Height of water gauge glass

Heres a little job I've been looking at doing for a while now, that is to take the fusable plug out, level up the boiler and fill it until it flowed out of the fusable plug hole.

So on Monday after the Bill Targett rally I was cleaning down the engine and washing out the boiler I hooked the plug out and tried it out.

The result is the below photo




as you can see the water is definately showing in the glass even though the plugs out, it was a little higher than this at the start but I waited till all the water had stopped flowing out of the plug and this is where it settled at. I was susprised it was as high as it was to be honest and shows that when I'm around that level going down steep hills I've got very little in reserve.

This is a batch one modelworks engine so cannot say if they are all the same, but I found it a worth while exercise to verify the absolute limits of water levels in the boiler and will make me pay even more attention to it in the future (not that I'm not on it like a hawk anyway )

This is quite common in the past I have made a small ring to go around the glass to remind me of the crown water level minimum
Hope this helps
Mark

I did a similar thing with my DCC, using lazer level, bore scope, telescopic rod, all very Heath Robinson. The long and short, when the level in my boiler is down to the top of the fusable plug, I have just about 10mm showing in the glass.

Seems like its across the board then, I was talking to another minature owner, cant remember the make they had but they said they had an engine that the crown was exposed with the glass 1/4 to 1/3 full and they made a similar band at that mark.

I found it a worth while test wonder how long you'd get before the plug would go at that level, suppose a lot of factors would be playing, a quick slosh of water would quickly cool things and the size of fire would play a large part.

I will be doing the same thing when I am ready to steam

Great topic OP, thanks for sharing your findings and others for their input.

I've often thought of doing similar to find out the exact min water level. After reading this I think I'll be putting a red indicator on or behind the glass a third of the way up from the bottom to show MIN water level, and make sure I have at least half a glass before going down any kind of hill!

I wonder what the max water level would be before the engine started to prime?

Something to bewarey of is the fact the take off for the top of the glass is from nearly the top of the boiler so, as I have found, anything on the flat above 3/4 or more of a glass and you find you dont actually have much room for steam, took me a while to fathom that one out.
I found I could have a good fire, plenty of water but setting off very quickly lost pressure as presumably there was little room for actual steam.
From personal experience and my own agri it seems about 1/2 a glass gives a good space for steam and not a huge requirement for lots of fire, however this means you have to be ready more for terrian change especially downhill sections.
I'm certainly no expert in the field and just observations from my own engine

3/4 of a glass is the usual upper limit for boiler water level - unless you're going up hill in which case the water all runs to the back-head. Traction engines usually have long gauge frames compared to railway locomotives, some builders had brass plates fixed to the back-head marked "working level" or "top of firebox". Running with too much water, having dirty water, running at too low a pressure or opening the regulator wide with a high water level are all routes to make an engine prime, lifting the safety valves with a high water level will also pick-up the water.
On the road with a full size engine it is good practice to shut the damper just before cresting a hill to calm the fire down and if you know you're approaching a falling gradient then put the injector on.
If you are going down hill with little water then occasionally slow the engine by easing back the reversing lever, this will cause the water to slosh back and forth and so cool the crown sheet.

The determine where the top of the crown is in relation to the water gauge an alternative method is simply to measure from the top of the firebox to the top of the firehole door ring with a simple gauge, then compare the measurement to the water gauge.

Make sure you know your engine and never steam without a fusible plug fitted.

For further useful reading see "The Modern Manual for Drivers of Steam Road Vehicles" by W. Michael Salmon

All things I do another very interesting read is the NTET guides here http://www.ntet.co.uk/owners-drivers/code-of-practice/