User:K.saunders/enes100/Sterling Engines

Link back to team 550_QSM page.

Give instructor top 3 project choice list
I was assigned to the Engines.

Write problem statement
How do you make a sterling engine and what are some techniques to getting one to work?

Assign Task1
In this week I will look up previous models that worked and how they were documented. I will also start finish my own sterling engine.

Compare actual work done to Task1
I started my own design before looking up past designs. This was beneficial and detrimental to the project.

Week1 Narrative
This week I really worked on getting my first prototype done. I immediately started constructing the engine from parts I found laying around my house.

Assign Task2
Correct mistakes made in my project and document how to correct them.

Compare actual work done to Task2
This week I tried less to build the model and get it done, and focused more on doing it right and completing the task at hand. I started my step by step instructions and they can be found here. I Also got advice from lots of people in the class about how I can improve my design and how to prevent possible problems from arising.

Week2 Narrative
Previous Design: Problems:
 * Poor displacer. The displacer's problem was that it wasn't close to half the volume of the piston. It needs to be able to move a larger volume of air.
 * Lack of precision. The displacer rod hole through the piston lid allowed the air pressure to escape.
 * Crank shaft is too big. The crank itself needs to be a 1/4 the height of the cylinder so the displacer makes a full motion

Solutions:
 * Add a piece of Styrofoam to the old displacer so that it is closer to half the volume of the displacer.
 * Add a sleeve of something to reduce the volume of the displacer rod hole.
 * Wait to make the crank until the majority of the cylinder is completed so that the crank reaches a full range of motion.

This week I worked on fixing the the displacer and the displacer rod hole. To increase the volume of the displacer I took a large chunk of Styrofoam and pushed it down till touched the soda can. I then took a marker and traced around the can. Because i wanted the Styrofoam to just fit inside the edge of the beer can I knew I had to remove all parts of Styrofoam that had marker on them. To evenly cut the Styrofoam I used the hot wire device and rotated the block about its center point. After shaving off all parts with marker on them the block of Styrofoam slid just inside the can. Once the block was in the can I set it next to the cylinder and cut it close to half the height of the cylinder.



I also worked on tightening the seal around the displacer rod. To do this I took a small blob of epoxy and worked it until it started stiffening up. I then scooped the ball on the lid and let gravity go to work. To make the drip even, centered, and straight I slowly turned the disc until the drip was even on all sides. Then I placed the lid upside down on the beer can and let it dry so that the drip stuck off the top of the lid. I then took my dial calipers and measured the diameter of my 16 gauge wire to be 1.29 mm.

Assign Task3
Assemble the engine and remake the crank. Test it!

Compare actual work done to Task3
This week me and Quifoor completed our first model of the Stirling engine. After analysis and group brainstorming we made a few modifications and tested our engine again. I also added on to my running how to page. This week I completed my second prototype engine after correcting previous flaws and still can not get enough power to continually turn the crank.

Week3 Narrative
This week after fully assembling the engine for the fist time we realized 2 mail flaws or places of friction:
 * The rod extending out of the power piston caused the piston to torque inside the cylinder and made the edges catch.
 * The displacer rod extending out of the cylinder lid was too long and caused the the displacer to do basically the same thing as the power piston.

Solutions:
 * To correct the power piston from twisting I set another piston that instead of a straight arm extruding outward, it hard a hook that could be loosely connected to a different crank arm.
 * Instead of having about 4 cm of displacer arm extend through the cylinder lid I cut it down to less than 1 cm so that less force would be applied horizontally.
 * Added more mass to the rotating disk to give a great rotational inertia.

After making these simple fixes and testing the engine, although I could get the engine to make about 3-4 cycles I could not get it to continuously rotate.

Problems:
 * Air pressure is lost around the new power piston and cylinder.
 * The disk might be too massive for the engine to turn.

Next step
My plan of action at this point is to use what I have learned about this engine and use it to make a new engine that harnesses the power of latex. Because such a high degree of precision is needed to correctly use a power piston I believe it is too hard to make one using simple everyday materials.

My plan: Follow my instructions from the beginning very similarly to my previous design. When it comes to making a new power piston I will instead make a cylinder and cover will latex/balloon. My challenges at this point is how am I going to attach a crank arm to latex since it is stretchy and tears very easily.

Assign Task4
Refine previous instructions to incorporate latex and make a time laps video of me making one.

Compare actual work done to Task4
This week I attempted correcting my flaws in the engine and made a poster board and made two presentations. One for the NSF STEM program and one in class.

Week4 Narrative
This week I decided to try and fix the pressure leak problems by covering the areas in concern with wax and seeing if it would harden so that less air could escape. I got this inspiration from the demo I did in the cafeteria. While using the candle to provide heat for the machine milled engine I noticed that once the wax melted off the candle and cooled on the the table, the cooled wax was actually quite hard and relatively smooth and slick. I then decided that if I could pour a small amount into the power piston that it would drip around the piston and make a better seal inside the cylinder. I then held the engine at a slant and poured melted max on top of the engine and worked it up the the displacer rod. I learned two things from doing this. 1) The wax is very hard to control when not contained (on the lid). 2) When it dried the wax had too high a coefficient of friction and rubbed too hard on the displacer shaft. However, pouring the wax into the cylinder the wax did a great job of sealing the piston. The down side to this was the wax sat on top of the previous piston so that when the piston was a its max height, the wax was entirely exposed breaking the seal inside of the cylinder. We got positive result from this because the engine now started showing signs of life and turned over occasionally. However once the wax extruded out of the cylinder the seal was broken and momentum was lost.