Hello Seabrook,
OK. Let's address the question in a few parts
- constructing the Ferris Wheel
- the "physics" of a Ferris Wheel
- getting the Ferris Wheel to school
- other resources that may be helpful
Constructing the Ferris Wheel
There are three main parts that need to be made:
- the frame to hold up the wheel
- the wheel itself
- the cars that hold the passengers
I assume the wheel will NOT be motorized and your child can turn it by
hand. Make a clarification request if you want ideas on how to drive
the wheel. I also assume you do not want to use a construction kit
like Knex (which does have a ferris wheel model)
The frame needs to be reasonably strong but open. A narrow / tall
cardboard box could be cut to make the frame (an "A" frame or inverted
"T" or "Y" shape). A dowel (or a long nail or a round stick from a
hard candy) serves two purposes
- the pivot for the wheel
- holding the two parts of the frame apart / strenghtening the frame
The pivot does not have to turn so it should be taped / glued to the
frame after the wheel is installed.
You could build a frame from any suitable material, wood (even balsa)
for example would be good. I recommend cardboard since it should be
strong enough and easy to cut / fold / glue into the right shape [plus
the only balsa I ever bought was for science projects].
The wheel is an interesting problem. You may get away with something
as simple as plastic straws (available from the grocery store / not
the bendy ones) for the spokes of the wheel. A 10" straw could have a
hole at the midpoint (to go through the pivot) to form a relatively
small wheel (10" diameter). If you have bendy straws, cut off the
bending part and use a hub.
If your pivot is too large or you want a larger wheel, something else
must be used to serve as the hub. The cardboard from the back of a pad
of paper is one alternative. Again balsa wood or some other material
would work as well. Cut to shape with a hole in the center.
Around the outside, I would use the same type of material (e.g.,
straws) to connect the spokes. If you use round toothpicks as the
pivots for each car, tape or glue the toothpicks to the straws (small
holes in the straw ends). I suggest you lay out each wheel on a table
and make everything fit before starting to assemble the wheels /
pivots / cars.
I would also suggest a simple "guide" to make sure the wheels are
round. Something as simple as a circle drawn with a pencil / string
will help with layout and assembly to make the wheel turn more
smoothly.
The cars do not need to be very strong and could be made from paper /
perhaps colorful paper to make the wheel look more interesting. The
cars could be "A" shaped with a pivot hole at the top of the A and the
passenger holding part of the car at the bottom of the A. Other shapes
should work as well as long as most of the weight is on one side of
the pivot hole. Put a relatively large hole (compared to the car
pivot) to make sure they turn freely.
Assembly should be straight forward once all the pieces are made. Something like
- assemble the two wheels (but not yet connected to each other)
- place pivots / cars to connect the two wheels
[confirm the cars pivot freely]
- put assembled wheel onto main pivot and secure onto the frame
You may want to decorate the pieces prior to final assembly. I would
try to avoid having to work on the wheel once it is assembled.
If you want to have passengers "fall out" as described in
http://www.nwrel.org/msec/nwteacher/spring2002/lingua.html
[about 2/3rds of the way down] you could fix one (or two) of the cars
so it does not pivot. If you do this, passengers should be something
light (that will not break nor break the wheel when they drop);
perhaps a paper cutout.
I also found a nice picture of a Ferris Wheel made by an 8th grade student at
http://www.ebecri.org/custom/hopkins%20rides.html
(down near the bottom)
Ferris Wheel Physics
Much of the material on the web on "Ferris Wheel Physics" is written
by college students for their reports (college level physics). The
main reason the people do not fall out is that described by
"siliconsamari" (the wheel moves too slowly). It is a little more
complicated than that however.
When the wheel is stopped, gravity pushes the cars so they are below
the pivot. As the wheel spins, the inertia of the cars makes them want
to "fly out" from the center. This effect is actually enough to
measure, for example:
http://home.snu.edu/dept/physics/frontier/presentations/Ferris%20Wheel.ppt
describes a project done by college students to measure the effect.
The effective force on each car (or passenger) is equal to the "sum"
of the forces. So we have:
- gravity pulling down
- the spin / inertia pushing out from the center
so the resulting force will vary as you go around the wheel (in both
direction and magnitude). The magnitude in the vertical direction
(preventing you from falling out) looks something like a sine wave,
centered on "one G" and the minimum is well above "zero G".
I would check several of the sites found with phrases like
ferris wheel physics
or
ferris wheel physics
and look for charts that illustrate this as well (be sure to reference
the original sources in your report!).
Consider the pivot (for the cars) to be a "hinge". Note that the pivot
allows the car to stay oriented "down" so the passengers are safe. You
can illustrate this with the "fixed" car as suggested before.
For a pulley, that is sometimes used in the Ferris Wheel to spin the
wheel. I have seen other wheels that are spun with gears instead. The
pulley is attached to the hub of the wheel, the loop goes to another
(much smaller) pulley on the motor, and as the motor spins the wheel
will spin as well. The ratio of pulley sizes will help control how
fast the large wheel spins.
Getting the Ferris Wheel to School
My oldest son (now 16) discovered that it is HARD to get a large
project to school on the bus. He also did not figure this out until it
was too late and had to fix it at school. A few tips:
- smaller is easier to transport
- a repair kit (an extra part or two, glue) should be brought just in case
- a sturdy box / padding can help
- a bag around the project to catch pieces that fall off or break
- some assembly at school is OK but practice at home
Note that mom / dad could take the project to school - but I do not
know your circumstances. [I know I didn't do that...]
