Thanks tkg. You answered my question in the begining and I appreciate it. I guess it somehow got off the subject.

I know the coil is a transformer..The spark coming out of the secondary jumps to the same black wire ground that the negative end of the primary is connected to...Yes, it is theoretically possible, if the spark plugs were inslulated from the cylinder and grounded to the circuit..Without this ground the spark jumps to the closest spot, the little black wire on the hall sensor...Or if the hall sensor is far enough away the spark jumps to the primary on the surface of the coil or down inside the insulation somewhere...
I think we're saying the same thing in different ways...
Hey TKG, how does the spark jump across the gap if there is no ground to the engine ? Air is a pretty good insulator
Somewhere along the line the engine gets connected to the negative side of the battery...

nobody said that the ground could be eliminated....or to isolate the plugs from the cylinders.

the ground would still be there, just connected to a plug terminal instead of the case. the spark just has to jump two gaps instead of one in order to get to ground. plenty of opposed twins have used this system. the only problem in our case is how to keep the spark from choosing the hall sensor as a ground instead of the second plug. i have sensors and magnets that'll work with a 1/4" gap and if that's still not enough then the sensor could be insulated with bakelite.......maybe

i'm not saying that this is a superior system but for a 44CC twin it might be preferable to using two separate CH ignitions...it would save at least 1/2 lb. and that can make a substantial difference for a model this size.


dave

OK since this rabbit is still running here goes.
You hook the coil to one spark plug like normal, BUT no ground.
Then you hook the ground wire to the OTHER spark plug terminal.
If you ground the engine to the ignition ground only the first plug sparks
IT works this way, remember that electricty actualy flows from - to +, the spark voltage is sent to the first plug. It jumps the gap and then the voltage is in the engine where it jumps to the sensor and everything burns up and the engine stops. OOPS wrong way.
The voltage goes to the second plug ground electrode where it jumps to the center of the second plug and returns to the ignition as a completed path.
P.S a CH ignition only weighs 3oz.

I defer to your superior knowledge of ignitions..

+battery+switch=around 1/2 lb.....unless of course both ignitions could run on a single battery. never used a CH myself but it has been said that they don't like a small capacity pack.

also, since the original question was about using two syncro-spark ignitions i'm wondering if the delay would be perfectly in sync between the two ignitions. are they that accurate?


dave

I have been using one of the C&H units on a 500mh pack for about a year. I usually get about 4 12 minute flights before I recharge at 4.8 v
The delay is for starting. When the engine gets up to speed the delay is out of the circuit.

The clock speed on the Syncro Spark is 100khz, at 3000rpm the spark speed is 50hz. So IF one of the clocks was at the upper tolerence and the other at the lower the Syncros would still be within a 1/10 of a degree. The machining tolerences are bigger than that