Stirling Engine

Group Project

TECH 4472

Fall 2022

2020 Video

The group project was definitely not the highlight.

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-Anonymous Student

I do not know if you can, but stress that the Stirling Engine project will be more difficult than expected. This was learned while taking the class and this point was stressed at the beginning of this class. The students who did not listen (myself included) were in for a rude awakening.

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-Anonymous Student

The Stirling Engine project was also not very organized and had conflicting instructions depending on where the student looked.

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-Anonymous Student

The individual scores of the group project (which was a major part of the overall grade) depended on the work of others.

-Anonymous Student

This is a communication and teamwork assignment.

You may have thought it was an NX assignment, but the NX part is easy.

The communication is the hard part. If you do the communication and teamwork part well (get the team to communicate) the NX part is duck soup.

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Reverse Engineer the LDT Stirling Engine

Stirling Engines

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UNITS

For the fall 2022 semester ALL models and drawings will be in:

Millimeters

Even if the information given to you is in other units (you will convert them). �

First Thing:

This project is a big part of your grade.

• Each and every file YOU create or source must have your UUID in the file name or you won't get credit.

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• If you change filenames after you assemble your model IT WON'T WORK.
• While this is a GROUP project, you will receive an INDIVIDUAL grade based on the files with YOUR UUID in the filename.
• If your group omits any components, everyone in the group will receive a grade reduction.

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Goals

To become fluent with NX modeling and drafting.

To gain experience and skill working as part of a team.

To gain mechanical design experience.

To gain experience and skill producing graphical communication.

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Hints on how to succeed:

Get started now. Get organized. Communicate clearly.

Known Information

The information here is what is currently known about the engine.

Your job will be to use the information shown here to guide your design.

Reverse Engineer the LDT Stirling Engine

FALL 2022:

Power piston:

Bore: .625 inches�Stroke: .388 inches

Displacer piston:

Bore: See Purchased Part I.D.�Stroke: .309 inches

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Photos

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Photos

Photos

Project Deliverables - PHASE I

Working drawings of each component. Note: Modified parts require a drawing. Purchased parts may use supplier’s drawings (and models).

• Each print should include material specifications.
• Note: “Stainless steel,” “plastic” or “aluminum” is not specific enough!
• Include tolerances. Pay particular attention to hole and shaft limits.
• You will submit your models & PDF files of your drawings.

Include Assembly drawings of logical sub assemblies and final assembly including BOMs.

Note: Every student will do an assembly of the overall assembly. Include at least one exploded view.

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PHASE II

Your prints will be given to another team and you will receive a packet of prints from a different team.

Create models & assemblies based ONLY on the prints you received.

If there are any dimensions that require clarity, use a red pen to highlight the area in question. A new print will be issued by the design team and attached the original.

DO NOT ASSUME, DO NOT SCALE

DO NOT SEEK INFORMATION ELSEWHERE (Or you assume responsibility for the error)

Component Groups

You may decide to break out the components by group if you wish (this is strongly encouraged). Some groups are harder than others.

You will notice that you cannot design any one group in isolation. They all depend on each other. That means that each designer depends on the others.

You will need to COMMUNICATE to design.

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Master List

Note: See speaker notes for list in text form.

CG1 Heat Chamber

Displacer Cylinder wall is acrylic, 6.0 O.D. made from https://www.mcmaster.com/8486k395

Need details of displacer to design. Leave .125 clearance above and below for stroke.

Two plates connected with flat head screws and clinch nuts. Screws have decorative cover.

CG2 Piston & Power Cylinder

For piston material: See https://www.mcmaster.com/9121k73

Power cylinder is made from� McMaster Part no.� 8729k45

Need to size bearings and determine hole limits.

Size rod and determine method of attaching

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CG3 Power Crank & Attachment

Note: more detail on power crank on the next slide.

Rod ends may be connected by a variety of means. The method is left to you, but design appropriately.

Bearing is press-fit. Document bearing fit design.

CG4 - Flywheel & Attachment

Flywheel diameter is 6.125 inches in diameter and is .125 thick. It is held to the power crank with four flathead screws. Countersink as appropriate.

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CG5 - Crankshaft Bearing Assembly

Note: The crankshaft is press-fit into the power piston crank (not pictured here)

Crankshaft bearing spacer is press-fit into the crankshaft bearing block.

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CG6 Displacer Drivetrain

Note: GC7 is responsible for:

41 - Screw, Set, Displacer, and

42 - Pin, Wrist, Displacer

CG7 Displacer & Connection

The displacer is made from EPS foam ½ inch thick. Leave .125 clearance all around to cylinder wall.

The actual method of connecting the EPS foam displacer is left to you to design. The illustration here is for reference only; it does not illustrate a known component.

The displacer bushing is PTFE.

