Compound Machine Project
Team: Danielle Morris, Noah Zahm, Daniel Deng
Date: September 23rd, 2015
Problem Statement:
A compound machine needs to be made that has at least 2 different types of machines and at least 1 gear system, pulley drive, or sprocket/gear system. 2 simple machines and 1 gear system or pulley drive or sprocket/gear system must have a mechanical advantage greater than 1. The compound machine must be able to lift a given object at least 6 inches off the ground in less than 3 minutes.
Learning objectives:
This project is designed to educate the participants of how the elements of design can affect the mechanical advantage of involved systems/machines. This project casts light on how simple machines can work in conjunction to address or solve a certain task or problem. In addition, this project compares the efficiency of different simple machines and explores the limitations and capabilities of VEX components (for use in future projects).
Project Criteria/Constraints:
The compound machine must contain at least 2 different simple machines and at least one gear system/pulley drive/sprocket system, all of which need to have a mechanical advantage greater than 1. The compound machine must be able to lift a weight of approximately 8 oz. at least 6 inches in the span of 3 minutes.
Brainstorm Sketch:
Date: September 23rd, 2015
Problem Statement:
A compound machine needs to be made that has at least 2 different types of machines and at least 1 gear system, pulley drive, or sprocket/gear system. 2 simple machines and 1 gear system or pulley drive or sprocket/gear system must have a mechanical advantage greater than 1. The compound machine must be able to lift a given object at least 6 inches off the ground in less than 3 minutes.
Learning objectives:
This project is designed to educate the participants of how the elements of design can affect the mechanical advantage of involved systems/machines. This project casts light on how simple machines can work in conjunction to address or solve a certain task or problem. In addition, this project compares the efficiency of different simple machines and explores the limitations and capabilities of VEX components (for use in future projects).
Project Criteria/Constraints:
The compound machine must contain at least 2 different simple machines and at least one gear system/pulley drive/sprocket system, all of which need to have a mechanical advantage greater than 1. The compound machine must be able to lift a weight of approximately 8 oz. at least 6 inches in the span of 3 minutes.
Brainstorm Sketch:
In the picture, each component and its involvement in a transfer of movement is listed in the lower section (with labels A - F).
First, a crank is turned to rotate a wheel and axle. The axle is connected to a bevel gear, so when the axle is turned, the bevel gear is also turned. The bevel gear is connected to a gear train, and thus transfers the rotary movement to the perpendicularly-stationed gear train. The last gear is connected to a large wheel, which turns as the last gear of the gear train turns. The wheel pulls on a string, which is connected to an idler pulley. The idler pulley redirects the string to make the connecting moveable pulley more efficient. The moveable pulley lifts the weight when the string running through it is pulled.
Final Design Proposal:
First, a crank is turned to rotate a wheel and axle. The axle is connected to a bevel gear, so when the axle is turned, the bevel gear is also turned. The bevel gear is connected to a gear train, and thus transfers the rotary movement to the perpendicularly-stationed gear train. The last gear is connected to a large wheel, which turns as the last gear of the gear train turns. The wheel pulls on a string, which is connected to an idler pulley. The idler pulley redirects the string to make the connecting moveable pulley more efficient. The moveable pulley lifts the weight when the string running through it is pulled.
Final Design Proposal:
The design is labeled as such: (sub-sections are additions to the information on the drawing)
A) Turn crank - input (Turn counterclockwise).
a. The crank acts as a wheel and axle, and decreases the amount of force needed by the user.
B) Bevel gear transfers movement 90 degrees to the gear train.
C) Gear train - Each successive gear (3 in total) increases torque. If necessary, the gear train can be switched for a speed increase.
D) Last gear of train transfers rotational movement to a small spool.
E) Spool pulls string into it (spools the string). Spool/gear is a wheel & axle system.
F) Moveable pulley lifts the weight.
In order to get the final design, my team and I used a decision matrix (pictured below this paragraph). This allowed us to compare the strengths and weaknesses of each of the designs. After the decision matrix was completed, my design and Noah Zahm's design had the same total number of points. We had a group vote, and this was split 2 - 2 for the designs. Thus, we had to turn to chance. All of us in the team were OK with either design being chosen, so we decided to flip a coin to decide whose machine we would use. We used an online coin flipper (Random.org). I got 3/3 heads, and so my design was picked to be our group's design.
Matrix criteria: Simplicity, size, mechanical advantage, ease of operation, durability, build time/modular.
A) Turn crank - input (Turn counterclockwise).
a. The crank acts as a wheel and axle, and decreases the amount of force needed by the user.
B) Bevel gear transfers movement 90 degrees to the gear train.
C) Gear train - Each successive gear (3 in total) increases torque. If necessary, the gear train can be switched for a speed increase.
D) Last gear of train transfers rotational movement to a small spool.
E) Spool pulls string into it (spools the string). Spool/gear is a wheel & axle system.
F) Moveable pulley lifts the weight.
In order to get the final design, my team and I used a decision matrix (pictured below this paragraph). This allowed us to compare the strengths and weaknesses of each of the designs. After the decision matrix was completed, my design and Noah Zahm's design had the same total number of points. We had a group vote, and this was split 2 - 2 for the designs. Thus, we had to turn to chance. All of us in the team were OK with either design being chosen, so we decided to flip a coin to decide whose machine we would use. We used an online coin flipper (Random.org). I got 3/3 heads, and so my design was picked to be our group's design.
