4-12-2 Union Pacific 9000 Class
Additional pics and information is available on my Flickr site: <iframe align="center" src="http://www.flickr.com/slideShow/index.gne?user_id=jayhurst&set_id=72157622490861128" frameBorder="0" width="500" height="500"></iframe>
Close up pics of the 3rd cylinder's driverod and crank system are here:http://www.flickr.com/photos/jayhurst/3995387832/in/set-72157622490861128/
Close up pics of the trailing truck are here: http://www.flickr.com/photos/jayhurst/3995387070/in/set-72157622490861128/
The locomotives of Union Pacific's 9000 class are the largest non-articulated steam engines in the world that were successfully operated. A total of eighty-eight of the these 4-12-2 locomotives were built by Alco between 1926 and 1930. The particular prototype represented by this moc is the 1st engine that was produced for the group, #9000. This engine, when delivered new from the factory, was unique from the rest of locomotives of the 9000 class in that it was equipped with an experimental BL Worthington feedwater heater, which was located on the fireman's side of the engine.
The twin water pumps that are prominently mounted on the smokebox front give the 9000's their distinctive look, and most of the engines in the class kept their water pumps in this location during their entire service life, although a handful did have their pumps removed from the smokebox area and relocated, one to each side of the boiler. Those particular waterpump-less smokebox 9000's were referred to by rail crews as "bald-faced 9's".
One feature of the 9000's, which was rarely seen on American railroads, is that the engine has a 3rd piston cylinder, valve gear, and drive rod set that is located in-between the two normal pistons, and underneath the boiler. This gives the 9000's a unique off-beat thundering sound while running- there are 6 beats for every full revolution of it's drive wheels instead of the normal 4 beat cadence that the much more common 2-pistoned engines have.
This Moc is powered by Power Functions. Two M-motors are located in the middle of the boiler, and are connected to the engine's wheel set at the 4th driver. The battery box and receiver are located in the front of the tender, with easy access for battery recharging/replacing made possible by the removable coal load that covers them.
The fully functional 3rd cylinder is modeled in Lego just as it is prototype-- even the axle spacing that exists between the 1st and 2nd drivers on the real 9000's was needed on the moc for the same reasons it is needed on full size engine: in order for the center piston's driverod to clear the 1st driver's axle since the center piston's driverod is connected to, and rotates around, the crankshaft-shaped axle of the 2nd driver. Creating a 4-wheeled leading truck that cleared the 2 outside pistons during corning, while still avoiding the rotating and moving, center-mounted 3rd driverod was the biggest challenge in building this moc.
The extra long, fixed wheelbase of the 4-12-2 made getting the engine to round the very sharp curve radius of Lego track quite the challenge. A specially designed trailing truck that pivots as normal, but additionally, allows the axle to slide sideways independently of the trailing truck's frame while the engine is cornering was necessary. An additional complication to the trailing truck is that the wiring harness that travels from the engine's motors to the tender's receiver had to be attached to it, and the wiring harness moves in concert with the frame of the trailing truck. This was done to accommodate the wide swinging cab of the engine, and allow the wiring to clear the bottom of the firebox during corning.
The cylindrical-shaped Vanderbilt tender was a fun part of the moc to build, as I have only ever modeled the standard box-tank type tenders before this moc.
Edited by jayhurst, 09 October 2009 - 01:16 PM.