Sunday, November 16, 2008
After building so many engines a person starts to look for something different and unusual. A geared engine seemed to fit the bill. I have only seen one actual model, plus pictures of a couple others. I understand that they were patented by a fellow named Murray in 1908, but I have no knowledge if they were ever manufactured.
The engine employs a planetary gearing system. A point on the pitch line of the small hear generates a perfectly straight line from side to side, this eliminating the need for a cross head and connecting rod. The piston rod connects directly at that point.
This is just one of several model engines that I have built using surplus Bimba Brand pneumatic cylinders, and that is where the name came from. To add interest, it is equipped with a chain driven rotary valve and painted gaudy contrasting colors. Hope you like it.
Watch it in Action.
The reason for building this model is that it has a valve operating mechanism that is a little different than the usual for a steam engine. The cam is forward, operated from linkages fastened to the connecting rod which keeps it out of the splash area of the wheel. Also it incorporates a triangular shaped cam, that provides a rather quick motion to the valve at each end of the stroke. Another peculiar thing about the cam is that it has such a shape that it maintains contact with both sides of the cam follower at all times.
The first 2 pictures show the cams in the process of being machined. The third picture is the finished cams in their followers prior to installation. The forth picture shows the finished model. This is not a scale model of an actual engine, it is just to demonstrate the valve motion.
And here is a little video of it running