Our truss was designed to be extremely strong, with the goal of minimizing the deflection of the structure during the lifting process. The design utilizes several unique features in order to achieve this goal. One of these design improvements was the addition of the tension member linking the base to the end of the mod section that extends out the window. This diagonal member greatly reduced the dipping of the extension arm. When the weight is being lifted, the diagonal member is pulled into tension, but its high stiffness prevents the mid section from twisting forward, thus keeping the extension arm straight. The diagonal member was not the only use of tension members, though.  Along the extension arm of the truss is are two more tension strips, one screwed to the back of the mid section and the other screwed to the front of the mid section.  The different attachment locations and the pre-tension of these members reduces the dipping of the extension arm and the twisting of the mid section.  This further keeps the extension arm stable, resulting in a higher lift. 

Another characteristic of our truss that distinguishes it from the other, competitor mechanisms is its weight-reduced base.   The middle section of the base plate was not contributing to the base's strength, so we decided to remove it. By cutting the middle 60% of our base out, leaving two wide strips, we thus significantly reduced with weight of the base without compromising its strength. 

Also critical to our design's success was the extensive use of a sheet metal bending brake to bend our aluminum strips into L shapes in order to increase the moment of inertia, decreasing bending.  To prevent torsion, we strategically placed cross members between the L beam frame.  This made our base and mid section strong, which is the key to a successful final product. 

The most notable of our achievements was our reduction of weight.  The first time we weighed our working prototype, it was 24.6oz.  That’s 4.6 oz too much, an amount of weight equal to the aluminum shown in the picture below.  By cutting out excess delrin in the lifting arm, replacing our original counterweight (a 3.1 oz plumb-bob) with a compact aluminum design, replacing all the cross members in the base and mid section with thinner ones, and cutting screws short, we reduced the weight to by over 4 oz.  We like to say that our truss is the “Jared” of the class.