Stirling Engines

[David NunesParticipant @davidnunes86795]

Over the past several years I have built and exhibited many Stirling engines, some of which use a diaphragm instead of a power piston. I usually use a latex glove to make the diaphragm but I find that they tend to biodegrade in a very short period, very often as quickly as 5 months. Can anyone suggest a more likely source of less biodegradable material that I might try. Condoms and ballons have been suggested but not yet tried.

[David NunesParticipant @davidnunes86795]

Diaphragm driven Stirling Engines

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Kevlar sheet .

[Ian S CParticipant @iansc]

A rubber or synthetic with a fabric reinforcing layer (maybe Kevlar) would be ideal, specially if concentric corrigations could be included. About 2 yrs ago, I was thinking of making up a mold to make some experimental diaphragms. Up to that time I had been making molds for rubber components for vintage millitary vehicles, mainly Willys Jeeps. There are quite a number of different rubbers for different uses. I lost my molds in Christchurch's earthquake, I don't know even now if they have been salvaged, about 6 or8 molds at a value of over $NZ1000 if they had been professionally made. Ian S C

[dcostaParticipant @dcosta]

Hello All!

Just for curiosity I invite you to observe two Stirling engines. Both are crude, made with simple materials, but functional. One even generates 12V, 4W.
Here **LINK** and here **LINK**

Best regards
Dias Costa

Edited By dcosta on 27/08/2012 16:01:32

[SkarvenParticipant @skarven]

I have no experience with stirling engines, but I think the efficiency seems to be on the low side. An input of about 1000 to 2000 watts gas flame heating for a battery charging of 2W, then increased to 4W by improvements.

Is this typical for stirling engines?

[Sub MandrelParticipant @submandrel]

This suggests stirling engineare more efficient than internal combustion, with achieveable efficiencies of 15-30%.

**LINK**

Certainly there are many practical applications on record.

Neil

Edited By Stub Mandrel on 27/08/2012 20:20:38

[Sub MandrelParticipant @submandrel]

Also:

"The MOD II project in 1986 produced one of the most efficient automotive engines ever made. The engine reached a peak thermal efficiency of 38.5%, compared to a modern spark-ignition gasoline engine, which has a peak efficiency of 20-25%."

from:

**LINK**

Much food for thought – why do model stirling engine have ssuch relatively low efficiencies – or is it lust that they are too small?

Neil

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Primarily because most small hot air engines are not pressurised .

For any hot air engine to produce higher efficiencies and a high power/weight ratio it must work at the same order of cycle pressures as an IC engine . This means a high average pressure and rapid input/output of heat to obtain large cyclic pressure variations .

[Ian S CParticipant @iansc]

Stirling engines can be made in model form with a reasonable power to weight ratio, as shown by a number of motors made and flown in model aeroplanes, a case of suitable materials, and good design work, I think all the ones I know of are unpressurised. Ian S C

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