V-twin engine from scratch - yet another interpretation of how (not) to build a

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Bernd:
Not going there Don. :offtopic: :lol: :lol:

Bernd

sorveltaja:
Spark plugs at progress:

Plugs have 3mm(0.118") holes through them, and 3.5mm(0.137") drilled for buttons at the business end. Above pic shows one button in place, that still has copper layer on one side. Some might guess already, that the material used for 'buttons' is fiberglass-based circuit board.

It stands heat, at least short periods at a time. I'm not sure, how porous it is under compression, but there is one way to find out :zap:.
One might wonder, why fiberglass; I have it already, it feels more solid, than ptfe, at the working end of the spark plug. It also has dielectric(insulativity) properties, that are needed at this stage.

Spark plug body, and center electrode, with one button, that has no more copper in it. White rod is ptfe, that is to be used to fill the rest of the spark plug's hole:

Center electrode is 1.4mm(0.055") steel, that will have an M1.4 thread at the end of it.

I'll make only one spark plug, to see if it works. Purely experimental, and not to be tried at home .

sorveltaja:
Spark plug parts before assembly:

Finished, after some super glue and grunt:

Ptfe insulator lost some of it's shape, when I pushed it in place. As usually, it behaved like a cooked noodle.

Anyways, it's done now, and brass terminal was added.

To start the testing phase, I'll do some basic spark testings.

sorveltaja:
I tested the new spark plug on the previously made engine, and it ran for a short time, then refused to start. Reason was the fiberglass button, that absorbed some fuel, causing almost short circuit -state.

Well not exactly short circuit, but the ethanol, that I used as a fuel, is conductive enough, to cause a non-sparking situation in that case.

So I removed the 'button', leaving bare ptfe for insulation. I also filed the center electrode's working end from round to t-shape:

Now the new plug is almost like one, that I had used on the test engine before. Appearance of the plug(s) is rather frivolous, but somehow it stands bit of flooding, though.

Anyways, what comes to that fiberglass button -thing, it should have been sealed with some hard, easily poured, dielectric material.

madjackghengis:
Hi Sorveltaja, it's good to see your posts up to date again, we missed you. Nice expose on the spark plug, as to a pourable insulator, I can only think of ceramics as having any long term life and pourable. You might pack chopped glass fiber into the space and then use a torch to melt it so it takes the heat, and allows the ptfe to work without melting, behind it. I've looked at half a dozen or so methods of plug making, and they all seem very temporary because of the insulator material. Remember sparks like to leave sharp pointy places and arrive at sharp pointy places best and you will need the lowest voltage for a spark. I don't particularly want to use ready made spark plugs for my radial engine, but reliability is more important than being able to say I made them myself, so I will try the make it myself route, but if necessary, use a set of ready made plugs. Your success in this may make the choice for me. I'm watching closely for your success. :headbang: mad jack

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