Background/Inspiration

This project was my first project as an undergrad; I was inspired to make this after taking my first college physics course. I wanted to make a device able to shoot a golf ball up to 50 feet consistently. I first thought about making catapult but I knew there would be too many inconsistencies.Therefore, I theorized if I built a rigid system, the barrel and spring system would yield in more consistent results.

The front end would slide off and the two cylinders would bend after a couple practice shots. To alleviate some of the force that the front end was experiencing, I used a flexible coupler to dampen the force exerted from the piston. This worked perfectly, although I had to remove the hose rings from the coupler and had to move it up to the PVC portion. Since tightening the coupler would cause the barrel to close in, interfering with the path of the piston.
The screw attached to the piston would bend after a few trials, causing the piston to scrape the interior of the barrel. To fix this, I simply went up in size and widened the slot until multiple trials were successful with no bending.
The trigger would bend from constantly loading/unloading. Therefore, I tried various shapes and the best results were achieved with the uppermost example in the picture to the right.

The trigger, even with the new design the trigger, was not as consistent as I wanted it to be, but this was also due to the lack of equipment I had available. The trigger was made with a metal hand saw and a metal file. If I was to do it again, I would want to make the trigger at a machine shop with a stronger and thicker material to get better consistency.
The horizontal adjustment, as of right now the height is adjusted by moving the wooden block at the bottom, that is held down by velcro. If I was to improve this, I would use a stepper motor and a linear rail system to move the block electronically and display the set range. The stepper motor would be driven by an H-Bridge, such as the L298N, and to display the numerical values I would use simple 7-segment displays (preferably with I2C). Finally, i'd add a micro-controller such as the Adafruit huzzah feather with two buttons to control the direction of the stepper motor.
Lastly, I would attach this to another to hold the mortar when it's fired. As of right, now every time it's shot I have to hold down the mechanism so it doesn't move. A fix here would slightly improvement in the precision.