The Mark Twain is and has always been steam powered.
The automatic marine boiler sits in the "cage" near the bow. Here, you can see the fire through a small peep hole, and you can see the water level in the sight glass over by the starboard companionway (right staircase). The boiler is automatically fired and operated.
You can see the pipe along the ceiling that carries the steam to the two long-stroke pistons at the stern. These are masterfully constructed--almost like two mechanical works of art. The valve gear that directs the steam into and out of the cylinders are the bright polished-steel rods on top of the piston. It's fascinating to watch them operate.
It's said that the cylinders themselves were designed by a steam aficionado who knew Disney named Ed Bagley. Bagley allegedly designed them after Walt gave him a woodcut showing a similar piston. Not much to work from, but the results are astounding. The large arm that rotates the wheel is called a "Pittman Arm." Feel free to stump your friends with that little piece of trivia the next time you ride.
The two large smokestacks at the front of the ship expel only diesel exhaust. You can find thermometers for each one on the main deck. Up on the other decks, you can place your hand on them, and feel the warmth. Often, only one stack is used to vent the exhaust.
The two stacks at the stern vent expended steam.
The paddle wheel alone propels the ship; If "thrown into reverse" when coming into the dock, it also acts as the ship's "brake."
The ship used to have a steam-driven generator that provided electricity for the lights and other electrical equipment, but now the ship uses a diesel generator--and this can be heard near the stern as a dull rumble, leading some to mistakenly think the boat's powered by an internal-combustion engine.
In the engineer's cage at the rear, you can see the throttle--a large plate-sized valve wheel near the ceiling that controls steam to the pistons. There is also a large reverse lever on the floor--called a Johnson Bar. You can also see the gauges that register the steam pressure. These are the only controls for the boat's movement. The pilot does have some responsibility--he communicates with the engineer though a series of bell signals. The engineers, fittingly, are the same folks who run the steam trains.
The boat is guided through the ROA on two "caissons" that follow the rail. Obviously, the large wheel in the pilot house is for show only--although the steam that blows the whistle is quite real. The headlight is also alleged to be an authentic old-time steam locomotive box headlight.
As Ward Kimball has said, Walt Disney was very proud of both the authentic steam trains, and the Mark Twain. He considered them "the seventh and eighth wonders of the world."
There you have it: the abbreviated version of "Mark Twain 101!"
Last edited by Steve DeGaetano; 02-05-2007 at 12:52 PM.
I have an old copy of a Disneyland Line, where a photo is shown of the ROA, when it was drained and you can see the track.
I remember when they were retrofitting ROA in order to put in Fantasmic in the early 90's. They had a fence going the length of ROA, but it stopped just about where the TSI rafts are now. At that point I was able to peek around the side of the fence and look at EVERYTHING. The river was drained and all I could see was a huge concrete ditch with tracks going along the bottom. I wish I had a camera! (Oh well, thank goodness I still have my memory!)
When I was little, I used to think that the paddle was real but everything else was fake such as the engine and the steam billowing out of the pipes in the back of the boat (I thought it was fog machines letting out massive amounts of fog at one time)