EI module phelon/prestolite research

[dynodave]

Got the dead 83 SXLAO prestolite module and WICO/prestolite flywheel from kysawman thursday in the mail. Many thanks to Jasper. Been trying to do an autopsy as well as a comparison to the points flywheels and a variety of issues.
First thing I noticed is the plug wire was not to secure. I unscrewed the wire from the post. Then looking in the end I saw no stranded wire. Digging in deep enough I'm pretty sure it is carbon resistor wire and is just shy of 9" long. The carbon may be burned back quite a ways. That spells trouble.
I will continue to dig until I make contact.

[sweepleader]

Yeah, that carbon wire is a bad deal with small engines. It might be that the metal wire is burned back too, if there was a gap (poor contact with the post), arcing will destroy most anything. The post would likely be burned off too in that case. The spark voltage will go up till something gives, usually if all is working right, that would be the plug gap. If a break develops in the wire or plug, the voltage will increase to jump whatever gap there is. That extra high voltage can burn distributor caps and magneto coils. It will be fun to hear what you find.

[dynodave]

Will be cutting back up the wire to find continuity and conductive carbon trace. Having been associated with EI repair in classic british motorcycles as a hobby and in high power/high voltage professionally for 40 years, I have learned that as the spark gap impedance grows, so does the reflected power get sent back to the coil primary which ends up at the controlling transistor/SCR. The reflected pulse might be described as a bee(voltage spike) stinging a balloon(silicon boundry). Since all electronics die from heat, the little holes/leaks start a destructive heating cycle that does not seem evident to the average person. But the fuse has been lit. Eventually a damaged transistor dies. This has been adequately proven and seen under electron microscope analysis. My whole career has revolved around trying to repair or prevent such events(in expensive equipment mostly radars and their subsystems).
In this case a faulty ground is not the problem but probably the bad HV wire.

I have also grown the sample of flywheel magnetic sequences N-S or S-N as well as the field strength (gauss).
I've measured the distance between the armatures that you can see on the edge of the flywheel that direct the placement of the magnetism. This is closely related to the width of the EI module armature. FWIW an armature is not only a round device in a motor but the shaped/stamped steel , laminations in the flywheel that encapsulate the internal magnet(that you do not see)... or the laminations that focus the magnetism through the wire copper coils inside the EI module.
to be continued:

[sweepleader]

Many folks don't realize that a spark is plasma, likely the hottest thing in the universe, and can burn/vaporize anything. Its why electric welding works.

Are you putting the data you are collecting in a chart or something? That would be very useful in substituting coils/modules. Might take a lifetime or longer to compile.

[kysawman]

I don’t know if that is the original wire, due to the fact that it had he strange spark plug boot. I think I have another one that is good I can check the wire. I try to convert all of mine to points ignition .

[dynodave]

Jun 9, 2018 9:12:20 GMT -5 kysawman said:

I don’t know if that is the original wire, due to the fact that it had he strange spark plug boot. I think I have another one that is good I can check the wire. I try to convert all of mine to points ignition .

I'd probably try solid wire if an EI module as being safer than an open burned back carbon wire. A carbon lead does have a function yes, but is more of a problem than a cure if it burns back and makes a huge gap for the spark to jump. Eventually the gap gets to be too big and besides being hard to start will cause damage to the EI.

On my 71 SXLAO, I was stunned to find a good cap @.227uF NO leakage at 400vdc

[sweepleader]

Most small engines don't seem to have enough spark to really deal with carbon wire, even in good shape. That is why they get hard to start with the carbon wire. It is meant to eliminate radio static coming from the ignition so an on board radio works well. Also to prevent a highway from messing up the radar at an airport or similar. Neither one a big deal with a chainsaw.

[kysawman]

I checked the module I have off of an 1985 sxlao and it has solid wire core. So I would say someone replaced the wire with one from a car.

