Design for manufacture and assembly
The combination of the planetary carrier for the first gear train and the sun pinion for the second gear train reduces any possible misalignment and errors either during operation or while assembly the product
The use of the U pin to hold the gearbox assembly is a simple and symmetric option that minimizes the need for more components like screws to secure one part to another, also the pin is easier to assemble.
Operation of mechanisms
Forward/reverse switch
The forward and reverse mechanism basically works by simply deciding if the positive end of the dc motor will be in touch will the positive end of the rest of the circuit or with the negative end of it. This task is performed by a polarity switch shown in both figures. After the switch is being turned to the position desired either 1 or 2 depending the case will be automatically in touch with the negative end of the motor, so when the switch is finally pressed the circuit is completely operating.
Handle pivot block
This mechanism is composed by the teeth part of both handle and motor clamshell cases, a lock bolt, a spring, and a lock nut. The mechanism works by pushing the lock bolt when all teeth for all parts are aligned, so the bolt can move downward with respect to its longitudinal axis and compressing the spring, which is located in the hollow part of the handle. So when the bolt is pressed and being able to move all the way down, rotation can happen until all the teeth are aligned again and the bolt is being pushed back by the compressed spring. The lock nut is located on the other side of the handle, opposed to where the bolt is inserted and its function is to hold the spring and prevent the bolt to be pushed too far away.
Power/manual option
In the figure to the right, the output planet carrier appears (metal part). This carrier has teeth around it. When the power/manual option is being turned to manual (clockwise), the output carrier, following the right-hand rule, will displace downward. The teeth of the carrier will match with the stationary inner teeth of the clamshell case of the gearbox making it impossible to rotate. If the switch is turned to power, the carrier will move upward and will be able to rotate with the planets of the second epicyclic gear train.
Was the project good and fun?
Indeed it was. Doing this project has provided me an insight into how simple mechanisms can be combined together to produce a more complex machine. Plus during the process CAD knowledge is being developed parallel with engineering concepts. So I have not only learned how to use CAD tools but what they meant in an engineering context or real life.