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Group Members
Wei Guo
Mr. Guo is a sophomore mechanical engineer major with business and material science minors. He enjoys long walks on the beach, sunsets and the occasional brunch. Wei was responsible for handling the business aspect of the project in other words, accumulation of wealth in supplies. Wei kept the group moving like a well oiled machine. Way to go buddy!
Kayla Aloyo
Ms. Aloyo is a sophomore mechanical and engineering public policy major who enjoys being a G, capital of course. Kayla is fast and also furious. Keep an eye out for her as she might be flying by at breakneck speeds in her super-fast super-fly buggy. Of the group, she has the most artistic eye and was responsible for making sure our project didn’t look like aluminum garbage.
David Chang
Mr. Chang is a sophomore mechanical engineer and enjoys Reese’s Peanut Butter Cups. David was the team mascot and provided the group with entertainment through various death defying stunts and energized dance routines.
Special Thanks
Group 1 wants to give a special thanks to Sara for her help and supplies during the manufacturing process.
We also want to thank Professor Steif for two semesters of great learning
Thank you
- Group 1
Goals
The objective of this project is to design and build a mechanism that will lift a pound weight when powered by a servometer.
The mechanism must comply with the rules of the game:
Must be clamped in the given position
May not touch the obstacle or any other surface besides the clamp
Must not weight more than 20.0 oz
Must lift the sliding weight up a vertical post by 2 in
How it works
- Our mechanism was designed as a three part design. First, the base was designed to maintain the overall torsional rigidity and bending stress stiffness of the structure. The base features a two long main support arms attached to the base, and additional supports centered on it. Next, we extended a long truss-like structure to the base. This was designed with transferring as much of the load as possible to the base and being torsionally rigid. Finally, our lifting arm was designed to maximize the rotational capability and lift of the servo. We added a large counterweight to the lifting arm, which helped lift the weight even higher. Thus, the lifting arm lifts the weight, transferring the load to the truss arm, which in turn transfers it to the base. This overall design maintained high stiffness and rigidity, and thus was successful in lifting the weight about 4 inches.
Calculations
The theoretical performance of the servo can be calculated using the dimensions of the lifting arm and the weight of the object that requires lift and the counterweight. The dimensions of the lifting arm are as follows; Total Length = 13.45 in, Distance from servo to the object that is to be lifted = 6 in, Distance from servo to counterweight = 8.825 in. The weight of the object is 1lb or 16 oz and the weight of our counterweight is 7 oz. Theoretically, if the servo is allowed to rotate completely without bending in the arm, the arm should be able to lift the weight a distance of approximately 7 inches. However, with the counterweight and weight in play, the actual distance will be less than the theoretical distance
We also calculated the theoretical maximum weight that our system would be able to lift using the counterweight and lifting arm. These calculations are as follows;
We found that the theoretical maximum weight we could have lifted was 20.75 oz which is 4 ounces above what we in fact need for this project. This gives us a good cushion for us to work with in terms of regulating the overall weight of the project. Also the theoretical maximum torque that the servo can apply is about 42 oz-in. Using the equation above and plugging in F = 16 oz. we are able to calculate the amount of torque we would theoretically use for lifting a 16 oz weight. This turns out to be T = 18.225 oz-in. This means that we are theoretically only using approximately 43.39% of the maximum torque that the servo can apply.
In summary, our lifting mechanism will theoretically lift the weight 7 inches high and use only 18.225 oz-in of torque from the servo which is 43.39% of the servo’s maximum torque.
Design & Manufacturing
We felt our design was efficient and overall innovative from most of the other projects. We were extremely proud of all our design aspects.
- Base – Improved from our initial design of using a plate to attach to the clamps, we instead used tabs on the main and sub long base arms. This countered the deflection when loads were applied to the initial plate base, and allowed us to transfer loads to the clamps.
- Base Arms and Support – The main base arm was innovative in that we tilted it at an angle below the vertical pointing away from the weight. This allowed us to effectively counter the bending stress and deflection caused by the load. Our design of the attachment to the base arms that supported the truss arm was also efficient and countered the loads well.
- Base Arm Connection – This was the last aspect of the design we implemented. Before, we had trouble with the base shifting towards the load as the tabs were able to bend in that direction slightly. By attaching the two base arms using a x formation of bars, this significantly stiffened the structure against that load and was pivotal in our success.
- Truss Arm – We designed this arm as decreasing equilateral triangles. This design deflected a minimal amount and transferred the load to the base successfully.
- Lifting Arm and Counterweight – This arm required a lot of experimentation because we needed a large enough counterweight to be able to the lift the load, but not be too heavy that the servo cannot relift it on the second lift. After experiments with the distance to the servo, we decided on the most effective distance that could successfully lift the weight two times
Design Review 1
The first design review was a measure of what aspects of our project were good and what aspects of our project we need to expand upon to improve. When we tested our initial design, we achieved a height of approximately 3.2 – 3.4 inches. We decided on a few areas where vast improvement could occur, most imminently, in the base of the object that was clamped down to the playing field. As we lifted the weight, we noticed that the square plate that we used for the base was bending costing us some height in the lifting of the object. Another problem that we noticed was that the entire base structure seemed to tilt at a large angle while lifting the weight. We decided if we could fix these two things that we would be able to lift the weight much higher. Another problem we noticed was in our manufacturing process. Our structure seemed to be non-symmetric. This was caused by us overlooking the importance of having holes for the screws in the same places on each of the symmetric bars used for the structure. For instance if one hole was drilled too far to the right of the bar, while the adjacent hole was drill too far to the left, the entire object would be uneven. This was another issue that we realize needed to be addressed for the final design review.
Design Review 2
In the final design review, we were able to achieve a lifting height of 4.3 inches while our design weighed a mere 17 oz. We used our extra equipment to create the base from scratch and made it so that the base was symmetric and straight. The arm we used was the same from the first design review. We removed the square piece that was clamped to the playing field and simply created tabs on the legs of the base which we clamped down to the playing field. This allowed for our base to be extremely stable which in turn gave us a full extra inch in lifting height. We also added a few cross beams throughout the base to make sure that the base would not move while the weight was being lifted. We successfully lifted the weight three times in a row with our maximum height reached being 4.3 inches which was an improvement of a full inch over our first design review trials.
2010