For my MECH 2412 Mini Design project, we were given an outline on a generator which utilized gravity that we, as part of a group, had to physically create. The outline for the project can be found here.
From the outline, we were given some constraints regarding the materials we used, and the cost to them. The list shown tells us what material we must used, and we were not allowed to go outside the list of materials for our final design. We also had to try and minimize the total cost as the group would get extra marks for a cheaper costing design.
Our group created the following 3 conceptual designs:
Of the 3, our group decided together that design 3 would be our best option based on the materials used, how quickly we could produce it, how it would generate energy, and the efficiency of the design.
Our group then worked vigorously to complete calculations of bending, stress, torque, force, and output energies that different sizes and variations of our design could produce.
One example page of a calculation is shown below.
As one can eventually see, we predicted that our design would only be able to sustain roughly 8.75 – 11.67 seconds worth of energy.
For this design, our 3D model looked like this:
However our group felt that we could strive for much more than 12 seconds.
As we researched what we could do, we found that by slanting our rack we were actually causing more of a problem for ourselves as it would cause the rack to push towards the gears since the mass would pull straight down (not sideways). This caused extra bending in both our gears and shafts that we did not need. We also wanted to try adding different amounts of gears, and changing the gear ratio on different designs to see how much it would impact the final time.
After making a few adjustments, and testing a couple prototypes with different gear ratios, we came to a final design which looked like this:
As you can see, our group added 2 more gears and we positioned the rack to fall straight down. We also added a breaking system on the far left gear as a way to stop the device in certain events. On top, we have a cover so that the gears would remain in position and not slide up and down the shafts.
Although it is not in the 3D model, we also had an idle gear in order to keep the shaft from toppling over.
Without the cover, this is what the final design looked like, with the motor attaching to the final gear, beside the solo shaft.
With the cover on, our completed design lasted for a total of 50.3 seconds, which was much more than our initially anticipated 12 seconds, and placed us top 3 in the class.
Click here to watch one of our prototypes in action.
Unfortunately I do not have footage of our final model lasting for 50.3 seconds.
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