How to Build Your Own K'NEX Soma Set

Scott's K'NEX Soma Set

Scott's K'NEX Soma Set

You can build your own K'NEX Soma Set using just the standard pieces in the original K'NEX building sets. The secret to creating correctly-proportioned pieces is to join together identically-sized cubes so that the resulting Soma pieces will all fit together properly. This becomes evident when thinking of the entire Soma cube (right) as consisting of 27 identically-sized cubelets.

The rest of this page details the procedure for building the K'NEX Soma Set.
K'NEX Soma cube

Here are the piece counts required for the K'NEX Soma Set:

K'NEX Piece Description Quantity Needed
White Connector 122
Yellow Connector 134
Purple Connector 354
Red Connector 216
Orange Connector 19
Dark Grey Connector 36
Green Rod 898
White Rod 757
Blue Rod 12
Yellow Rod 32
Black Rod 2

Total 2582

The K'NEX Soma Set construction technique consists of the preparation of 27 cubelets, each with one or more open faces that are used to connect it to other cubelets. This approach provides a smaller and more varied part count than using a closed structure for all walls of a cubelet, and provides space for internal bracing that makes for sturdy Soma pieces. These cubelets can be organized by the number of open faces that each has (visit SomaSite for a definition of the terminology used for Soma pieces):

Soma Piece Cubelets with
One Open Face
Cubelets with
Two Open Faces
Cubelets with
Three Open Faces
Y 3 1
3 2 2
9 2 2
L 2 2
Z 2 2
T 3 1
V 2 1
Total 16 9 2

Cubelet Side All cubelets are based on the same construction technique, which will be illustrated here first for a cubelet with one open face.

Four sides of this cubelet are each constructed as shown (left). Sixty-four of these assemblies are required to build the sixteen cubelets that have one open face.
When the four sides are assembled, the resulting cubelet (right) begins to take form. The open face of this cubelet will be aligned along the smooth edges of the yellow connectors. First Stage of Cubelet
Back Side of Cubelet The back side of the cubelet (left) is added using a similar arrangement consisting of a white connector and white and green rods.
The pieces shown (right) are used to construct sharp "corners" on each cubelet. These are the only standard pieces that can be used to create a smooth corner; scaling the Soma Set with larger pieces produces too much of a "stub" protruding from the corner. Eight sets of these pieces will be needed to form the corners of one cubelet. Cubelet Corner Pieces
Cubelet with Corners The cubelet (left) is shown with all eight of its corners added. Note that the red connectors on the open face are oriented with their flat sides in alignment with the flat edges of the yellow connectors. This makes it easy to abut this face of the cubelet to the open face of another cubelet.
The cubelet (right) is now shown in its completed form. A single yellow rod has been added to provide diagonal internal bracing without blocking the opening. This opening is also used for longitudinal bracing consisting of yellow and white rods joined by an orange connector. The longitudinal bracing is used to hold adjacent cubelets together. Dark grey connectors attached to each end of the bracing are inserted over white rods in the outer face of each cubelet (these white rods may need to be removed temporarily to allow the bracing to be added).

Finally, two white rods are attached to the remaining "teeth" of the red connectors at opposite corners of the open face. These rods will be attached in a like manner to red connectors of the next cubelet. This connection may be made more easily by detaching just the two corresponding red connectors from the next cubelet, connecting them to the white rods, then attaching the cubelet by sliding its open green rods over the exposed red connectors. The orientation of the diagonal yellow rod and the two white connecting rods can be switched as needed to line up with attached cubelets and provide room for internal longitudinal bracing.
Completed Cubelet
Cubelet Connections This image (left) shows details of the connection between two adjacent cubelets, with only a small portion of the foreground cubelet shown. When connection is complete, the longitudinal bracing prevents the attached cubelets from separating along the free play in the white rods connecting the cubelets.
This cubelet (right) has two adjacent open faces. A blue rod is used to complete the cubelet edge between the open faces and provide internal support. Red connectors at each end of this blue rod are oriented in such a way as to preserve openings at diagonal corners for white rods connecting each face to the next cubelet. Longitudinal bracing is not shown, but needs to be added later as determined by the geometry of the Soma piece being constructed. Cubelet with Adjacent Open Faces
Cubelet with Opposite Open Faces This cubelet (left) is a different version of the previous design, but with its two open faces opposite each other as required for the Soma L piece. The front and back of this cubelet are identical. Longitudinal bracing can still be used with this cubelet, but it will run completely through its interior, connecting to the other cubelets in the Soma L piece.
This cubelet (right) has three open faces and is used in the Soma T piece. With proper arrangement of the red connectors, white connector rods can be oriented at opposite corners of each open face. Cubelet with Three Open Faces
Cubelet with Three Open Faces This cubelet (left) has three mutually adjacent open faces, and is used in the Soma Y piece. With proper arrangement of the red connectors, white rods can be oriented at opposite corners of two of the three open faces. White and green rods attached with an orange connector form the cubelet edge between two of the open faces.
This image (right) shows the brace used to connect two adjacent cubelets together. Sixteen of these braces are required in the complete Soma Set. Two-cubelet Longitudinal Brace
Three-cubelet Longitudinal Brace This image (left) shows the brace used to connect three cubelets together in a line. Two of these braces are required in the Soma Set, one each for the L and T pieces. The brace runs slightly on a diagonal to connect white rods at opposite corners of the Soma piece faces.

The completed K'NEX Soma Set can be used for thousands of creative designs! For more information on the Soma puzzle, and a gallery of Soma designs, visit SomaSite.


Copyright © 2002 Balmoral Software. Portions copyright © 2002 K'NEX Industries, Inc. All rights reserved. Republication or redistribution is expressly prohibited without prior written consent.