Instructions

DEFINE THE PROBLEM

Ask students what they know about wells. Have they seen pictures of wells in storybooks? Together, ask them to draw a well from memory or consult a picture.

Share that a winch is a mechanism that lowers and raises the well’s bucket. Point out the posts, crank, drum, and rope in the picture, and then explore with them how a winch works. Ask:

• How will the drum and crank need to work together? How can you keep the crank from slipping?
• Why are the supports important? Which force(s) are they resisting?
• How do pulleys work? How can you use pulleys in your winch to make it lift the bucket better?

Share the challenge, success criteria, and constraints with students. Ensure that each team has a suitable ledge from which to lower and raise their buckets and let them know whether they can tape directly to a flat surface or if you want them to build their winches on bases.

BRAINSTORM SOLUTIONS

Ask teams to explore the materials to start generating ideas for designs.

Encourage them to sketch some ideas for how to build their own well winches, keeping their materials and constraints in mind.

BUILD AND TEST

Tell teams to build their winches. How should the bucket attach to the string so that it so that the contents don’t spill out of the bucket? Will it matter which way the drum rotates to wind the string up or let it down?

For the test, one team member should be ready to measure how far down the bucket can drop, remembering that it needs to drop by at least one foot. Another team member may need to hold the base of the winch steady, if it has been built on a base.

Once the bucket is lowered, fill it to the brim. Then slowly raise the bucket to the lip of the ledge, or as high as it can go.

EVALUATE AND REDESIGN

How well did the winch work? Ask each team to describe their results, including any problems they encountered. For example, if the drum didn’t turn, what did the team change to make it move? Engineers rarely get it right on the first try and they learn a lot from their mistakes. Each team should listen to the others so that they can get ideas for improving their own winches.

Make improvements and try their winches out again.

Or, try a different version. Can teams make a winch that lowers a bucket into a bowl of water and brings the full bucket up again, the way a real well winch does? What if they made a bigger winch that hangs from part of the playground? How heavy a load could it hold?

Engineering & Science Connections

Simple machines are tools or devices that help us accomplish tasks. They make work easier by providing a mechanical advantage, which is how much force the simple machine adds to our efforts. The handle that rotates the drum of the winch is the part that provides a mechanical advantage. It makes it possible for someone to pull up a heavy bucket of water that they’d never have the strength to do otherwise.

When you pry open a can or move up and down on a seesaw, you are using the simple machine called a lever. In modern winches, there are two kinds of levers. The handle of the winch is one lever. The other is the gears inside the drum; these produce torque, the twisting force of rotating around an axis, which is the drum of the winch. The faster the winch works, the more rope it pulls every time the handle rotates, and the less powerful it is. The more slowly the winch turns, the more power and torque it produces.

The kind of winch used to hoist water from wells was known as a windlass. Nowadays, a windlass is a big winch that raises and lowers anchors from boats. Boats also use windlasses for hauling mooring lines. A chain or cable winds around a barrel, and a crank attached to the barrel rotates it. For big ships, engineers have created a windlass that distributes the very heavy load of the anchor among many cables instead of just one. A system of pulleys—another example of winches—works together to coordinate the cables and work the anchor.