Other Resources
Knex toys (available from several sites)
http://www.iqkids.net/knex.html
The Ferris Wheel kit is in the lower right (may need to scroll) and
was priced at about $50. Has a nice picture of the assembled kit.
"Amusement Park Physics"
(ed. Carole Escobar, pub. Amer Assn of Physics Teachers, 1994)
See if your local library (or college library) has a copy of this book.
Search phrases for more information:
Ferris Wheel Physics
Ferris Wheel Physics "high school"
Newton's laws
elementary explain [put a physics phrase here like inertia, hinge, pulley, ...]
elementary science project
elementary science project ferris wheel
"high school" science project
knex ferris wheel
Please make a clarification request if some part of the answer is
unclear or you need additional information on some part of the answer.
--Maniac |
Clarification of Answer by
maniac-ga
on
27 Feb 2005 11:35 PST
Hello Seabrook,
Let me take the follow up points in order.
#1 Difficult to visualize the construction of the rest of the model.
It would be nice to have a step by step assembly guide on line, but I
could not find one.
I believe you understand how to make the frame. For the cars, they can
be just about any shape as long as they have a loop (or hole) on top
to mount onto the bars that separate the two wheels of the Ferris
Wheel. I was thinking something shaped like an open top bag with
handles but another shape should work as well.
To make the big wheels of the Ferris Wheel, I would start with a
circle (say on a big sheet of paper) with the diameter matching the
length of the spokes. If you use 10" straws, that would be a 10"
diameter circle. Mark the center as well. Lay the spokes (let's say 8
of them) evenly and measure the distance between the spoke ends to
figure out how long the outside pieces will be. I would build one
wheel as a "sample" and make sure it spins smoothly before you build
the second wheel (or throw the first away & make two new ones more
carefully).
Once you have two wheels you need to separate them by a short distance
with the pieces that will hold the cars. I suggested using toothpicks
- below you mention "metal bars". I am not aware of any "easy" way to
do this assembly step - other than having two hands hold the wheels in
place while another person separator pieces and cars into place. This
should give you the wheel assembly, ready for mounting on the base.
Putting the wheel onto the base should be similar to putting a wheel
onto a bicycle.
#2 Do you know what materials were used in that model? It looks like
some type of metal.
Look at
http://www.ebecri.org/media/MVC-011F.JPG
for reference [apparently the picture on the web site has MUCH more
detail than what you see on the page...]
I cannot be certain but...
- the frame looks like a premade bar - I have seen thin steel bars
drilled like that (but not a "household item") so you are probably
correct. The axle may be a threaded bolt. Also note there are
reinforcing bars between the A frames low in the picture (appear to be
glued on).
- the spokes are attached to a hub - perhaps a thick wooden dowel
with a hole in the middle for the axle (or as I said before "pivot for
the wheel"). The hub could also be a cardboard tube (like for paper
towels) but then you would need end covers with holes for the axle.
Cannot be sure of the spoke material - could be wooden dowels, plastic
straws, or something else. Note also the reinforcement pieces - I
believe this was necessary due to the size of the wheel. If the wheel
is relatively small (like the 10" one using straws) the reinforcement
may not be necessary.
- the chairs (or cars) appear to be a combination of paper and pipe
cleaners. Again it is hard to be sure.
Much of the Ferris Wheel appears to be glued together other than the
frame which appears to use threaded bolts and nuts.
#3 What would we use to make the car hang freely from the metal bars
between the two wheels.
A loop (or hole) of some kind. Expanded more on #5.
#4 Unable to tell where the round toothpicks fit in.
OK - metal bars (perhaps pieces of a wire coathanger) would work.
Otherwise, replace the "metal bars" between the two wheels with
toothpicks. [I was trying to use "household items"]
#5 I saw your note to put a hole in the top of the paper car. How and
what would we use to attach the car to the bar? Are you able to
diagram the construction of the car? Show how it is attached to the
bar between the spokes?
Diagrams are hard when using text only and I did not find a suitable
picture. I was thinking of something like a bag with handles for the
car and the toothpicks (bar) serving two roles:
- separating the two wheels of the Ferris Wheel
- going through the loop (or hole) to hold the car in place
Note that if you take a bag with handles and put your arm (or a dowel)
through it, the bag should rotate smoothly. You could cut a piece of
paper / fold it to make a "car" with the hole on top to put the
toothpick (bar) through.
Another way to look at this is a curtain rod (separating the wheels)
and the hooks that hold up the curtain.
From the picture example - if they used pipe cleaners, you would make
a loop with the end of the pipe cleaner to go around the bar
separating the two wheels.
#6 You kept mentioning pivot and pivot hole.? Pivot for the car and
pivot for the frame? Where is that? That is the part that I am not
understanding.
Think axle for the wheel for the "pivot for the frame". [and in
retrospect I should have used that word...]
The "pivot for the car" works in a similar way. The bar between the
wheels that holds up the car is what I was referring to. It is
important that the car move smoothly on the bar (or pivot) - that's
why I used pivot instead of "separator" or "bar" or some other term.
Good luck with the project and let me know if you need further clarification.
--Maniac
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