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**Bunkerbarge** · 05-08-2005

The next stage of the construction was to fit the major parts of the steam plant to the base and then work out the details of the rest of the installation. As can be seen in the attached pictures the boiler and engine assembly has now been fixed to a brass base, which should allow removal from the model as one piece. This was tested through the hole in the Quarterdeck many times to ensure that this was achievable. The base is held down by brass screws that are set in resin in the bottom of the boat and I made a wier across the hull to try to contain any water leaking from the engine and the stern tube which could then be easily removed when the boat comes in for a fill.

The alternatives with the feed water system was to use an engine driven pump with either a controlled or a manual three way valve that can fill the boiler or return to the feed tank or a manual pump connected up to the boiler. As I was apprehensive about sapping power from the engine I went for the manual pump option so I will have to bring the boat along side to fill the boiler. This isn’t a bad thing as I will have to bring it in anyway to empty the separator tank and I am hoping for a duration between fills of about 25-30 minutes.

Also worthy of note is that the construction of the kit would have allowed me access to the internals through the forward hatch and the aft accommodation block only. This would have been quite restrictive to operate and considerably more difficult to remove items when the model is finished. To greatly help this I followed the advice of John Hemmens and I am making the entire bridge section removable as well. This makes for considerably more thought as regards the construction of the bridge and its locating means but will be well worth it in the long run.

Any steam plant seems to have one or two inherent challenges, the most irritating seems to be the fact that the gas in the on board tank cools as it evaporates to the point where it cools the tank itself. This has the knock-on effect of slowing down the evaporation rate of the gas and hence the flame in the boiler reduces. This affects steam production and the whole thing slows to a halt. The cooling of the gas tank is directly proportional to the rate of gas use so the obvious starting point is control that use. For this I purchased a Cheddar gas control valve, which controls the release of gas to the burner depending on boiler pressure. This means that if the engine is not being used much the burner shuts down to a pilot flame and conserves gas.

Another main factor in this effect is when the boiler is brought up to pressure in the first place. This obviously requires the burner to be on full for a considerable amount of time so when the boat is first put in the water the gas tank is already cooling down. To get past this I have made a valve arrangement on the gas tank, which enables the initial pressure raising to be done with an external tank. When the boiler is up to pressure and the gas control valve is operational then I change over to using the on board tank prior to putting the boat in the water.

A final modification not yet in the pictures but will be the next step is to introduce some heat into the gas tank. This is going to be done with a copper saddle fitted between the gas tank and the separator, which will transfer heat to the gas tank. I hope that this will warm the gas tank enough to ensure excess pressure, which will then be controlled by a Cheddar pressure regulating valve. As soon as the plant is in operation the separator becomes quite warm so there is a good supply of excess heat.

The final points to note are the separate batteries for the radio gear and the Cheddar Gas Control Valve as interference could be an issue with the valve and the temporary servo set up at the back end. This is simply to provide control ready for the first sea trials and to see if the whole thing actually works.