Joanne Park and Nick Solonko
Transfer the Load with Winch Challenge
Functions: The robot needs to be able to lift 200 grams from the ground, turn, and put it on the table. We will have 60 seconds to lift as many weights as possible. We can help the robot hook and unhook weights. We have to use gears and gear ratios to maximize the speed of the lifting process.
Systems: We will utilize a few gears, NXT motors, NXT brick, turntable, and other lego components to make the robot lift the weight fast. We will attach gears to the motor in order to make the torque in the ideal range(13-17 N-cm). That way, we are using as much power as possible and can lift the weight faster. We will use another NXT Motor to turn the turntable with the help of a tube with an inclined plane wrapped around it.
We began the day by building the machine we planned in our initial design. We found some issues with it being too slow. So, we planned a new design and it worked way faster. We switched the gears and in order to make the ratio less than one. We also redesigned the gears in order to put the winch on the outside instead of in the middle. Then, we tested this but it was unable to lift the weight. We decided that we needed to put the winch in the center again. We decided to use 2 motors instead of one and therefore divided our ideal torque gear ratio by 2. Out GR was .2. We build a system and tested it. There was not enough torque due to friction so we will use .4 as our GR. Unfortunately, we have not been able to get our gears to line up correctly yet. End of day 1: We have not been able to get the winch gears to match up well yet so we still don’t have a working design.
We increased our gear ratio to 0.6 because consistency is more important than speed. We got a working winch and a working turntable. The construction can barely handle the mass, therefore we will add more support and 100 grams counter weight. Our turntable and gear from the motor are not touching each other, but it is very close. Next class, we will put them closer together. Overall, our system is able to lift 200g, but now we need to make sure it does not fall over.
Today we focused on making the robot stand when the 200g hang on it. We added 100g of counterweight and removed the wheel in the front. That way, our robot was shorter and stood straighter. Basically, the robot is a first class lever with the turntable being the fulcrum. By shortening one side, we made the robot in equilibrium. We ran our first trial and got 35/40. We now need to make sure that the rope does not tangle during the process. We replaced our winch with a smaller one. Now, our robot is a lot slower, but at least the rope does not slide off often. The turntable can barely handle the pressure of the upper part of the robot with the 200g. After we get 40/40, we will work on adding more torque to the turntable and implementing a larger winch(the previous one) on the robot. We made some minor changes to the structure so that the turntable does not collapse.
Today, we made our robot a lot slower and we succeeded in our trial. We earned the full 40 points. We did not change the design much. We double the width of our winch in order to prevent the string from slipping. We got 1 run in and later worked on improving it. We made the gear ratio smaller for more speed. We will work next class to make a better robot than we had today.
Today we increased the speed of our robot and got 4 successful runs. We chose a smaller gear for our turntable for additional torque. This was a successful project.
Our robot was able to lift 800g within one minute. Our gear ratio was nowhere near ideal, but the extra torque allowed our robot to be much more consistent. Our turntable was somewhat able to tolerate the mass on it, only slightly struggling at times. The extra torque that we added made the movement much more smoother. Our robot was able to unhook itself and only needed assistance hooking on the mass. Our winch was smaller than planned originally for more torque and therefore higher consistency. Overall, we are happy with our progress and with our creation.
Learning and Improvement:
Throughout this project, we learned a lot about gears and their ratios. We learned about how to find the optimal torque we could get from a motor. We also learned how to choose our gear sizes in order to optimize speed or power. We both got deeper understanding of how counterweights work because we compared them to levers. If we were to do this project again, we would make our gear ratio smaller, possibly .4 or .2 because the group that got 8 runs was successful with such a small gear ratio. For our turntable, we would use an even smaller gear to add more torque. We would use the same basic structure, but possible make it a little bit shorter to reduce the shakiness.