Stuart V10 steam inlet port seal.

This topic has 8 replies, 7 voices, and was last updated 14 February 2026 at 08:06 by scotty.

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12 February 2026 at 06:15 #837239
scotty
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@scotty
Hi, After a l ong absence due to illness in the family I am beginning to get back to building the Stuart V10. I have managed to assemble it and have done a dry run by setting it up on the lathe to run it in.

Can someone tell me how the steam inlet joint ( I have used a 1/4 x 32 thread) seal is achieved. I purchased copper tube size: 1/8″ x 22g (0.7mm wall thickness)

Scott.
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12 February 2026 at 08:17 #837249
Paul Lousick
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@paullousick59116
I don’t exactly understand your question but you need a fitting on the end of the copper tube that screws into the 1/4×32 thread.
12 February 2026 at 08:27 #837251
scotty
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@scotty
Ok. Thanks for that. Can you tell me what fitting is required. Does there need to be a nipple soldered on to the tube?
12 February 2026 at 09:00 #837252
JasonB
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@jasonb
If you intend to run on steam then you need a fitting with the 1/4 x 32 thread on one end and on the other it is usual to have a nut and nipple (ferrule) where teh nipple is soldered onto the end of the copper tube then much like a domestic plumbing fitting the nut draws the tapere dend of the nipple tight into the fitting. To seal the screwed thread you can either use soft copper washers or a thread sealant.

This sort of fitting but check the thread as a lot of suppliers use 40tpi rather than 32, stuarts do one with 32tpi but for 5/32″ pipe.

If running on air just for display then make up a simple threaded fitting with a spigot to push a piece of flexible hose onto.
12 February 2026 at 09:07 #837256
Buffer
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@buffer
Hopefully this wil be of some help. The pipe is just threaded and spun in.
12 February 2026 at 12:56 #837263
Richard B
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@richardb44403
<p style=”text-align: left;”>Where I run them off a car tyre compressor I just thread in in bit of copper tube as it fits the compressor coupling.</p>
12 February 2026 at 16:21 #837280
Clive Foster
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@clivefoster55965
Pretty much whatever you do the connection is going to look “a bit odd” relative to full size practice on an enigine of the basic type the Stuart model is representable.

Personally I’d use a proper threaded fitting as the extra work involved is not great and the engine can be run on air or steam as desired. In my view a nicely made Stuart with an equally nicely made boiler is much more impressive than the engine alone.

Whatever you do plugging the ports, with screw on or push on caps, when not in use is probably prudent. Given reasonable care in storage, and post run drying out after running on steam, the chances of corrosion or other bad things happening due to uncovered ports is very small. Which doesn’t alter the major embuggeration of sorting things out if something does get in.

Clive
12 February 2026 at 17:58 #837301
John Purdy
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@johnpurdy78347
Clive

You mean like this?

Scott

Here is how I did mine. If I remember I threaded both the inlet and exhaust 1/4-40 ME.

John
14 February 2026 at 08:06 #837505
scotty
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@scotty
I think I have a better understanding of what is required now. Thanks to all who responded.

Scott.
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