Fairbanks Morse Battery/Buzz coil Ignition?

HotrodBill

New member
Bought my first old engine yesterday, it from everything i can tell is a 1924 1 1/2HP Dishpan Flywheel. I took a few things apart and cleaned them up, greased an oiled things, it is however missing the coil, but in getting ready to figure out something for a coil thought is would at least learn a little about how it is supposed to work. there is a wire from the battery box down to the timing control, i am assuming this to be a ground wire that would work similar to a set of points, the timing lever is there as well. i am hoping someone here could give me a little description of how that actually works. I was reading it with an Ohm Meter and turning the motor over but never could get a reading to ground?
 

Andrew Mackey

Moderator
The timer works the same as the ones used on the Special Electric ZA engines. The camshaft lobe is stepped, unlike that used on magneto engines. As the push rod for the exhaust valve recedes it comes to a stop. When time for ignition comes the pushrod recedes even further. A steel collar on the pushrod makes contact with a brass assembly mounted and isolated that is attached to the governor assembly. When contact is made it completes the ignition circuit and causes the buzz coil to operate. That in turn fires the spark plug. The timer completes the ground circuit for the buzz coil. A buzz coil must be used due to the ay the timing mechanism works. Spark is made at time of contact, not on the break as with a modern auto coil.

Electrical path is as follows: battery + (positive) to coil. Coil ground to timer. battery - (negative) to engine ground. The exhaust valve pushrod completes the grounding at the proper time. If you have the original battery box, a model T coil is used along with 4 large carbon zinnc batteries. A small 6 volt battery, like that used in emergency lights (4 amp) will work the coilfor a day or 2 before having to be recharged.

The main difference between the Special Electris ZAs and the Competition engines is the power source for the coil. On the SE engines, the power comes from a resister panel within the generator control box that reduces 32 VDC to around 6 to 8 volts DC. The Competition Engines used batteries for ignition power.

Timing can be adjusted by moving the isolation washers above or below the brass collar, in order to cause the timer makke contact earlier (advanced) or later (retarded). You must make sure that the contact collar is isolated - the mounting screws have washers and a bakelite sleeve that prevent the collar from shorting out.

Hope this helps.
 

HotrodBill

New member
Andrew, Thank You Thank You! that is exactly what i was looking for. I suspected that was the case, but the part i could not get to understand is that the collar that completes the ground circuit moves a little further back, i will take a look and see if i just wasn't being thorough enough to see that.
Thanks Again!
 

bartlett0815

New member
A buzz coil must be used due to the ay the timing mechanism works. Spark is made at time of contact, not on the break as with a modern auto coil.

A small 6 volt battery, like that used in emergency lights (4 amp) will work the coil for a day or 2 before having to be recharged.

I'm not sure how I did it, but I rigged my dishpan up to run with a modern 12V coil with 6V emergency light battery. It was generally hard to start but ran fine once it did. I've not run it in years.
Kevin in NC
 

JWitt

Subscriber
Just a thought but make sure that your exhaust pushrod is spring loaded to pull the pushrod all the way back to the cam. It will be a coil spring around the rocker shaft, they can get broken or if the rocker assembly was replaced with one from a throttler it wouldn’t have a spring and not work properly.
 
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