Simple Stirling 1 Engine Bill of Materials V1 and Material notes

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(see general material notes at bottom)

Item Number	Part Name	Quantity	Material	Description	Part Notes/ Building suggestions
1	ABS 3 inch dia x 1.5	1	ABS	Plumbing fitting	Make the pipe end to be glued against the hot plate square and smooth. It must make an air-tight/water-tight seal with the hot plate. It is easier to leave the pipe long until it has been glued, then cut to the finish length.
2	ABS Coupling 3 inch	1	ABS	Plumbing fitting	Use sandpaper on a flat surface to smooth the edge of the ABS coupling that will go against the gasket. When gluing the ABS pipe into the ABS coupling with the hot plate sandwiched between the two, be sure to use ample ABS cement for an air-tight/water-tight seal. Maintain pressure on pipe so that it does not pop out while the cement hardens.
3	Cold plate	1	Galvanized steel	4 inch square electrical cover plate	Match drill the center hole in the cold plate with the corresponding tube in the main mounting tube. Drill the cold plate first, then with the support tube holes in the main mounting tube you can clamp the two pieces together and use the cold plate as a guide for drilling the main mounting tube.
4	collar .062	1	Brass or Steel	Du-Bro #137 or other source	This collar is used to keep the Displacer fork pin from falling out. Du-Bro parts are available from hobby stores or online.
5	collar .125	1	Brass or Steel	Du-Bro #138 or other source	This collar is used to keep the Crankshaft bearing tube in position. You may need to add some washers or other spacers to fill the space between the Crankshaft support angle and the Crankshaft support backup. Be careful to use light pressure on the collar set screw to avoid crushing the bearing tube and causing high friction on the Crankshaft.
6	Cover Plate	1	Galvanized steel	4 inch square electrical cover plate	The base of the engine. You can add or substitute a wood or other base as desired.
7	Crank pin	2	Music Wire	K&S Engineering .062" dia x .875" long	Debur the ends. Press one into Flywheel arm. If the fit is too loose or if the pin moves use epoxy or other adhesive to lock it into position. You may adjust the length depending on where the rod-end rides.
8	Crankshaft	1	Music wire	K&S Engineering 3/32" dia x 1-5/16" long	Debur but keep ends square for clamping, especially on Displacer Crank 2.
9	Crankshaft bearing tube	1	Brass Tube	K&S Engineering 1/8" dia x .014" wall x .75" long	Debur. A light grease inside will reduce friction.
10	Crankshaft support angle	1	Aluminum Angle	3/4"x3/4"x1/8" x 5-3/8" long	The three holes that are also in the Crankshaft support backup should be match drilled. Rounding on ends and relief angle are not critical. Hardware-store aluminum is fine.
11	Crankshaft support backup	1	Aluminum flat bar	3/4"x1/8" x 2.5" long	Match drill with the Crankshaft support angle. Hardware store aluminum is fine.
12	Displacer	1	Styrofoam or Balsa wood	3.4" dia x 1" long. May be built up in layers	1" Foam insulation board such as sold at Home Depot is fine. Layers of thinner material may be used. Epoxy the displacer shaft in the exact center of the displacer and make sure the shaft is perpendicular. Use a drill press to hold the shaft while the 5-minute epoxy sets.
13	Displacer Crank 2	1	Brass square tube	K&S Engineering 1/4" square x .014" wall	You could also make this piece from 1/4" square solid aluminum. Be careful when center-punching holes not to crush the tube. The triangular cut to the .062 hole was done with a triangle file. It could be slit with a saw as on the other end. I was concerned that sawing into the small hole would destroy it. The triangle file gives good control. The screws need only be tightened lightly to lock them in position. The forces on them are low.
14	Displacer cylinder hold-down angle	4	Aluminum	3/4"x3/4"x1/8 inch aluminum angle	The holes in the angles are oversize to allow some freedom in positioning the displacer cylinder over the displacer. You can make the holes even larger if you need to.
15	Displacer Fork pin	1	Music Wire 1/16 dia	K&S Engineering .062"dia x 1-3/8" long	Bend one end of the pin or use two collars and a shorter pin. Anything that will keep the pin from drifting out of the fork.
16	Displacer gasket	1	Soft Gasket material	WonderLiner solid shelf and drawer liner	The gasket material needs to be reasonably soft and thick enough to tolerate some unevenness in the cold plate and ABS coupling. Because it will see maximum pressures of less than one PSI, soft material is not a problem. You need a good seal for the engine to operate, but you cannot crank down too hard on the hold-downs or you risk bending the cold plate. I'm able to get a good seal with the WonderLiner using only finger tightening of the hold-down nuts.
17	Displacer rod shaft	1	Music Wire .047 dia	K&S Engineering .047"dia x 3-1/4" long	You can use .062 music wire too. I chose .047 to save a little weight. Make sure to use music wire (spring steel) and not a softer steel.
