Self Loading Trebuchet

This project takes a traditional trebuchet and automates its loading and firing via a winch with a string, a stepper motor, two servos and a locking gearbox. To load the trebuchet, move the potentiometer to the desired setting and press the yellow button. Once the trebuchet is loaded , press the green button to fire. Press the red button at any time to stop the loading of the trebuchet.

2x SG90 9g microservo https://www.sparkfun.com/products/9065

1x rgb led https://www.sparkfun.com/products/11120

1x TRONX SL42STH40-1684A-23 Stepper motor or 12V 200 steps/revolution equivalent https://www.tronxyonline.com/SL42STH40-1684A-1-8A-78Oz-in-42-stepper-motor-p64966.html

1xArduino Uno https://www.sparkfun.com/products/11021

1x Sparkfun TB6612FNG motor driver https://www.sparkfun.com/products/14451

1x trimpot potentiometer https://www.sparkfun.com/products/9806

1x 10K ohms resistor https://www.sparkfun.com/products/11508

3x pushbutton https://www.sparkfun.com/products/97

1 3ft length 1/4 in all thread bolt

3 1x2x8ft firing strips

Bulk fasteners

Vaseline or grease

4 2.5x3/4in bolts

1 roll of duct tape

1 roll of electrical tape

Super glue

1 1/16 diameter set screw

3/4 in diameter spool

3-4 rubber bands

Twine

1 short length of pvc

Access to a 3d printer

1.Cut all of the pieces for the trebuchet.

Wood:

4x 6.5in pieces

2x 20in pieces

1x8in piece

1x7in piece

1x19in piece

1/4 in Threaded Steel Bolt

1x10in piece

There is a detailed video of these instructions in the google driver folder

https://drive.google.com/drive/folders/1Dy7wlOWwI2cp7yFcDXQMD_nHU67RSfZH?usp=share_link

1. Cut a 2 1/4 in piece of pvc. Cut it in half again to form a half pipe structure. Screw it into the top of the arm and slide a rubber band around it. Drill a quarter hole near the top of the arm to insert your twine later.4
2. Drill a quarter inch hole 13 inches from the pvc side off the arm on center for the main rod.
3. Drill a quarter inch hole 1 inch from the bottom of the throwing arm on center for the basket
4. Pass the 10 inch threaded steel rod through the first hole and then place a washer and two nuts on each side to lock it in place
5. Pass the 4 inch long threaded steel rod through the second hole and place a washer and a nut on each side to lock it in place

1. Stack two of the 16.5 inch pieces on top of each other. Then use a 1/4 in drill bit or spade bit to drill a hole between the two pieces of wood 1 inch from the top on center.
2. Attach these two pieces to one side of the throwing arm and then put a nut on the outside to lock it
3. Repeat the first two steps for the other side, these will be the legs.
4. Lay two 12 inch pieces of woof side by side so that there total length is 20 inches, screw these two pieces together. this will be the bracing
5. Place this bracing on the side of bottom of the legs so that there an eleven inch gap from leg to leg. Screw the bracings into the legs once you have achieved the correct gap length.
6. Repeat the last two steps for the other side.
7. Then screw the bracings from both the front and the back with a 7 inch piece of wood and a 8 inch piece of wood respectively
8. Attach two 6.5 inch pieces of wood side by side with screws to create a platform for the gearbox to sit on. Screw this platform at the rear of the frame in the corner.
9. Place a 3 inch piece of wood with a quarter inch hole drill through the center a half inch from the edge. Screw this piece into the edge of the platform.

1. Lay three 4 inch pieces side by side so that they create 6 x 4 inch base
2. Place two 6 inch pieces of top of each other on each of the long sides of the platform.
3. Place two 3 inch pieces of top of each other on each of the short sides of the platform.
4. Screw all these pieces together. When done you should have a 6x4x4 inch crate
5. Take two 3 inch pieces of wood and and drill a quarter inch hole half an inch from the top on center.
6. Attach these two pieces to the insides of the crate and use the holes to attach the basket to the bottom of the throwing arm.

Print all the stl files. They are in the drive folder.

Follow the instructions in the video linked in the google drive folder.

https://drive.google.com/drive/folders/1Dy7wlOWwI2cp7yFcDXQMD_nHU67RSfZH?usp=share_link

The code is linked in the google drive folder as an .ino file. The code is explained with commenting.

https://docs.google.com/document/d/1uYqPy4ZEdo7pZAGogwgVhx9vVTuavaT10Xl03FQ5n7A/edit

The wiring diagram is linked above and a more comprehensive video is linked as the wiring video in the drive folder.

https://drive.google.com/drive/u/1/folders/1Dy7wlOWwI2cp7yFcDXQMD_nHU67RSfZH