Saturday, August 17, 2013

Motor Mount 3.5

The initial trial fitting revealed that the 3.75" tall x 4.0" wide flange required more mounting surface at the bottom edge.  New flanges measuring 5.0" tall and 4.0" wide were then fabricated, trial fitted, and hot glued together.



Picture DSC00371 showing the side (viewed from the front of the car) of the new taller flanges fitted to the sectioned BMW OEM parts.




Picture DSC00372 of the passenger side (left) and driver side (right) after being hot glued together.
 
 
It was then desired to weld the sectioned engine mount directly to the flanges.  Although the flanges were known to be alloy 6061, the BMW OEM parts were of unknown composition, and it was unknown whether the two metals would be compatible to welding.  To determine the alloy type of the sectioned engine mount, it was tested with a Glow Discharge Atomic Emission Spectrometer.  The test sample surface was first sanded and then placed within the vacuum chamber of the instrument.  After ablating the surface with a laser, the spectral analysis indicated the approximate (100.19%) composition to be:

Aluminum 81.9%
Silicon 12.40%
Copper 2.99%
Zinc 1.78%
Iron 0.78%
Manganese: 0.20%
Tin 0.14%
 
This data is consistent with an aluminum die casting alloy similar to alloy 380 or 384.  A professional welder was then able to test weld the two parts together using a TIG welding apparatus.  Unfortunately, the hot glue was not strong enough to hold the pieces during the welding process and the precise orientation of the flange to the sectioned piece was lost .  The next attempt will again use the hot glue for proper initial orientation and removal of the two pieces from the car, but, it will then be attempted to spot weld the two pieces with a MIG welder prior to taking the parts back to the professional for final circumferential welding.  

 
 
Picture DSC00373 showing the circular impact point left on the sample section of the BMW OEM part after the laser ablated the metal. 

 
 
Picture DSC00 showing the first try at welding the BMW OEM part to the flange just prior to drilling the mounting bolt holes.

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