The Essential Beginners Guide to Live Steam Models:
This guide is a short edited extract from
"The Complete guide to Miniature Steam" which is now available on CDrom or Internet download.
Tips on running Stuart Turner Engines in a Model Steam Boat
The excellent range of Stuart Turner steam engines, if they are well built, are very well proven designs of miniature steam engines.
At this point I must mention that I have no connection whatsoever with Stuart Turner Ltd in any way.
The popular types for use in model steam boats are the 10V & "Twin Launch" series of vertical steam engines. These engines are a robust resign & if they are well engineered in the first place, will give great results in a model steam boat.
The Stuart Turner 10V is a single cylinder slide valve engine, 3/4 inch bore & 3/4 inch stroke.
The Stuart Turner Double 10V is a twin cylinder slide valve engine, again 3/4 inch bore & 3/4 inch stroke. It is basically two Stuart Turner 10V engines on a common bedplate.
An option available with these engines is "Stephenson link" reversing gear, if the reversing gear is not fitted, then it is possible to use a reversing gearbox in the steam boat in order to go astern. To successfully operate this steam engine in a model steam boat, a suitable boiler is required. A boiler of at least 4 inches diameter, either centre flue, Scotch return tube or Firetube types can be used. A "Babcock" type of steam boiler with external water tubes exiting underneath can be used, but does not in my opinion look very good in an open steam launch application. Good for a stationary plant though.
The Stuart Turner "Twin Launch" engines have 1 inch bore cylinders and are also slide valve engines, again, like other engines in the Stuart Turner range, the optional extra available with these engines is "Stephenson link" reversing gear, if the reversing gear is not fitted, then it is also possible to use a reversing gearbox in the steam boat in order to go astern.
These Stuart Turner "Twin Launch" engines are very powerful, and to successfully operate these larger steam engines in a large model steam boat, a quite substantial, efficient steam boiler is required. A boiler of at least 4 inches diameter, or preferably even larger in diameter - either centre flue, Scotch return tube or Firetube types can be used.
The 1 inch bore Stuart Turner steam engines are very powerful engines and they use quite a lot of steam when running, therefore an efficient boiler which is a free steamer with a large heating surface area is definitely preferred. A reliable boiler water feed pump is essential too. Increased steam usage equals increased water usage also. Successful gas firing of the larger type model steam boilers relies on maintaining a good gas pressure which equals a constant hot fire.
For the larger 1 inch bore "Twin Launch" steam engines, a coal fired boiler is a good option, although they are smelly & dirty they are great! The "Stuart Turner "Compound Twin Launch" steam engines are more economical on steam but are not self starting, so it is not the best option for a radio controlled steam boat.
With the even larger Stuart Turner steam engine range, everything needs to go up in proportion. Running a really nice large steam engine is a very frustrating experience if the boiler cannot supply enough steam to keep it going properly.
The cylinder blocks of most of the Stuart Turner range of engines including the 10V, Double10V, & Twin Launch (simple or compound) are made from cast iron, so it is important to lubricate them correctly both during & after steaming. A steam engine needs either a mechanically driven oil pump, or a displacement lubricator fitted in order to provide constant lubrication when running. Any water left in the cylinders over a period will cause pitting of the cylinder or worse, the cylinder can "rust up" solid. Always inject copious amounts of steam oil into the steam inlet pipe whilst rotating the engine in its normal forward direction, in order to liberally coat the cylinder & piston with oil. Any steam engine with cast iron cylinders, valves or pistons needs "after run" oiling with steam oil to displace the water.
I never personally use WD40 as I find that it can cause the silicone "O" rings to stick - especially on certain small model "Weir" pumps. In standard form, the Stuart Turner 10V range of engines have a gunmetal piston with simple oil grooves cut around the piston. This is fine if the engine is well made & the piston is not worn through use. In practice, for use in a steam launch I recommend re-machining the piston(s) with a groove to take suitable silicone "O" rings for a better seal which equals more power & less steam wastage by the steam leaking past the piston(s). It is important to mention that the cylinder bores must be smooth in order not to wear out the "O" rings prematurely.
High superheat is best avoided with silicone "O" rings. Steam grade silicone is heat resistant, but there are limits! On the Stuart Turner "Twin Launch" & "Compound Launch" steam engines, cast iron piston rings are used, which are fine. They usually wear very well if lubricated correctly. Remember that adequate cylinder lubrication is necessary in all steam engines both during & after steaming, but especially if cast iron rings are used. Again, after a run on steam, it is important to internally oil the cylinders liberally after use to prevent internal rusting.
I have a Stuart Turner 5A single cylinder steam engine with Stephenson link reversing gear. I ran it on a test boiler of only 4 inches diameter - that is far too small for a steam engine with a 2 1/4 inch cylinder! All that happened was that the steam engine ran slowly with no steam pressure at all showing on the gauge. After a very short time the water was at the bottom of the water gauge glass, so more water had to be pumped in - this of course stopped the engine & I had to wait until the pressure went up on the gauge again. Definitely not the best way to run a large steam engine! I am currently looking for a good large boiler to run this engine, which I would like to fit in a small full sized steam launch. So far, all I have is the propeller!