Questions about experiments / Stirling Engine / Mechanical Engineering Series / Otona no Kagaku product version / otonanokagaku.net

Stirling Engine

■ Troubleshooting

Problem	What to check	How to check and what to do
It is difficult to get started moving	Displacer	Check whether it can move smoothly inside the glass cylinder. If it moves sluggishly, twist the steel wool to make its outer diameter smaller. Ideally, the displacer should move just well enough to fall out when the glass cylinder is held vertically. If the outer diameter is too small, it will start better, but torque will decrease.
	Displacer	Check if there is any rattling in the stroke direction between the displacer and the 1-mm stainless steel shaft. Major rattling can make starts bad and cause insufficient power. When it is truly large, remake the displacer following the instructions in "Making Your Own Displacer" (attached).
	Connecting rod washer	On rare occasions, the displacer shaft and the connecting rod can become out of parallel. This may be improved by removing the washer (7 mm) under the connecting rod. Please try that. Operation and durability should not be affected by not having a washer.
	Cylinder adjustment	Remove the displacer and glass cylinder and readjust by the adjustment method that uses the batteries. When adjusted to an appropriate height, the piston will move back and forth smoothly.
	Heat	If the heat is very low, the engine may have difficulty starting. There should be enough flame to cover the tip of the glass cylinder.
Unstable rotation	Displacer	Output becomes unstable if the displacer shaft is not in the center of the steel wool. Re-form the steel wool and assemble the displacer again.
	Glass cylinder	Residue from steel wool or the like inside the glass cylinder can make rotation unstable. Remove the glass cylinder and clean it.
	Glass cylinder	If there is any play in the way the glass cylinder is screwed in, compression can leak, causing unstable rotation. Tighten it. (Be careful not to overtighten it! Tightening it with your fingertips is sufficient.)
	Displacer	Output can become unstable if the steel wool is positioned badly. The best position is where it almost touches the inner surface of the glass cylinder when the displacer is at the top dead center (farthest forward).
	Displacer shaft	Rotation sometimes becomes unstable if the displacer shaft is bent. If it is, fix it.
	Steel wool	If the steel wool is too long, there may not be sufficient power. 60 mm is a standard length. Should it be too long, cut it with scissors.
Does not generate electricity	Connectors, switch	Check that the switch is on and that connectors are not loose.
Propeller does not turn	Gears	Check that the gears rotate smoothly.
Propeller does not turn	Clutch	Sudden clutch operation can stall the engine. Start it again with the clutch engaged.
Does not run	Rear wheel shaft	Check whether it turns smoothly with the clutch lever off. Torque is transmitted to the right rear wheel.
	Front wheel shaft	Check that the front wheels turn smoothly.
	Front wheel tilt	Motive force is transmitted to the right rear. If a front wheel is off the ground, it could be the result of tilting of thefront wheel holder. Remove the 7 mm washer at the center of the front wheel holder. If a wheel is still floating, bend the front wheel unit a little at a time in the direction that raises the right front wheel.
Alcohol lamp wick works poorly	Wick holder	Repeatedly raising and lowering the wick can cause it to fray and slip. Remove the wick holder, hold the ends of the wick, and pull hard. The frayed part should firm up and perform better.

Left rear wheel is spinning free.

The rear wheels are set up so that the left wheel rotates freely while torque is transmitted to the right wheel only. When both wheels are fixed in place, turning around a corner creates a difference in rotation speed due to different turn radii for the inner and outer wheels, generating large loads. In real cars, a "differential gear" is used to absorb the difference in left and right rotation; this kit instead allows the left wheel to rotate freely as a way to avoid increased load due to rotational differences.

	The manual says that the shaft should stick out approximately 30 mm beyond the displacer adjuster when attaching the connecting rods. Isn't that too much?
The optimal adjustment position is when the displacer tip just about touches the end of the glass cylinder. In many cases, that turns out to be around 10 to 15 mm, depending on the relationship between the assembly positions of displacer and shaft.

	It is difficult to get started moving.
Movement involving the displacer, piston and gears may be sluggish. Check the description of adjustment in the manual (page 14) as well as the troubleshooting guide.

	Where do I get alcohol?
Ask for "alcohol fuel" at a drugstore or the like.

	The steel wool is falling apart.
You can use wire wool sold for washing dishes.

	What does the displacer do?
It facilitates heat exchange between warm air and cold air. Air moves around the displacer, so a slight space is required between it and the glass cylinder. A material that is heat resistant, has low heat capacity and is lightweight is ideal.

	How precise are the piston and cylinder?
We use a tolerance of 1/100 mm in our production control. Compression leak can cause engine power to decline. Contact us in the unlikely event of wear between them.

	Should I oil the engine?
The piston and cylinder are coated with polymer compounds, so they should never be oiled. Should oil get on the piston or cylinder, remove the piston and wipe off any oil on the piston and cylinder with alcohol.

	How are the piston and displacer shaft related?
The piston and displacer move back and forth offset 90 degrees in phase. For that reason, the displacer shaft needs to slide very smoothly inside the piston. Compression leak is also bad, so we control dimensions to keep the gap between them very small. Handle the parts very carefully.

	The connecting rods do not fit with the flywheels.
If the cylinder position is extremely high, you may not be able to assemble them. Adjust the height with the adjustment screw. At the final adjustment, the center of the cylinder should align with the place where the two flywheels mesh. (Fine tuning comes later.)

	What is the thermal insulator (F5) made of and how safe is it?
It is Superwool 607 made by Shin-Nippon Thermal Ceramics Corp. It is used to thermally insulate combustors, stoves, boilers and the like and as refractory investment material in buildings. It is not asbestos. Superwool 607 is made to be environmentally friendly and safe and should it somehow be ingested, it dissolves. Please rest assured.