Sterling Engine

ME 355 Course

Spring Quarter 2023

Objective

In ME 355: Introduction to Manufacturing Processes, our lab portion of the course involved mill & lathe training and practice, as well as a quarter-long project in which the entire lab section worked together to build a sterling engine. We were split up into pairs and each given 4 parts to manufacture. My partner & I chose the power piston assembly (the brass cylinder & piston on the outside of the engine) which gave us tight tolerances to meet and a crucial working part of the machine’s function. For each part, we first created a rough process plan which was approved by a shopmaster before making the part.

Full sterling engine assembly running.

Process Plans

Meant to plan out the steps and setups necessary to manufacture each part
We did not design any of the parts, each plan began with a provided drawing of the part
Great practice to think through the crucial functionalities of each part, while also considering the advantages and drawbacks of the materials and tools used

(Example Below)

The power cylinder and base press fit together.

Challenges

Time

There were only a couple of hours structured into our lab on Friday afternoons when we had the machine shop to ourselves. More importantly, with packed schedules this time my partner & I had to together on these parts. This meant our process plans had to be made efficiently and intelligently outside of class so that we could maximize our time in the shop. Fortunately, we stuck to the schedule and completed one of our parts each week. In the final weeks of the quarter, our class came together as a whole and assembled the engine. It did not run upon first assembly, but after several hours of tweaking, we got it to run, fast.

Tight Tolerances

With practicing our manufacturing skills on the mills & lathes in the machine shop, our assembly required an air-tight fit between the power piston and cylinder, as well as in the press fit between the cylinder and its base. However, we achieved both after some sanding on the power piston to perfectly fit the cylinder, and a second attempt on the press fit by using the opposite end of the cylinder. See the photo above and video below:

My partner, Micah, demonstrating the air tight seal of our assembly while attached to the engine base. Notice the motion of the crank journal (the steel rod poking out of the cylinder) before and after he removes his finger from the air inlet in the base.

Key Takeaways

Mill & lathe experience
Manufacturing thinking and creating process plans
Teamwork & working through assembly obstacles/malfunctions
Broad manufacturing processes knowledge (through lecture portion of course)

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