Geevor
Scrapheap challenge
Name of school:
Names of team members:
Team name:
Name of Water wheel:
Mission Water wheel
Your task, should you choose to accept it, is a race against time to create a water wheel made
entirely of scrap materials. This water wheel must be able to harness enough power to pull a
cart up an inclined track. Great honour and prizes are to be won!
Prizes
We are looking for the wheel that will pull the tram the furthest along an inclined tramway in two
minutes. In the event of outrunning the track, the fastest time to complete the track will win.
Prize for taking part in Scrapheap Challenge - Certificate for every participant.
Prize for best team within each school - NSEW badges to each team member.
Prize for most pulling-power of all 5 Penwith Schools - The Geevor Challenge Trophy!
Rules
1.
The competition is open to one year 7 class from each school.
2.
Each class will divide into teams of 1-3 people (MAX. 16 teams).
3.
The wheel must be made only of scrap materials provided by Geevor
on the day.
4.
The construction of the wheel must take place entirely at Geevor, using the
equipment provided and within 1 hour.
5.
The wheel must be of a portable size.
Things to consider
On the following pages are some ideas you may want to consider when
devising your waterwheel.
What type of design do you think will be most successful?...
© Geevor 2011
Scrapheap challenge
Geevor
Parts of a water wheel
Wheel Shaft
Paddle
Winding Shaft
Wheel
Stand
Line to the tram
© Geevor 2011
Scrapheap challenge
Geevor
Design variation– Amount of Head
The head is measured as the difference between the height where the water enters the wheel
and the height where it exits the wheel. The more head, the more power the wheel can
harness from the water. Different types of water wheels have different amounts of head.
NB: At Geevor, you will have a tank of water with a non-pressurised pipe to drive your wheel.
4
Undershot Water wheel
3
The
water passes under the wheel.
2
Head = 0
1
0
4
Breastshot Water wheel
3
The water enters half way down the wheel
2
Head = 2
1
0
4
3
Overshot Water wheel
2
The water enters at the top of the wheel maximising
the head.
1
Head = 4
0
Design choice
Which type of water wheel design would you build to harness the most energy from the water?
Undershot
Breastshot
Overshot
© Geevor 2011
Scrapheap challenge
Geevor
Design variation– Wheel Shape
The shape of the water wheel may determine where the paddles can be attached to capture
the water. Traditionally a circle has been used with paddles at regular intervals around its
circumference, but other shapes are possible. Think about shapes that don’t have the same
radius around the centre compared to those that do, e.g. an ellipse may create a more
irregular turn than a circle—does this matter? Which is more important; the shape of the
wheel or the placing of the paddles?
Design choice
Circle
Ellipse
Pentagon
Triangle
Square
Cross
Other ideas...
Rectangle
© Geevor 2011
Scrapheap challenge
Geevor
Design variation– Paddles
To harness the most power from the water the paddles should be shaped to catch as much of
the water as possible and angled to hold on to it for as long as possible. You will only be
given a set amount of water and will have to make the most of it. Consider whether you need
many or few paddles—more paddles potentially hold more water so greater pulling power,
but also means more weight on the wheel to turn and possibly restricts water capture….
Design choice
Which type of paddle would you build to harness the most energy from the water?
Bucket
Flat
Angled
Curved
Few
Many
Other ideas...
© Geevor 2011
Scrapheap challenge
Geevor
Design variation– Wheel Size & Ratio
The weight of the water on the wheel’s paddles acts like a ‘lever’ to rotate the wheel around it’s
central point. The length of these ‘levers’ is the length between the paddles (on edge of wheel)
and the central winding shaft. Longer ‘levers’ have greater power to turn the wheel, and so
wind the string to the tram better, than shorter ‘levers’.
A larger wheel can have longer ‘levers’ (i.e. paddles further away from central shaft) and so
greater it’s potential to harness power from a large amount of water. BUT only if the water has
a lot of excess power. Only the energy left after the wheel has been turned will be used to pull
the cart. If the wheel is too big it may be too heavy to turn. If it is to small it may not harness all
the power available from the water and so be inefficient.
The ratio of wheel diameter to winding shaft
diameter is also important. The larger the
diameter the winding shaft, the less wheel
rotations required to wind the most string, so
may be quicker. BUT the larger the winding
shaft, the shorter the ‘lever’, and so less power
to turn the wheel, so may be slower.
Winding
Shaft
‘Lever’
To
tram
Wheel
Design choice
What radius would you consider using for your water wheel?
The largest diameter wheel possible to maximise water power
The smallest diameter wheel possible to save weight
The best diameter wheel to suit the water flow available
What ratio of wheel size to winding shaft will you use?
I will make a longer
‘lever’ by having a
large wheel and small
winding shaft.