18	Displacer shaft	1	Music Wire .062 dia	K&S Engineering .062"dia x 3-5/8" long	Make sure to use .062 dia music wire. This wire makes a good seal with the 3/32 dia tube that it slides in. The music wire is spring steel and will not easily get bent like softer steels.
19	Displacer shaft fork	2	Aluminum	.5" x .875" x 1/16" thick	You don't need to buy this material separately, you can use some of the same material used in the Main mounting tube. Match drill the two pieces.
20	Displacer shaft fork center	1	Aluminum	.5"x .375" x 1/8" thick	Made from the 1/8" x 3/4" bar. Match drill with the Displacer shaft fork. Cut the V-groove with a triangular file. It doesn't need to be deep, just enough to hold the displacer shaft in alignment with the fork while you tighten the screws.
21	Displacer shaft tube	1	Brass Tube	K&S Engineering 3/32" dia x .014" wall x 1-3/16" long	Debur. You will 5-minute epoxy this tube to the main mounting tube. Don't put any epoxy on the face that clamps against the gasket and cold plate, Use epoxy on the inside of the main mounting tube. Reach in with a tooth pick or other tool to apply the epoxy as best you can. You only need to hold the tube in place, it does not have much force on it. A light grease may reduce the sliding friction of the displacer shaft inside the tube.
22	Flywheel arm	1	Aluminum	1/4" x 1/2" x 5" long	You might have difficulty locating 1/4" x 1/2" aluminum bar at a hardware store. You can cut down a 1/4" x 1" bar or consider buying it online.
23	Hose Clamp, 4.5 inch diameter	1	Steel or Stainless steel	Range includes 4-1/2" diameter	A standard hose clamp that should be available in the plumbing section. It may be a 4"-6" size range. 4" -5" would also work.
24	hot plate	1	Galvanized steel	Made from 4 inch square cover plate	It should be a slip fit.
25	Main mounting tube	1	Aluminum square tubing	1" x 1" x 5-9/16" long x 1/16" wall	The 1/16" wall isn't critical. My tube has a .047" wall. A 1/8" wall will work too.
26	Main mounting tube gasket	1	Soft Gasket material	WonderLiner solid shelf and drawer liner	See discussion on displacer gasket. If you have trouble getting a good seal with this gasket, look to see if the cold plate is warped. If it is warped put the convex side against the Main mounting tube and the seal should improve when the two pieces are bolted together.
27	No 10 FH x .5	2	Steel	Flat head 10-32 or 10-24 x 1/2" long
28	No 10 FH x .75	2	Steel	Flat head 10-32 or 10-24 x 3/4" long
29	No 4 FH x .313	1	Steel	Flathead 4-40 x 5/16" long
30	No 4 nut	6	Steel	4-40 nut
31	No 4 x .5 cap screw	4	Steel	4-40 x 1/2" long cap screw, socket or Phillips head
32	No 4 x .75 cap screw	1	Steel	4-40 x 3/4" long cap screw, socket head	The socket head is recommended for this screw because you may need a fair amount of torque to lock the flywheel arm to the crankshaft. This is easier to apply with the socket head.
33	Nut 10-32	28	Steel	10-32 or 10-24 nuts to match FH screws and threaded rods	I used 10-32 on the FH screws and 10-24 on the threaded rods. The coarse thread is easier when you are running a nut down 5 or more inches of threaded rod. The 10-32 grips tighter. You can use 10-24 for everything and it should be fine.
34	Power cylinder	1	Brass Tube	K&S Engineering 21/32" dia x .014"wall x 2-1/4" long	Debur ends and make sure the end that goes against the gasket is perfectly square to avoid leaks. Be very careful not to distort this tube out of round when clamping, cutting or epoxying to the Main mounting tube. Before epoxying the tube in position make certain the piston skirt slides freely in the power cylinder under its own weight.
35	Power piston rod shaft	1	Music wire .047	K&S Engineering .047" dia x 4.5" long	You can use .062 music wire too. I chose .047 to save a little weight. Make sure to use music wire (spring steel) and not a softer steel.
36	Power piston skirt	1	Brass Tube	K&S Engineering 5/8" dia x .014" wall x 1" long	Debur ends and make sure the piston top end is square. Be very careful not to distort this tube out of round when clamping and cutting. Oil or grease will greatly increase the friction of the piston sliding in the power cylinder. Keep it clean and dry.
37	Power piston top	1	Aluminum	1/8" thick	Make from 1/8" x 3/4" bar
38	Rod end	4	Aluminum	1/8" thick	Make from 1/8" x 3/4" bar
39	Support Rod	4	Threaded rod	10-24 or 10-32 threaded rod, 10-1/4" long	Cut all four to the same length. Debur the ends so that nuts will thread on easily.
40	washer no 10	26	Steel	#10 washer
41	Washer No 10 x 1.25 fender	4	Steel	#10 fender washer, 1.25" OD
42	Washer No 4	1	Steel	#4 washer
43	Wrist Pin	1	Music Wire .062	K&S Engineering .062 dia x 1/2" long	Make sure the wrist pin is long enough that it cannot slide out of the wrist pin bearing tube when inside the piston skirt.
44	Wrist pin bearing tube	1	Brass Tube	K&S Engineering 11/32"dia x 1/2" long	This tube was chosen as a good fit with the #4 washer. A slightly larger diameter tube could also be used but not a smaller tube.

