Cranking Device Dilemmas – say that three times fast! Ha! It’s hard to say, I know!
These challenges were also hard to invent a good name for. One of them is just called… “Cranking Devices”. #clever The other is called “Rescue Devices”. The two challenges have similar features, but share the dilemma of that crank!
So, what exactly is a crank? That is a great starting point for these challenges and it is exactly where I started with groups of students as we tested these.
A crank is a device that you turn in order to make something move. That is the simplest definition I could find. And I found many- some of them really inappropriate and also one that means a really unpleasant person. For these challenges a crank is something you turn to make your job easier.
So, what is the purpose of this task?
In both of these cranking device dilemmas, students are trying to rescue someone that has fallen over a cliffside. The person is not hurt. They just need help getting out! In one challenge we rescue Legoman and in the other the passenger carrier brings up cargo.
Students must design a structure that will lower a passenger carrier to the bottom of the cliff and then successfully wind back up to the top.
Cranking Dilemma #1: Why does it need a crank?
In my test class students made a device like the one pictured. Their idea was to just “wind up” the rescue sled.
Now, this will work, as long as you are rescuing a bunch of mini-marshmallows.
But, what if you are trying to wind up a 200 pound person? Can you really sustain that winding motion with a heavy weight?
Now, we have to back up and think about the materials being used for the device. The idea with this challenge is that a group of people are hiking. When the person falls over the cliff the rescuers must use what they have on hand. I mean, do you go hiking with rescue tools? Probably not, but if you needed to build something what would you use?
You would use what you have in your backpacks – bungee cords, rope, carabiners, cutting tools, duct tape. You might have a tent pole or walking sticks. You would also grab things found right there on the trail- say a tree limb.
Now, just suppose that cranking device in the photo above was made of rope, tree limbs, and bungee cords. Would it work? I would say, yes! But could you twist a heavy tree limb? This made students think more about this dilemma!
Cranking Dilemma #2: You really need that crank!
After talking about the reality of the heavy tree limb, my students were still not convinced.
So, I brought out my tree limb! Yes, I have a tree limb in the lab that is about an 8-inch diameter and about 3 feet long.
You would be shocked at how heavy this is. Students definitely were!
They tried, but with that very small tree limb, they soon realized that turning it without some sort of handle was going to be extremely difficult. Hence, the cranking device dilemma!
So, they were now convinced a crank was needed. Take a look at that photo above. Isn’t that super! The string winds up around the “tree limb” that is being turned with a handle made from the flexible part of the straw (tree limb).
Speaking of materials… We used string for the rope, rubber bands for the bungee cords, masking tape for the duct tape, and dowel sticks or straws for the tree limbs.
Cranking Dilemma #3:What we need is a pulley!
I totally agree with this! But, would you be carrying around a pulley in your backpack on a hike? Probably not!
The team in the photo decided to make their own pulley. They attached a handle to the far side of it that you cannot see!
In this photo you can see how far it was to the bottom of our “cliff”. That is a 3-foot drop.
You can also see Legomen being rescued in that bucket.
The materials in these two cranking challenges are slightly different. The one in the photo is the Cranking Device challenge.
I know- it’s confusing.
Here is another difference in the two cranking device challenges.
In the Rescue Device challenge, students work in two teams. One team builds the crank and the other builds the passenger carrier. The teams then join together the two parts to make them work!
It’s a really interesting way to complete a challenge. The two teams must work together constantly to make sure the parts fit and work.
Cranking device dilemmas, indeed! #right Either challenge is a win-win with students. They really enjoy the back story about falling over the cliff and rescuing someone or something. Click on any of the images to see these resources in my Teachers Pay Teachers store!
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