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14xx steam chest questions

14xx 57xx steam chest questions

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Lee Griffiths13/01/2017 13:50:25
19 forum posts
26 photos

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 ?

wp_20170112_10_50_17_pro.jpg

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

wp_20170112_18_58_46_pro.jpg

thanks

Lee

Brian Oldford13/01/2017 14:17:44
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567 forum posts
4 photos

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.

Lee Griffiths13/01/2017 14:23:40
19 forum posts
26 photos

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

MichaelR13/01/2017 15:32:20
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341 forum posts
57 photos

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.

Brian Oldford13/01/2017 15:43:01
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567 forum posts
4 photos
Posted by MichaelR on 13/01/2017 15:32:20:

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. . . . . .

Lee Griffiths13/01/2017 16:14:04
19 forum posts
26 photos
Hi,

Remember it's a 14xx between the frames cylinders so what you are looking at is the valve for the cylinder which is not there so to speak. 😊
duncan webster13/01/2017 16:17:45
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2234 forum posts
32 photos

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.

MichaelR13/01/2017 16:20:52
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341 forum posts
57 photos

Hi Lee,

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

Mike.

David Taylor16/01/2017 02:04:50
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128 forum posts
39 photos
Posted by Lee Griffiths on 13/01/2017 14:23:40:

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

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.

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