Tin Can Stirling hot air engine.pdf

Tin Can Stirling hot air engine

Thank you for purchasing the Tin Can plans. I hope they are informative enough

to get you through the whole project. If you have any questions email them to lez t-

link.net . I will try to answer them in my free time. Thanks again and have fun.

One note before you get started. When you’re working with tin cans its best to

wear gloves. These cans can be very very sharp when cut and some of the operations

require a little persuading and can easily slip and cut you. Be very careful. Be

forewarned I will not be liable for your actions and safety precautions .

I’ve included the “Stirling Formula” page in case you can’t find all the right size cans.

You want to make sure you follow this formula fairly close or your engine may not run.

Also, the clearance between the displacer piston and displacer can should be as close as

you can get it without touching the sidewall. Most of the ones I’ve put together had

about 1/16 th to about 1/8 th inch clearance depending on the cans. More than 1/8 th inch

creates a lot of dead space and won’t run as well or possibly not at all.

The power piston and cylinder should be a very close fit. You want as little leakage here

as possible. I used a 1 1/8 th inch aluminum tube with a .062 wall thickness. This allows

for a 1 inch piston to fit fairly nice. If you have access to a small machine shop this

would be helpful for sizing it. If you don’t….. You can find a 1” piece of aluminum

(solid) and use sand paper to size it. It should fit snug but travel through the tube without

any drag or very little. You can use a light oil to make it slide smoothly.

When gluing the parts together I mention the use of JB Weld. This works very well,

there are other brands out there that work well also so if the JB brand isn’t available use

PC-7 or something equivalent. I use the JB Quick because it sets up in about 4 minutes;

the other takes 24 hours to completely set up. Unless you have a lot of patience and a lot

of time to hold parts use the JB Quick.

Drawing 3 shows the Burner pot made from a coffee can. It states to use Hi temp

silicone around the top edge. You want to make sure the cylinder and displacer can is

positioned in the motor mount board prior to doing this. If you glue it without

positioning it in the motor mount the burner pot could be to high or too low. There is no

real need to seal this can if you choose not to. If you do decide to seal it and lock it in

place do it after the unit is mounted.

Drawing 4 shows the “Cooling can” made from another coffee can. This unit can be

installed prior to mounting the engine and you should check it for leaks. You will put

water, ice or snow in it to keep the cold side cold. The colder you can keep it the faster it

will run.

Drawing 5 shows the “Displacer piston”. This is made from 2 beer can bottoms. When

pressing the two pieces together use some JB to assure a good seal and that the parts

won’t come apart when running. Try to get the center

hole as close to center as possible. If you’re off by a

little it could mean the piston will drag along the

displacer cylinder wall and create friction not allowing

it to run properly. Instead of threading the rod you can

use JB weld to seal both openings where the rod will

be inserted. If you have a threaded end use a nut and

JB weld to hold it. This is just a precaussion to assure

the rod and can won’t come apart.

Drawing 6 shows the Displacer can top and rod

bushing. This is made of a bolt with a 1/8 th inch hole

drilled down the center. You want to make sure the

rod slides freely through the hold without binding and

also not sloppy enough to create a leak. This rod gets

light oil for lubrication and sealing.

Drawing 7 shows the placement of the Displacer can

top. I usually smear some JB weld around the can top

inside and around the larger piece where the can will contact the can then slide the unit

together. Its best to insert the unit without any JB first and work the displacer rod and

piston up and down to make sure there are no binds or dragging going on. This is the

time to find them … after its glued you can’t fix it. After the top is pushed into place and

glued mix up a batch of JB and smear it around the outside allowing it to build up so no

edges are showing. After the JB has set up blow into the power piston hole and listen for

leaks, If you hear a leak find it and seal it with JB again.

Drawing 8 shows the sizes of the wood base, backing, engine mount etc. These are

basically a general layout and none of the dimensions are set in stone. If your cans are

different in size then you must cut the wood accordingly. The same is true for Drawing

8.1

Finalizing you motor with the rods. I used all 1/8 th inch brass stock and threaded the ends

and made my own ends. An easier way would be to visit your local Hobby shop and use

the rods they have already made up. They also sell the slick little threaded ends that

screw right on. The timing is set already because the displacer rod and power piston is

set at 90 degrees from each other and the mounting on the flywheel is shared by both

rods.

The following are some pictures that will aid in the placement of the rod connections and

other parts. Notice this engine has separate mounts for all the different components. The

better way is to combine the mounting brackets into two pieces. This motor is shaky

when running at high speeds. When all the mounting boards are combined this cures the

problem.

This shows the configuration of attaching the displacer

rod. This was done using a 1/8 th inch brass welding rod bent to line up with the walking

beam. You must use a link to keep the geometry correct otherwise a direct connection

will cause the displacer rod to bind.

The rod ends don’t have to be threaded, you can drill through a small piece of plastic, aluminum or whatever you have and glue

with JB weld. Also, ends could be made from an L bracket material of some sort. Let your creativity flow… this isn’t a

precision piece of machinery only a sample of how easy it is to make one of these engines.

This picture shows the general layout, front and back view of the machine.

I’m not sure if it helps but they say a picture is worth a thousand words so here is the top

view for reference.

This is a view of the piston and rod. A basic straight blade screwdriver screw is threaded

into the piston. The screw has a brass tube attached to it for mounting the piston rod.

This can be soldered, brazed, or even glued with JB weld. Make sure all the connections

are cleaned and sanded.

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