 HP

 Jeff can do the p-port thing for you.
 jeff.doddridge@gmail.com

 A lot easier than making a manifold however you must
 be willing to disassemble and reassemble your engine.
 Mazdatrix will also build a P-port engine for you with
 Jeff's modified p-port rotor housings.

 Since you are using carbs you won't need the slide throttle.

 Read this. http://www.rotaryeng.net/intake.html

 If you still want to use a side port a lot depends on how
 much room you have under the cowl when building manifolds.
 What kind of airplane are you building?

 Is your engine a 4 port or six port?
 Are you good at tig welding aluminum? Steel welding?
 Steel tubing is the easiest to use as the welding skills
 required are minimal.

 Here is a trick for the transition of round tubing
 to oval intake ports. Don't try to flatten a round
 tube. The area will be much reduced which will seriously
 affect the HP you get. We have been all over this in years
 past. A lot of people have been disappointed in the results
 when building side port manifolds.

 Paul Lamar

 Let me try the attachment again.


 Regards,
 Franklin


 There seems to be enough parts for a two rotor but they
 must be rearranged. I am not sure as there is no picture of
 the flywheel showing the position of the charging coils
 and firing coils. Do you have  a digital camera or a cellphone
 with camera?


 BTW I just found a source for magnets. This is a major
 breakthrough for us.

 http://www.maxrules.com/fixomccdi11.html#MAGNET

 I can now go wild designing a magnet holder which is the key
 to the whole works.

 Paul Lamar

 Attached are pictures of the flywheel from the Johnson.  As you
 can see there are sets of magnets embedded into the flywheel and
 then machined smooth.  There are 6 sets of magnets or 12 magnets
 all together.  I'm not certain but I do believe that the sets
 are opposite in polarity.  I'm fairly certain I read that
 somewhere.

 I'm planning on building an aerocanard and I'm trying to keep it
 as simple as possible.  Don't believe I will be able to do the
 gravity feed fuel system, so I'll have to go redundant on the
 low pressure fuel pumps.

 Franklin Canosa

 Lots of magnets in there. I think I have found a picture of
 what goes with it which I included. Do those look familiar?
 The two light colored coils are the charging coils for the
 CD ignition. The other two are the generator coils.

 The big challenge now is making a light weight holder for all
 those magnets that will fit the e-shaft. Do you have a friend
 with a lathe? You will get an alternator out of the deal.

 Paul Lamar


 Paul,

 Yes those are part of the CD system.  The blue ring device is the
 'spark advance mechanism' that we can probalby do without as you
 suggested we just time the engine to 22 BTDC.  The stator is
 correct and you are correct (I believe) about the different coil
 purposes.

 I don't have direct access to a lathe, but would be willing to
 send down the parts from my old outboard for experimentation
 purposes.  I still have the stator, flywheel, a couple of good
 coils and perhaps even the power pack.  I was going to try and
 sell them on ebay, but I would probably get 10 bucks for the lot,
 and this is a far more fun and useful application of the parts.

 Let me know your thoughts.

 Franklin


 I would like to take a close look at that flywheel.
 Most of the other parts are interchangeably or can be bought
 used or new.

 I would like to put it in a lathe can cut it down
 to drastically cut the weight and then make an aluminum
 hub for it to fit the flange on the e-shaft. The flywheel
 aspects of it are not needed and in fact it is not good
 to add rotational inertia to the front end of the e-shaft.

 This. I think, is the key to making this system practical.

 With the flywheel I have all I need do is drill out
 the rivets to remove the magnets. I can then mount
 them in an aluminum hub.

 Paul Lamar


Paul it may be simpler than that. Machine the outboard flywheel
to fit under
the damper, machine it lite and use as is. a stupid suggestion by
milo!

I'll investigate that option shortly. I have one of Tracy's
dampers sitting right here.

-------------------------------
Here is what I have so far. I just had an idea this morning
on how to make this a bit cheaper and better.

If I chuck the front hub with
the bolted on pulley in the lathe I can take an small internal
cut out out of the steel pulley to insure it is concentric.
Then press in something that looks like this.
The groove will be filled with uni carbon to cut
the rotational inertia and increase the burst strength.
Important at 7500 RPM.

Paul Lamar