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chuck foster:
well here's tonight's installment on this adventure :ddb:

i need to fabricate an ignitor for this engine and here is a picture of the one i'm copying

and here's the business end

so i began with a hunk of bronze

i then milled out the basic shape

used the edge finder so as to locate the various holes in the ignitor body

all the holes are now drilled, the hole on the far right is for bolts to hold the ignitor on the engine, the next hole is for the movable electrode, the next hole is for the insulate electrode and last but not least is the other bolt hole.

the finished ignitor body beside the original that i copied from

now i guess it would be a good idea to explain what an ignitor is and how it works, so i have copied a page that i found on the net that should explain it all

If the ends of two wires forming part of an electric circuit are brought in contact, closing the circuit and then quickly separated, a bright spark will be produced as the contact is broken. This phenomenon underlies the operative principle of what is known as the MAKE and BREAK system of ignition. In old stationary gas engine practice, the simplest kind of ignitor used city lighting direct current, with an incandescent lamp in series in order to prevent the current from being too strong.

An ignitor is made up of a set of mechanical points, much like the points in early vintage automobiles, except they are located INSIDE the combustion chamber. One side is insulated, the other side is at frame ground and they are mounted to an assembly that PROTRUDES INTO the combustion chamber. A capacitor (condenser) is NOT used across these points because sparking across the points is WANTED, unlike in a car where the heat and metal consumption of sparks would wear away the surface of the points needlessly. When the ignitor points "make" or close, a current will build up in an inductive coil that is in a series circuit. Then at the appropriate time, the points "break" and an inductive "kick" causes an arc to draw across the opening points. The gap opening is about 1/16". Even battery voltage itself will cause a small spark, but the more coil inductance that is in series with the points and battery, the hotter and bluer the arc created.

i hope that explains what an ignitor is and what it does.

chuck :wave:

NickG:
Cheers Chuck - that was going to be my question, I have never heard of or seen one of those before. Is this engine a hit and miss type? Ignore that, I have just looked at the pic and I can see it is.

Great project. What is the bore and stroke? This will actually have some useable power won't it?

Nick

ozzie46:

Great stuff on the igniter. Just the kind of stuff I need.

Ron

chuck foster:
i'm glad the ignitor info was of some use. i have worked on the full size engines for the last 30 years so i sometimes
forget that some people don't know all the little details of these engines.
if i forget to explain something just ask and i will do my best to clarifiy it for you.

now on with tonight's adventure, making the trip pawl for the ignitor. it is the silver part circled in red

now i could have fabricated this part by silver soldering two pieces together but i thought i would try and making it out of one piece using my RT.
so i started with a round hunk of steel and drilled a 1/8" dia hole in the middle (using the lathe)

first i laid out a rough sketch of it with a marker then i just plunged a 1/8" dia end mill in to the steel to a depth of .300". i went to .300" because when i
part this finished piece off it has to be .250 thick.

then i advanced the RT 5 degrees and plunged the end mill again doing this procedure till i had the trip pawl outline cut.

next i put the piece in the lathe and parted it off, now this next picture shows the job half done

and finally the finished part beside the old one, it just needs to be trimmed to length.

the next piece to make was the movable electrode this was a fairly simple thing to make so i will only show the finished part.

it consists of three pieces silver soldered together, all that is left to do to it now is silver solder the nickel contact points were the red square is.

hopefully tomorrow i will be able to finish the ignitor and see if it will spark.
now it is off to listen to an old time radio program you british gent's might remember..............hancocks half hour.

chuck :wave:

Bernd:
Chuck,

Nice bit of work making that all out of the solid. Who needs CNC. :clap:

Bernd

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