04/20/04

     There is one particular aspect of this structure that makes it stand out from all of the other submitted projects: the counterweight.  This structure houses a very long arm to make way for a very light, but highly effective counterweight to assist the servo in lifting the 1-pound weight up several inches.

     We are very proud to have finally succeeded in making this design work.  After 3 iterations, all based on the same frame (see below), we finally accomplished a maximum lift distance of 8.5 inches.  During these iterations, different platforms, gear ratios, counterweight positions and cradle arms were built, tried, rebuilt and integrated into the final structure.

     There are other characteristic of our structure and design that we are proud to showcase:  one such aspect is the platform on which the servo, the shaft and the gears are all housed.  It was created to be used with several gear ratios without requiring much change.  It also contains an opening that was specifically created to fit the servo.  (to quote another classmate: "If there were little people, they could all stand right there [on the platform]!!!")

     Another aspect of the platform that we are proud to show is the "C-arm" that holds the end of the shaft, on the opposite side the gears of the lever arm.  Many of the earlier problems with the lifting were due to the fact that the gears were slipping, as a moment was created on the shaft by the 1-pound weight.  The purpose of the "C-arm" is to counter that moment with an upward force on the shaft; thus, there is no more bending and the gears mesh perfectly every time, all of the time.

     Although this frame concept is not particular to our structure and design, it was built before the first design review and has remained virtually unchanged (aside from a repair when one of the members was found to be broken).  The first component that was built is the A-frame (seen in the back).  It is by far the strongest part of our structure; the reason for its strength is that it must resist the bending force created by the top member.  It is the top member (see above image) that we are proud of in our frame design, for it actually allows us to have a lightweight frame (only 10 ounces, including platform): it is a tension member that keeps the platform in place, and prevents it from deflecting down when the 1-pound force is exerted upon it.

     Another part of our mechanism that is not found on any other project is the thin wire that was cut out of long strips.  Since we know that none of the forces involved with this project are strong enough to break aluminum in tension, we saved weight by making the members in tension as thin as possible - more specifically, those connecting the cradle to the cradle arm.

Stress Analysis Project 2004 | The Mechanism | Performance | Features

This site was last updated 04/20/04