Outcome

This is an addition to K'nex sets that will teach children 12 and up about about mechanical advantage. They can use this add-on set with regular K'nex sets to build small mechanical machines or build a Rube Goldberg machine.

Manufacturing of this toy will be more on the expensive side compared to other small toys. Cheap plastic isn't the best choice, because these parts should be durable enough to be used as actual gears. Metal parts may be too expensive to manufacture, so maybe something like acrylic can be used.

As for safety, these parts present a choking hazard, but the set is meant for ages 12 and up. As long as this doesn't fall into the hands of a young child, this toy is very safe.

Attach and football to the spring-loaded gun and shoot the football as far as you can. The spring compresses to store potential energy and locks into place. When ready, the trigger can be pulled to shoot the football into the air. Children ages 8 and up can use this to play catch, or can play around with different spring compressions and angles to learn kinematics and see what combination results in the largest distance.

This toy will be cheap to make, since all that is required is a football, cheap plastic, and a spring. Choosing a stiff enough spring so it doesn't deform with continued use is the most critical part of making this toy. The football will be foam, so there is little safety hazard in playing with this toy.

Water Hoops will teach kids how things move in water and will teach them about angles. One person uses the buttons on one side to maneuver the ball into their opponent's hoop, and their opponent uses the buttons on the other side to do the same. Depending on how the ball moves in the water, a thicker fluid may be used to show that things move differently in fluids with different viscosities.

This toy might be a little pricey because of the way it needs to be manufactured to contain the fluid inside. The buttons may get stuck, and it would be difficult to disassemble the toy to fix those buttons because the fluid needs to stay contained. As long as everything stays enclosed, safety shouldn't be an issue at all.

Reflection

There's a lot more to children's toys than you see at face value. Wind up toys, for example. On the surface it seems to simple to turn the crank and set the toy down to make it move, but the internal mechanisms to produce the walking action are far more complicated than a simple crank. Designing the toys with moving parts and figuring out how I might make them work was a challenge.