The InEfficient Estabrook Elevator A powerful motor that incorporates a gas fired piston as the sole source of Energy.

Transcription

1 Dec The InEfficient Estabrook Elevator A powerful motor that incorporates a gas fired piston as the sole source of Energy. Project by Brad Jenkins, Ken Pearson, Kevin Pittman, and Warren Raburn

2 Basic Overview The elevator we designed relies on pressurized Carbon Dioxide (CO 2 ) as the sole source of energy. The CO 2 is contained in a small canister and regulated by a specially designed head generally used for filling up bike tires. Plastic tubing, originally used in a refrigerator, was fitted with a tire head, which allows it to be screwed seamlessly into the canister. The other end of the tube is attached to a piston we built from aluminum and PVC pipe. The rod of the piston only travels nine inches, so we used a lever to obtain the extra distance needed. One side of the lever was attached, by a hinge, to the wooden platform of the motor. The piston rod pushes on the bottom of the lever, causing the top of the lever to swing a greater distance. A pulley was also attached to the platform, approximately as high as the top of the lever. The string was attached to the top of the lever and ran nearly parallel to the platform until it reached the pulley. From the pulley, the string hangs down and attaches to the weight. We get 41 inches of effective lift from the 9 inch piston. The entire process takes about two seconds when lifting only one kilogram. Our effective maximum mass is at least 3 kg, without increasing the pressure. Our structure is capable of much more weight simply by increasing the pressure to the piston.

3 Summary of Project The initial brainstorming session began on Tuesday, November 13 th, and lasted for about an hour. We used this initial brainstorming time to clarify many of the ambiguous details about the project. In fact, many of our initial ideas were discarded simply because we had not understood the details of the project. After receiving clarification, we simplified the motor s functional definition as to pull a string with enough force to lift one kilogram in about ten seconds. This started the second phase of our first day of brainstorming. We had to figure out a way to pull the string without dropping a counterweight off the table, per the initial instructions (Later, we learned that many of the initial guidelines had been mostly discarded, and hanging a counterweight was eventually allowed). We talked about various concepts for powering the elevator, including springs and ramps, but in the end we decided pressure gave us the best possibility for a truly self-contained, portable motor. After we decided on pressure, two other conceptual details remained: whether to use a turbine, waterwheel, or piston to convert the pressure into power, and a method of creating the pressure. Based on input from Warren that led us to believe he could find an old piston on used truck campers, we chose that method for harnessing the energy. As for creating the pressure, boiling water was almost immediately discarded because of the time it would take to start. Eventually, we decided to try a common chemical reaction involving acetic acid and sodium bicarbonate. Warren agreed to start work on finding a piston that weekend. We met the following Tuesday at Wal-Mart with the intent of refining our ideas and purchasing needed supplies. Warren informed the group that he was unable to locate a piston, but he would be able to build one that would work just as well. Following a guarantee that building and sealing a piston was not the near impossibility some group members felt it was, the group agreed that he should work on the

4 piston at his house, while the rest of the group tested the initially planned reaction. Following more discussion on how to initiate the reaction, we bought a tea pot, baking soda, vinegar, and balloons. Our plan was to use the tea pot to contain the reaction, seal the lid, and put something on the spout to direct the pressure. A balloon would be full of vinegar, and could be punctured to initiate the reaction. Much to our surprise and dismay, the acetic acid/sodium bicarbonate reaction was too weak for our purposes. After some brainstorming, we decided Diet Coke and Mentos had the potential for a very fast reaction. Again, our reaction was much too weak to push a piston. Following further discussion, it was decided that dry ice mixed with warm water was our best remaining option for creating enough gas to push the piston. Ken agreed to test this over Thanksgiving weekend. True to his promise, Warren put in about 6 hours over the weekend to build a functioning piston. To make the piston, he used part of a Swiffer Sweeper (3/4 metal tube), some PVC pipe small enough to fit in the tube, some oil for lubricant, and metal and rubber scraps he had lying around. The end of piston, where the air would enter, was welded to a metal face. He then attached the intake hose to a matching piece of metal. The intake hose unbolted whenever we needed inside the piston. Warren had also built a rubber seal to ensure there was no leakage out between the metal faces when they were bolted together (see appendix). Over the weekend, Ken had also bought and tested the dry ice theory. He reported it a success. Optimism ran through the group as we observed the amazing amount of potential energy we were creating with the dry ice. The piston was experiencing some leakage, so we began the time consuming process of trouble shooting. Specifically, we used a bathtub to look for leaks. A look of pain crossed Warren s face when dozens of large air bubbles floated up from a section of his piston. The day ended pretty soon afterward for most of us, though Warren spent some additional time finishing up his piston. Unknown to the rest of the group, Warren attached the piston to the tea kettle, and ran a quick test to see how well it would work. Apparently, it was impossible to keep the lid on. Even when Warren

