Hit and Miss ignition systems...

[10K Pete]

I've seen a lot of posts and pics showing spark plug ignition systems on
hit and miss engines. Some with Hall Effect pick-ups, some with points,
and most using a neat little electronic unit. Those I understand fairly well.

But tonight I saw a couple of pic of engines without spark plugs. There
is some sort of mechanism in the side of the cylinder near the head with
a push rod going to it. It doesn't look like a magneto, at least not a type
I'm familiar with.

I tried searching for it but don't know what it's called. Can anyone please
set me on the correct path for this device?

Also, has anyone successfully scaled down a magneto for use on one
of these engines? I'm not sure how it could be done but.....?

Thanks,
Pete

 

[Jasonb]

They are called "ignitors" The circuit is quite simple, a battery, and a LOW tension coil is all that is needed.

If you watch the action of the actuating rod it moves in two stages, first cloese the two contacts of the ignitor together so electricity flows through the coil and the second stage lets the contacts spring open quickly, the electricity still wants to travel in te circuit so it sparks across the two opening contacts.

This ones not adjusted up quite right I have also made smaller ones

[ame]https://www.youtube.com/watch?v=J5FLysBwmT0[/ame]

And the contcats from inside

Better description of how they work here

http://www.oldengineshed.com/ignitor.html

There is a commercial small magneto kit available, a couple of designs have been in Model Engine Builder and there is a guy her in teh UK who make them about 1"x1"x1.5"

http://minimagneto.co.uk/Products.php

 

[10K Pete]

Jason you've come through again! I had never heard of this ignitor thing
before. It's so simple! And the links really are great resources.

Thank you!:bow:

Pete

 

[10K Pete]

Ok, now that this has penetrated the grey matter a bit a question has
found it's way out; what material are the contacts made from? I can see
robbing some auto contacts for the moving side but the rod material is
the real mystery.

And another; Does this mechanism need frequent cleaning?

And another; Since it doesn't mount like a plug, does it require an access
'chamber' or passage to communicate with the combustion chamber?

And.... I'm sure there will be many more as I develop this picture in my
mind!scratch.gif

Thanks,
Pete

 

[Jasonb]

I used some bits cut off a Tungsten TIG electrode and silversoldered them in place.

Does need the odd clean

The engines that I have done with them have a small chamber for the spark and a passage through to the combustion chamber.

This is the side of te Galloway cylinder

The IHC one goes into the larger of te two holes

 

[10K Pete]

Jason,

Ahhhh, yes. One more request on this ignitor please. Could you post a pic
of the outside of that ignitor you show the inside of? I found great info
on the oldengineshed.com link but the ignitor he pictures there is painted
all black and it's hard for me to see exactly the relationship of the various
parts.

Also, I notice there are two springs; a heavy one and a light one. It looks
like both are pulling in the same direction. Couldn't it all be done with the
heavier one?

Thanks,
Pete

 

[deverett]

To improve the reliability of new engines as technology advanced, the ignitors and low tension coils were replaced by spark plugs and high tension coils.

For older engines that were originally fitted with ignitors, some were later modified to make use of the high tension spark. An adapter plate was fitted in place of the ignitor and the new spark plug was screwed into this adapter plate and the low tension coil was replaced with a new high tension coil.

Dave
The Emerald Isle