Stress Analysis (24-262): Design Project
Group #21: Humberto Gonzalez. David Keyser. Cameron Hall
Our mechanism is made up of three main parts, our base, our extension, and our servo/perpendicular arm. Our base is a 4 x 4 x 6 box with cross beams that is meant to hold up the extension and keep it from twisting as little as possible. Our extension works to get our servo as close to the weight as possible in order to get as much lift as possible. Our extension is a 2 x 2 x 14 box with cross beams. At the end of our extension is our servo with a 10 long lever arm with a counter weight attached to it. These three parts come together as one in order to effectively lift the weight the required two inches.
Extension and Lever Arm
How it works:
Our servo provides a torque of 72 in.*oz. The weight that we have to life weighs 16 ounces and is connected to a 5 inch lever arm creating a 80 in*oz. torque in direction opposite to that of the servo. To make up for the difference we added a 4 oz. counter weight and placed it 5 inches away from the servo to aid in lifting the weight. This creates a total torque of 92 in.*oz. which is greater than the 80in.*oz. torque created by the weight, which allows us to lift the weight.
Using a rotation angle of ninety degrees, our should theoretically be able to lift the weight by about 7.1 inches since our lever arm lifting the weight is 5 inches long.
Our mechanism incorporates a couple of interesting design elements. First, is our base and how it clamps down. Our base has a hollow bottom unlike many other designs and to clamp down to the clamp area we clamp four screws/holders in order to maximize the clamps use. Another original design idea was to have a smaller extension part so that we could add use a larger weight for the counter weight. These two design idea allowed us to cut out some weight which in the end contributed to us making the 20 ounce weight limit. Another key design detail was the use of the Delran as a lever arm since it was sturdy enough to lift the weight without bending or deforming.
about our Mechanism, and what we would change:
If we were given more time or could do this project again, there are several things we would change. First, we would make our extension stronger and sturdier since it tended to twit and bend when the servo would try to lift the weight. By doing this, we could maximize our total lift. Another thing we would change would be the way our perpendicular arm lifts the weight. Because of our design we couldnt get the Delran to stay under the weight consistently so it took a lot of trial and error. We would create a sort of hook or holder to consistently hold on to the weight and lift it. The last thing we would change would be to minimize the amount of counter weight we use in order to shave off as much weight as possible.