The PRR Q1 was an experimental hi powered freight locomotive with unique 4-6-4-4 driver arrangement. It wasn't an articulated locomotive, but they were described as "duplex" in PRR terminology. It had 2 sets of "opposed pistons". See how rods move! The first set had traditional layout. It was just bellow the smokebox. The second set it was located bellow the firebox. I guess the reason was to have the shortest drivers wheelbase. The second set under the firebox proved to be the Achilles' heel. Ashes will fall onto these cylinders and the heat contributed to far more maintenance work and wear. The prototype that followed, the PRR Q2 with wheel arrangement 4-4-6-4, was very successful. It had the most horsepower of any steam locomotive ever produced, but it came during the time that the more economical and flexible electric diesel locomotives were started their in runs on class 1 railroads.
About the model: This is one of two model releases ever made in brass or HO scale. This early 80's model it was produced by Daiyoung, an early brass maker and sold by NJCB. Because of being a early korean brass model, it had some constructions issues. Mainly, cracked solder joints. Also the gearboxes had very delicate fiber idle gears that worn away and strip in a shot time. I redid much of soldering work with a resistor solder and I upgraded the drivetrain with a new modern can motor and Samhongsa gearboxes. Now, it runs ultra smooth. After all modifications and custom paint, I installed a Tsunami sound decoder. The Tsunami decoders may have more "bells and whistles" on the sound part, but they are poor performers in the drive part. They are very hard to adjust with to many CVs, have poor BEFM, they like to overheat (and shut down) and they have mediocre low speed motor control. These problems get amplified with large or articulated locomotives. However, in this Q1 locomotive, it works pretty fine. The sounds make a nice doppler effect. I still have to adjust a little of drive and sound.