For our Design Engineering for Physicists course we were tasked with the designing and building of a highschool project that showcases a physics principle. We decided to create a flywheel which demonstrates the conservation of angular momentum. To achieve this in the best way we wanted to build a suitcase with a flywheel in it, so that when you spin the wheel and lift the suitcase, you will notice the conservation of angular momentum yourself.
A heavy wheel with an axis around which it can move(diameter 38 centimeter)
Screws and nails
Wooden plates of different thickness
A tall gear for the pullstarter
A threaded rod(M10), with a bolt and a ring
Sand (with plastic bags)
A (electric) screwdriver
Step 1: Making the Frame
To start we made the top and bottom of the frame of the suitcase. We start by sawing the planks. Four planks of 40cm, these will be the base, two for each side. The need to be put together perpendicularly. The two center planks making up the frame are nailed to each other. Then you need to make eight fitting sloping planks, these will strengthen the base. The angled planks were glued to the center frame as you can see in the pictures.
The holes in the center were made by drilling through.They are 4 different sizes to accompany the different parts used on the wheel. One frame has two bigger holes to accompany the pullstarter and the part to which it connects. The second frame has smaller holes in the center to put the axle of the wheel in and to secure it, so the axle does not move. Also the first frame that holds the pullstarter has a larger hole filed out, to make space for the flywheel, as you can see in the third picture.
When the frames are ready you can add the pullstarter on top op the top frame, making sure it is well centered.
Step 2: Making the Wheel a Flywheel
Secondly we had to make sure the wheel has enough weight so that it can demonstrate the desired effect. Angular momentum depends on mass and speed. By putting sandbags in the wheel we added enough mass to achieve our goal. The sandbags were then closed in by a wooden plate, glued to the sides and attached with screws. The total weight is just over 4kg.
The flywheel also needs to spin very fast. For this we added the pullstarter. Attaching this to the wheel was a challenge, but by adding extra layers on the wooden plate that protects the wheel we were able to do it as shown in the last picture. You start with sawing a circle with a radius of about 17.5 cm and a smaller hole of a radius about 2 cm in the middle. Now we have a platform to put our "hill" of planks on, on which we can put the gear. The gear was slammed into a piece of plywood and is somewhat secured with glue. This piece sits on top of the "hill." To secure the "hill" we used glue at first to get it perfectly in the middle and after that we screwed it in place from the top and bottom. You need to make sure that the gear is perfectly in the middle and that the axle can still with through. When the sand is in the wheel you can fasten the whole plate to the wheel, making sure that the gear is perfectly centered.
(NOTE: it does not matter what side you put the sand in.)
Step 3: Putting It Together
So now we have the top and bottom of the frame and the flywheel, but we are not done yet. To attach the flywheel's axle, we put the threaded rod on the top of the axle and filed it to fit in the center of the pullstarter's allen head. Also the length of the rod should be about 9 cm, but this all depends on your axle that came with the wheel. Next we put the wheel in between the frame and used 4 extra pieces of plank to connect the top and bottom by screws, when finally adjusted the right way. The length of these vertical planks depends on the height that is required. We suggest that you put the wheel in the bottom frame and then try and put the axle on the allenhead in the pullstarter which is attached to the top frame and then measure the height. Also you need to be very careful with the height as the pullstart still has to make contact with the gear when pulled, but not when at rest. Finally we added a handle to lift the entire thing while the wheel is spinning.