A Home-made Balance Scale

If you want to get into amateur pyrotechnics, a scale is essential. A commercial triple-beam balance scale can cost $85 to $100. Electronic scales will cost you at least as much. If this kind of expense is a big obstacle to your pyro ambitions, then you might be interested in this low cost plan to build a balance scale.


The heart of a balance scale is the balance beam. This plan uses a piece of hobby poplar, 1/2" X 1 1/2" X 16". You make a low resistance fulcrum with two sheet rock screws which protrude slightly from the beam to form the bearing points.
Some careful precision is needed to ensure that the screws are placed on a line which is perpendicular to the line of the beam. I used a T-square to draw the line and a drill press to drill guide holes for the screws.
The ends of the beam are constructed as shown to lower the swivel point of the weight pans. This is done by simply gluing another block of poplar to the bottom of the beam at each end. Next, the hooks are added from which the weight pans are hung. Finally, pieces of threaded rod are screwed into the ends of the beam and 2 or 3 nuts are screwed onto the rods. These are used as adjustment weights to cancel any asymmetries in the balance beam.
A pointer stick may be added to make it easier to detect when balance has been achieved while measuring chemicals. I used a left over piece of a model rocket kit and sharpened one end for the pointer. This is simply glued on with help of a square for alignment.
Weight pans can be suspended from the beam ends in many different ways. My first method used 2 loops of nylon kite string threaded through a square piece of fiber board bathroom paneling. A later improved method used coat hanger wire to support the weight pans.
The final part of the project involves constructing some kind of a stand for the fulcrum bearing surface. This can be accomplished with a simple vertical piece of wood which has a small metal plate mounted on top. A shallow groove is scored in the plate and the sheet rock screw points of the balance beam are placed into the groove. I used a surplus microscope stand for my scale. I then made weights from pieces of plumber's solder which were weighed on a high precision electronic scale and trimmed to the desired weights. The final result is a scale which is highly accurate and incredibly cheap to make.

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