Automatic Pool Cue

I worked with a team of four students to develop an easy to use and robust automatic pool cue.

The objective of this project was to create a automatic pool cue that would both have enough force to propel pool balls a sufficient distance as well as package it all within a lightweight and portable package.

I was responsible for designing and fabricating the variable trigger. Since in pool one needs to adjust the amount of force used within a shot, the trigger of our automatic pool cue needed to have the ability to release the cue at any point within the draw distance. I created a rail along which the trigger latch slides and can be pulled up no matter how far drawn the cue itself is.

In the gallery below you can see my sketching and ideation process for coming up with the final trigger design as well as hand calculations I did to validate our drivetrain components.

Initial design sketch

My initial design was to have an intermittent gear driving a rack to pull the cue back but that design wouldn't allow us to release the cue at different points to vary the force.

Initial design sketch

I took a lot of inspiration from how a crossbow works for the pool cue as the other methods of propelling the cue forwards such as using a spring or small explosive would have been less space efficient/more difficult to package and too dangerous respectively. In the sketch to the right you can see our initial ideation for packaging and where to place the motor that drives the rack and pinion.

First trigger iteration

My initial ideation for the trigger mechanism involved a lever that the user had to pull in order to actuate the latch holding the cue back. This design was scrapped as it would mean that during different points in the travel of the cue the user would have to exert different amounts of force to actuate the lever depending on where the lever was in relation to the latch.

First iteration of final trigger design

I came up with a design that both allowed the cue to be released at any point and would not yield an inconsistent trigger pull (in theory) by creating a channel that the front of the latch slides along. If the channel itself is pulled upwards, the latch will be actuated and the trigger is released.

Torque hand calculations

These were done to determine necessary motor torque and gear ratio between the pinion gear sprocket and the drive sprocket

Rendered CAD of final pool cue

Final SolidWorks assembly of the pool cue

Exploded view of final pool cue assembly

Animation of variable trigger

The animation shows the trigger being able to actuate and release the cue along any point in the cue's travel

After modeling all components in a SolidWorks assembly, I began to machine the parts necessary for the pool cue. For the front and motor mounting panel, we chose to waterjet the profiles out of aluminum as those sides would need to remain rigid under forces that would cause acrylic to yield.

I CNC milled the variable trigger components out of aluminum as they would also be subject to relatively high forces that 3D printed parts would not be able to sustain.

After machining all critical mechanical components, I lathed each standoff/spacer out of spare aluminum stock for aesthetic purposes.

Finally, we assembled the pool cue using standard metric hardware.

Waterjet trigger latch and lathed trigger dowel

CNCed trigger slides and trigger latches

Assembled trigger latch with dowel

CNCed trigger slides

Assembling the final pool cue

To the left is a video of the mechanism working and another video we made for fun to showcase our project.

Automatic Pool Cue

Zihan Sun

jsun1324@gmail.com