Talk:Vuilleumier cycle

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This most definitely seems like a variant of Stirling/thermoacoustic principles. Stirling motor/cooler is not limited to one piston, contrary to what the article says, additionally, it is known in common configurations of 1, 2 and 4 pistons. And certainly some of the variants in this documents have been constructed as Stirling engines independently of this knowledge here http://dtic.mil/dtic/tr/fulltext/u2/a027055.pdf

Maybe this needs some reworking. I do not want this to turn into Tungsten/Wolfram debate, but I think it would be best to clarify this. It is also interesting how this information was kept hidden from all the people researching Stirling cycle, none of them mentioned Vuilleumier in the last 30 years at aleast. And yet, some of the configurations are identical, and the large/small displacer that is used as a toy demonstration of the Stirling hot-air engine is classic.