Mag coil tester

[Norman]

Here is the test rig for testing the magneto coil on the bench. Crude red neck
engineering again. Gutted engine case no crank shaft just a straight through shaft to spin
the rotor. Right now I'm using an electric drill to spin the shaft 2500 rpm max.

left the shaft long for now this is the back side view

looking down inside no flywheels or crank. cobbled together but it works

shot with a coil on it for testing

 

[Norman]

I don't know if you guys do this or not but when I mount the coil I use spacers between the rotor
and the coil they are made from aluminum 0.014 thick nothing fancy. Using the shims/spacer helps
to center the mag coil to the rotor this helps keep the rotor from hitting the mag coil.
Once the screws are tight pull the shim/spacers out and your ready to go.

shot of the aux coil it to the left side of the rotor. This is the thing I've been plying with whining and crying trying to get it to light up a 6 volt light bulb. it will light up the LED tail light brightly
hardly lights a regular light bulb 3 volt . I since rewound that coil it now will light a 6 volt bulb but it still dim when spinning the rotor at 2500 rpm.
the mag coil is also one I've wound up it needs to be redone didn't have enough 26 gauge wire on the bottom of all the 36 gauge winding. So I need to remove around 4000 turns of the 36 gauge wire just to get to the 26 gauge wire which is a real pain in the butt. You guys who have unwound a coil know what I'm saying, those of you how haven't removed the wire from one of these coils that 36 gauge wire is like hair very fine and breaks easily.

 

[Norman]

couple of shots off the rewound coil throwing a spark nothing great with a light attached to the
coils white wire that spark is cut to about less than 1/8 ".
the spark now with no light attached will jump about 1/2" rotor is spinning at 2500 rpms.
Touch that and you won't do it again if you can help it!!!! That spark will knock ya back a step
or two.

 

[2door]

Norm,
That looks good. Should provide you with a good way to bench test a mag/CDI too. As for the spacing shims during mag install, I use a regular old business card to get the space betwen the rotor and coil. Seems to work for me. Keep us informed. Do you plan on increasing the shaft speed to see what effect higher RPMs have on coil output? If you're getting that great spark at 2500, wonder what would happen at, say, 4000?
Tom

 

[Norman]

2 Door the spark photos is with no lights hooked up just the ignition coil firing at 2500 rpms
the spark drops to around 1/8" max it will jump with the lights turned on. But it is one of my hand wound ignition coils. A good factory wound coil will do the same thing. The coils that are factory made that die at idle with lights on do not throw as good of a spark. This test probably isn't a real good way to test them I don't know if a guy can measure the voltage or amps? If I could then that would be maybe the way to test them. I'm a little afraid to put the meter on it
I'm afraid it would burn something up in my meter.
Unless someone knows the setting on a volt ohm meter to use then I would give it a try.
maybe?!!

I'll maybe look at getting an electric motor and a couple of sheaves so I can spin it faster.
Yes the business card works too. I'm a bit rough on them I'm always tearing them up.