SS7D Class Co-Co
The SS7D was the fourth out of five variations of the SS7D and the final to utilise the Bo-Bo-Bo wheel arrangement. Comparatively for Chinese locomotives, very few were built with the class totalling only 59 units over a three year period from 1999 to 2002 by the Datong Locomotive Works, before production was superseded by the SS7E with conventional Co-Co wheel arrangement. Top speed was 170kph and power rated at 4800kw. The SS7D's were originally used east of Xian to Zhengzhou, however after a few years, their operating locations extended from Baoji to Guangyuan and Chengdu. With the rapid production of the HXD series electric locomotives, their future is looking bleak.
Bachmann's SS7C is possibly the biggest release of 2013 with not much on the way (that we know of at least) and is the first Chinese model with the Bo-Bo-Bo wheel arrangement. These are particularly difficult locomotives to handle as there is no fuel tank to grip, it is inadvisable to grab the center bogie, and if you pinch the center of the locomotive a fraction to high, you run the risk of popping out some of the window panels!
The SS7D's are in a nice thick two-piece cardboard box with the model being housed inside a plastic clam shell with sleeve. There are some small foam pieces attached to the clam shell to prevent paint damage while in storage.
These are very nicely detailed locomotives. The details cast into the body are excellent. The paint work is very good, however there are some minor imperfections, chiefly around where the blue paint work meets the silver. There is some extremely minor overspray in areas, the most obvious being around the front of the locomotive along the top of the bottom blue line. My example is #0002 which I chose after I photographed it back in 2006. One prototypical error I've found is the cab side number plates which are the stencilled painted on style that most of the class wore, however 0002 has separate side cab number plates.
Roof details are very good and the pantographs look pretty good, aside from the rear most tripod mount which is a very oversized large plastic cylinder that looks rather ungainly. I suspect this is to allow a wire to the pantograph for electrical pick up, but could have been made a lot better than it has been. Air conditioners look fantastic, as do the windshield wipers, brass air horns with incredibly fine pneumatic lines. The bogies are very beautiful with very intricate brass step ladders and an impressive depth. There are some extra details to be added by the owner being side mirrors, antennae and bogie linkages.
My model runs a little buzzy out of the box, which improves slightly at higher speeds. I was hoping a gearbox lubrication will solve the problem, alas it appears something is a bit out of quarter and will require more serious investigation. It weighs just over 600 grams and the motor is strong. The model is 4 axle drive with a free floating unpowered centre bogie. Wheel pick up is excellent and supplied by copper plates picking up electricity from the axles. I much prefer this system to copper wipers on many models from other manufacturers.
Power is ferried from the rails (or pantograph and rail if you wish) via a circuit board to the motor and the lighting system. At the time of writing, I have not converted my example to run on DCC, nor have I opened it up. I am presuming like other Chinese models the board will accept an 8-pin decoder. The selector switch to convert electrical pickup between the pantograph or wheels is under the brake resistors (centre most large box on the roof). The lighting system is good. Lights are directional with a whiteish blue main headlight and yellow marker lights in forward direction and red in reverse.
For those who like Kadee couplers, they can be easily replaced with #56/156's).