Author Topic: Stuart 10h valve dimensions.  (Read 2630 times)

Offline Gas_mantle

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Stuart 10h valve dimensions.
« on: December 27, 2016, 03:17:20 PM »
Firstly seasonal greetings to all  :)

I'm trying to make a slide valve for a Stuart 10h but a little unsure exactly what the dimensions should be and wondered if anyone can help please.

I don't have the original or the drawings and I've never made a slide valve before but am I right in saying that as soon as the valve starts to cover one inlet port it should be uncovering the opposing one or should there be an overlap ?

Should the cutout exhaust pocket match exactly the cylinder ports so that as it directly in line with the outer edge of the cylinder inlet port it lines up with the furthest side of the cylinder exhaust port ? In other words does the cutout just fully expose 1 inlet and the exhaust without an overlap ?

I understand how the valve operates but without drawings or the original it's not obvious if there should be overlaps when you haven't made one of these before.

Many thanks
Peter.

Offline kvom

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Re: Stuart 10h valve dimensions.
« Reply #1 on: December 27, 2016, 02:23:56 PM »
It seems that there is some leeway in valve dimensioning.  If we consider the pocket length, you'd expect it to be equal to the widths of the exhaust port, one steam port, and the space between.  On my Joy engine it's 25 thou longer.  On the Stuart triple it's 1/64" shorter.  Making it equal is a reasonable design.

The external length also has some leeway.  Given the throw of the eccentric you want each exhaust port fully open at each end of the throw but the exhaust port covered.  On the center of the throw both ports should be closed.  Imagine the valve centered over the ports.  Then 1/2 the valve travel should uncover one port.  So the nominal maximum length is distance between outsides of steam ports + valve travel.

Offline SandCam

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Re: Stuart 10h valve dimensions.
« Reply #2 on: December 27, 2016, 03:13:21 PM »
Hi Peter,

Does this attachment help... you will need to measure the ports and spaces on your own engine to get the exact dimensions but lay it out as shown.

I hope this explains things enough for you.

Best regards.

Sandy.

edit... not sure why the document attached twice.
« Last Edit: December 27, 2016, 03:17:16 PM by SandCam »

Offline Gas_mantle

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Re: Stuart 10h valve dimensions.
« Reply #3 on: December 27, 2016, 05:52:39 PM »
Hi,

Thanks for your help, it's reassuring to know a bit of leeway shouldn't make too much difference.

The drawings are useful - I've saved a copy as they may come in handy for other projects at a later date.

I was gutted that I lost the original valve, I bought the engine from someone else and although it was in a poor cosmetic state it's an excellent runner and appears to be well machined so I was really hoping to make a valve that will allow it to run equally well.

I lost the part when stripping it all down for painting and even after moving my lathe, mill, searching the contents of the Hoover etc it appears to have vanished never to be seen again.

Peter.

Offline pgp001

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Re: Stuart 10h valve dimensions.
« Reply #4 on: December 27, 2016, 06:05:07 PM »
Peter

I found this drawing which you might just be able to get some dimensions from if you zoom it up a bit in the top left corner.
The valve looks to be 1/2" long and 3/8" wide to me.

https://static.rcgroups.net/forums/attachments/1/4/0/7/7/3/a3617765-202-IMG_1588.jpg

Phil

Offline steve-de24

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Re: Stuart 10h valve dimensions.
« Reply #5 on: December 27, 2016, 06:57:51 PM »
Phil, if the dimensions for the 10H valve gear are the same as the 10V then these pics are of the relevant pages from  "Building a vertical steam engine" by Andrew Smith.

If any moderator thinks I'm violating copyright by posting these two short extracts then please delete this post.

Steve

Offline Gas_mantle

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Re: Stuart 10h valve dimensions.
« Reply #6 on: December 27, 2016, 07:47:05 PM »
Thanks guys, I've now made a valve based on the info given earlier - I haven't had chance to try it yet but it seems to correspond with the Stuart plans you have shown so I guess that's a good start

I'll give it a test tomorrow  :)

 

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