Well the natural progression in developement of the Single Cylinder Oscillator is, of course a twin.
The first arrangement I have here is a horizontal parallel twin which was an Ebay buy a couple of years ago. What caught my eye was the elegant long rods of the pistons and the fact that I had never seen such an arrangement before.
As you can see there are two identical cylinders, each with it's own ports supplying steam at the correct time of the stroke. The big advantage now is that the cylinders can be arranged at 180 degrees apart so the engine should now be self starting.
Unfortunately this engine is not quite as well made as it looks and the crank webs are fixed to the crank with grub screws. These pretty quickly come loose and I now have to set up the timing again and try to come up with a more secure arrangement for the webs.
Nevertheless I still think it is a very attractive arrangement although for practical purposes it would need a lot of steam to drive it.
Another by far the more popular arrangement is the 'V' Twin as you can see in the picture of my model boat engine. This is, once again, another arrangement of two cylinders but this time we have taken it a significant step further and made it double acting. The means that steam is applied to both sides of the piston so the piston is actually driven in both directions. This has two major advantages namely the ability to reverse as well as self start and a good power to weight ratio.
These are the main reasons why they are so popular for model boat applications as steam propulsion units as they can now give complete control via a servo linkage and give a good amount of power for a small unit. The main disadvantage is maintaining a seal between the cylinder face and the main frame which can leak steam if not looked after. This tends to make them more suitable for an open boat where steam leaks are not so much an issue as they are in an enclosed boat.
So why did I put one in an enclosed boat? What a good question!!!!
