Piston trip igniters

[Barnbikes]

Has anybody built a model engine with piston trip igniter?

Was looking at an old Patent drawing and the engine had this on it. I understand the concept of less moving parts but it puts ignition after TDC. Can't believe the engine would run very well.

 

[Ogaryd]

I believe Henry Fords original quadricycle used the piston trip igniter, it seemed to run OK, I've not seen this used in a model but would be interesting to try.

 

[idahoan]

My Pacific engine uses a piston trip ignitor.
http://www.homemodelenginemachinist.com/showthread.php?t=17832

Sadly I haven't finished it yet; but I know that it will run on the ignitor because my buddy built one and it runs real nice!

Dave

 

[Barnbikes]

Not very good picture but here is the patent.

 

[kadora]

Good idea
How it works ? In cylinder electrode in contact with piston serves as switch for ignition coil
or between electrode and piston jump sparks from ignition coil?

 

[Charles Lamont]

I understand the concept of less moving parts but it puts ignition after TDC.

Are you sure?

 

[Barnbikes]

Are you sure?

Spark would happen when points broke open. Which would be after TDC.

 

[idahoan]

What if the points were normally closed and the piston opened them? A switch (spark saver) located somewhere on the engines linkage would only allow current to flow just before the points opened; thus saving the battery and coil?

Just some thoughts.
Dave

 

[Barnbikes]

In the drawing the pin on top of the piston is half of the point set.

 

[idahoan]

That would complicate things; I guess I was thinking of a two point system.

Dave

 

[Fidlstyks]

I am interested in Piston Trip Ignitors. Were talking about them in another thread.

 

[dsage]

I believe what you have is a low tension ignition system common for the period. The system is simply an inductor wired in series with a (typically dry cell) battery going to the stationary point in the head. That point would be insulated from the head and inside the cylinder. The battery would be grounded to the head. When the piston comes up, the contact on the piston makes contact with the wire in the head completing the circuit. The inductor is charged. When the piston moves back down and breaks the contact an arc is generated between the two contacts due to inductive discharge.
I have a make-break inductive ignition on an old marine engine from about 1930's which uses the same principal although the mechanics are different but the two points are inside the cylinder.
I wound the inductor for it from a laminated iron core and several hundred turns of copper wire. You can Youtube search the subject. It's common on many old hit-miss engines before magnetos became popular.
It's a very good system for marine engines because there is no high voltage EXCEPT for what's between the two contacts and they are inside the engine. So you can soak the whole engine even in salt water with no affect.
And yes the arc happens after TDC but - who cares. These engines are typically low revving and mixture is very poor so no need for any advance. They run fine.
Simple is good when your out on the ocean. And this is about a simple as it gets.