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?...
Parts of a water wheel Wheel Shaft Paddle Winding Shaft Wheel Stand Line to the tram
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 3 2 1 Undershot Water wheel The water passes under the wheel. Head = 0 0 4 3 2 1 Breastshot Water wheel The water enters half way down the wheel Head = 2 0 4 3 2 1 0 Overshot Water wheel The water enters at the top of the wheel maximising the head. Head = 4 Which type of water wheel design would you build to harness the most energy from the water? Undershot Breastshot Overshot
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? Circle Ellipse Triangle Pentagon Cross Square Other ideas... Rectangle
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. Which type of paddle would you build to harness the most energy from the water? Bucket Flat Angled Curved Few Many Other ideas...
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 Wheel Lever To tram 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:
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. Radius Radius Wheel Minimum height for stand Wheel Minimum height for stand What design of stand will be most stable? Wide-bottomed Wide-topped Base attachment. Or. Free-standing? Straight Symmetrical Wheel held high.. Or. Wheel held low?...or Asymmetrical Thin supports..or... Wide supports Wide-apart supports... Or. Close supports?
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. How will you fix your turning shaft to the stand? Attach winding shaft directly to the stand Fix non-moving axle to stand. Axle goes through hollow winding shaft and wheel. Fix a hollow non-moving shaft in stand. Winding shaft moves inside No fixings but a shaped stand. Let winding shaft rest on top. Make a hole in stand. Allow winding shaft rest in hole Attach loose bracket over winding shaft, to keep it in place I will reduce unhelpful friction by: 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
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! Tick which quality the following materials and fixings have best: Wood Cardboard Plastic Polysterene Metal piping Metal wire (other) Strong Water-proof Lightweight Smooth Flexible (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 /
This page to be filled out on the day Geevor Name of school: Names of team members: Team name: Name of Water wheel: Your design specifications: Water wheel type (Head): Wheel Shape: Paddle Design: Size & Ratio: Stand: Winder & Friction: Materials: Other design features: Final Design Sketch your final waterwheel design. Note key features, both good and bad.
This page to be filled out on the day Geevor Scrapheap Challenge 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?