How To Make A Pressure Gauge Syphon?

[MEinThailandParticipant @meinthailand]

I need to make a pressure gauge syphon for a 1″ dia pressure gauge to fit on my model 3/4″ scale Burrell traction engine.

The photo shows one taken from my Stuart Models 504 steam boiler.

The problem is the tiny, tiny, olive under the 3/16″ X 40 TPI union nut. How can it be made and secured to the 3/32″ pipe reduction where the union nut is?

 

Why make one, why not just buy one from Stuart Models? Because it’s a nightmare trying to get anything through Customs here in Thailand. Last time cost me a fortune and a 10 (yes, ten) hour round trip to the Customs House!

[Speedy Builder5Participant @speedybuilder5]

Swage the copper tube to fit. Paint the olive and nut with white “Tippex” away from the joint. Hold the nut away from the joint and put a ring of fine wire silver solder around the joint and heat.  Even better if you can hold the nut in some sort of vice arrangement so that it can not get up to the melting point of the silver solder. A 3/16″ x 40 tpi steel bolt would be ideal (You would have to make one!). That would take the heat away from the nut and the olive end of the joint just leaving the siphon and tail of the olive exposed to the flame.

[JasonBModerator @jasonb]

I’d make a new nipple to suit your mismatch of pipe sizes or get some 3/32″ pipe. If making an new one I’d drill have it longer and sized to fit INSIDE the 5/32″ pipe. This is a long nipple supplied with teh gauge and intended ot fit inside the pipe and ht has a single dia hole right through so no “stop” for an inserte dpipe.

 

[noel shelleyParticipant @noelshelley55608]

With pipe so small, if you want the gauge to work then great care is needed when silver soldering to avoid the pipe being blocked with solder – though as the pipe is straight it can be drilled out. Good Luck. Noel.

[JasonBModerator @jasonb]

A piece of pencil lead down the hole will often work with a small hole or as mentioned above a resist such as solvent based correction fluid or nail varnish applid inside the hole will prevent anything sticking

[MEinThailandParticipant @meinthailand]

JasonB your photo tells it all. I can see now that there is a small pipe with a union nipple already attached – could have been turned from solid brass. That is secured to the pressure gauge by the union nut. It then becomes a ‘simple’ matter to extend that pipe probably by inserting it into a larger copper pipe.

This is possibly what Stuart Models did. The challenge is not to let solder get into the pipe bore and not melt the pressure gauge during soldering. Maybe I’ll make a CAD drawing of the arrangement.

Anyway, your photo and explanation has answered my basic question so thank you very much.

Thank you also to everyone who has responded to my request for help.

[JasonBModerator @jasonb]

Undo your nut and nipplegrom the gauge, solder then screw back on. No risk of cooking the gauge which it will. Infact you would have a job silver soldering it if attached as the gauge would draw all the heat out of the nipple.

Turn a new longer nipple as yours looks too short. The longer nipple not only allows sufficient length to go INSIDE the copper pipe it also allows you to keep the captive nut away from the joint as unlike a standard nipple where you can slide the nut along the pipe to keep it out the way the small hole in the nut means it can’t pass over the copper.

That long nipple came with the gauge as have others I have bought so it is a common option

[MEinThailandParticipant @meinthailand]

CAD Drawings for Small Pressure Gauge Syphon Connection

Thank you JasonB again for mentioning that pressure gauges commonly come with the long nipple. My pressure gauge – 3/4″ diameter – for my 3/4″ scale Bassett Lowke Burrell model (1950 design!) has just arrived and it has a long union nipple of 3/32″ diameter, as shown in JasonB’s photo above.

I have now made two CAD drawings for the small pressure gauge to syphon connections one using standard dimension pipe fittings and one with the long 3/32″ pipe union nipple. As a thank you to all who have helped me in the post and also to assist others who might have similar requirements I am making these freely available for download.

These are small sized images of the full sized CAD drawings:-

 

The full sized CAD drawings can be downloaded by clicking here.

Once again many thanks to everyone who has helped me with this query.

PS CAD Drawings for the Banjo Connection

Since I’m going to make the syphon myself including a 1/4″ threaded union to screw into the boiler bush I’ll be making CAD drawings of these components too and will made those freely available for download too.

 

[MEinThailandParticipant @meinthailand]

Now Available – CAD Drawing for the Banjo Connection

This CAD drawing is for a typical ∅5/32″ pipe Banjo fitting (as used for pressure gauge syphons) for small steam pressure gauges in the range of 3/4″ to 1″ diameter.

This Banjo Fitting is intended to be used with the pressure gauge connection fittings as shown above.

As before, the full sized CAD drawing can be downloaded by clicking here.

[JasonBModerator @jasonb]

It is often better though a bit trickier to cut the cavity into the banjo. This means that the bolt is not weakened by the radial cut so less risk of snapping should it become a bit tight when you wnat to remove it.

[MEinThailandParticipant @meinthailand]

JasonB that’s a good point about putting a grove in the banjo body instead of a grove in the stud. Accordingly I have made a version 2 CAD drawing showing an annulus:-

As before, the full sized CAD drawings can be downloaded by clicking here.

Anyone following that drawing would have to make sure that the syphon pipe does not block off the annulus.

Your 3D CAD representation of the banjo body showing the annulus will be a great help in explaining the principle. I note you have added a nice curvature to the outside of the banjo body – nice detail.

Again, many thanks for your help on this subject.

[Author]

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