Summary: We prototyped/built the main body and discussed the lifting mechanism.
Based on our previous Solidworks models, we cut pieces of foam coreboard to form the body. Nothing was glued to allow for further cut outs to be made. Assuming the glued version is sturdy enough this can be our final body, otherwise we will laser cut identical parts out of acrylic.
Pictures:
We also discussed the lifting mechanism: DC motors would allow the body to move up, but would not hold it in place for loading or for climbing stairs. We could incorporate some sort of ratchet (see here) with a servo to release the hook, but this would further complicate the design. Additionally, this would allow for only an uncontrolled descent. A stepper motor will allow more advanced control and has a holding torque that is maintained as long as voltage is applied. We will use the Adafruit motor shields with the Sparkfun stepper motors.
These motors have a reported holding torque of 2.3kg*cm, which means that theoretically with two motors and a .5 inch diameter gear the robot can be supported as along as it is under 7 pounds.
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