Sparkplug extension at plug wire end

[Brian Rupnow]

Has anyone ever seen or know of a sparkplug extension that looks like the one in this picture? The plug is a Rimfire .25-32. I want to nest this plug down between two rocker arms and not have the spark shorting out and snapping to the rocker arms instead of to the end of the sparkplug. The red and yellow parts I show is the extension. The purple is the original rimfire sparkplug. The red part would have to be steel or brass. The yellow part would be something non-conductive that was resilient like rubber so it would "grip" the end of the sparkplug. Strange question, I know, but I have a reason to ask.---Brian

 

[Ghosty]

Brian, I have seen people make there own, they used a mold and silicon and talc powder, seen it on You-tube also, just can't remember who though.
Cheers
Andrew

 

[stevehuckss396]

Send me a drawing and I'll have a few in the mail by Wednesday.

 

[Brian Rupnow]

Thanks Steve---I'll try something I have in mind first. Back a year or two ago, when I was trying to set up a governor on that twin, I designed and built a set of heads that moved the sparkplugs up to the center of the heads. The heads were great, but the sparkplugs were so short that sparks were jumping over to the rocker arm towers.

 

[propclock]

yes I know it is crude but simple silicone rubber fuel tubing for RC airplanes
works fine . There are 2 basic sizes you want the larger. It stretches amazingly
and is an excellent HV insulator. There are automobile vacuum fittings
that look very realistic, but it is hard to beat the simple solution.

 

[Longboy]

 

[gbritnell]

Brian, Steve and I and many others have been making our own spark plugs for years. For a special application like yours why not just make one with a longer insulator?

 

[Brian Rupnow]

I buy my sparkplugs. I think I've got it sorted as to how I'm going to lengthen them. I will post a full explanation when I do.---Brian

 

[stevehuckss396]

That was my thought george. Just make him a plug with custom insulator to a good length. I have bases and caps made so the insulator and assembly should be easy. Couple days and in the mail.

 

[Brian Rupnow]

I find that Corian is rather brittle stuff to work with. Is there any other material that is commonly available but is still machinable and a good insulator? I have made my own sparkplugs in the past with Corian, but wasn't terribly impressed with it.

 

[Gordon]

Would a 3D printed insulator work ?

 

[GailInNM]

Brian,
I made up some small plugs, 10-40 thread, a while back using pulltruded fiber glass - epoxy rod. According to the specs I was able to find it has slightly better insulating qualities than Corian. and as good heat tolerance as Acetal which is the base material of Corian. Very stiff and not brittle as all. I ran one plug for about 20 hours and then examined it under a microscope and the insulator showed no sign of deteriorating. Ivery easy to machine using either HSS or carbide. I drilled using a carbide circuit board drill but HSS drill should work as well.
If your insulator is less than 1/4 inch diameter then an easy source of material is the rod used for bicycle safety flags. Probably can find a used one as most replacement flags are sold with a new rod and the old rod it thrown away. Even if you have to buy a new rod (with flag) they are only about US$ 10 and are generally about 6 feet long.

 

[Brian Rupnow]

Thank you Gail. I will see about the availability of that stuff in Canada.----Brian

 

[Brian Rupnow]

Okay---Don`t laugh.--I have a solution. The inner portion will be made from brass. The outer section will be kiln dried oak wood. The brass core will be Loctited into the wooden outer shell. The wooden outer shell will be Loctited to the sparkplug. The sparkplug never gets hot enough to burn the wood. The wood is a good insulator, and the brass passes the current down to the sparkplug. best part of all is that I have the material to do this.

 

[werowance]

Brian, how i did my rim fire adapter to full size automobile plug was this:
i found a 90deg vacume hose line that one side just fit over the rim fire. then the other end i machined a brass tip that looked like the tip of a full size saprk plug. but it had a narrow shaft that inserted just right into the other end of that spark plug boot. i used spring out of a click feed lead pencil that my kids used to get at the window in grade school (the cheap ones) that spring worked and wound up the machined brass tip and the other end pushed against the tip of the rim fire

 

[werowance]

the vacume boot looked like this

then forgive the horrible drawing

and here it is on my upshur engine
(and when i went to get a copy i realized i ended up not using the elbow but rather a straight in line fitting but i tried the elbow as well and it worked but didnt like the way the full size wire hung down so i used the same type straight vacume fitting same spring and all but)

so here is a photo of the second type of vacume fitting i used in the pic above.

 

[Brian Rupnow]

Thanks Werowance.--I will probably post my modified sparkplugs at the end of the week.---Brian

 

[Brian Rupnow]

Tomorrow I will probably do my "lengthen the sparkplug trick". I will post a few pictures as I go along.

 

[Brian Rupnow]

Okay, the game plan has changed a little bit. instead of having part of the brass turned to 1/16" diameter, it's a lot easier to drill a 1/16" hole completely thru the brass and silver solder a piece of 1/16" diameter cold rolled steel in there instead.

 

[Brian Rupnow]

So, here we have two sparkplugs extended 1". I'm not sure how this will work, but I will leave them to "set up" for 24 hours so the epoxy is totally cured, and then we'll see.