5 sat on it, he could not keep the pressure contained. A section of the tea kettle bent with the force of Warren holding down on the lid. Though we didn t know at the time, at least fifty pounds per square inch of pressure would be needed to push the piston, and trying to seal a nearly ten square inches lid would have required at least five hundred pounds of force on the lid. Based on a flash of inspiration, Kevin and Warren got together for a couple hours Wednesday night to try a new idea. Warren had a small CO₂ canister and an inexpensive, specially designed regulator. The regulator was threaded to allow it to screw into bicycle tires. It was a relatively simple matter to attach our piston s intake hose to a bicycle head. They attached the canister to the piston and it worked amazingly. Up until this point, we still had not worked out exactly how we were going use the force generated by nine inches of a piston to lift the one kilogram one meter. Initially we had planned to use a pulley system, but in another stroke of genius, Warren and Kevin had decided to take advantage of the fulcrum properties of a lever to give us the extra distance. The base of a 0.4 meter long board was attached to the wooden base with a hinge. The piston, too, was attached to the base by hinge. Next, the piston rod was attached near the base the lever by a metal pin that ran through the rod of the piston and into the board. Then, when the piston was fired, the rod would push into the base of the board, moving it a total of 9 inches, however the top of the board would move much further (see appendix). The entire group met the next morning to finish the project. Thanks to the efforts of Warren and Kevin the night before, the design was essentially complete. When doing some final testing, we found out the string was still not being pulled far enough. We also discovered that the distance the string travelled depended how high the pulley was in relation to the lever. The problem was a relatively quick fix. We simply lowered the location where the rod attached to the lever, and ensured the lever was at a good height to maximize the distance along the x axis. The lever completes its motion just past 90 o with respect to the base of the board. It worked perfectly; we ascertained 41 of lift, or about one meter.

6 A final meeting was scheduled for Monday night at Warren s house to rehearse the power-point presentation, calculate the energy lost and celebrate our success with some very fine home smoked BBQ pork. Encountering no other problems we enjoyed ourselves and prepared for the next day. Conclusion All in all, we consider our project to be a success. We created a completely self-contained motor capable of lifting at least three kilograms one meter high. We use no counter weights and require no additional setup. Our biggest failure was our inability to reduce the lift time to ten secodns. We had several plausible designs to slow down the lift, but the extra time required would have been unreasonable based on our constraints. Our project was also quite inefficient, though a lot of that inefficiency is due to the fact that the momentum of the lever and elevator were stopped by a chain after one meter. This group was very efficient when it came to solving the problems we faced. Most of the issues with our design were discovered by individual members of the group working independently, and possible solutions were brainstormed or developed before the group met again. All this independent work allowed us to make the maximum use of group time. Our biggest problem was finding a way to create the needed pressure. Considerable time, especially independently, but also as a group, was spent before the problem was solved. Finally, there is very little we would have done differently as a group. Certainly, in hindsight the solutions to our problems seem obvious; however, our approach to solving these problems was outstanding. We used our knowledge of physics to weed out poor ideas before we wasted time building, and then tested individual aspects of our design prior to trying to put the entire thing together. For example, while Warren was using his air compressor to test his piston, other group members were testing different reactions to find the best way to create that pressure.

7 Each of our group members comes from a very distinct background, with very unique experiences. However, we each had past experience working in teams, and I think our ability to work as a team was our greatest strength. We were able to act efficiently and effectively as a group to solve the problems we faced. Also, we started on the project early, and spaced the meetings out so that none of the group sessions last more than two or three hours. We avoided the last minute cram, and had a good time with the project. We complicated our project when we decided that it should be gas powered, operate without a counterweight, and be totally self-contained. However, given a second chance, no one in the group would have had it any other way. Calculation of Efficiency Measured Units: Pressure applied to piston: 75 psi Internal diameter of piston:.75 Distance rod travels in piston: 9 Derived Units: Cross sectional area of piston: π =.442 sq. in Force exerted by piston:. 442 sq. in 75 lb sq.in 3 4 ft = ft-lb of work, or Joules of Energy Energy required to lift object: 1 kg 9.81 m kg m 2 s2 1m = 9.81 = 9.81 Joules of Energy output S 2 Efficiency: 9.81 J J = 29.1% efficient Most energy was lost to friction, or absorbed by the chain used to stop the momentum of the lever after the piston had traveled nine inches.

8 Appendix Group Members: Brad Jenkins Ken Pearson Kevin Pittman Warren Raburn Pictorial Clarification: The metal face allowing the piston to be opened and closed at will This is where the piston rod attached to the base of the lever, allowing us to get the extra lift we needed