[dynodave]

Jun 9, 2018 11:20:59 GMT -5 sweepleader said:

Most small engines don't seem to have enough spark to really deal with carbon wire, even in good shape. That is why they get hard to start with the carbon wire. It is meant to eliminate radio static coming from the ignition so an on board radio works well. Also to prevent a highway from messing up the radar at an airport or similar. Neither one a big deal with a chainsaw.

I know there are 2 reasons for resistor wire, but more modern saws deal with it with resistors plugs instead... which are very common...I have plenty of OPE with resistor plugs.

A lot of retrofit digital EI makers for the classic bikes insist on resistor plugs. Those that don't do it, often have trouble with the EI malfunctioning. The noise pulses come right back down the HV wire and confuse the microprocessor and probably is a significant reason for so many later failures.

[dynodave]

unscientific play in the shop yields results!


I decided to try a phelon ignition that was laying around as a spare.
I gently drilled out the ground strap spot weld against the armature to free up the bobbin..
Kind of mounted it on the donor SXLAO coil armature, strapped some stainless safety wire to hold it in place.
Remember to connect the ground strap to the armature/ground- or solder a wire with a round lug...
Tightened the SXLAO armature with the business card against the flywheel.
spark plug laying on the cylinder.
Impact gun on the crank nut and lightly spun the crank in the stripped bare SXLAO motor core that was mounted in the bench vise.
While I am not sure why, it sparks very nice and blue in BOTH directions.
EI bobbin pn 530039167 is from a poulan 2150 saw. The test was done with a genuine poulan/phelon.
Aftermarket is as cheap as $14.


More play to follow....

[sweepleader]

Both directions would seem OK to me and explainable because the magnetic polarity remains the same in both directions. Nothing happens magnetic coupling wise until both poles line up with the core legs, the field in the core builds in the same way no matter which direction the magnet approaches. The polarity is the same, the currents in the module/coil are the same polarity, spark in both directions.

Do be careful with the impact gun, the inertia of the crank and flywheel are likely enough to cause damage to the threads if the impact gun is used with too much gusto. A drill motor would be safer. I expect you know this, just letting others who do not know save themselves some grief.

[dynodave]

Jun 9, 2018 16:59:33 GMT -5 sweepleader said:

Both directions would seem OK to me and explainable because the magnetic polarity remains the same in both directions. Nothing happens magnetic coupling wise until both poles line up with the core legs, the field in the core builds in the same way no matter which direction the magnet approaches. The polarity is the same, the currents in the module/coil are the same polarity, spark in both directions.

Do be careful with the impact gun, the inertia of the crank and flywheel are likely enough to cause damage to the threads if the impact gun is used with too much gusto. A drill motor would be safer. I expect you know this, just letting others who do not know save themselves some grief.

Sorry, not really going to buy your assumptions. The reason why I was SO surprised is because a few months ago while "debating" polarity matters...over on AS, I had driven another saw under the same conditions with the original EI. It would spark in forward direction but NOT in the reverse direction. Therefore solidifying my view against the similar previously offered theory. While I can understand the electronics possibility for firing both directions but not as a function of purely magnetism alone. In practice yes it is possible but not assured without adequate sophistication in the electronics design.

Thats why I'm doing all this work...to find out why?

[dynodave]

I don't want to seem overly argumentative, I will concede that in a very simple configuration an EI "could" spark in either direction. The principle of the magnetic flux being concentrated between the pole pieces then jumping onto the EI armature is valid and making voltage in any internal windings, in either direction as you state is not so much in dispute.

Consider a hall sensor internal to the EI blob triggered by the specific polarity of the trailing edge magnet. The magnets would be making the bulk energy yet only the correct polarity magnet would properly trigger the device.
Running in reverse rotation the trigger would come first and bulk energy would come after..so no spark could result.

