It's A Matter Of Balance
The Home Handyman|July/August 2020
It's A Matter Of Balance
In this fun marble machine project we’re going to use basic hand-tools to create a toy for the learning experience of the force of gravity, balance of mass, the laws of momentum for which the basic design dates from the 19th century where it appeared as a toy made by the Amish community for their kids. What more could you want from a project?
Jeff Hollingdale

Since early times everything from trade to toys and games has relied on balance to perform. See-saws to weighing scales and more, the scientific properties of why it works gradually appearing from the work of a many among whom Isaac Newton to Henry Cavendish are well known. Cavendish explained the relationship between gravity and mass, rotational force which advanced our knowledge to the age of space exploration.

You can follow the design details which follow, scaling it up or down to suit your own changes. In this view, the counterweight is fully down with the marble cup in position to receive a marble by pushing-up against the pin which tilts-up the round disc which releases one marble.

The marble cup then descends as the weight of the marble overcomes that of the counterweight. The counterweight rises. The marble drops into the marble box allowing the weight of the counterweight to bring the marble cup up again and repeat the cycle. The cycle will continue until marbles are released to the marble box.

For this project, a few basic hand tools are required, a fretsaw, a power drill plus bits; a 16mm Forstner or spade drill bit plus some scrap lengths of 3.5mm MDF, 15 x 5mm hardwood lath. Some other scraps of wood – pieces required are detailed in the drawings. I got a lot of the wood I needed by scrounging the waste bins at my local hardware store. In addition, you will need a length of 6mm dowel rod, some 8mm nuts and washers.

Step-by-step guide

Step 1: Begin by making the top marble track and the support framework. Mine was made from scrap pieces of 3.5mm MDF and hardwood strips and offcuts left-over from other jobs. You can adjust the pieces to assemble in other thicknesses or materials. A key factor is to check the average diameter of the marbles you will be using, mine were around 15mm in diameter. If you are using bigger marbles adjust the width of the track and the exit hole to suit.

Cut two strips of 15 x 5mm pieces 280mm long. Cut one piece of 3.5mm MDF, 300mm x 27mm. Using a Forstner drill, cut at one end a 16mm hole. (if you don’t have such a drill, use a Spade bit drill); offset the hole 45mm from the end. Also drill a 7mm hole offset by 20mm from the end.

Using wood glue, glue the 15 x 5mm strips flush to the edge of the MDF. Note the strips are offset by 40mm from the end with the two holes drilled into it. The drawing which follows shows dimensions and how to assemble.

The marble release is a wood wheel left over from a toy project with a piece of 6 x 50mm dowel glued into it. The steel washer and rubber tap washer are mounted after the wood wheel is inserted through the 7mm hole. We’ll see how this looks, later.

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July/August 2020