Final Design

Full assembly with CubeLab attached

Motor/Drive Assembly

     This assembly consists of the motor, shaft, bearings, and brakes. It also contains the associated electronics to control these components, such as the motor driver, the microcontoller, the brake's external power supply, the e-stop switch, and the single board computer. The motor is mounted on the bottom and connects directly to two planetary gearboxes, which in turn output directly to the keyed shaft. The shaft and bearings have been rated to last at least 1 billion cycles (rotations) under these conditions, and the motor is relatively low cost and can be easily replaced in the event that it wears out, which is a possibility since normal operation of the machine would rely heavily on back-driving the motor.

Overview

     The center stack will be driven by a Vex Robotics CIM motor geared 50:1. The arm is attached to the motor via the center stack assembly, which transmits power from the motor while the bearings minimize friction. The center stack assembly also contains a shaft-mounted brake, which is used to stop the arm's rotation suddenly when needed to more accurately replicate the acceleration profile shown below. The brake is used in conjunction with back-driving the motor, is powered by an external power source, and is also set to be used in the event of an emergency stop.The arm is balanced on one side with a removable counterweight assembly, whose weights can be changed out to accommodate different sized loads. One the other side, the CubeLab is bolted to a sheet metal sling, which allows the system to more precisely replicate the conditions of launch by controlling the direction of the resultant acceleration. This entire assembly is contained within a hexagonal aluminum frame, which is in turn covered by a removable polycarbonate safety covering. During the manufacturing process, it is expected that the users will be able to interact with the microcontroller through a single board computer running Linux, as well as a physical e-stop switch.

Cutaway of Drive Assembly

Beam Arm and Attachments

    This assembly consists of the arm, the arm-shaft coupling, the counterweight racking system, and the swinging bucket/sling, and the associated connectors for these. The counterweight rack and weights are made out of low carbon steel, and the weights were designed in 15lb, 10lb, and 5lb increments (with the possibility for more as needed.) They are pinned in place to minimize their dynamic effects, and the entire rack is bolted to the main arm. The sheet metal sling on the other side is screwed to the CubeLab and pinned to the arm with a clevis pin. As the arm rotates and follows the acceleration curve, the sling's angle with respect to vertical will change.  

Arm and Drive Assembly with CubeLab attached

Sling (left) and Counterweight Rack (right)

Frame & Safety Covering 

This assembly consists of the hexagonal frame, removable polycarbonate safety covering, and shaft couplers. The hexagonal frame is assembled out of square steel tubing, and coupled to the center stack assembly with 2 machined couplers on the top and bottom. The top coverings are removable to allow the weights and payload to be changed out.