piston packing

[ANORAKParticipant @anorak]

is graphite packing or O rings, best for cylinder packing?

[ANORAKParticipant @anorak]

[Tony MartyrParticipant @tonymartyr14488]

You really need to define the engine type and the materials used in the bore and piston.

For bronze / gun metal type cylinders and pistons in steam engines, where the pressure load works on both sides of the ring, graphite is quite forgiving towards surface finish and, to a degree, self lubricating over the working temperature range. Some leakage past the ring in a double acting model steam engine doesn’t seem to me to be too critical as to need an O ring, which I reserve for installations such as boiler feed pumps where the delta t is quite small and leakage is to be avoided.

In small IC engines with cast iron bores and steel pistons I have only used split cast iron rings working in a honed bore because of the high max surface speed.

In stirling engines, where the internal friction has to be very low I have never used rings of any sort but used PTFE or graphite pistons.

Horses for courses?     

Tony M

[Tony MartyrParticipant @tonymartyr14488]

As soon as I posted the response I realised that because I had just been fitting rings on an IC engine I was going off in the wrong direction!!

I still think that gland packing is best when using graphite – it beds in while O rings wipe the lubrication off and then wear.

Tony M

[mgjParticipant @mgj]

that square PTFE yarn works well too. Both on steam glands and boiler feed pump.

 

You could use packed hemp and Boss White too. Very cheap, very effective.

[ANORAKParticipant @anorak]

i have got the chassis running on air, all be it forward only, but it looks impressive.

[Author]

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