The type of joint you use on your bridge can drastically change its strength.

Lap Joint:

The lap joint is one of the strongest, and you should use it whenever you can. It strengthens compression members because it adds stiffness. The lap joint has one drawback, however. The joint is only as strong as the face of the wood. That means that only one part of your piece of wood is in contact with each other. The face of Balsa wood is typically not strong, and tears easily. So make sure your lap joints have plenty of surface area for the glue.

End Joint:

The end joint is not a very strong joint, especially for tension members. In tension, the two pieces of wood will just pull right away from each other. In compression, this joint will allow the piece to bend in a perfect arc. The lap joint holds the piece stiff, which does help it to hold more.

Notched Joint:

The notched joint gives more strength than the end joint, but less than the lap joint. It is more difficult to build, so it is not very common.

Gussets:

If you have to use an end joint, it is a good idea to add a gusset to make it stronger. The gusset creates a lap joint, which is strong in both tension and compression. Usually I try to make each part of the gusset the same length. If there is more glued to one piece, the one with less surface area for the glue will pull away first anyway.

Post Tags: bridge, building, gusset, joints, tower

761 views |  Print this Post |