Traction engine, Gasket between Zylinder a. Boiler

[karl07Participant @karl07]

 

Hello Everyone

After my second attempt to seal the cylinder to the boiler, I need to ask for your advice. I’ve used a 0.5 mm thick gasket twice now. Would it be better to use a 1 mm thick one to bridge any unevenness? And what sealant should I use? Last time I used Weicon thread sealant because of the screws that go into the boiler. I would be very grateful for your help.

Best regards

Karl

[noel shelleyParticipant @noelshelley55608]

How good is the fit of the cylinder to the outer shell of the boiler ? Do all the studs or bolts tighten down properly ? .5mm gasket should be OK. Noel.

[Nigel BennettParticipant @nigelbennett69913]

The gasket will not compress very much. It is important that the boiler outside diameter is accurately round and the inside radius on the cylinder is the same radius as the cylinder plus the gasket thickness. Your choice of gasket thickness must be such as to enable the two curved surfaces to fit properly.

[karl07Participant @karl07]

Thanks for the tips, I’ve now ordered the Rocol Steam seal. It’s a big can, but oh well, I need it. Regarding its use: I’m taking a 0.5 mm gasket and coating it completely on both sides. I’m also lubricating the screws and threads with it. Assemble the zylinder on the boiler and  wait 24 hours and than make a pressure Test. What do you think?

Best regards,

Karl

[duncan webster 1Participant @duncanwebster1]

This always seemed a fairly poor bit of design to me. Surely a hot pressing rivitted to the boiler to give a flat mounting surface would have been a lot easier

[MichaelRParticipant @michaelr]

Duncan, The Marshall S type traction engine has the flat cylinder mounting, the model of the S type also has the flat cylinder mounting.

As you say a lot easier way for fixing a cylinder to boiler.

 

[Dave HalfordParticipant @davehalford22513]

Consulting the book of Minnie

Tube 2.5″

cylinder base 1.25″ rad

Gasket cartridge paper (which comes in various thickness)

So no allowance for gasket thickness and start bolting from the middle of the cylinder base curve.

[Harry WilkesParticipant @harrywilkes58467]

Karl I used the Rocol steam seal when I refitted the cylinder back on my 3″ Burrell worked a treat

H

[karl07Participant @karl07]

Tnanks a lot !

Well, I’m curious to see how the sealant turns out when it arrives. Of course, a straight flange would be ideal, preferably like the one in the photo, with screws that don’t protrude into the boiler. The same goes for the base of the counter-guide (sorry, I don’t know the exact English term).

I’ll let you know how it goes.

Until then, and thank you very much!

Best regards, Karl

[karl07Participant @karl07]

Hello everyone,

here’s an update and a new question. I’ve now sealed the cylinder with Rocol steam seal and waited four days before doing the pressure test. The result: sealed at 3 bar, but a very slow drip appears at 5 bar. I think I’ll leave it at that, as it’s tricky, especially since the threads in the copper won’t last forever. Now, another question about the piston seal: I have a 3 mm groove and have inserted a 3 mm graphite cord.Do you think this is okay, or should I use something else? The problem will be having to take everything apart again once the front crosshead support is attached and sealed. In any case, I’m not buying another tractor with such a poor cylinder mounting.

I would be grateful for any tips!

 

best regards Karl

[Martin Johnson 1Participant @martinjohnson1]

There are better alternatives to graphite packing now.

An Viton O or X  ring would be good, but you may need to re make the piston to suit.

Assuming the groove in the piston is 3mm wide and 3mm radial depth, I would fit two 1.5 mm section O rings (Viton) and then make a PTFE piston ring just thick enough to squeeze the O rings a little when assembled into the cylinder.  If you can get carbon filled PTFE that is even better.

Martin

[karl07Participant @karl07]

Hi Martin,

is 1.5 mmnot  to small? And if so, what’s the best material for the O-ring? Viton or EPDM? I’ve read that EPDM is very good for hot steam, but not for oils. I’ve now found a cylinder seal for hydraulics. It’s quite tough and suitable for pressures and temperatures. Maybe that will work. But it’s a pain if I have to take everything apart again.

[Martin Johnson 1Participant @martinjohnson1]

You would have two 1.5 mm O tings at the bottom of the groove side by side.  On top of the O rings you would have a 1.5mm radial depth x 3mm axial length piston ring in PTFE.  All dimensions are nominal as I don’t know the precise piston and cylinder dimensions.  The assembly should be such that the piston ring is gently pushed against the cylinder bore by the O rings.

I would use Viton O rings as I have had good experience with them.  Google “difference between Viton and EPDM ” if you want to dig deeper.

Martin

[karl07Participant @karl07]

Thanks a lot Martin ! now I will see what I do. I got a new 3 mm seal which is normaly for hydraulik pistons for nearly all fluids. i try this first. otherwise i have to get first a pair of BA 5 taps, to make a new piston.  EPDM is better for steam, but not ideal for mineral oels . Best would be Calretz, but a single o-ring could be 30 €.

Thank you again and best regards

Karl

 

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