gauge glass

[Garry ColesParticipant @garrycoles69390]

Hi everybody.

On my 5in gauge loco boiler, the backhead gauge glass bushes are 1 1/4″ from center to center. When I fit the top and bottom fittings and insert the gauge glass, the amount of glass showing is about 7mm. Will this be enough to show the right water level.

The boiler is a Doug Hewson design.

Garry

[Speedy Builder5Participant @speedybuilder5]

That is not much to show especially if you encounter inclines on the track.  Did you mean 7mm or 17mm ?  If 7mm, you need to re-think the size of the gland nuts and use O rings instead of packing perhaps ?

Can you give us the drawing or photo ?

Bob

[noel shelleyParticipant @noelshelley55608]

If there is only 7mm of visible glass I would say something is wrong. Even 17mm isn’t much on a moving loco. Check the relative position of the crown sheet to the bottom fitting – how much water will you have over the crown sheet as the water is just in the bottom nut ? Good luck.  Noel.

[Paul LousickParticipant @paullousick59116]

The Australian AMBSC Code Part 1 for Copper boilers states that:

The bottom visible end of the glass shall be above the highest point of the crown of the inner firebox by not less than 10% of the distance from the crown to the outer wrapper. (top of bottom nut or a cover around the glass if nut is lower)

You also need to know what the highest water level is so you do not overfill and prime the engine.

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