evinrude rbm coil test and repair

[joecb]

In retrospect, some thoughts on the subject… looking at the last photo that Tubs posted ( the bare armature) It appears that the "V" portion about which the coils are wound is integral with the left shoe, see the radius at the shoe. the right end is likely inserted into the right shoe lamination stack. That said, there is no way to install a long coil like a Johnson because of the "V". As for shorter coils, the shape of the armature core being rectangular would not accommodate any modern coil that I know of. Also interesting that both of the original coils had both primary and secondary windings, I had understood that one was primary and the other secondary, this was wrong. Thanks again for posting.
Joe B

[The Boat House]

A or J coils are way to big. I had intended to try
to just put a coil on one side but I couldn’t get
the laments out of the coil I wanted to use
without braking the coating. I have come up
with a option#-4. I have it all together but
I’m struggling on how to attach the spark
plug wire. I’m pretty sure it will make a spark
but will it be strong enough to start when
pulling it over by hand ?

[george-emmanuel]

there is no way to install a long coil like a Johnson because of the "V". As for shorter coils, the shape of the armature core being rectangular would not accommodate any modern coil that I know of

I agree. But what I suggest is machining that core so you can fit another coil in. The issue with the Evinrude mag plate is the raised wall that was used to hold the tar in. I don’t think it is needed structurally.– And it prevents installation of a coil from one side of the heels to the other.

If you look at an Evinrude Speeditwin coil,(and I’m only using this as an example) the laminate has a step on each side and the cores the coil mounts to has a step. One side is up and the other down, and the coil only has a machine screw that fastens the core to the heel. There is no interlocking of the laminates. So in theory, if a Speeditwin coil would fit in the space (yes, I know it is for twin cylinders) between the heels, and if you cut out the middle of the core, machined a step on each side to match the Speeditwin’s steps and mounted it like it is on a Speeditwin mag plate, it should produce spark.

This thread has encouraged me to seek a bad mag plate and experiment! I’ve done 4 other mag modifications installing other style coils with great success. I put a later Speeditiwn coil in a model R Fastwin, a Johnson S/V-45 coil in a 30 cu in Caille and in a 1916 Koban, and 2 OMC coils in a Caille Master 5-Speed.

George

[The Boat House]

[george-emmanuel]

It is as I said, the raised ridge that is the reservoir for the tar is the complicating factor, but wow, what a nice job you’ve done! How’s about one of those Mercury Chainsaw coils? Which coil did you use?

George

[david-bartlett]

Man Tubs! You do some fine work!

[jim-moffatt]

Any single cyl coil should work, if its small enough to fit in the flywheel and mag plate. The original coils were so big most likely because very thin gauge wire wasnt available in those early days. Any modern single coil should be "hot" enough. The coil can be placed anywhere on the laminate.
And its likely that grinding down the laminate to fit a modern coil would cause no problems.

The laminates can be cut in a staircase fashion if the heels cannot be removed. But that would require separating the layers from each other.

What Tubs has done using a tight fitting butt joint between the old laminates and the coil laminates should also work.

I have to complement Tubs on his very careful work to this point. The light at the end of the tunnel is in sight now, And its a good light!

[kees]

quote Tubs:

what a solution, WOW !
hats off, a great compliment for your work here
and that you share it with us
including the attached photos
😀 😀
.

[The Boat House]

quote kees:

quote Tubs:

what a solution, WOW !
hats off, a great compliment for your work here
and that you share it with us
including the attached photos
😀 😀
.

Well Kees I haven’t gotten it to
work as the coil is too tall and hits the
top of the flywheel. The pictures show
what challenges I face as to getting more
room. Still no solution as yet.

The faster a magneto spins the stronger
the spark. If I can get this worked out I’m
sure it will make a spark and the motor
would run but will it be strong enough for
it to start pulling the motor over by hand.
The original configuration is essentially 2
coils. It may turn out to be a waste of time.

quote George Emmanuel:

the raised ridge that is the reservoir for the tar is the complicating factor,

The raised wall that holds the tar could be
removed for more width if you needed it.
My issue is the height.

quote Jim Moffatt:

very thin gauge wire wasn’t available in those early days.

The coil can be placed anywhere on the laminate. And its likely
that grinding down the laminate to fit a modern coil would cause no problems.

What Tubs has done using a tight fitting butt joint between the
old laminates and the coil laminates should also work.

The wire looked awful fine to me Jim and
there seemed to be a ton of it.

My attempt to file down the laments and just
put a coil on one side ended when I couldn’t
the laments out of the coil without damaging
the cover. I didn’t know if having the coil off
center would work. You have answered that
question for me but I was using the same coil
so it wouldn’t have fit anyway.

I did make an effort to have the laments I
shortened touch Jim but I don’t know if its
necessary. Some coils just have one lament
inserted into the rest. So my thinking
was if the centers didn’t touch the over and
under contact should work. What do you
think?

The wife was sneezing and coughing all
last week and now I got it. Hard to be
creative when you feel like crap.

[gofastgramps]

Tubs Could you mill a pocket in the mag plate and set the coil in it ? you would have to stager the laminates.

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