Note: GC7 is responsible for:

41 - Screw, Set, Displacer, and

42 - Pin, Wrist, Displacer

File Name Format - This is important. Read it.

EVERY (prt, pdf, etc) file you create MUST have this file name format:

[teamID]_[CGn]_[ITEM]_[UUID]

Team id, component group you were assigned, item number, and your UUID.

For example:

W2_CG1_3_rwhewitt

Wednesday, team 2, component group 1, item 3

For assemblies, use ASSY as the item number

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NOTE: This is a group project but you will be graded INDIVIDUALLY. Your grade will come from the files that have your UUID in the filename.

Let me be clear:

You will get NO CREDIT for any file not properly named.

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This assignment is worth enough of your grade that you can fail the course by improperly naming your files in this assignment.

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What about purchased parts?

If your supplier (McMaster-Carr, for example) has part files available, you may use them in your assembly.

BUT they need to follow the same naming convention except the word “VENDOR” will be added as a suffix.

An example PDF files from McMaster-Carr might be renamed the following:

W2_CG1_3_rwhewitt

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IF purchased part must be modified, YOU MUST CREATE YOUR OWN MODEL & PRINT.

For instance, the cylinder is made of acrylic tube. You need to create a model and drawing of this. The supplier model and print is NOT sufficient.

Directory Structure

Put all your team’s files in a SINGLE directory (folder).

DO NOT organize into sub-directories.

BACKUP your team’s work often.

Using the “Z” drive:

\\itnas.memphis.edu\groups$\hcoe\hewitt4472

Note: If you access or delete another team’s files, you will receive a zero for this assignment (12.5% of your total grade).

I’m going to suggest here that you put your files in a single directory. Do not group parts into subdirectories. This will make your life easier, but it’s up to you.

PHASE I - You will be graded on your working drawings

Every member of the team will:

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1. Design components
2. Create detail drawings and assembly drawings of their components.
1. Each person will do an exploded view of their components.

Also, a note about the Stirling engine project prints. The issues listed below have constituted about 90% of the points deducted in previous semesters.

• Using the wrong scale. Using a very large border makes the text unreadable. Using a border that is too small crowds the views. Find the happy medium.
• Dimension holes in the ROUND view. A leader with an arrow is preferred for holes.
• Dimension solid cylinders (rods, etc.) in the RECTANGULAR view.
• Long
• Use ASME as the "drafting standard" in NX . This will solve about half of you dimensioning problems.
• Use SECTION views for complex geometry when it makes things more clear.
• EVERY hole needs to have a 1) Diameter, 2) Horizontal location and 3) Vertical location. This can be done different ways (such as 3X EQUALLY SPACED, etc.), but it needs to be explicitly stated on the print. I should be able to point to a hole and you show me where it tells me those three things. Use the DIAMETER SYMBOL (Ø).
• Be sure EVERY feature (thickness, for example) has a dimension.
• Dimensions must NEVER overlap visible lines, drawing border, other dimension text, etc.
• Drawings should have a WORKMANLIKE appearance. Be neat, professional, and clear.
• Material notes must be specific and unambiguous. “Aluminum” or “Stainless Steel” is NOT sufficient.
• Use hidden lines or put in a note saying they are omitted for clarity.
• Datums CSYSs and sketch geometry should NOT be on the print.
• ALWAYS USE ALL CAPS ON PRINTS.
• Don’t overlap text or dimension lines.
• Do NOT dimension to the EDGE of a hole! Always to the center.

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DON’T LOSE POINTS BECAUSE OF THESE COMMON ERRORS.

Remember this video?

More...

Dimension array of bolt holes with a bolt hole circle. Look it up.

What is wrong with this picture?

You can expect to get zero credit for work like this.

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Datum CSYS is present.

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Ø.4 is dimensioned in two views.

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No Ø symbol.

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Wrong standard (not ASME)

Similarly poor print. Zero credit.

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Datum CSYS in all view.

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No overall length dimension.

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R0.2 Radius specified improperly.

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Solid cylinder dimensioned in round view.

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Redundant dimension (.5 step).

MORE

Very poor print.

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Needs a section view.

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Datum CSYS showing.

Extraneous + marks.

Hole locations?

Solid cylinder dimensioned in round view.

Teamwork Problems

First, to avoid problems:

1. Start early (now)
2. Get organized
3. Communicate
1. With all team members
2. With me
1. If a team member misses a scheduled meeting, notify them and me via email. Tell them what they missed at the meeting. They need to reply all when they respond.
4. Do NOT edit someone else’s model if it is incorrect. Communicate the problem (to both them and me if necessary).

Weekly Project Reports

These reports will be part of your grade. They are designed to improve communication within your team.

If you are having trouble, be sure and document it in your report. Feel free to add pages as necessary.

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Note: Expect team members to disappear as the deadline approaches. Find out who those people are early. Set early due dates.