Who I Am
Hi, I am Abe. I am 16 years old and am a a junior attending Denver Jewish Day School. For my stater project I am building the Mintyboost mobile phone charger (). For my intensive project I am building a mechanical ball launcher, which uses a a spring loaded arm to launch a tennis ball. I choose this project because I find projectile motion fascinating. I am interested in engineering because I enjoy building projects.
Gears (STL Files;Requires a CAD program to open)
Small (24 teeth): https://drive.google.com/file//0B4xPXcoqijhOOElTYnF3T0lIdmN4dG5rYWNrUGQ2ekR4RjFZ/view?usp=sharing
Big (60 teeth): https://drive.google.com/file//0B4xPXcoqijhOUHJuNWxPcWlDNzEzdGZyRVhVOE83OUFVUE40/view?usp=sharing
My third mile some was mainly comprised of reinforcing the structure of the machine and building a switch into the machine. The only problem I encountered was a lack of time. I was not able to complete all of the improvements that I wanted to.
For my second milestone I have added a gear series to increase the torque of the small arm, the gear attached to the motor has 24 teeth, and the gear attached to the arm has 60 teeth. I have also replaced the spring with one that produces less force, additional I have removed most of the outer casing of the launcher. While continuing my development of the prototype I encountered many problems with the gears and with the axle transmitting force to the arm. I was not originally able to cause the axle to turn because the larger gear was not properly secured. My first solution to this problem was to place locking washers on either side of the larger gear, this solution worked. I did not continue using the solution because it limited the about of force I was able to put onto the arm. My next solution was to add a lever to the gear that would transmit torque more directly to the axle. This solution enabled me to tension the arm with two spring as opposed to one.
I am building a ball launcher that uses a spring to pull an arm, which impacts the ball, at high speed. A windshield wiper motor is used to tension the spring. As the the spring is tensioned the arm is forced against a nut on a smaller arm, which is attached to the motor. This nut prevents the arm from being pulled back by the spring to a neutral position and is essential to the functioning of the launcher. When the arm rotates enough the nut will be parallel to the force vector of produced by the spring on the arm, as opposed the the perpendicular position that it occupies for the majority of the rotation, and the arm will then be pulled forward by the spring and hit the ball. While building this prototype I encountered many problems. The first of the problems was the small arm attached to the motor. My original plan called for me to attach a belt wheel to the motor and to attach the arm to the motor on top of that. I solved the problem by attaching the arm to the smaller arm attached to the motor. The second problem I encountered was the anchoring system for the spring. Originally I used two springs and the combined force sheared both of the anchors in half. I solved this problem by using steel bolts instead of aluminum pseudo rivets, and by decreasing the number of springs to one. The third problem was also related to the springs. The Motor was not able to tension the spring. I will solve this problem by utilizing a gear complex that will increase the power and torque of the arm at the cost of speed.
The Mintyboost uses a boost converter to increase the three volts provided by the two batteries to the five volts used by the USB. The Boost Converter uses an inductor in a closed circuit to build up a magnetic charge, when the circuit is opened the magnetic field is destroyed and creates additional voltage, this voltage, along with the voltage provided by the source is forced through a diode, which prevents back feed, and then into the load. The Mintyboost also uses two voltage dividers, which provide a small charge to the middle pins of the USB port. This charge is used by IPhones to recognize ‘safe’ charging devices.