In ME130: Design of Planar Machinery, the final project called for a motor operated mechanical mechanism.
My group and I came up with an automated cabinet we dubbed the Auto-Spice.
- The Auto-Spice is a prototype cabinet that contains two shelves designed at spice racks in order to help rid kitchens of clutter and ultimately optimize kitchen space. Designed to be hung from an above-the-head position on a wall, the shelves are cycled out of the cabinet and lowered by way of a six-bar mechanism that is run by a motor. The sides of the racks on the shelves are open for easy access to spices on them. All components of the Auto-Spice including the motor are contained within housing. The six bar mechanism functions with a dyad allowing the motor to cycle continuously in order to both extend and retract the shelf from and into the cabinet. Motor operation is located at a position lower than the mounting location to enable greater ease of access.A detailed report including many engineering drawings can be found here.
The prices of the material used to put the AutoSpice together can be found here.Team Members: Gordon Yang, Kevin Dias, Noah Horowitz
- The motivation for the project stemmed from the desire to have as large as a target audience as possible. In order to cater to a large population, the product had to be useful and/ or wanted. The product had to be one which had the potential to make its way to every person’s hands, if not at least every household. One of the requirements of the product was that it had to be driven by motors. A product that would make its way into the household seemed like a plausible compromise between the desire of a large audience and the requirements of the project. This was in the form of a improved kitchen cabinet.
The motivation for this particular component of the household was that traditional kitchen cabinets are inefficient for storage. Not only is it difficult for the user to reach for items in general, due to the height of standard kitchen cabinets, it is also difficult to scramble for an item that may get buried in the very back. To answer this, a solution was to create a cabinet with shelves with the capacity to extend to a more accessible position for the user and retract back if necessary via motor operation.
- Initial Proposal
- The entire design is to be powered by a single motor connected to a reversible switch. When the switch is activated, it turns on the motor. Initially, we proposed that the motor will transmit the work done through miter gears and into the rotating input link. The dyad then moves the supporting links of one of the shelves, and the mechanism causes the shelf to cycle out of the cabinet and downward. Once the shelf reaches its fully extended position, further activation of the switch causes the dyad to return and pull the shelf back into the cabinet. Activating the motor in the opposite direction will cause the exact same process to occur in the second shelf, due to the motor’s connections to the input links via freewheels and miter gears.
- As for assembly and how the freewheels would actually allow single-motor usage, the freewheels would be attached to the motor via miter gears (bevel gears with a 1:1 torque ratio and at right angles). Therefore, the axis of rotation for the motor would be vertical, while the axis of rotation of the freewheels (connected to the respective input links of the shelves) would be horizontal. As can be seen from the image to the right, the two freewheels (the green and red gears) would be set up as mirror images of each other with respect to the motor (blue gear). Reversing the direction of the motor would thus reverse the direction of the drive shafts of the shelves (green and red).
- What We Actually Did
- Unfortunately due to the prohibitive costs of custom order freewheels and miter gears, this original design had to be abandoned before the prototype stage, however the group still maintains confidence that it would function properly if the necessary parts were available.Since the freewheel design could not be applied, the placement and orientation of the motor was changed since the use of gears was no longer necessary. This meant the motor was now directly connected to the input link. The actual mechanism itself was not changed at all as a result of the change in lack of freewheels and gears. An alternative to the single-operating shelf design would be two shelves with two motors, however that would have simply been the same prototype created twice, thus creating an expensive redundancy not needed for the scope of this prototype. In order to simulate the initial proposed design, however, the final prototype still includes two fully functioning (extending and retracting) shelves, to show that with the necessary motor setup the two shelves mechanisms can indeed function within the same housing.
- Synthesis of the Necessary Dyad Driver
- The first step in adding a dyad driver to the mechanism was to draw the shelves and their supports in each of their extreme positions, with one shelf vertical and the other lowered to an angle of 30 degrees with the horizontal.
- The next step was to make a kinematic drawing of the relevant links, specifically 2 and 2’ which we intended to connect the dyad to. The dyad synthesis steps were then followed by manipulating the SolidWorks drawing (for higher accuracy than measuring by hand).
- The constraints imposed on this drawing set the conditions for a dyad capable of accomplishing the motions we desired. The first condition was ensuring that link 5 attached to links 2 and 2’ in the same place, such that O2C = O2D. The second constraint was on the range of motion available to the dyad. Link 6 (the motor link) is represented by a circle radius is set equal to half the value of CD. This means that the motor and dyad links will be collinear (in opposite orientations) at each extreme position.Having satisfied the dyad constraints, the design was left with several free variables/choices. The choice was made to make our motor link small so that the motor would require less torque to drive it; however, the compromise was that link 5 must then attach lower on link 2, which increases the required torque. Having settled on this balance, the final choice was the length of link 5, which was manipulated to ensure that the motor assembly fit inside of the cabinet area.
- Having made these choices, measurements were taken of the length of the motor link, the
length of the connector link, and the x-y position of the motor (O6) relative to O2. These values
were then used to guide the construction of our prototype.