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.

Witness!



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:

Bob Hensley said...

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