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Stuart boiler feed pump

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Tomasz Osakowicz12/03/2019 20:54:48
10 forum posts
3 photos

Hi all!

I'm currently building stuart boiler pump and got stuck on the steam chest. On attached photo you can see that some of the steam passages need to be drilled through from outside and then blanked.

What would be the best way to blank this 1/16 holes?

Steam chest is gunmetal casting. Should i turn small brass pins slightly oversize and push them in? Or should pins have small taper?

Another idea is to tap these holes 7 or 8BA and screw pins in. Would loctite be of any help and withstand the temperature?

Any suggestions please?


JasonB13/03/2019 06:57:05
15023 forum posts
1531 photos

I would tap the holes then thread a short way up a suitable rob leaving it full length. Apply some high temp retainer such as Loctite 648 and then screw in the rod right up tight to where the thread stops. Once loctite has dried saw off and then file flush.

You could also use JBWeld rather than Loctite as your sealant.

Tomasz Osakowicz13/03/2019 07:24:03
10 forum posts
3 photos

Thanks Jason. I thought that thread will be a safer option. Wouldn't like to see these little pins leaving holes under pressure and flying towards my face

JasonB13/03/2019 07:34:21
15023 forum posts
1531 photos

Actually one of the members of another forum I frequent did some tests on JB Welded plain sided plugs and they took a lot of pressure to the point of the test pump not being to its limit. Only risk of using JBW on this one is you could push some spare into the bores.

Tomasz Osakowicz13/03/2019 07:40:31
10 forum posts
3 photos

You're right. As for the bottom holes it wouldn't be a big problem the top ones are going through the valve bore and a bit of excess adhesive could do a mess and affect valve movement.

Tap and thread it is then. Thanks for your help

Maurice13/03/2019 17:47:15
431 forum posts
50 photos

I made one of these a long time ago. At the time there several people warning that they had one and it would run very fast then stop. I had the same experience, and found that it was only happening on steam, not air. Hydraulic lock! I found that the steam piston covered the drain cock holes before the stroke was complete. I cut small half round grooves from the mouths of the bore to the drain cock holes. Turned on steam with the drains wide open. Steam came from one; closed it till the piston moved to the other end; slowly closed the second drain. off it went. After it had warmed through for a minute or so, I fully closed the drains and I "ran like a watch". Still does. Once it's hot it can be slowed right down with no problem. I did tell Stuarts about it at the time. I should be most interested to know if they ever changed the drawing?

Regards Maurice

Tomasz Osakowicz13/03/2019 18:15:25
10 forum posts
3 photos

Drawings calls for 2 holes 5/32 x40tpi at distance 3/16 from the cylinder end. It doesn't show any groves from the bore side.

Appreciate that you mention this it might save me a lot of head scratching later on trying to work out why the pump stopped.

Maurice13/03/2019 19:11:46
431 forum posts
50 photos

Thanks Tomasz. Does the drawing still show the steam ports drawn symmetrically, (as you would expect) but dimensioned to be asymmetrical? It used to. Should be symmetrical. Also one of these dimensions was taken from the centre of a drilled hole instead of a proper datum line such as the end of the cylinder block. I spoke to someone at Stuarts about it; they agreed with me and promised to change it.

Regards Maurice

Tomasz Osakowicz13/03/2019 20:07:43
10 forum posts
3 photos

I don't think that the drawings has been changed as most of the holes position still needs to be measured of the centre of another hole instead of the end of cylinder. However with the help of digital height gauge marking holes position wasn't that difficult.

As for steam ports they are symmetrical on my plans.

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