Ignition damping box

C. Beaty;n1132533 said:
Of course the amplitude of back-swing voltage depends upon the amount of “leakage” inductance. I don’t have a Rotax engine in front of me but my recollection is that the ignition transformer has a complete magnetic circuit without an air gap.
Chuck,
Without air gap, the magnetic flux in the iron does not return to 0 after the inductor current disappears, due to the résidual magnetization. So, Each new pulse of the same polarity will gives more quickely the saturation and will produce the flux variation outside the magnetic circuit. Hence the leakage inductance, even without air gap.
 
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C. Beaty;n1132538 said:
The condenser prevents arcing at the points; slows down the rate of voltage increase when the points open, giving time for the points to separate.
I agree with that, Chuck.
 
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Jean Claude;n1132543 said:
Chuck,
Without air gap, the magnetic flux in the iron does not return to 0 after the inductor current disappears, due to the résidual magnetization. So, Each new pulse of the same polarity will gives more quickely the saturation and will produce the flux variation outside the magnetic circuit. Hence the leakage inductance, even without air gap.

You’re right, JC, there has to be an air gap to prevent saturation of the transformer core.
 
(Sorry for out of topic.Did not know how to send a private message to Chuck Beaty. Although the topic is kind of Engines.)
Hi,Chuck.
Merry X-mas and soon happy New Year! Hope everything is as good with you as possible.I was watching this video ( https://www.youtube.com/watch?v=AXddqiuDL2Q ) and in the post comments talk about power and torque. Immediately started thinking how millions years ago you were helping people on the Forum to understand this topic.
See you one day.Regards.Georgi.
 
The circuit diagrams given(I'm assuming for Rotax engines) seem over complicated and 'ancient'. First of all, ignition coils, being Tesla coils, are among the first types of electronic transformers, which generally increase voltage, while decreasing amperage. Ignition coils have two coils each. The primary coil has thicker windings, with only 20 or 30 turns, and today usually runs at 12 volts(battery voltage). The secondary coil consists of much finer wire, but has hundreds of windings. This secondary coil usually runs at 15-25 thousand volts. The primary and secondary coils are not directly connected to each other.

For many years in the automotive world, the primary ign coil would be charged up at 12 volts by the car's battery, by the generator, or by the alternator. This charging would only take 5-10 thousandths of a second, depending on engine rpms. The car's distributor controlled this 'dwell' time as it rotated a lobed cam. The cam opened the points, thus briefly turning off the low-voltage current to the primary coil, and collapsing its electromagnetic field. The collapsing field then 'induced' a high-voltage current into the secondary ign coil, which fired the spark plug in the proper cylinder, a predetermined number of degrees before Top-dead-Center(also selected by the distributor lobes). A fairly large capacitor was connected to the primary coil circuit and to ground. In small 2-4 cylinder car engines, the capacitor was screwed to the outside of the distributor. In 6-8 cylinder engines, there was room for it inside the distributor, under the distributor cap. The capacitor was needed to prevent the 200 or so volts of primary back-voltage from oxidizing(burning up) the points prematurely in a couple hundred miles. Even with capacitors, the points would burned up in 6-12 thousand miles.
 
I am assuming that the older cars' capacitors provided the same dampening as the boxes on the Rotax engines. Today's cars incorporate solid-state circuitry, with no moving parts, that provide the same service. Don't know what Rotax does.
 
Georgi;n1140913 said:
(Sorry for out of topic.Did not know how to send a private message to Chuck Beaty. Although the topic is kind of Engines.)
Hi,Chuck.
Merry X-mas and soon happy New Year! Hope everything is as good with you as possible.I was watching this video ( https://www.youtube.com/watch?v=AXddqiuDL2Q ) and in the post comments talk about power and torque. Immediately started thinking how millions years ago you were helping people on the Forum to understand this topic.
See you one day.Regards.Georgi.
Thanks, Georgi; merry X-mas and happy New Year to you also.
 
In simple terms (from a simpleton) I always believed the Rotax ignition damper was to stop any spurious sparks created from reversed primary current from the rotating magneto being induced into the ignition coils and firing the plug/s out of time, (in probably most cases at a time that does not cause any harm). The engine runs perfectly fine with the damper disconnected but won’t fire at all if it’s hooked up back to front.
I hope you all had a merry xmas
Tim
 
Hi everyone, I found this thread after pulling my hair out with my Rotax 501. I have been troubleshooting a rough running/ low power output problem for some time now. The good news is that I have learned a lot about how everything works and have put on a lot of new parts that may have been functional but aged... so when I do pinpoint the problem, I will have a lot of confidence in the various components.

So, the reason for my post. In troubleshooting this engine the damping box came to mind. I was told it was not likely causing my issue. That being said I was told to run the engine with it disconnected. Well, upon doing so I was quite quickly greeted with loud popping sounds from the engine... imagine a backfire.

I have read through this thread and it seems many say the box is unneeded. If that is the case, I would like to know why I am getting these "backfires" when I run the engine with it disconnected. Could this be evidence for another problem I may have in the ignition system?

Here is some info on what has been done to the ignition system:

New external coils
New solid core wires
new spark plug caps
New plugs ( properly gaped)
Timing verified on both cylinders 10 degrees advance BTDC
Verified problem not due to the ignition cut off switch or wiring inadvertently grounding (via disconnecting them altogether)

If anyone has any ideas why the absence of the damper would have such a pronounced effect on the engine running I would love to hear them as it may help me hone into what is happening.
 
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