I will make my winding
shaft diameter large to
winder the string
faster.
Other ideas:
© Geevor 2011
Scrapheap challenge
Geevor
Design variation– Stand
In order for the wheel to turn freely, it needs to be held upright above the ground. The
height it needs to be will depend upon the largest radius of the wheel. A larger wheel needs
to be held higher. The higher the wheel, and the heavier its weight, the more secure and
balanced the stand needs to be. Otherwise, the wheel might topple with the weight of the
water or the pull of the tram.
iu
ad
R
s
Wheel
Ra
d
Minimum
height for
stand
Design choice
What design of stand will be most stable?
ius
Minimum
height for
stand
Wheel
Wide-bottomed
Wide-topped
Base attachment…. Or…. Free-standing?
Straight
Symmetrical
Wheel held high….. Or…. Wheel held low?
...Or…
Asymmetrical
Thin
Wide
supports ..Or... supports
Wide-apart supports... Or…. Close supports?
© Geevor 2011
Scrapheap challenge
Geevor
Design variation– Winder & Friction
In order to pull the tram up the inclined track, the energy harnessed by the paddles of the water
wheel needs to be used to wind the tram’s string around the winding shaft. If the winding
shaft doesn’t turn with the wheel, the tram won’t move and all you would have made is a nice
water feature!
But how will you secure the moving parts to the stand, without stopping them from moving?
Also, you need to think about friction, which is caused by the moving parts rubbing together.
Overcoming unhelpful friction uses up precious energy so that a wheel has less energy left to
pull the tram. Often engineers will use oil or grease to help moving parts slide past each other
easier and so reduce friction. Alternatively, unhelpful friction on moving parts can be minimised
by using smooth materials, a smaller surface area or reducing the pressure (or weight) on parts.
Design choice
How will you fix your turning shaft to the stand?
Fix non-moving
axle to stand. Axle
goes through hollow winding shaft
and wheel.
Attach winding
shaft directly to
the stand
Fix a hollow
non-moving
shaft in stand.
Winding shaft
moves inside
No fixings but
a shaped
stand. Let
winding shaft
rest on top.
I will reduce unhelpful friction by:
Make a hole in
stand. Allow
winding shaft
rest in hole
Attach loose
bracket over
winding shaft,
to keep it in
place
Other ideas:
Using smooth materials for the moving parts
Reducing the weight on the moving parts
Reduce the contact area of the moving parts
Using grease on moving parts, if necessary
© Geevor 2011
Scrapheap challenge
Geevor
Design variation– Materials
The heavier the wheel, the more energy will be needed to turn it, and so less energy left to pull
the tram. The weight will depend on the types of material used and the amount of materials
used. Some materials can be strong but heavy, whereas others can start light, but can
become waterlogged and so heavier during use or may break. Although the scrap materials
available at Geevor will vary, you need to know what type of materials you want to look for, to
help your salvaging and give you more construction time.
Consider which parts of your waterwheel need which qualities.
Also, what types of fixings will you use for your wheel, as this will also affect the wheel’s
strength and endurance under the water!
Design choice
Tick which quality the following materials and fixings have best:
Strong
Water-proof
Lightweight
Smooth
(other)
Flexible
Wood
Cardboard
Plastic
Polysterene
Metal piping
Metal wire
(other)
PVA glue
Hot glue
Sellotape
Electric tape
Staples
Blu tac
String
(other)
What type of materials will you look for on the day at Geevor?
“It is most important for the following wheel parts, that it’s materials are…”:
(circle most appropriate)
Stand
Wheel
Paddles
Winding Shaft
Strong / Water-proof / Lightweight / Smooth / Flexible / ______
Strong / Water-proof / Lightweight / Smooth / Flexible / ______
Strong / Water-proof / Lightweight / Smooth / Flexible / ______
Strong / Water-proof / Lightweight / Smooth / Flexible / ______
© Geevor 2011
This page to be filled out on the day
Geevor
Scrapheap challenge
Name of school:
Names of team members:
Team name:
Name of Water wheel:
Your design specifications:
Water wheel type (Head):
Stand:
Wheel Shape:
Winder & Friction:
Paddle Design:
Materials:
Size & Ratio:
Other design features:
Final Design
Sketch your final waterwheel design. Note key features, both good and bad.
© Geevor 2011
This page to be filled out on the day
Scrapheap Challenge
Geevor
Results & Evaluation
Results
Distance:
Time:
Observations:
What happened to your waterwheel? Did it stand up to the challenge?
Evaluation
Why was/wasn’t your water wheel successful?
What design factors do you think are the most important to consider?
If you had a second attempt, how would you improve/change on your water wheel?
© Geevor 2011