What’s toasting?! This week, we focused on our initial construction and electronics setup.
We obtained wood for construction and began gluing and drilling components together. We assembled the base beams, vertical beams, and both axles.
We also decided upon the following additional design considerations:
Place the base beams as close as possible (increase the flexural stiffness of the 2 axles—shorter beams are less prone to buckling and deformation)
Place spring to the arm as far away from the pivot point as possible (maximize torque)
Place axle 1 as low as possible to decrease force experienced upon impact with arm
Place solenoid as far away from pivot point as possible (maximize torque)
Make the arm as long as possible (maximize angular acceleration of bread!)
Use a 6-pointed servo (maximum area of contact on flat peice)
Make the hole for axle 2 larger than holes in vertical beams (so arm freely rotates & beams are locked by servo motion)
Cyborg arm (“Bucky”/”Winter soldier”) with bottom half (hitting axle) comprised of wood 12in, and top half 3D printed (reduce weight, increase angular acceleration, easy replaceability)
Balsawood cuts for servo 1
Have the piece attached asymmetrically to servo 1 (maximize torque)
Springs that we’re considering
On the electronics side of things, we were able to pick up our servo motors, potentiometers, buttons, and other various components. We began coding, and after a few minor setbacks (rip to the smoking potentiometer), we were able to complete the code for Servo 3 (which controls the vertical beams) and begin working on implementing Servos 2 and 4, which hold down the arm as the spring extends.
Build a working catapult that is able to launch bread across the dining hall
Be able to control the distance the bread travels to accurately hit our targets
And these design requirements to achieve those goals:
Feature
Description
Implementation
Launch Mechanism
An automated way to torque the arm and launch bread
Servo motor, Spring
Securing Arm
To secure the arm in place while the spring loads
Solenoid
Launch Angle
To change the angle of release, impacting distance of travel
Servo Motor, Potentiometer
Bonus: Bread Supply
Wheel device to continuously supply bread
Stepper Motor
Bonus: Panning
Rotate entire catapult to acheive 360° of attack
Servo motor, potentiometer
We've also started developing the physical design for the frame, pictured below! Next steps are to obtain wood and begin construction of the physical frame.
Secure the vertical beams in position to provide support for the structure.
Drill larger holes in the arm where axle 2 will pass through (The holes in the vertical beams should be smaller to keep the beams locked in place while allowing axle 2 to rotate freely inside the arm)
In the base, position axle 1 as low as possible.
Drill a hole to keep the axle securely in place at the lowest point.
Attach axle 2 to the arm at the farthest possible point from the pivot.
Drill a hole in the arm to fit axle 2 and ensure it's securely mounted.
Arm Construction
Bottom half (12 inches). Use balsa wood for the bottom half of the arm. Cut it to 12 inches in length to balance torque and weight.
Top half (3D printed).
Servo Mount 1. Cut and shape a mount for Servo 1 from balsa wood.
Mount the servo asymmetrically to maximize torque (try to position the servo as far from the pivot point as possible to increase the force it generates when pulling the spring)
Spring and Solenoid mechanisms
Position the spring on the arm as far from the pivot point as possible
Place the solenoid as far from the pivot point as possible
Servo and Control
We are using a 6-point servo. Use a 6-pointed servo for maximum surface area on the flat piece (for stronger grip)
Check that Servo 1 is securely mounted using the balsa wood mount.
CAD
Before printing, we need to refine the arm’s dimensions, make sure that parts like the arm, base beams, and servos align properly and that there is enough clearance for rotation.
If we have time: design the wheel mechanism
Assembly
Start by attaching the two base beams together as securely as possible. We need to make sure they are positioned close to each other to increase their strength. We can use strong glue or screws or bolts to keep them stable.
Next, secure the vertical beams to the base. Once they’re in place, use screws or bolts to hold them down securely.
Position axle 1 in the base as low as possible. Secure it tightly in place with screws.
Drill a hole for axle 2 in the arm (the hole should be a bit larger than the one in the vertical beams, so axle 2 can move freely inside the arm without being too tight)
Slide the axle through to check if the arm can rotate.
Now, attach the arm to the base by placing it on axle 1 and axle 2. We need to make sure that the arm can rotate freely.
Check that axle 2 is aligned correctly.
Take your balsa wood mount and position Servo 1 on it. Mount the servo as far from the pivot point as possible (asymmetrically).
Position the spring at the farthest point from the arm’s pivot
Hook the spring securely to both the arm and the base
Place the solenoid as far from the pivot point as you can.
Secure it to the arm or base with screws or a mount