Slow-Car and Hill-Climb Projects
The Project:
The task was to build a vehicle that would trace six inches in the longest amount of time, using only the provided lego kit, and making sure that the vehicle can travel on its own as one unit (without dragging or sliding), without stopping.\
The Design:
For this project, it was essential to reduce the gear ratio. This can be accomplished by always having a small gear driving a bigger one. In our design, the motor spun an eight tooth gear, which turned a 24 tooth gear, this creates a 1:3 ratio. The 24 tooth gear was connected by an axle to a worm gear (for our purposes, a one tooth gear) which turned a 40 tooth gear, this creates a ration of 1:40. The 40 tooth gear was connected by an axle to an eight tooth gear, which spun another 40 tooth gear, this creates a ratio of 1:5. The second 40 tooth gear was connected by an axle to an eight tooth gear, which spun a 24 tooth gear, creating a ration of 1:3. Now, with a lack of room, the 24 tooth gear was connected by an axle to a small pulley on the outside of the car, which spun a larger pulley, creating a 1:3 ratio. The larger pulley was connected by an axle to an eight tooth gear inside the car, which spun a 24 tooth gear, creating a 1:3 ratio. This spun another set of eight and 24 tooth gears, which spun another set of eight to 24 tooth gears. Finally, the last 24 tooth gear was connected to a 1:3 ratio pulley system, which spun the wheels. It was calculated that the final drive ratio was 1:437,400. This means that the motor has to spin 437,400 times before the drive wheels will turn once.
The result:
Testing consisted of setting two points (with masking tape) six inches apart, and timing how long it took for the design to move that distance. However class time was limited, and the design only ran for 23 minutes. In this amount of time, however, the design moved an amount that was not measurable, the front tires were less than one millimeter from the starting position. 25 points were earned as a grade.
Experience, lessons learned:
The design was very successful. The most important element in the design was the final gear ratio. This means that a small gear always needs to be driving a large gear, the opposite would speed up the system, not slow it down. The second most important experience was improvisation. In order to get the gear ratio to an optimal low, a large number of gears had to be used. Because of the amount of gears, the space in which the gears were held had to be used efficiently. Our group was able to do this by constantly improving the design on the go, as well as simply placing the gears as close to each other as possible; using up all of the space that was available. The pulley system was an example of an improvisation, there was no space on the inside of the car's body, the pulley could easily be used on the outside in order to preserve space, and to place the next axle far enough away so that there would be enough room for the next set of pulleys. Another example of improvisation was the first set of gears and the mechanism that held the worm gear in contact with the 40 tooth gear. The electric motor could not be placed anywhere near the 40 tooth gear, or else it would get in the way. It also had to be fastened above the gear system, for the same reason. The worm gear allowed for an axle to extend away from the gears, and the pair of eight an 24 tooth gears allowed the chain to move upwards, so that the motor did not interfere with another part of the system, but was still able to power it.
The task was to build a vehicle that would trace six inches in the longest amount of time, using only the provided lego kit, and making sure that the vehicle can travel on its own as one unit (without dragging or sliding), without stopping.\
The Design:
For this project, it was essential to reduce the gear ratio. This can be accomplished by always having a small gear driving a bigger one. In our design, the motor spun an eight tooth gear, which turned a 24 tooth gear, this creates a 1:3 ratio. The 24 tooth gear was connected by an axle to a worm gear (for our purposes, a one tooth gear) which turned a 40 tooth gear, this creates a ration of 1:40. The 40 tooth gear was connected by an axle to an eight tooth gear, which spun another 40 tooth gear, this creates a ratio of 1:5. The second 40 tooth gear was connected by an axle to an eight tooth gear, which spun a 24 tooth gear, creating a ration of 1:3. Now, with a lack of room, the 24 tooth gear was connected by an axle to a small pulley on the outside of the car, which spun a larger pulley, creating a 1:3 ratio. The larger pulley was connected by an axle to an eight tooth gear inside the car, which spun a 24 tooth gear, creating a 1:3 ratio. This spun another set of eight and 24 tooth gears, which spun another set of eight to 24 tooth gears. Finally, the last 24 tooth gear was connected to a 1:3 ratio pulley system, which spun the wheels. It was calculated that the final drive ratio was 1:437,400. This means that the motor has to spin 437,400 times before the drive wheels will turn once.
The result:
Testing consisted of setting two points (with masking tape) six inches apart, and timing how long it took for the design to move that distance. However class time was limited, and the design only ran for 23 minutes. In this amount of time, however, the design moved an amount that was not measurable, the front tires were less than one millimeter from the starting position. 25 points were earned as a grade.
