Our mechanism design is based on the principle of stability. After failure due to structural deformation in the first two iterations of this project, we decided to use the stock we had to make the most structurally stable system possible. This design, consisting of a single strong U-beam stock, a machined T-beam arm and a single compressive support made from aluminum rod, has a servo attached to the end of the arm with a supportive hook of aluminum sheet used to lift the weight. Aluminum tabs are attached to the base of the U-beam to provide a strong, steady support for the clamps to attach to.
In order to maximize the simplicity and sturdiness of this particular
design, we needed to minimize its lift capacity. Given the torque specs
of the servo motor and the 90* rotation limitation, our performance
predictions were as follows:
Rated motor torque = 42 oz-in
The servo was a consistent 1.25 in away from the weight, which meant it needed to overcome a torque of 20oz-in (16oz x 1.25").
In a perfect system, or looking at the max lift this could provide,
when disregarding twisting or friction effects.
This use of only so much torque meant that a 42oz-in servo motor would contribute another 22oz-in of stall torque that the structure would have to overcome. After doing some back-of the envelope torsion resistance calculations, we determined that a compressive structural element would be needed to keep the T-beam from buckling, and this was added and tested accordingly.
- Sturdiest structure around
- Lighter than maximum at 14oz
- Well-constructed with a coherent design
- Incredibly simple