The examples given below are based on a 3/4/5 right triangle (as seen on the left). Obviously, any triangle will work in a truss, not just a right triangle. However, right triangles are convenient and easy to use in a project. The link below is to download a spreadsheet I created that gives tables for many right triangles using LEGO bricks. Excel 2000 version: triangle2000.zip 106 KB. Excel 97 version: triangle97.zip 322 KB.

Simple Side View Larger Side View 3D View of Side

A Small Truss The images to the left are of a very simple 2-dimensional truss made of a 3/4/5 right triangle. Axles or 3L friction pins can be used to connect the ends of the members. The pictures show an open hole with the axles or pins left out. Because the diagonal members are made of axles with #1 connectors, they can pull apart if loaded in tension. To help negate this effect, solid vertical members (like the grey links on the ends) should be placed every 3rd or 4th diagonal. The main horizontal members (the black Technic beams) can be connected end-to-end with 1x plates. This connection may seem rather week, but because the truss structure minimizes bending and twisting, the connection will hold rather well.

Simple Side View 3D View of Whole Structure Top View of Structure

A Larger Truss This truss is a larger version, but uses a 3/4/5 right triangle. This particular truss was used to make the boom for the Crawler Crane . The truss is basically two main truss types connected together. The first type makes the vertical parallel sides which are composed of black 1x16 Technic beams connected with gray 1x12 Technic beams. The second type makes the horizontal parallel sides which share the same black 1x16 Technic beams, but are connected with string in an X pattern. The horizontal parallel sides are also connected with axles. These axles are compressed as the string "X" is tightened. The resulting structure is held stiffly together and does not wobble much. The string-connected truss works well, and is very simple to build. How it works is explained in the CONCEPT section. The key to building it is to tie the string tightly from joint to joint. This truss is light, easy to build, and very strong. It is well suited to make large structures with the capacity to handle heavy loads (see the Crawler Crane ).

Two other examples that use a truss:

Arched Truss Bridge

Straight Truss Bridge

The trusses are made from varying triangle sizes and they are not all right triangles. Their construction is very similar to the Large Truss Example above. The vertical parallel sides are composed of Technic beams, and the horizontal parallel sides connect the vertical parallel sides with strings in the X pattern.

The bridges differ from the above example in two ways:

1. 2x plates are used instead of axles (to connect the vertical parallel sides).

2. The main members are not "continuous" (Technic beams connected end-to-end with 1x plates). You'll have to go to the bridge links above to see this. The Arched Truss Bridge has a close up schematic of the joints.

The previous parts:

CONCEPT - The concept of a truss: how it works.

EXAMPLES - Look at real-life trusses (actual structures that exist).