[AT] Coating for small engine mag

Rena Glover Goss rlgoss at twc.com
Sat Dec 9 09:37:48 PST 2017


Surface rust isn't going to make any difference, Mike, but as the iron continues to deteriorate and more of it turns to "red rust" the magnetic field will slowly change its shape.  It doesn't take much to start reshaping the magnetic field.  I suspect you are right in thinking that this problem is associated with the newer electronic ignitions rather than the old "points and condenser" style.

I asked my dad once about the weird single loops of heavy iron wire that were often added to the laminations of electric motors, and he explained to me that those were specifically placed to control the shape of the magnetic field.


Larry
---- Mike M <meulenms at gmx.com> wrote: 
> Care to explain further? Can rust re-channel the shape of the magnetic 
> field as to make it less available? Too many real world experiences to 
> simply dismiss it.
> 
> Mike M
> 
> 
> On 12/8/2017 12:25 PM, Rena Glover Goss wrote:
> > Umm.  Hey guys!  This has been an interesting thread, but I think there are a lot of "old wives tales" floating around on it.  Please learn the difference between a dielectric and an insulator, and that magnetism works differently than electricity.  You can channel the shape of a magnetic field, but there is no such thing as a magnetic insulator.  Just because red rust is non-magnetic does not keep a magneto from working, and polishing or painting the laminations of an electro-magnet will have no effect on its operation.
> >
> >
> > Larry
> > ---- Ken Knierim <ken.knierim at gmail.com> wrote:
> >> A lot of modern electronics are potted with a very thin layer of plasma
> >> deposited PDMS. I would guess that in the case of the small engine ignition
> >> parts they aren't coated as that material is a bear to make electrical
> >> contact through once it's been applied. It's tough to see too; it's very
> >> thin. It's largely replaced lacquer because of the environmental and
> >> handling issues except in potting of magnetics (they're still lacquer
> >> dipped in many cases).
> >>
> >> For me, I'd consider using some sort of lacquer, either dipped or sprayed
> >> on heavily to prevent moisture from getting into the coil. If it has a
> >> magnetic pickup side (next to a flywheel with a magnet for instance),
> >> you'll want a light coating of something non-conductive to keep the rust
> >> off the cores as rust degrades the magnetic operation. You also want to
> >> keep this layer thin as you need to have a rather specific gap between the
> >> magnet and the core laminations. The magnetic field drops off at the square
> >> of the distance and a large gap can make it a bear to start.
> >>
> >> As far as the points are concerned, the newer (cheaper, "environmentally
> >> friendly") metals don't hold up well to corrosion and arcing. Arcing can be
> >> mitigated by using the proper condenser (or an electronic ignition) as I
> >> remember this being a subject of my old 4-H Petroleum Power manuals (how
> >> the arc erodes the points could tell you if the condenser size was wrong
> >> and how to adjust for this).
> >> Since chromium and other materials formerly used in points manufacture that
> >> resisted corrosion can be expensive and have toxic application phases (like
> >> hexavalent chrome), manufacturers in this country can't use them. Silver is
> >> good but very soft (and not cheap) and silver is one of the few metals
> >> that's also conductive in oxide form. (the other I can think of is ITO,
> >> indium tin oxide, which is also transparent and you're probably actually
> >> looking through it right now in your LCD computer screen.) Lots of contacts
> >> (heavy AC contactors for example) use silver and other metals to provide
> >> good contact when exposed to air... these are usually costly and most
> >> ignition points are considered wear items (meaning "keep 'em cheap") so
> >> quality isn't what it used to be. So keeping them clean requires regular
> >> maintenance or a dry environment because anything that drives the water o
> >>
> >> Sorry for all the off-topic stuff this morning. Mind is wandering from lack
> >> of coffee.. Hope some of this helps someone.
> >>
> >> Ken in AZ
> >>
> >>
> >> On Fri, Dec 8, 2017 at 4:41 AM, Henry Miller <hank at millerfarm.com> wrote:
> >>
> >>> I'm sure there is a reason, but I would guess cheap. These engines are
> >>> designed for machines that are expected to be replaced every 7 years or
> >>> so. If it runs that long they have their money and the customer thinks
> >>> it was reliable since it lasted that long. That it could last much
> >>> longer with just a little more cost is a bad thing.
> >>>
> >>> --
> >>>    Henry Miller
> >>>    hank at millerfarm.com
> >>>
> >>> On Thu, Dec 7, 2017, at 08:24 PM, John Hall wrote:
> >>>> I've can't ever recall encountering a flywheel magnet or a magnet inside
> >>>> a magneto that was coated---must be a reason.
> >>>>
> >>>> John Hall
> >>>>
> >>>>
> >>>> On 12/7/2017 1:25 PM, Mike M wrote:
> >>>>> My wood splitter wouldn't start the other day, had plenty of gas, wet
> >>>>> plug, but weak spark. I suspected rust on the flywheel, so I tore it
> >>>>> apart and I was right. Cleaned it up, and now have a nice strong spark.
> >>>>> Question is, can I coat the mag and coil pickups with anything to
> >>>>> prevent the rust from re-occurring?
> >>>>>
> >>>>> Thanks,
> >>>>> Mike M
> >>>>>
> >>>>>
> >>>>> -
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