All done! The paint on the engine bed bolts is done, the name plate is attached, time for final photos and videos to wrap up the build.
To recap, back last spring I went to the antique engine show at Mystic Seaport Museum, displaying my Sabino engine based on the one in their steamship. They were demonstrating a number of the engines in the museum collection, including one like I had never seen before:
At first I thought it was some sort of anchor winch, but the spiral grooves on the drum didn't match that type. When they operated it, by turning the handle just visible in the upper right of the photo, the drum went back and forth with the handle movement (was designed to have the steering wheel connected from up above onto that shaft). I was intriqued, it was a giant steam servo! After I got back home and mentioned it on the forum here, forum member Michael posted a couple pictures of the real steering engine he restored and owns, rescued from the scrap pile after it was taken off one of the river sidewheelers on the Elbe River in Germany:
That started a great conversation, and I knew I had to build a model of it. He supplied drawings of the original engine, lots and lots of photos of it during his restoration, plus videos of it running. This is the type of ship that it was used on:
There are still a number of the ships running tours on the Elbe, and there are videos of them and their steering and main engines online.
So, I started drawing it up in 3D CAD to make model plans from, based on all that information, here is one of the screen captures from that:
To help understand how it works, also did this cutaway version:
Its quite an interesting mechanism, with the steering wheel turning the inner upper shaft, which moves a follower connected to the control valve. As the engine comes on, it turns the lower shaft with a large gear that turns the outer upper shaft, which via a half-lap drives the follower back the other way, turning off the engine when it meets the position that the wheel is now at. The control valve swaps the steam and exhaust between two pipes leading to the cylinders. The valves on the cylinders are spool type (aka piston valves), and the swapping of the steam/exhaust flow makes them swap between inside admission and outside admission, which reverses the direction on the engine. Quite clever how they did it! Here are diagrams that show how that works. First, a diagram showing the parts:
When the control valve is in the stop position, the control valve sends nothing to the cylinders:
When the control valve moves up, it sends steam down the lower pipe and takes exhaust back from the other, making the spool valve work in Outside Admission mode, running the engine one way.
When the control valve is moved down, it sends steam through the upper pipe, making the spool valves work in Inside Admission mode, running the engine the other way:
Here is the completed engine (full build log is over in the other section on the forum)
Behind the model the chains lead back to a 'rudder', to show how it operated from the engine. This setup is based on pictures from the real ship.
Closeup of the gear/control mechanism:
Here is a video showing the engine in operation, moving the 'rudder' behind it back and forth with the steering wheel. The engine cycles on and off and self-reverses as needed.
When the engine or boiler is down and the steering engine cannot be used, it has an option to steer manually with no power assist. This clip shows how that works. Dog clutch on the lower shaft is disengaged and the one on the steering wheels is engaged, and the large wheel has a screw that clamps onto the outer upper shaft, locking all of the shafts and screws together. That way the control valve is bypassed, and the large gear on the lower shaft and its attached chain sprocket are moved. The larger steering wheel gives more leverage for the helmsman (or possibly two helmsmen) to move the rudder and steer the ship.
Thanks very much to all who followed along and helped out! Biggest thanks to Michael for all his help, information, pictures, and drawings! Without his help this project would not have been possible.
Chris