Matrix criteria: Simplicity, size, mechanical advantage, ease of operation, durability, build time/modular.
Design Modifications:
We made a few modifications to our design. We adjusted the height of the entire thing to be taller than I had anticipated. This allowed our parts to have enough clearance, as well as the object to be lifted a full 6 inches. This made the machine operate better than it had been before. In addition, a gear box was put on the machine to distance the hand crank from the machine body (and allow the user to turn the crank much more easily). This definitely helped to make turning the crank easier, and almost completely reduced all crank issues.
Final Design Presentation:
We made a few modifications to our design. We adjusted the height of the entire thing to be taller than I had anticipated. This allowed our parts to have enough clearance, as well as the object to be lifted a full 6 inches. This made the machine operate better than it had been before. In addition, a gear box was put on the machine to distance the hand crank from the machine body (and allow the user to turn the crank much more easily). This definitely helped to make turning the crank easier, and almost completely reduced all crank issues.
Final Design Presentation:
In the official presentation, my team’s machine worked very well. Despite a few minor flaws in the system, the machine performed as it was designed, with no major deviations.
Stats:
The IMA of the crank is 15.175. The IMA of the wheel to the spool is 5.13. This ratio was originally measured by calculating two different wheel and axle systems (IMA of gear to axle = 30.256; IMA of axle to spool = 0.17. The IMA of the moveable pulley is 2. The total IMA (the product of all of the component IMAs) returns a value of 155.7. The AMA of the compound machine was found to be 4.8. The efficiency of our machine was a surprisingly low 3.08%. It took less than 20 seconds to raise the weight using the machine.
Team Evaluation:
Noah Zahm was a very good contributor to our group and to the project. He did a lot of the work in the group (more than his share), and was always doing something related to the project. If a problem came up, he had an idea ready almost immediately, which greatly helped when we encountered issues. Also, if we needed something done quickly, Noah was usually there to complete the necessary task. Noah followed the group norms. He did not really let any of the other group members help him with his work; however, he did this because he works much better alone, when he can enact his solutions without any interference. Overall, Noah was always on task and a very beneficial contributor to the success of this project.
I (Osric Nagle) was similarly on task and dedicated to the project. If something came up or needed to be done, I was quick to volunteer myself and get the problem solved as fast as possible. Also, I was the driving force behind the team conversations, and behind the delegation of work to Danielle Morris and Daniel Deng. I tried to include Danielle and Daniel into the project; however, much like Noah, I prefer to work alone, so my part of the project was mostly done alone (albeit, there was some help from everybody). I followed the group norms. Overall, I believe I was an active and beneficial member of the team.
Daniel Deng was very enthusiastic. He had plenty of energy, and it was not always focused on the task. However, when work needed to be done, he was ready to be put to work. He spent most of time working on the crank of the machine, and after he got over the learning curve of new parts, he managed to put one together. Daniel was also available for small, quick jobs. However, he relied totally on Noah and me for guidance on the project (especially for the mechanical advantage calculations). Daniel followed the group norms. Overall, Daniel was distracted and somewhat off-task but a hardworking member of the group.
Danielle Morris was the quietest of the team. She rarely spoke up, except when prompted (in the group conversations and in the presentation). In addition, she relied totally on Noah and me for information about the project. She did not seem too invested in this project, as she did not make much effort to participate in any of the activities we did as a team. I feel that, provided the right motivation, she could have easily made a much more significant contribution to the project. She completed any small jobs related to the machine construction. Danielle followed the group norms. Overall, Danielle seemed disinterested and under motivated.
Post-Mortem:
1. Out of all of the IMAs we calculated, the pulley was the easiest to determine (because the IMA is equivalent to the number of strands – counting strands is significantly easier than manipulating numbers).
2. It was the most difficult to determine the IMA of the crank, because it was hard to measure the amount of force required to make the compound machine function. The available spring screws were not meant to measure rotational force, but we had to make do with the available tools.
3. If our team had more time, I would put some distance between the crank and the wall, so the supports of the machine would not interfere with the input force, as well as tighten the crank to ensure stability and less energy wasted in situationally non-manipulative vectors. I would increase the width of the vertical supports of the spool, to ensure that the weight would not bump into anything while it is ascending or descending and thus lose efficiency. Also, in the same context, I would take out the idler gear in our gear train, because all it does is drop the efficiency of the machine.
4. If I had more time, I would add more components on the machine, just to make it look more interesting.
What I did and what I learned
The first thing my group (including me) did was create our group norms and establish channels of communication. Then, we each developed an idea and then reviewed it together and chose my design as the final. When we started building, we split up the work. I worked on the first half of the compound machine (everything from the crank to the gear train), as well as helping to create the initial "skeleton" for the rest of the components to be placed on. I worked every class until we finished; during the presentation, I tried to include all of the necessary reasoning behind and information about our machine based on the questions I was asked.
I learned that working in a group requires a good leader, especially if not all of the group members know exactly what the final design should look like. We needed someone to delegate work throughout the project to Daniel and Danielle because they were not sure what to do. I also learned that changes to an original design should be at least looked at initially, so that the final design results in a reflection of our team.