caradoc question

Roberts wood light railwa · Post by **Roberts wood light railwa** » Sun Apr 12, 2015 4:59 pm

a friend of mine accuired a caradoc yesterday and whilst looking over it we noticed theres no water gauge glass on it so you'll be able to guess the next question ..... how do we know when its ran out of water? cheers

Big Jim · Post by **Big Jim** » Sun Apr 12, 2015 5:42 pm

Pressure goes up and loco stops!
Seriously though, the loco is designed for the gas to run out before the water.

Roberts wood light railwa · Post by **Roberts wood light railwa** » Sun Apr 12, 2015 5:56 pm

in theory then only fill the gas tank up once per run and dont top it up during the run?

Big Jim · Post by **Big Jim** » Sun Apr 12, 2015 6:27 pm

People do top up the gas and water (if you have a water top up valve fitted) during a run. But it then becomes a bit 'suck it and see'. It depends how high the gas is turned up and how had the loco is working. As to how long things last.
I tend not to bother topping up with mine.

As you get used to a loco you will start to work out when to add more water or top up the gas.

Never top up a gas tank when the burner is lit.

TonyW · Post by **TonyW** » Sun Apr 12, 2015 11:23 pm

Big Jim:110054 wrote:Pressure goes up and loco stops!

Errr.... No water = no steam = no pressure. I remember somebody telling me years ago that a boiler that runs dry will explode, yet he couldn't explain how exactly that might happen...

Roberts wood light railwa · Post by **Roberts wood light railwa** » Sun Apr 12, 2015 11:23 pm

Right thanks for that information I'll pass it on to my friend

Chris Cairns · Post by **Chris Cairns** » Mon Apr 13, 2015 6:20 am

I recently picked up a 2nd hand Caradoc that has been fitted with a water top up valve, and have pondered how this can be used properly without a working sight glass. I'm not a fan of the 'suck it and see' theory being used to operating full size locomotives with 2 working sight glasses.

On my Ragleth & Edrig I worked out that the boiler is full with 240 mls of water (up to the top of the safety valve bushing). The water level check valve effectively removes approx. 50 mls of water, so on my Edrig I fill the boiler full then remove 50 mls using a syringe with a piece of silicon tubing, and do not bother using the water level check valve. My Ragleth is a bit more fussy so I remove 53 mls of water.

As I only run on other's layouts or Garden Railways for now I just run on one tank full of gas which always runs out first leaving water in the boiler. If I complete more runs I go back through the process of filling up the boiler full then removing 50 (53) mls of water.

Only run my Caradoc on blocks so far (Group's running day next weekend) and removing 50 mls of water works OK here as well.

Having inadvertently run one of my Regner's dry (their sight glasses are very hit & miss and I was otherwise distracted and had forgotten to count how many laps I'd done prior to topping up the water) I can confirm the loco slows down with zero pressure indicated - in this case immediately turn off the gas and allow the loco to cool down naturally - Do Not Add Water

Chris Cairns

TonyW · Post by **TonyW** » Mon Apr 13, 2015 11:13 am

All of my locos are fitted with top-up valves, but only two recent purchases have sight glasses. An unreliable sight-glass is less use than no sight glass.

The method I use is to pump water in until the pressure gauge is back to zero after about 10 minutes of running. I find that this puts sufficient water in the boiler to continue the run but without filling it to the top, and that working pressure is regained reasonably quickly.

mikewakefielduk@btinterne · Post by **mikewakefielduk@btinterne** » Mon Apr 13, 2015 12:05 pm

An unreliable sight-glass is less use than no sight glass

I couldn't agree more. Only one of my locos has a reliable sight glass and that's the Mamod Brunel.

Keith S · Post by **Keith S** » Mon Apr 13, 2015 5:36 pm

TonyW:110078 wrote:
Big Jim:110054 wrote:Pressure goes up and loco stops!
Errr.... No water = no steam = no pressure. I remember somebody telling me years ago that a boiler that runs dry will explode, yet he couldn't explain how exactly that might happen...

They probably just believed that because that's what happens on a full-size locomotive-type boiler when the crown sheet isn't covered with water.

However I have heard that it is very dangerous to attempt to put water into a model boiler which has run dry and is still red-hot inside. Somewhere on the internet I have seen pictures of a single-flue model locomotive boiler that was tested to destruction. It blew up like a rugby ball and the flue collapsed, but it still didn't explode!

Big Jim · Post by **Big Jim** » Mon Apr 13, 2015 7:03 pm

Pressure goes up and loco stops!

Sorry meant to say pressure goes down and engine stops.

humble grovelling type apologies all round.

I really should read what I write before hitting the submit button

Roberts wood light railwa · Post by **Roberts wood light railwa** » Mon Apr 13, 2015 7:43 pm

cheers for the replies guys i shall let you know how we get on when running in a few weeks

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