As a real world example, some old points type (70's) Briggs and Straton engines MUST have their flywheels returned to the factory for magnet regaussing to reverse the polarity or they won't run if upgraded from points to EI. I have a half dozen of these engines. I have measured the magnetic polarity to confirm old VS the newer engines flywheel magnetic sequence. With a bit of machining to build the gausser armatures I could do that myself with my gausser. 1600vdc @ about 1000amps during the cap bank discharge.
Sounds like a shot gun went off.....

I do have another (different) phelon that actually has a direction arrow on it -rotation->?
I also have a SEM Walbro EI unit that has a significant bump on the edge of the case?

Will continue with my tests and I'll let you all know what I find.

[sweepleader]

The hall sensor thing is certainly a possibility. I have wondered just how the timing is controlled on the EI systems and if that is how its done, it is clear that it might not work in reverse direction. Is that a fact, that is how the trigger works on these systems?

By the way, I don't want to seem argumentative either and I think you are doing just fine, I hope I am too. This is my kind of discussion. :{)

[dynodave]

A bit more data generation by doing some tests on a test rig consisting of a bifilar coil. A being a CW winding and B being a CCW winding both are the same number of turns and the direction is referenced by looking down from the top. I made as many turns as possible for the 22 gauge wire that I had. ?maybe 25 turns? both coils have a 1000 ohm load'
The leading magnet is N/+ trailing magnet is S/-

The difference in lead edge and trailing edge over shoots, I believe to be from the different widths of the EI armature, leading edge(narrow) and trailing edge (broader).

[sweepleader]

You don't mention, are you reading both coils wired in series or one coil? It is hard to see in the picture. What are you trying to show?

I would expect to see a peak as the magnet poles line up with the coil poles and the mag field builds, then the inverted peak as they disengage and the field collapses. That is what I see on your scope, I think.

Why do you have them wound opposite? It seems the flux in the core will be from (or maybe reversed but in one direction through the entire core) the bottom of the left coil to the top and from the top of the right coil to the bottom and that would lead me to believe they should be wound in the same direction. (or maybe its a 3 leg core, can't tell)

It has been a very long time since I studied any of this, like 40 years so forgive me if I am way off base.

[dynodave]

The EI armature is a simple upside down U. The points/coil armature is an upside down W with the coil on the center leg.
I am only showing the CW coil waveshape, the CCW coil signal is exactly the same but polarity reversed. I made it bypolar so I could play with or use the polarity I was wanting to to experiment with, without having to reconstruct the wire end mountings.
The leading edge of the + slope is when the "snap" of final full magnetic first brings the magnetism onto the full coil armature alignment,
From the + peak to base line is during rotational dwell until it unsnaps and the gauss lines are disconnected out of the core/armature, this makes the base line to -peak part of the wave shape. It appears the gap between the flywheel armature poles are .385 long and the coil is .350 long which accounts for the slight S shape between the sharp fall and leading edge of the neg part of the wave shape. Not sure why it's that way on the EI coil armature.
I did notice on the points/coil magnet gap and coil armature are exactly the same size... to possibly increase the power and efficiency of the wave shape by better joining both wave shapes at zero crossing to make a better spark. Both are WICO flywheels. Both flywheels types keyway/magnet gap center are at the same angle but the coils positions are understandably not the same on the saw body.
I'm now using the drill to spin the crank, and getting about 1052RPM and 1.3volts or 2.6vP-P
The EI magnet is about 1200 gauss.
The points/coil magnet is about 1570gauss

[sweepleader]

If the points armature is a W or E shape, does the flywheel have 3 poles, NSN (or SNS)? It would seem to me that there should be more peaks as the magnet aligned with the first two poles then all three then the last two with polarity reverses. This is probably a discussion that should really only take place in person, with eyes on the project. I have too many questions to really be reasonably answered this way.

You wanna swing by the house tonight with your stuff and we can really have at it? No, I forgot, I am busy tonight, it will have to be some other time. Keep at it, interesting stuff