Durability of aluminium parts

Discussion on Stirling or "hot air" engines (all types)
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Wellington
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Durability of aluminium parts

Post by Wellington » Thu Sep 01, 2016 9:51 am

Question: I'm concidering making all of the mechanical parts of a gamma stirling engine from aluminium (not including displacer, displacer housing or power piston). Would this be a mistake or is aluminium durable enough to last for years?
Wellington

Ian S C
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Re: Durability of aluminium parts

Post by Ian S C » Fri Sep 02, 2016 2:15 am

Yes aluminium alloy is quite ok, but don't use it for bearing surfaces, aluminium against aluminium does not work. Use steel shafts, and either use ball races(best)bronze, or cast iron bushes, or a bearing grade plastic. To get a good seal on the displacer rod, a good fitting bush of at least 4 diameters long, and close fitting will do it.
Ian S C

Wellington
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Re: Durability of aluminium parts

Post by Wellington » Fri Sep 02, 2016 9:13 am

Ian S C wrote:Yes aluminium alloy is quite ok, but don't use it for bearing surfaces, aluminium against aluminium does not work. Use steel shafts, and either use ball races(best)bronze, or cast iron bushes, or a bearing grade plastic. To get a good seal on the displacer rod, a good fitting bush of at least 4 diameters long, and close fitting will do it.
Ian S C
Thanks Ian, but after googling bronze ball races I still don't know what they are or look like. do you mean bronze ball bearings?

Ian S C
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Re: Durability of aluminium parts

Post by Ian S C » Sun Sep 04, 2016 3:51 am

No, I mean plain bronze, or better still, Oilite sintered bronze bearings for the crankshaft etc. For ball races, either use shielded bearings, or open ones, it's best to keep away from sealed bearings unless you feel like digging the rubber seal out because it causes friction. For the displacer rod, plain bronze (brass is ok), or cast iron.
With most metals, like metal should not be run against like metal, the only exception is cast iron, that is why a cast iron piston in a cast iron cylinder is about as good as you can get with ordinary metal, a steel cylinder is a very close second.
Ian S C

masaruneema
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Re: Durability of aluminium parts

Post by masaruneema » Wed Nov 23, 2016 3:14 am

but after googling bronze ball
goldenslot

Ian S C
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Re: Durability of aluminium parts

Post by Ian S C » Thu Nov 24, 2016 1:57 am

I'm a slow learner, I did it twice on the same motor before changing to a stainless steel displacer, this is why I don't like aluminium in the hot area, apart from the fact that the aluminium conducts heat from the hot end to the cold end too fast. Ian S C
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