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Teflon rings are probably the best choice for minimizing rust issues, they usually require a two or three peice piston design, since they will not expand and contract like an o-ring or metal ring for instalation. There are commecially made teflon rings made with the wiper shape, some with a spring metal part inside that make up of tolerances, creep and wear, these are wonderful seals for steam applications with. There some Teflon(TM) ring designs wich incorporate an o-ring also.
O-rings will work with the right bore and surface & gland tolerances and the correct surface finish, but they will have to be replaced perodically due to wear. Viton(TM) is proably the best choice for material. Silicone is not recomended for dynamic seals. If cylinders and or pistons are cast iron or steel then rust may be an issue, and could tear up o-rings very fast.
Bill Shields who contributes on here a lot has Teflon seals in Camel Back, I am sure he would be willing to share his piston & ring design.
All in all non-metalic rings work very well when tolerances and surface finishes are done right. They will not wear in like a cast iron ring will, all in all the old cast iron ring design is tolerant of larger surface finish and tolerance limits.
There is an Allen Mogal at our club with Teflon rings that has been running trouble free for several years. The owner just gives then a good squirt oil through the snifter valve ports running. I am not shure how the rings and pistons were configured.
Rob
We had a brand new 27.5Kva generator delivered and the man in charge could not wait to start it up.
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This genny is air start but of course it had no air in the tank until it had been started. It was started with the attached starting handle and the air pump engaged and then when 600lb was in the tank the engine was switched down. Later it was started up again using the air start motor which made a funny noise but no one took notice. At that point I started a service of the machine and found no oil in the air start motor. Decided to strip it and found one piston with a broken ring so decided to make another as there was no chance of spares.
I found one of those racking base stands and gave it a rub with a file and it seemed soft enough so turned up a new ring and split it and heated it up and then put it on the piston and re-assembled the motor. Remembering to put oil in as well ! Started up again with no funny noise and as far as I know still going strong.
clive
Teflon rings are probably the best choice for minimizing rust issues, they usually require a two or three peice piston design, since they will not expand and contract like an o-ring or metal ring for instalation. There are commecially made teflon rings made with the wiper shape, some with a spring metal part inside that make up of tolerances, creep and wear, these are wonderful seals for steam applications with. There some Teflon(TM) ring designs wich incorporate an o-ring also.
O-rings will work with the right bore and surface & gland tolerances and the correct surface finish, but they will have to be replaced perodically due to wear. Viton(TM) is proably the best choice for material. Silicone is not recomended for dynamic seals. If cylinders and or pistons are cast iron or steel then rust may be an issue, and could tear up o-rings very fast.
Bill Shields who contributes on here a lot has Teflon seals in Camel Back, I am sure he would be willing to share his piston & ring design.
All in all non-metalic rings work very well when tolerances and surface finishes are done right. They will not wear in like a cast iron ring will, all in all the old cast iron ring design is tolerant of larger surface finish and tolerance limits.
There is an Allen Mogal at our club with Teflon rings that has been running trouble free for several years. The owner just gives then a good squirt oil through the snifter valve ports running. I am not shure how the rings and pistons were configured.
Rob
We had a brand new 27.5Kva generator delivered and the man in charge could not wait to start it up.
This genny is air start but of course it had no air in the tank until it had been started. It was started with the attached starting handle and the air pump engaged and then when 600lb was in the tank the engine was switched down. Later it was started up again using the air start motor which made a funny noise but no one took notice. At that point I started a service of the machine and found no oil in the air start motor. Decided to strip it and found one piston with a broken ring so decided to make another as there was no chance of spares.
I found one of those racking base stands and gave it a rub with a file and it seemed soft enough so turned up a new ring and split it and heated it up and then put it on the piston and re-assembled the motor. Remembering to put oil in as well ! Started up again with no funny noise and as far as I know still going strong.
clive