04 – DaVinci’s Giant Crossbow Design and Story

Lazy to read? Watch my 3D animation here.


This is a story about a giant military machine. Let see how big this thing really is and how it is supposed to work.

This drawing of the crossbow is the only thing that Da Vinci left behind for us. Any research comes out only from this picture anyway. Therefore, I decided not to look for any information initially and remain unaffected until I finish my own study and form my own opinion.

Original Da Vinci’s Drawing


A little bit of history. The drawing is a part of ”Codex Atlanticus” and is one of many inventions that Da Vinci never built up. The historians believe that the goal was to gain the favour of Ludovico Sforza, and as with Da Vinci’s tank, nobody really expected this battle machine would be ever built.

Dimensions and Weight

Da vinci's giant crossbow - dimensions -poster
Da Vinci’s giant crossbow – dimensions -poster

Based on the figure on the original Da Vinci picture, I believe that dimensions are approximately 24,5 m – length of the shoulder, and 22 m – length of the body.

It is easy to calculate the volume of anything in the 3D world. Blender showed me that the volume of the wooden parts is 38m3 and 1,6m3 of the iron parts. Therefore, we can suppose that the weight of the wooden parts is almost 20 tons and the weight of the iron parts is 13 tons. Of course, there must have been using different kinds of wood but this is beyond my knowledge. I think it is enough to know to create an idea of what the weight of this thing was. As you can see, not a little.

How Does It Work?

Let’s take a closer look at each section.


The most important part of the crossbow. While I was working on the 3D model, I realised that this could not work on such a scale. Wood is not a rubber. You can bend it, but you cannot squeeze it. Then I noticed that the inner side is made up of several smaller parts, probably separated from each other by gaps. Everything started to make sense. This is to prevent the string holder from sliding and at the same time to use the advantage of the flexibility of the rope.

The beams are close to each other sliding out the string holder.
The gaps between the beams prevent the string holder from sliding out.


The charging mechanism is simple. The problem is that such a wooden coil would have had the high friction even if it had been made very precisely and had been sufficiently lubricated. The charging would have taken 10 minutes and would have been tedious for the operator, which does not make this battle machine very efficient.

Da Vinci's Crossbow cocking mechanism
Da Vinci’s Crossbow cocking mechanism


Da Vinci suggested two ways to release the string. Either with a hammer blow or with a lever. I would certainly choose a hammer.

Da Vinci's Crossbow triggers
Da Vinci’s Crossbow triggers


Notice the inclination of the wheels in the original picture. Such talented artists and skilled inventors like Da Vinci certainly did not draw it like this only as a coincidence together with a very weird construction. It will definitely be a way to change the angle of the shot. In my opinion, Da Vinci relied on wheel spikes to help keep the wheels in the right angle. Such a chassis would not have worked according to Da Vinci’s ideas in the real world. The weight would have also been a problem. A much more complex mechanism should have been produced, perhaps similar to today’s car axles.

Da Vinci's Crossbow - sideview
Da Vinci’s Crossbow – side view


I remember a document, in which a group of experts made a prototype. I cannot find it now, but if I remember correctly, they fired to the distance of 4-5 meters.

So would it work? No. But it is a nice piece of military technology history. Isn’t it?

Author: shubol3d