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Chris's avatar
1w (edited)

Doble Piston Rings

The first of the new piston rings arrived yesterday , just unpacked them for a look, very pleased, these rings are stepped/lapped joint rather than the traditional angled cut, the idea being that there is less chance of steam leaking through this design, this is hopefully an improvement on Dobles angled cut. they are more difficult to make and therefore more expensive however unlike an ic engine that probably is always running at 500rpm and above the steam engine is direct drive and runs full pressure on piston from 0 rpm, steam leakage at low speed hopefully will be improved with these

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Oct 11, 2026
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Replies (5)
ShawnG avatar
· 1w

Are steam piston rings made of the same materials as IC engine rings?

Chris avatar
· 1w

not necessarily, the main high pressure piston and valve rings are exposed to 750 plus F temperature and cast iron would not be any use at those temps, we are also using some plasma coating to try and reduce corrosion, most of the corrosion in these engines is a result of intermittent use and condensation from the last steaming

alsancle avatar
· 1w

Chris,  is steam oil leakage in to the water as big a deal on the Doble as it is with a Stanley?

Chris avatar
· 1w

it is not leakage into the steam as in oil getting past the rings, these are double acting engines so steam is present on either side of the piston on alternate strokes, it is the fact that you must inject steam into the oil in order to lubricate the rings ( a bit like a two stroke ic engine) but then when you come to condense the steam the oil becomes a problem,  often forming an emulsion in the water, reducing the efficiency of the condenser generally and forming carbon inside the generator, the solution has always been  to use as little lubrication as possible to minimise this issue, however there are oil separating centrifuges available now which would be a sensible addition

alsancle avatar
· 1w

Did the Doble originally have any oil separating apparatus?   None were originally installed on the condensing Stanley's but you see them once in a while installed now.