Tuesday, June 9, 2009

Location, Location, Location!

Our department was tasked with building a portion of our new Orientation Gallery that featured a series of panels mounted on a solid with a cross-section of an equilateral triangle. These spun on an axle, allowing the visitor to rotate them to complete a puzzle or have a question/answer display.

How to get the faces to locate consistently? The plans by others called for each "Trilon" to use a spring-loaded "bullet" that would locate in one of three dimples on the end of the "trilon."

This was problematic for a few reasons:
  • The "trilons" would not locate correctly 75% of the time.
  • The mechanisms would be subject to extreme wear.
  • This arrangement might work is there were only two on an axle, but there were sometimes as many as four. No clearance for this device in "trilons" 2 and 3.
Our solution was to machine a set of UHMW rings that would be press fitted with series of rare-earth button magnets. One formed the end of the "trilon", the other was affixed to the axle with a shaft collar.

Polarity was arranged such that when a "trilon" was positioned at 0, 120, or 240 degrees the magnets attracted. When located in between these angles the magnets repelled. The "trilons" were assembled as a unit within a frame and placed on a flat surface - aligning the faces to that plane. The cap screws on the shaft collars were then tightened.


This mechanism has no moving parts other than the bushings that support the "trilons." I am hoping for the device to have an extremely long and trouble-free life.

1 comment:

Anonymous said...

Data could not have fiured that out. My brain hurts. Bob