Going up?

The pre-K/K kids have been really interested in machines for a few
weeks now. When I first heard about that interest, I (with Linus's
permission) brought our set of Gears!Gears!Gears! to the room for a
long-term loan.  Since then, I have seen kids playing with the gears
every morning I drop Linus off.  When we saw a slightly more advanced
set of Gears!Gears!Gears! in Costco one Sunday (with different size
gears and a loop gear, plus some non-gear bells and whistles), it was
a no-brainer to buy that and bring that for a long-term loan as well.
The kids seem to really be into it.

So I thought of building on that interest by doing something with
pulleys, and I settled on building a simple elevator as an activity
which seemed doable, but still challenging enough to be interesting.
I borrowed a big old pulley from the physics department, brought some
of my own ropes and weights, and counted on the school having some big
dairy cartons and a decent place to hang the pulley.

After some looking around and testing, I settled on a certain tree
branch as a good place to hang the pulley, and I found a dairy carton
big enough for a kid to climb into.  With the first group, I started
from scratch, asking them what they thought would be necessary to
build an elevator, and they suggested a basket (they even found one)
and rope (which I supplied).  They needed a bit of prodding to suggest
a pulley, but they got that too after I suggested looking above my
head.  Most of them didn't really know what a pulley was, so we
discussed that.  I strung a rope through it and we each verified that
pulling down on one end of the rope made the other end go up.  The kid
were really excited at this point!  It was difficult for some of them
not to grab the rope, jump up and down, etc.  I pointed out that one
advantage of the pulley is that the puller (the kids in this case, a
motor in real life) need not be on the roof to make the elevator work.

Then I attached the large milk carton and put some heavy object in it
for a first test.  The more excited kids volunteered to pull on the
other end of the rope.  They were able to lift the elevator, but it
was quite difficult; they had to recruit help and I think it was
successful only with four boys pulling at once.  I warned them that if
they let go suddenly, the elevator would crash to the ground and hurt
the (imaginary) people in the elevator.

So I asked them to think about what could make the pulling and the
letting down easier and safer.  They thought of all kinds of crazy
ideas before they spotted my weights.  So I attached the
counterweights (in a small basket so we would adjust the amount of
counterweight) and we saw that the elevator was much easier to lift
and also easier and safer to let down.  So then we were ready to give
rides.

The problem was that the dairy carton tilted too easily when lifted
off the ground, threatening to dump the passenger out.  I tried to
stabilize it with additional ropes and by telling the passenger to balance,
but it never really worked.  So starting with the second group, I
forbade rides.  Instead, we used three containers full of sand to
represent three people.  This was actually nice for the lesson because
I was able to put in just enough sand to balance the particular
counterweight I had; with a human passenger, the counterweight was a
help, but never really made it super easy to ascend and descend.  With the fake
passengers matched to the counterweight, ascents and descents were very easy,
and I could tell the "motor" to let go, simulating a broken motor.  The elevator
did not crash to the ground because it was attached to the just-right
counterweight.

So, once we got it going smoothly, I repeated these steps for each
kid: remove the counterweight; ask them to lift the passengers to the
top floor and have them discover how difficult that is; have them feel
how tricky the descent (from whatever point they reached) is; after
finishing the descent, add the counterweight and ask them to lift the
passengers to the top floor and see how easy it is this time; ask them
to let the passengers descend safely and feel how easy that is; ask the
motor to "break" and see how the passengers do not crash to the ground
because of the counterweight; finish the descent and start over with
another kid.  I repeated this whole cycle about a million times
because many kids wanted to do it over and over!  I was exhausted by
the end.

This was a pretty simple activity and the kids had a lot of fun.  This
is a good lesson for me because I'm often tempted to think that a
potential activity is too simple and that I have to add a lot to it.
Simple can be good!  If I ever try rides again, I need to experiment
beforehand how to make the elevator "car" tip-proof.  But I think the
rides may have been a distraction.  Each child was quite happy in the
"motor" role, so much that they wanted turns over and over, and of
course the motor role is the instructive one.

A small improvement would be to use two pulleys, to give some
horizontal space between the elevator car and the counterweight.  One
thing which would take this to the next level would be to crank the
whole thing with some gears attached to a drum which winds up the
rope.  I'll keep my eye out for surplus equipment which might be used
for this.  And for a toy gear set with these kinds of pieces, which I
will then have to buy and put on long-term loan!