Making steamtight seals.

[Gas_mantle.Participant @gas_mantle]

Hi all,

I'm thinking of making a simple double acting steam engine about the size of a Stuart S50 but much simplified and to my own design.

I've never made a double acting engine before and am unclear how to achieve steamtight seals where the piston rod exits the cylinder bottom and in the steam chest area.

I did 'Google' it but the information I could find was sparse to say the least, am I right in saying I need to pack and additional chamber with treated lagging rope where rods etc exit ?

What sort of lagging do I use on a small engine and is it just a case of compressing the rope in the closed chamber around the rods ?

Any help would be greatly appreciated.

Thanks.

Peter.

[Gas_mantle.Participant @gas_mantle]

[Nigel BennettParticipant @nigelbennett69913]

Graphited yarn has been used for years with a great deal of success. You need a suitable cavity in which to fit the sealing medium, which is, as you surmise, compressed by tightening up the gland.

Depending on how the crosshead is attached to the piston rod, it may be possible to use O rings. Some have used conical-shaped PTFE seals whereby tightening the gland compresses the PTFE against the piston rod.

Whatever system of seals you use, the piston rod should be a very smooth finish, or you'll wear your seals out very quickly.

Have a look at some Stuart Turner or similar drawings; Model Engineer has shown the arrangement of seals for locos (eg Martin Evans, LBSC, etc), traction engines and stationary engines (eg Anthony Mount) over the years.

[JasonBModerator @jasonb]

Another thing that can be used as gland packing is plumbers PTFE tape, take a few strips and twist them together to make a "rope" this can then be would around the rod as you poke it into the gland cavity and then compressed with the gland.

J

[michael howarth 1Participant @michaelhowarth1]

I will second the method described by Jason. I used to prefer "O" rings but PTFE is superior in my opinion. The pressure of the gland nut compresses the PTFE to a perfect "bespoke" sealing washer. And very easy to replace if needed.

Mick

[Gas_mantle.Participant @gas_mantle]

Thanks for the help

PTFE certainly sounds worth a try, I've just had a look on Amazon and can't believe how cheap it is.

Hopefully I'll make a start in the next day or 2.

Peter.

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