The Goblin - an adjustable catapult
(This catapult is adjustable so you can accurately hit distances)
This is the Goblin catapult. And it is a small table top sized catapult that is ten inches in length. But it is a bit unique in that it allows you to adjust the throwing distance pretty easily. One of the difficult things about a catapult is that it can be difficult to get an accurate throw to different distances. This little catapult solves that issue by using a series of holes that you can set a pin or dowel through. So, you get a variety of different strengths from the rubber band. And you can further adjust this distance of throw by using different sized rubber bands.
Let's take a look at how this catapult is adjustable. The picture below shows the five holes that I have in this catapult. You simply put a wooden pin in a selected hole to hold the rubber band at a different location. see how this will stretch the rubber band to different tensions? That is how we get the adjustability of this catapult. And I have five holes (2 in the throw arm and 3 in the structure but you could put more holes to get more adjustability. And, remember that using different rubber bands will also get you even more flexibility and adjustment.
Some Design Improvements
This project is still being worked on and it will be a while before I have them ready for production and sales so bookmark this page and check back in the future if you want to get a goblin for yourself.
See this catapult in action and learn more about it
Let's Build this catapult
Can you build this goblin catapult? You sure can! Here is a picture of one that was built by Abhinav. My thanks go to him for sending in this picture!!
Some Building Notes before we get started
I use mortise and tenon joints for this catapult and I will show you what these are but you don't necessarily have to do this. You can use screws or possibly nails or you could even use a glue gun to glue it all together. I have built small catapults like this with a gluegun and my multipult is a good example of this. But, if you want the strongest catapult you can get, which means the potential for the longest shots, then the mortise and tenon set up is your best choice.
So let's take a look at what a mortise and tenon is and how we make one. It is reallly quite simple. It is just a way to strongly secure two pieces of wood together and you can do it without glue or with glue. I recommend you use glue, it is easier and you don't have to worry about the dowel and hole being perfectly sized.
So let's build this catapult
Here is what you will need in terms of wood and a few other things.
The wood is all 1/2" square and the dowels are all 1/4" round. You can use pine or any other kind of wood except for balsa wood which is too weak. You can buy this wood very easily at home improvement stores, harware stores and most hobby stores.
Lengths of wood: from left to right
Okay, lets build the rubber band adjustment plateau first. It's important that you build this first. Otherwise you won't be able to assemble the catapult! Build it just as shown. It is all mortise and tenon. Be sure to use the two pieces that are 4 1/4 inches in length for the center two pieces. They are about an inch in from the ends of the horizontal pieces. (not critical)
Drill three holes through these 4 1/4 inch pieces either before or after you assemble it. The placement is not critical. These holes will be for a dowel that you hold the rubber band with. These are the adjustment settings. When you want to change the tension you move the dowel and rubber band from hole to hole. If this is unclear it will be cleared up when its built.
Don't forget to put the four tenons in the ends as shown.
Now build the two sides of the catapult. Put the vertical pieces three inches from the left end. Here are the locations of the holes to drill. In each of the two uprights drill a hole 1/4 inch from the end. In each horizontal piece drill a hole (measuring from the left) at 1/4 inch, 2 1/4 inch and 9 3/4 inch. Be sure to make two of these sides!
Table of Contents for this tutorial
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