Cooling the Alternator (??)

YamadudeXS650C

Central New York XS650
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Over the past 4 years or so I've noticed an occasional thread regarding cooling the left case.

Example:
http://www.xs650.com/threads/1980-xs650-wont-charge-battery.1156/
An XSJohn contribution

XS650 Cooling the Stator and Rotor .jpg


So, I'm wondering what the current thinking is on this.

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I'm of the opinion that cooling the alternator is a solution in search of a problem. I read XS Johns comments in your link Jeff. I know Johns revered 'round these parts... including by me, but I disagree with him. My rotor testing showed about a 100°f temp rise on the rotor at full charge. That was on the bench in still air. In the grand scheme of reciprocating engines, that ain't much.
Johns thoughts that excessive heat reduces the rotors life is belied by bikes that are 40-50 yrs old and still running the original rotor. I'd say it's done alright for itself... heat and all.
 
Amen, Jim. Heat may have some impact, but insulation on rotor windings deteriorates with age as volatiles are lost, and it's doubtful that ventilating the cover will do much to slow that process down. I can't buy the idea that opening the alternator to moisture and grit is going to be helpful.
 
I'm of the opinion that cooling the alternator is a solution in search of a problem. I read XS Johns comments in your link Jeff. I know Johns revered 'round these parts... including by me, but I disagree with him. My rotor testing showed about a 100°f temp rise on the rotor at full charge. That was on the bench in still air. In the grand scheme of reciprocating engines, that ain't much.
Johns thoughts that excessive heat reduces the rotors life is belied by bikes that are 40-50 yrs old and still running the original rotor. I'd say it's done alright for itself... heat and all.
Pretty much what I thought - good airflow to front of engine a lot more important!
 
4 wheels drive's alternators, driving in the outback over here, are exposed to major dust and water so i can't see your XS's being ridden on black tops and hardly ever get ridden in the rain having a problem from dust and grit if the cover has been opened for ventilation
 
Maybe so, Skull, but I can't think that exposing slip rings, brushes, and brush connectors to the elements will produce anything but trouble in the long run. That could be one reason why ATVs use permanent magnet alternators as opposed to excited field systems.
 
Pop the hood of your car and look at the alternator. The only alternators I ever rebuilt that were totally enclosed were for Marine use (no sparks in the bilge please) , all the rest were ventilated, most also had a fan mounted with the pulley.
 
Pop the hood of your car and look at the alternator. The only alternators I ever rebuilt that were totally enclosed were for Marine use (no sparks in the bilge please) , all the rest were ventilated, most also had a fan mounted with the pulley.
That being said a XS650 alternator has such low output it doesn't generate much heat. The stator is where most of the heat is produced.
IMHO there is no need to worry about cooling the alternator. Stators seem to last forever.
I think the reason for our rotor failures is 2 things, age and being crank mounted. When I was rebuilding automotive alternators the reason for most failures was worn out brushes, diode failure, regulator died or stator failure in that order. The reason for replacing a rotor was bad shaft from bearing failure or the slip ring worn out.
 
Pop the hood of your car and look at the alternator. The only alternators I ever rebuilt that were totally enclosed were for Marine use (no sparks in the bilge please) , all the rest were ventilated, most also had a fan mounted with the pulley.

That being said a XS650 alternator has such low output it doesn't generate much heat.

I'm not going to profess to taking measurements of any of this stuff, but that's where I sit. I know automotive alternators are basically all open cases with pulley mounted fans (liquid cooled ones being the only exceptions to that I'm aware of) but I don't know how much correlation you can draw comparing an alternator with divorced controls sticking out on the end of an air cooled motorcycle engine and one that is up to 10 times more powerful and internally controlled sitting under the hood of an automobile.
 
As mentioned, if heat was an issue for these components, there probably wouldn't be many left around today. I feel a modern regulator upgrade does more, reducing the strain on the rotor and stator.
 
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