Fourth Meeting (Saturday, February 5)

Weighing the weights

Lever-and-Pulley Design

Setting up the Inclined plane-and-pulley design

3rd design: Inclined Plane-and-Pulley

Done with the inclined plane-and-pulley!

Inclined plane and pulley design

Our workspace

  
     Today we met at Ashley’s house, and we ended up experimenting with two different designs.
     First, we started making the new lever-and-pulley nifty lifting machine. We ran into a problem right away; there was no place to put the fulcrum. The only solution we thought of was connecting two wire ties and  making it hang off the top of the frame and putting the paper towel roll through the loop so it could act as the fulcrum. We taped the wire tie loop to the roll to stabilize the fulcrum. We used the textbook as a guide and attempted to create the most efficient lever we could possibly make, which was a first class lever. We read that the closer the fulcrum is to the output force, the greater mechanical advantage it has, so we followed this and tried to set up a first class lever. Unfortunately for us, although we spent ages trying to secure the wire tie onto the roll, we discovered a fatal flaw; we accidentally taped the wire tie near the input force, not the output, which would require more force than necessary.
    After we pried the fulcrum off and put it in its correct place, our lever was done. We hung the 600g weight off of one side of the roll, and on the other, we attached a string that was wrapped around a block and tackle pulley. The input weight was attached to the block and tackle pulley.  As we inserted weight into the input can, our machine was not moving at all. After much inspection, we found two problems with this design; first, the fulcrum was not flexible, which didn’t allow the lever to work, and second, the block and tackle pulley’s outputted force upward, not down, which meant that no downward input force could be applied to move the lever.     As a solution, we found that we could make an inverted block and tackle pulley to change the direction of the input force, but we didn’t bother experimenting with this because there was no way that we could think of that could create a flexible fulcrum for the lever.
    After that design, we decided to use a different combination of simple machines for our project; the inclined plane and the pulley. We decided to use a block and tackle pulley for a mechanical advantage of three, and a long inclined plane to increase distance and to decrease the amount of force needed. We were sure that this new design could help us make an efficient nifty lifting machine, so we started making a design and gathering materials.
    We set up the inclined plane with cardboard and a paper towel roll underneath the cardboard for support and made a block and tackle pulley. We tried to use the upward force that the block and tackle pulley exerted to try and lift the 600g can up the inclined plane by attaching weight to the pulley itself.
    We anxiously put weights in the input can, but nothing was happening. The weight was creeping up the inclined plane, but soon, our input weight became greater than 600g. When the input force is greater than the output force, there is no mechanical advantage, which does not meet the requirement of our assignment.
    We wondered why this was happening, because if we pushed down on the input can and let go, it was enough force for the weight to go up 5 cm. We figured out that this was happening because of friction. The friction stopped the weight from going up 5 cm like it was supposed to. We attempted to put plastic, matchbox cars, snowboard wax, and lip balm beneath the input can to reduce friction, but it still required too much friction. This machine was not successful because of too much friction. However, we thought that this machine could create positive results, so we decided to stick to this plan and replace the string with metal wire to reduce friction and think of other ways that could also reduce friction that was being caused by the inclined plane.
    This meeting taught us how different a design on paper and an actual machine is. There was so much friction, and we learned that it can hurt our machine because lots of energy is being wasted. Next meeting, we are going to stick to the inclined plane-and-pulley design and try and think of more ways to reduce friction.