SwEm Technical Bulletin Number 2  06/02

Attention Alternator Upgrade Owners:

This Technical Bulletin applies to all who have installed the SwEm Alternator Upgrade Kit on their B18 or B20 (or are planning to).

Recently, two alt. kit failures have occurred.  In these instances, it was not the bracket which broke, but the pivot bolt!  Close analysis shows, that these failures also, were totally preventable, and so presented here is tech Bulletin#2, analyzing the cause(s), and to (hopefully) prevent additional occurrences. 

Pivot Bolt Failure

After the bracket is securely mounted to engine block, the alternator must also be mounted securely by the pivot bolt and fan-belt tensioning bar.  At the risk of stating the obvious:  This means not being allowed to vibrate for any reason

Close inspection of both failed pivot bolts shows evidence of galling at points where the mounting boss of the alt housing makes contact with bolt (galling is where the surface is fretted and worn due to repetitive pounding).  This galling can only occur if the assembly is allowed movement...and under the constant vibration from the engine, the  alternator will certainly vibrate with respect to the bracket if allowed to.  The galling and the pattern in which it occurred shown below, pretty much confirms that the space between the pivot points of the bracket was not closed.  Even though the pivot bolts supplied are exceptionally strong (Thermo forging heat treated after thread rolling), eventually even these fatigued and failed in two similar instances.


Failed Alternator Upgrade Kit pivot bolt.  Highlighted are galled areas on opposite sides of bolt.

 

The SwEm bracket is designed for proper fit of the nominal 2 inch pivot boss of the alt., but I have noticed:  Variations in this dimension occur do occur!  Some alternator housings are slightly shorter!  Who knows for what reason...but if we try to install one of these into the bracket, it would first require excessive tightening of the pivot bolt to lock the alt. from pivoting (an experienced mechanic might  trial fit the alt onto the bracket before mounting it to the engine, and notice this excessive clearance, and would also notice excessive tightening of the pivot bolt was required to lock the assembly after the pivot bolt head contacted the front wing); and secondly, would result in the faces of the bracket being pulled in so far that they would not be anywhere near parallel (and this would allow movement/vibration of the assembly), while the bracket and bolt were at the same time under tremendous additional static stress and additional stress once the motor was running and things began vibrating. 

Although the exact fit of alt into bracket is out of my control, since the alternator is procured by the installer, the instructions clearly point out that this condition can occur and show to use the washer supplied in the kit as a spacer to make up for any excessive slop which may be present.  The rule is:  If the washer fits, use it!

 

Would you like a picture?

 

Conclusion:  Failure was due to installation deficiency.  No bracket change or improvements are called for, however, installation instructions will further emphasize detection and prevention of the condition which lead to the failure (its already highlighted...I guess I'll write it bigger too).

 

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