In this post I will show how to make Leonardo Da Vinci’s self-supporting bridge. So I will show how to make a drill press jig to cut the notches so the wooden posts fit perfectly.
It doesn’t mind whether you are old or young, Leonardo da Vinci’s inventions always grab our attention. Sometimes due to the uses he wanted to give to his inventions in the time he lived. Sometimes due to the limited resources he had to use in that time. But also because his inventions are very nice. Ok, they look so nice because the are mainly made of wood.
Even using our modern DIY electric tools, it would take a lot of time and effort to copy any Leonardo Da Vinci’s inventions in a simple and small woodworking shop like mine. But one of those Leonardo Da Vinci’s projects, the self-supporting bridge, seems to be simple enough so we can try to make it. At least we can try to make a small one. If it is actually a Leonardo Da Vinci’s invention or a Chinese invention, that is not important now.
First I have to select the wooden posts I will use. I decided to use treated wooden posts, because the bridge will probably end up in the garden. So, I select the straightest posts. And I also try to select the posts with no very big cracks. Once I have selected them, I cut them to the wished dimensions. In this case the treated wood posts are 58mm in diameter. So, I cut 5 pieces 91cm long (those are the horizontal pieces), and another 10 pieces 109cm long. Well, those are the final dimensions. Actually, first I cut all the pieces some centimetres longer, because as you can watch in the video, I had to retouch the ends of the wood posts after cutting the notches.
I only have to sand the short pieces. But in the long pieces I hace to cut three notches. One notch in the middle, and another one in each end and at 180 degrees with the first one. It was very easy to cut those notches using a hole saw and a simple drill press jig. Well, actually I make two simple drill press jigs.
To make the first drill press jig, I simply screw a wooden strip to a piece of board. The strip works as a drill press table fence so all the notches I cut will be the same depth.
Then, I measure the distance from the end of the post to the notch I will cut, and I drill one notch in just one end in all the long pieces.
Now I have to drill the other two notches in the wood posts. But first I have to modify the first jig. I simply put a piece of post, vertically, at the right distance from the hole saw.
Like this I can fit the notches I have already cut, around the vertical piece of post. Now I fit the first notch around that vertical piece, I move the post against the strip in the jig, and I drill the notch in the middle of the post. Now I fit the notch in the middle around the vertical piece, and I cut the third notch in the other end of the post. Like this the notches in the ends are at the same distance from the notch in the middle, and at 180 degrees with it. You can watch in the video how to make the jigs and how to use them.
Now, before I put together all the pieces of this self-supporting Leonardo da Vinci’s bridge, I sand them and I paint them with a waterproof wood protection. These are treated wood posts, but some extra protection can’t be bad. And because this is a walnut stain, the posts will look better than with the characteristic green we always see in treated lumber.
Once the wood protector is dry, I can put together all the pieces of this Leonardo da Vinci’s self-supporting bridge. At first we can think it will be difficult to assemble this posts structure, but once we put the first pieces we already realise how to put the others. You can watch in the video how easy it is. It would be very different if we make one bridge using big tree trunks. For example to cross a river.