Strong Handmade Bridge from Wood

Really neat handmade bridge, wish I had the skill to make something like this.

Great skills, sadly they may be lost soon unless we learn it ourselves now.

This looks like a version of a Leonardo DaVinci bridge that he designed in 1502.  It’s a really neat concept.

Did you notice the little wooden wedges that he put into the bottom ends of the vertical railing supports? The receiving holes must have been wider at the bottom than the top - so as the post was hammered in, the wedges would have been forced further in, spreading the wood enough to trap it permanently - so subtle, but so effective! A similar principle is used to attach a handle to an axe, but in the axe's case you tap the wedge in after putting the head on the handle. In the video, it's done in a seriously sneaky way!

Also, many of the cross pieces are the very same principle as dovetail joints - just one long continuous piece, but essentially the same shape.

Yes, that level of skill with hand tools is being lost, but the principles being shown in the video are not anything that I can't see if I look at quality furniture from 100 years ago. We have it easy because metal fasteners are cheap, quick and available.

I'd also like to point out that the skills needed to keep those tools sharp is also being lost. I can remember watching a show with my sister about building a castle using old stone-mason techniques. One comment made was that the blacksmith was kept busy *every* evening sharpening the tools for use again the next day. Nowadays, many people don't even know how to do a half-way decent job of sharpening their kitchen knives! We haven't been trained to recognize that the wood-working skills are only useful when accompanied by the tool sharpening skills!

One of my favorite youtube channels. This man does more with simple hand tools then some of the poeple do with $5000.00 shops & $5000.00 in power tools. Love his break down & carry stools.

Jay Angler wrote:I can remember watching a show with my sister about building a castle using old stone-mason techniques. One comment made was that the blacksmith was kept busy *every* evening sharpening the tools for use again the next day.

On a related note, I saw a similar show where they made a side hand comment that the blacksmith would sharpen a pick or chisel by heating and forging it out to a new point.  If you sharpen it with a file or grinder, you end up with the same sharp point but you remove a lot of metal in the process.  So the blacksmith can get many more sharpenings out of a tool than a guy with an grinder can.  

Beautiful. Peaceful. Lovely.

 Jay Angler wrote:
Did you notice the little wooden wedges that he put into the bottom ends of the vertical railing supports? The receiving holes must have been wider at the bottom than the top - so as the post was hammered in, the wedges would have been forced further in, spreading the wood enough to trap it permanently.

I don’t even know if the receiving holes need to be wider at the bottom (though that’s even better). Depending on the type of wood, it will compress enough that the hole could be straight. What’s happening is the friction between hole and peg increases so much it won’t come out, just like the axe head (also not a tapered hole). I grew up with wood heat, and the dry air led to chair rungs and legs coming loose. We’d glue them in, only to have them come loose again. Then my dad discovered the tiny hidden wedge trick, and they stayed tight.
Unrelated, but along the same lines of just how much the friction is responsible for holding things in place- an engineer explained to me how, when you properly bury a wood pole in the ground for a structure or power line, up to 80% of the support the pole provides (vertical weight bearing) comes from friction on the sides of the pole, vs the bottom of it sitting on a rock or gravel or concrete footer.

Another cool self supporting structure is the reciprocal roof truss system used on some timberframe gazebos and yurts. No fasteners, no locking joints, just simple notches with pieces loose laid on top of each other. This can be a fun homeschool experiment too! It’s interesting how the weight transfer is perfect, and smaller pieces of wood can hold a significant load.