MS6 Recap

The engineering for our most critical module turned out well.  We're pleased with our progress so far, but there are some points that we need to take care of looking forward:

1.  Should we replace the wooden toggle arm motor riser with an aluminum block?  In our discussion during MS6 it sounded like the compound wooden block will be challenging to machine.  It may be better to simply buy  an aluminum block of similar dimension and mill it to size.

Breakdown of buying AL versus using wood:
Pros:  Simpler manufacturing
Cons:  Increased cost, possibly increased weight compared to wood.

2.  How will we locate and attach the pillows with the base plate?  There are two options that we are currently considering.

Option one:  Use two bolts for each pillow (this is our current setup).
         Pros:   Simpler to machine, lower tolerances.
         Cons:  Pillows not self-aligning, possibility for "drift" if bolts aren't tight enough.  Poor engineering
                    practice to use threaded fasteners to constrain shear loads.

Option two:  Use two dowels to locate each pillow and a single bolt to hold it down.
         Pros:   Excellent alignment.  Better engineering practice to use dowels to constrain shear loads.
         Cons:  More steps in manufacturing (drilling + reaming).  Slight error in machining could be cause for
                    part rejection.

Dowels pins.  Useful for accurate location of a part.
Source:  

http://en.wikipedia.org/wiki/File:Steel-Dowel-Pins.jpg

Since machining begins on Monday, we will be making a decision on this in the next few days.