Conclusions and Design Improvements

Conclusions / Improvements

The electric hand screwdriver achieves its desired output of a high torque through the amplification of torque through a gear system using a high angular velocity, relatively low power and correspondingly low volume motor. This allows the screwdriver to be an useful household tool, while remaining portable with a low charge time. However, were I to do a redesign of the mechanism, I would address several complaints I had with the tool.

The battery life for the mechanism is very short, despite having a low charging time. To address this, I would consider replacing the motor with something smaller and less powerful, and using this extra space in the tool to add another layer of planetary gears and a carrier. This would increase the torque amplification of the system, while requiring less power from the motor, and thus would increase battery longevity while maintaining the portability and output of the mechanism.

If one wanted to convert the design of this tool to increase the applied torque output, they could achieve this in a number of ways, all of which would likely result in an increase in the size of the tool's components, necessitating a redesign. As previously stated, adding another layer of planetary gears would increase the tool size vertically while increasing torque amplification. One could also increase the transmission ratio between the sun and the carrier by increasing the amount of teeth on the sun or decreasing the amount of teeth in the ring. To maintain proper meshing between the gear systems, this would correspond to an increase in radial size of the tool in exchange for increased torque amplification. Lastly, one could simply increase the power of the motor to be transmitted throughout the system. It should be noted that for all torque amplifications, the upper gear set will likely have to be changed to a stronger material, as the current plastic may not be designed to sustain repeated cycles of a higher torque application.

Lastly, it might be useful for more powerful tools to have a way to adjust the output torque. One method of accomplishing this would be to use a variable speed motor, or the addition of a gear transmission that can readily increase or decrease the gear ratios through the use of an external dial or switch. Both methods would likely take up considerably more space and would not function in the current form of the screwdriver, requiring a major redesign of the tool.

Overall, the reverse engineering of this screwdriver gave me a better understanding of how gear systems function within parts. I wasn't expecting such a simple, small mechanism to accomplish such a large amplification of torque with such high power efficiency. I hope to carry this understanding of gears through to other projects, knowing that gear sets can be incredibly compact and effective if well designed.