Probably the question I get asked the most is “What bridge design holds the most weight?” or “What bridge design is the strongest?”
The answer to that question is not simple and probably is not going to be what you expect. The truth is, I cannot answer the question. There are too many variables that are [...]
There are several reasons you should cut your own strips of wood:
It saves money
It saves time
Helps you get familiar with the wood
Increases your skills as a builder
Video Tutorial
Video is about 4 minutes long.
DISCLAIMER:
I am not responsible for any injury caused by someone using this technique. I recommend that students cut strips of wood only [...]
Now Updated and Expanded
I wrote an ebook, 5 Steps to Building a Model Bridge PDF to answer the most common questions people have about building bridges. In the ebook I show all the steps of building a model bridge, and then walk people through the actual construction of a bridge. The ebook contains many photos [...]
Objective: To build a boomilever with the greatest efficiency.
Basic Design:
There are two basic types of boomilevers. First is the tension boomilever, where the tension chord is longer than the compression chord.
Second there is the compression boomilever, which is the opposite of the tension.
It is generally accepted that the tension boomilever is inherently better than the [...]
Balsa wood is unique from all other woods. Its properties make it valuable to bridge builders, wood carvers, surfers, and many others.
My favorite article about Balsa wood was taken down, but I found a copy of it at Archive.org.
Balsa or Basswood?
I have heard a lot of people claim that nobody should use Balsa. They claim [...]
Lateral What? Exactly. Perhaps the most important aspect of your bridge and you aren’t sure what it is.
Lateral bracing is the term I use to refer to any pieces on a bridge that help keep the top chord from bending horizontally. In the figure before, lateral bracing is red:
Why is lateral bracing so important?
As you [...]
The concept of stiffness is one I have been delving into this year. The stiffness of the wood you use directly translates into the strength of your bridge. Density no longer matters much, and is almost not worth calculating unless you can find a relationship between density and stiffness. I have not been able to [...]
How Changing Height Affects a Bridge
I found it slightly difficult to come up with the right title for this post. Perhaps a better one is What happens when you change the height of a bridge assuming nothing else changes. I am talking about the forces that act on a bridge, of course.
I get asked all [...]
1. Humidity affects the weight of your bridge. Keep your bridge in a closed container with a few grains of rice.
2. Go easy with the glue bottle. As a general rule of thumb, if you can see it than you are using too much.
3. Keep your hands clean! Oils and grease from your skin can [...]
An L-beam is more efficient than a square the same width. It is not going to hold as much, but it is going to be more efficient. An L-beam is also more efficient than a square with the same mass of wood. Of course, you have to count in the glue weight for an L-beam.Balsa, [...]
Compression:
Compression is a pushing (compressing) force. You can take the middle a straw and squeeze it between two fingers, the straw flattens. However, if you hold each end of a straw and push together it is harder to make the straw compress, or flatten. The shorter a piece of wood is, the more compression it [...]
Question:
What’s your take on the new scoring. Do you think the bridge should just aim at holding 15 kg… or try to build one that’s lighter and hold less possibly getting a higher efficiency score?
I used to think that you should go lighter, holding less. But now I think that you should aim at holding [...]
The type of joint you use on your bridge can drastically change its strength. These pictures are not of glued joints, I simply laid sticks together. On a bridge, you want to make sure that the joints are clean and there are no gaps between the wood. Glue does not work well as a filler, [...]
Common trusses used in engineering:
Warren
Pratt
Howe
K Truss
The following figures are shown under a load. The numbers represent percentage, where the total load = 100. The numbers are rounded to the nearest 5. For absolute numbers, visit the Bridge Designer.
Red represents tension, blue represents compression, and green is no load.
On this Warren truss, each of the [...]
There are several ways to test model bridges:
With a machine
By pouring sand
Textbooks
Pushing down on your bridge
Using a machine
Obviously, if a machine is being used to test your bridge, there isn’t a lot you can do. You can stand watching the destruction of your bridge. Or turn away and cover your eyes with your hands. I [...]
What you want to look for in glue:
Drying time
Price
Weight
Strength
CA Glue. This is a very common glue used for a variety of projects. It dries in seconds, like super glue. It is also widely available. Numbers of hobby stores and online companies sell it. However, it is not cheap. CA glue can be bought in three [...]
I am constantly asked whether balsa is better than basswood. Here are some of my notes comparing the two woods.
Balsa is cheaper and more available than basswood. This means you can buy more wood, and build more bridges for the same amount of money. By building more, you will gain valuable experience and improve your [...]
