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danny_galaga

Rotax 912 alternator

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Just wondering how well the rotax alternator performs. I’m guessing the setup is similar to motorbikes in that the rotor is directly ly driven off the crankshaft. The advantage being no belt to worry about and also more compact. Disadvantage being harder to get to. Is the rotor brushed or brushless? Guessing brushed. Anyone had any probs? Maybe had to replace the brushes?

 

 

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Just wondering how well the rotax alternator performs. I’m guessing the setup is similar to motorbikes in that the rotor is directly ly driven off the crankshaft. The advantage being no belt to worry about and also more compact. Disadvantage being harder to get to. Is the rotor brushed or brushless? Guessing brushed. Anyone had any probs? Maybe had to replace the brushes?

The standard charging system on the rotax isn't an alternator in the conventional sense. It has magnets on the flywheel and coils around the outside. Some of these coils are used for the ignition system and some of them used for the charging system. The coils produce a fluctuating (like AC but more pulsy I believe) voltage of up to about 40v depending on rpm. There is a "regulator" that converts this fluctuating voltage to fixed DC voltage of about 14 volts. In some installations the regulator is prone to failure supposedly due to overheating.

 

Rotax do sell a larger alternator driven off a belt as an option.

 

 

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Just wondering how well the rotax alternator performs. I’m guessing the setup is similar to motorbikes in that the rotor is directly ly driven off the crankshaft. The advantage being no belt to worry about and also more compact. Disadvantage being harder to get to. Is the rotor brushed or brushless? Guessing brushed. Anyone had any probs? Maybe had to replace the brushes?

I’ve been associated with 912ULS engines that have done over 20,000 hours. All have had the internal alternator and we have not had one alternator problem. Most engines have gone to 2000 hrs.

 

 

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Nice! The more I look at the Rotax 912 the more I like it :) I used to be an auto electrician so naturally questions of an electrical nature pop up first!

 

 

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The Rotax Installation manual has a bit of a description of the system as well as a graph showing the output with RPM. It also shows the optional external alternator .

 

 

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