Experience, lessons learned:
The design was very successful. The most important element in the design was the final gear ratio. This means that a small gear always needs to be driving a large gear, the opposite would speed up the system, not slow it down. The second most important experience was improvisation. In order to get the gear ratio to an optimal low, a large number of gears had to be used. Because of the amount of gears, the space in which the gears were held had to be used efficiently. Our group was able to do this by constantly improving the design on the go, as well as simply placing the gears as close to each other as possible; using up all of the space that was available. The pulley system was an example of an improvisation, there was no space on the inside of the car's body, the pulley could easily be used on the outside in order to preserve space, and to place the next axle far enough away so that there would be enough room for the next set of pulleys. Another example of improvisation was the first set of gears and the mechanism that held the worm gear in contact with the 40 tooth gear. The electric motor could not be placed anywhere near the 40 tooth gear, or else it would get in the way. It also had to be fastened above the gear system, for the same reason. The worm gear allowed for an axle to extend away from the gears, and the pair of eight an 24 tooth gears allowed the chain to move upwards, so that the motor did not interfere with another part of the system, but was still able to power it.
Hill Climb Project.
The project:
The task was to build a vehicle that would travel the fastest in a competition against other teams in the class, up a slope, using only the provided kit. Some of the criteria for the design were that it could only incorporate the materials that were provided, the vehicle had to be one complete unit, the vehicle must roll, the vehicle could not disrupt the travel of it's opponents.
The design:
Our team's design was intended to find an optimal middle ground between a drive ratio that was based on speed and one that was based on torque. Because of the steep incline, it was necessary to have a good ratio, if the gearing was to fast, the wheels would slip and the vehicle would not make it up the slope. If the gears created a ratio that was too slow, the competition would defeat our vehicle.
The final design was simple, and had very few gears. The motor spun an axle which spun a bevel gear. The bevel gear turned another bevel gear at a 1:2 ratio. The second bevel gear was connected to an eight tooth gear by an axle. The eight tooth gear turned a 40 tooth gear at a 1:5 ratio, which was connected to the drive wheels through an axle. The final drive ratio was 1:10.
The Result:
The design did not meet the medium between speed and grip. The design placed seventh overall in the competition, based on time standings. The design was able to travel up the hill in 39 seconds. The fastest in the competition climbed the hill in ten seconds. The design earned 70 out of a possible 100 points for a grade.
Experience, lessons learned:
The most important lesson learned was about intentionality. This design was structurally the same as that of the slow car project. The gears were placed inside of a frame, which, although useful for lining up gears nicely, created a bulky and large shape, which hampered the vehicle in the competition, and created a host of other problems. Another large problem (linked to the poorly designed structure) was weight placement. Because of the torque producing nature of the design, the front end of the vehicle would 'pop up'. This was solved by adding weight to the nose of the car. This caused another problem, because the majority of the weight was over the front axle, the rear axle did not have any traction. More weight was added to the rear in order to balance the design. At this point, the car was very heavy and the increased weight when working against gravity was a hindrance to the design.
The design did not perform well because of a series of compromises, that were only necessary because of a structure that was not intended for the purpose for which it was used. If a design had been created that was more intended towards the hill-climb, it would have been more successful. A common analogy says: "Never send a boy to do a man's job". In this project, we sent a slow car to do a hill-climb car's job, and the result was not the best.
The task was to build a vehicle that would travel the fastest in a competition against other teams in the class, up a slope, using only the provided kit. Some of the criteria for the design were that it could only incorporate the materials that were provided, the vehicle had to be one complete unit, the vehicle must roll, the vehicle could not disrupt the travel of it's opponents.
The design:
Our team's design was intended to find an optimal middle ground between a drive ratio that was based on speed and one that was based on torque. Because of the steep incline, it was necessary to have a good ratio, if the gearing was to fast, the wheels would slip and the vehicle would not make it up the slope. If the gears created a ratio that was too slow, the competition would defeat our vehicle.
The final design was simple, and had very few gears. The motor spun an axle which spun a bevel gear. The bevel gear turned another bevel gear at a 1:2 ratio. The second bevel gear was connected to an eight tooth gear by an axle. The eight tooth gear turned a 40 tooth gear at a 1:5 ratio, which was connected to the drive wheels through an axle. The final drive ratio was 1:10.
The Result:
The design did not meet the medium between speed and grip. The design placed seventh overall in the competition, based on time standings. The design was able to travel up the hill in 39 seconds. The fastest in the competition climbed the hill in ten seconds. The design earned 70 out of a possible 100 points for a grade.
Experience, lessons learned:
The most important lesson learned was about intentionality. This design was structurally the same as that of the slow car project. The gears were placed inside of a frame, which, although useful for lining up gears nicely, created a bulky and large shape, which hampered the vehicle in the competition, and created a host of other problems. Another large problem (linked to the poorly designed structure) was weight placement. Because of the torque producing nature of the design, the front end of the vehicle would 'pop up'. This was solved by adding weight to the nose of the car. This caused another problem, because the majority of the weight was over the front axle, the rear axle did not have any traction. More weight was added to the rear in order to balance the design. At this point, the car was very heavy and the increased weight when working against gravity was a hindrance to the design.
The design did not perform well because of a series of compromises, that were only necessary because of a structure that was not intended for the purpose for which it was used. If a design had been created that was more intended towards the hill-climb, it would have been more successful. A common analogy says: "Never send a boy to do a man's job". In this project, we sent a slow car to do a hill-climb car's job, and the result was not the best.