 Alternator Bearings, Double shielded vs. doubled sealed |
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| ScooterD |
 Oct 15 2009, 06:50 PM
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ScooterD  Group: Members Posts: 80 Joined: 6-August 06 From: Los Altos, CA. Member No.: 6,589 Region Association: None   |
Being the cheap SOB that I am and not needing a new alternator at the moment, I am rebuilding a spare that I had lying around.
The factory uses double shielded bearings where the shield does not actually contact the rotating part of the bearing, there is actually a small gap on the circumference. The 914 pumps air through the alternator via the fan shroud and over time pumps dirt into the bearings. Has anyone used doubled sealed bearings that actually have a rubber seal that rubs on the rotating part of the bearing and keeps the dirt out? Also the factory bearings have a C3 designation for use at elevated temperatures where the internal clearances are greater so they don't seize up. Any experiences you want to share would be appreciated. (IMG:style_emoticons/default/pray.gif) Scott |
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| ericread |
Oct 15 2009, 08:20 PM
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The Viper Blue 914 Group: Members Posts: 2,177 Joined: 7-December 07 From: Irvine, CA (The OC) Member No.: 8,432 Region Association: Southern California |
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| Bartlett 914 |
Oct 15 2009, 09:29 PM
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Advanced Member Group: Members Posts: 2,215 Joined: 30-August 05 From: South Elgin IL Member No.: 4,707 Region Association: Upper MidWest |
QUOTE(ScooterD @ Oct 15 2009, 07:50 PM)  Being the cheap SOB that I am and not needing a new alternator at the moment, I am rebuilding a spare that I had lying around. The factory uses double shielded bearings where the shield does not actually contact the rotating part of the bearing, there is actually a small gap on the circumference. The 914 pumps air through the alternator via the fan shroud and over time pumps dirt into the bearings. Has anyone used doubled sealed bearings that actually have a rubber seal that rubs on the rotating part of the bearing and keeps the dirt out? Also the factory bearings have a C3 designation for use at elevated temperatures where the internal clearances are greater so they don't seize up. Any experiences you want to share would be appreciated. (IMG:style_emoticons/default/pray.gif) Scott My experience in the motor repair business tell me that sealed bearings will only seal out fluids less than 1800 RPM. Faster than that they will act as a shielded bearing. I believe that the sealed bearings will still be ok to use but are not truly sealed at the speed the alternator will be spinning. C3 is also the proper fit. A more precision bearing will overheat and lock up. |
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