14xx steam chest questions

Hi,

I'm putting a MW 14xx kit together (and improving it) and I'm looking at the steam chest wondering how the valves seal against the cylinder ports ? It is the steam pressure entering the chest ? or should there be some kind of spring arrangement between the two valves ?

whilst I'm at it you can see the gland covers that come with the kit - just pressed out of a bit of plate so I *had* make something that looked a bit more substantial

thanks

Lee

I'm a little unsure how the MW valve is attached to the piston rod but normal practice is for the steam chest pressure to be ample to seal the valve against the valve face. Prototype Great Western slide valve rods were forged into a rectangular shape, known as a "buckle", that surrounded the slide valve proper to allow it to float a little. This would take up a degree of the wear that inevitably takes place but more importantly to allow the engine to coast more readily when the regulator was shut.

Thanks, that is what I thought.

The recessed section you can see is "loose" but snug fit in the slide valve buckle which has the rod screwed into it. So I'll lap the face of the valve pieces a little before I put it all together

Lee

Please correct me if I am wrong, but is your valve block upside down the recces I see is the exhaust cavity and should face the ports.

Mike.

Now you come to mention it. . . . . .

Probably an optical illusion, but it looks as tho' the buckle will shroud the ports. I would expect the buckle to be above the valve face by at least the max port opening.

Hi Lee,

I stand corrected thanks for putting me right, all the best with your project.

Mike.

The local guru at my club recommends not lapping the valve and port face but leaving them as machined as long as the finish isn't too rough. He says otherwise they won't seal properly because there is nowhere for oil to hang around in between them.

The story goes when making his first loco (of about 50) he couldn't get the valves to seal no matter how much he polished the faces until his father took pity on him and told him to rough things up a bit which fixed the problem.

Given I have only made my first set of cylinders and valves last year and don't yet have them running I cannot say whether this is a good advice, but he's seen the finish on mine which is far from perfect, and says they should seal fine.

Regards, David.