Introduction: Froggy World 1 the Catapult

About: I am an author and a maker. My current project is Santa's Shop. I'm working on a science fiction type book--more later. @EngineerRigsby

Froggy World is an amusement park for adventurous frogs. 

This ride is the first in a series.  Each ride receives a signal from the previous ride "You've got the frog;" and each ride signals the next that "Frog has left, you've got the frog." Eventually, the frog will be returned to the catapult (by another ride) and the cycle will repeat.

The concept for winding and releasing the catapult spring comes from Arduino Controlled Catapultby UnusualTravis

Step 1:

There is no real "beginning" or "end" to this amusement park, but I had to start somewhere.  The signal on Arduino pin #13 (brought low) will cause this ride to catapult the frog, return to "ready" position and notify the next ride (by a low signal on pin #11) that the frog is now in their hands.

The code "winds" the spring servo, then moves the "release servo."  The spring servo unwinds (catapult falls back to start position) and the "release servo" moves to the latch position.  Then the "frog has left" signal is activated.

#include <Servo.h>

Servo myservo;

Servo release;

int start = 13;

int next = 11;

int val = 0;

void setup ()



pinMode(start, INPUT);

pinMode(next, OUTPUT);

digitalWrite(next, HIGH);




void loop ()










digitalWrite(next, LOW);


digitalWrite(next, HIGH);


Step 2:

I had to start somewhere . . . and this frog is actually #7 in my design sequence.

Design and 3d print files are available at:

Step 3:

I used magnet wire to tie the 1/4" x 3 1/4" x .025" spring to the catapult arm.

Step 4:

The catapult restraint keeps the arm in a position such that it will return to rest when the wound spring is released.

Step 5:

I cut a 1/4" x 3 1/4" x .025" spring to fit in the restraint.

Step 6:

The spring sticking out looks hazardous . . .

Step 7:

So, I cut the spring off and added a "safety button" on the end.

Step 8:

The 8" x 15" by 1/4" plywood base should be painted at this time.  (I didn't--had to remove everything to paint).

Add the base and the restraint with screws or small bolts.

Step 9:

Take the "servo extender" and drill two 1/16" diameter holes through the extender and the servo horn.  Use magnet wire to secure the extender to the horn.

Step 10:

Mount the servo (Hi tec HS 311--available at into the servo spring bracket.

Step 11:

Secure this with the spring servo bracket lid.

Step 12:

Install the catapult lever using a 3" long by 1/4" diameter wood dowel.  Attach a 1/4" x 3 1/4" by .025 spring to the catapult lever and the servo extender using magnet wire (#22).

Attach the servo horn to the servo motor and stretch the spring just enough that the catapult arm will lie at rest when the servo horn is in the leftmost position.

Step 13:

Fasten the "release servo" so that it prevents the catapult arm from lifting.

Step 14:

Secure the servo arm with the servo screw.

Step 15:

Secure the 9 volt battery holder to the plywood.

Solder jumper pins to the ends of all wires (use heat shrink tubing to protect the solder connections from shorting).

Step 16:

Screw the AA battery holder to the plywood.

Step 17:

Screw the Arduino to the plywood. 

Download the software from step #2 to the Arduino if you have not already done so.

Step 18:

Remove the sticky back paper and attach the perf board to the plywood (you'll never get it loose--be sure it's where you want it). 

Neaten up the cable runs with cable ties or holders (some printed ones are available if you are 3d printing parts).

Step 19:

Fasten everything together, as neatly as possible.

Step 20:

The frog should be ready to fly!

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