Material notes:

Brass tubes:

The power cylinder and piston skirt are critical items and should not be substituted. When in a vertical position these two brass tubes slide with very low friction while providing a reasonably good seal. The K&S Engineering brass tubes are widely available from hardware stores and hobby stores or you can buy them online. Note that all of the brass tubes called for in the BOM (bill-of-materials) have a .014” wall thickness. K&S also makes tubes with a .028” wall which would not work. I would recommend that you use the K&S brass tubes for all the tubes (five round tubes and one square tube) although you may substitute solid ¼” square aluminum for the ¼” square brass tube.

Music wire:

The BOM also calls out K&S Engineering music wire. Any music wire of the correct diameter may be substituted. Music wire is a high-strength spring steel and you should not substitute other types of steel such as welding rod that have much lower yield strength.

Gasket material:

The gasket material needs to be reasonably soft and thick enough to tolerate some unevenness in the cold plate and ABS coupling. Because it will see maximum pressures of less than one PSI, soft material is not a problem. The WonderLiner solid shelf and drawer liner is about 1/16" thick and the best material I have found so far for this application. The WonderLiner solid shelf and drawer liner was available in my local hardware store. It came in a 12” x 5 foot roll. It’s also available online but you may have to shop around for single rolls. Make sure to get the solid type.

Aluminum:

The aluminum bar, angle, and square tube are extrusions and any allow used in these extrusions should be adequate for this engine. If you have to make a selection from an online merchant or other store opt for either 6061-T6 or 6063. The few small parts that require 1/16” flat aluminum can be made from the wall of the 1”x1”x 1/16” wall square tube. You should be able to find the aluminum at your hardware store with the exception of the .25” x .5” bar. You might have to cut this down from a .25” x 1” bar. You can also buy these materials online and most will sell material by the foot, some by the inch. Two suppliers I’ve used are:

OnlineMetals.com

Speedy Metals

Electrical cover plates:

This design uses three 4” square electrical cover plates. One is cut and filed into a disk for the hot plate. The plates are galvanized steel and about 1/16” thick. They were chosen for low cost, readily available and already cut to size with mounting holes. Use the solid sheet type, not the ones that have a knockout for conduit. If you don’t know what these look like see the base in the engine photo.

Collars:

The 1/8” and 1/16” diameter collars are available from hobby stores (the kind that sell RC airplanes). I’ve included the Du-bro catalog numbers for a package that includes four collars and a socket wrench for about $1. You need a 1/8” collar, you might find another way to retain the 1/16” pin other than a collar.

Styrofoam & Balsa:

To make the displacer you need some light, rigid material. My engine initially used the foam sold at Home Depot as a building insulation. You can also use various types of rigid foam sold at craft and hobby stores. Balsa wood works well too. For engines that run above boiling water temperatures (not the present configuration of this engine) the foam will melt. Balsa wood can take higher temperatures.

Epoxy

Where epoxy is called for it is always the 5 minute variety widely available in hardware stores. This epoxy mixes and sets quickly so there is very little time waiting for the epoxy to cure. The 5 minute epoxy is not appropriate for any joints that will see high temperatures (> 200 F). If you need to release parts that have been epoxied together you can use a heat gun to soften the epoxy.