Stuart Beam Engine Slide Valve

[Phil PParticipant @philp]

Does anyone know why the slide valve on the Stuart Beam engine is asymetrical, ie the nut mounting posts are offset to one end. I cannot think of a good reason for this but there must be one. See images below.

Thanks
Phil P

[Roderick JenkinsParticipant @roderickjenkins93242]

It may be that the slide valve is common the several Stuart models, one or more of which need the offset but for some it doesn’t matter.  They used to be supplied as a hot pressed brass item but I understand are now CNC machined.

Rod

[JasonBModerator @jasonb]

Possibly gives you a bit more adjustment before the larger diameter threaded section of the valve rod hits the bottom of the valve chest

Does not make much difference, for the versions of the Real and James Coombes that I made most parts from scratch I just put the nut in the middle.

 

[Phil PParticipant @philp]

Thanks for the replies.

A good friend of mine is building this engine at the moment, and I have redrawn it in Solidworks 3D to make the drawings clearer for him to read, the originals leave a lot to be desired.
He rang me last night and asked this question, hence me asking on here before getting back to him.

I see no reason why it cannot be symetrical, there is plenty of room for everything in the steam chest.

Phil P

[John PurdyParticipant @johnpurdy78347]

Phil

I just checked my ST Beam and the valve is slightly offset. The plans are dated May 1972 and also show the ears on top of the valve as offset just like your drawing, so it has been like that for at least 54 years! The parts list calls the valve gunmetal, and looking at it, it looks like a casting, and if it is asymmetric it is very little. The plans don’t actually show any dimensions for the ears on top of the valve.

John

 

[Paul LousickParticipant @paullousick59116]

If the slide valve was mounted in the opposite direction to that shown in the image, it would allow the control rod to have more thread exposed at the top and not intrude into the guide hole and seal.

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