Ringbom had change direction or stop?

[Sameman]

I've done a little engine. When it ran on little candle(about 45 Watt) before full warming-up it rotate 3-5 or 10 times enough quickly then stopped and began reversed rotate about as. After total warming-up it rotated in one direction with gud speed(240 rpm) but after 3-5 minutes just very qucly (2-3 sec) stopped. After stopping at a burning candle run with force, as is well spun 3-5 minutes and so on. What is the reason for this work?

[Ian S C]

Sameman, have you tried a slightly heavier flywheel. I'v got 3 Ringboms, and I never had that problem, the only other reason I can think of is the diameter of the displacer rod, I can't remember the ratio between the displacer and the displacer rod, mine have been done mainly by guess work. When I get home tomorrow I may have some more info.
Ian S C

[Sameman]

Perhaps you are right. Dimensions of my engine barely corresponds to Mingfei Chen(2.19, from him book) formula (1-Tc/Th-Ar/A)*L*A/(lp*Ap) < 1,
where is
Tc cooler temperature
Th heater temperature
Ar cross section area of displacer driving rod
A cross sectional area of displacer
L 1/2 stroke of displacer
lp 1/2 stroke of power piston
Ap cross sectional area of power piston
for my engine :
Tc 323 K
Th 400 K
Ar 78.5398 mm^2 (D10mm)
A 5026.548 mm^2 (DD80mm)
L 3 mm
lp 11 mm
Ap 314.159 mm^2 (d20mm)
0.94 < 1
But I thinked, that displacer from steel wool have cross area much less than the geometric cross-section. But this is not the case, the difference is not noticeable. There is not any way to solve this problem only change dimensions. And I have some troubles with overdriving mode - engine work on its limits.
For example, data of Tapper Ringbom
Tc 323 K
Th 523 K
Ar 24.630086404144 mm^2
A 193.592793295837 mm^2
L 14 mm
lp 15 mm
Ap 126.676869774374 mm^2
0.36 < 1
And last question on the side could work two Ringbom engines on a joint flywheel, each with its own piston? With this law motion to power pistons?
[youtube]http://www.youtube.com/watch?v=v3f3GUwb7gA[/youtube]

[Ian S C]

I'v not had much success with steel wool for displacers in any hot air motor, I prefer a light weight hollow stainless steel displacer, although thin walled steel is OK.
Ian S C