spark plug wire

[kendo]

Hi Guys
After reading several posts on making spark plugs,especially the excellent
one by Gbritnell. I have noticed reference to music wire being used for the
electrode.
Could any of you guys tell me what the UK version of music wire
might be. Or could any wire be used such as copper wire or welding wire.

Also i have been looking to find a 1/4 x 32 unc tap but not been able to
find a store that sells these, They only seem to stock 1/4 x 18 or 20 Taps.
Or maybe i should use a metric thread for the spark plug and spark plug
ports.
Any information or recommendations you guys can give would be gratefully
received.
Ken

 

[Kermit]

You want the terminal metal to be hard and refractory. High melting temp and something like a carbide for hardness. Tungsten carbide is one with both hardness and high melting point. When the spark "hits" the electrode the local temp can be way above the melting point of most things known to man.

Why not use fire brick then?

It has to be a 'metal' because it must conduct electricity.

One of the high temp copper alloys used for welding would work well. It is not as hard as carbide and will wear away much quicker. The negative electrode will usually wear away faster. Electrons are negatively charged, which means they are leaving the negative electrode. Pretty much the same way it works for welding.

Most any hard steel will work. With low operation duty cycles like most hobby engines see, it would probably last for years.

 

[gbritnell]

Hi Kendo, When I submitted the drawing for the spark plug it was just a general guide for building one. You could use any fine thread for the plug. The main reason for using the 1/4-32 thread is that there are commercial spark plugs available with this thread size. As far as the music wire for the center electrode, I have used stainless steel wire also. I am including a link to a supplier who stocks music wire here in the U.S.
gbritnell
http://www.smallparts.com/index/?utm_campaign=Site_Index_Header

 

[SKIPRAT]

Hi Kendo

The UK definition of Music Wire is Piano Wire as used by aero modellers i get what i need from my local model shop hope that puts you out of your misery .

Cheers Paul

 

[Alan J. Richer]

Guys - not to wander off course - but what about TIG electrode (tungsten rod)? I'm sure the spark plug won't care if the wire is thoriated or otherwise treated. FUll packs of this stuff are not all that expensive - and a stop at a welding shop might net you a stick or two for short money or a box of donuts.

I have a TIG welder - and the electrode wires used in these things are harder than the hinges of Hades. normally, I buy them longer and snap them off by nicking on the grinder and breaking - works great if smoothed off and shaped on the grinder afterward.

Not sure how well this stuff would thread for attaching a wire - but I would think it worth a try.

Alan

 

[kendo]

Hi Alan, Paul,George,and Kermit.

Thankyou for all your input,Its been great to hear your advise. I had a feeling
music wire might be piano wire or something like. There is a welding shop not too
far from me in Llandudno,may give them a visit this weekend. Also there is a model shop i could visit for piano wire.
George, i will probably use metric threads for the plugs,as metric is more wildly used here in the UK now,not like in the good old days when every thing was in old money,
(Imperial). Although the company i work for still uses imperial,but mainly for work
done for our friends on the other side of the Atlantic

Once Again Thanks To You All
Ken

 

[stevehuckss396]

The main reason for using the 1/4-32 thread is that there are commercial spark plugs available with this thread size.

Another advantage to the 1/4-32 is that most of the glow plugs use the 1/4-32. I know more than one builer that like to start there engines on glow fuel. After working out the bugs then switch to ignition and work out those bugs. On a new startup it helps to minimize problems.