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1:87 Scale



DF7B Class Diesel-electric Co-Co

ChangMing Model Train Studio

Production Summary

Prototype Information

The DF7B was an improved version of the original DF7 diesel electric locomotive. They were designed and manufactured by the Beijing 27 Locomotive Factory between 1990 and 1998 with 215 units built. They were originally designed to operate in heavy industry and marshalling yards, however towards the later years of production, the design was modified with a tweaked engine to be more suitable for short haul mainline work as well. 

The locomotives have one of two types of V12 diesel engines, with both putting out 2500hp and can operate at a maximum speed of 100kph. The original designed primarily for shunting and are numbered between 3001 and 3143 and the modified version numbered between 6001 and 6072. They are not overly common locomotives and many are heading towards extinction as more modern motive power becomes available.


General Information

ChangMing's DF7B models are an ABS plastic shelled body on a heavy alloy frame. ChangMing (formally Charming) was renowned for using die-cast for the body shells, but this seems to have been abandoned for some time (with their QL160 class railcar being the exception). Four liveries were made with fourteen road numbers, including two decorated versions. All road numbers were made available in either DC or DCC/Sound/Smoke control. ChangMing have made a very good range of variations between most versions, something most manufacturers avoid due to expensive tooling costs.   ​



ChangMing's DF7B's come in their standard modernised packaging. The locomotive is screwed onto a frame (no tool required to remove). A clear Perspex cover clips onto this turning it into a display case. This is then suspended with polystyrene end supports in a high quality sleeved two-piece cardboard box. The model is given extra protection in the display case for shipping with a folded plastic clam shell with a soft plastic sheet to prevent paint damage. Unlike most other ChangMing products, the models are now shipped with the fastening screws mounted into the coupler mounts rather than the fuel tank which is done to prevent damage during transit, however they have also provided screw mounts in the base to attach it via the fuel tank once the couplers are fitted (by the owner). 


The box includes a small Philips head screw driver, instruction sheet (Chinese language only), bag of couplers & air hoses, other detail parts (specific road numbers only) and chains for handrails (specific road numbers only). 



The main shell is ABS plastic injection molded. The detail is absolutely amazing for plastic, with exquisitely sharp and sometimes tiny features. The louver details on the engine room access doors and the checker plate pattern on the walkways is beautifully done. Detail parts are steel, brass or plastic. 


Some of the variables between road numbers include the following:

  • Two or three beam handrails, some with full length or split/chain style

  • Single lens or double lens marker lights

  • Main headlights with or without visors

  • Crews with different uniform and in different positions

  • Air horn placement

  • Short hood with plain front, doors, single window, double window or triple window glass

  • Additional handrails on cab roof

  • Factory plates showing specific year of manufacture (!)

  • Different styles of electrical cover plates


The cab interior has a staggering amount of detail. Each locomotive comes with a driver facing long end leading and are wearing either a yellow or orange safety vest. Not only that, the yellow safety vest guys are pointing at the signal ahead, while the orange safety vest guys are much more chilled out, smoking a lit cigarette… of course. The cab controls are immaculately detailed and include separately painted controls (black, yellow, green & red buttons and silver handles) and cabs and floors are painted in correct colors. The gauges even illuminate (at least in DCC versions), although unlike previous ChangMing releases that have this feature where they can be individually controlled, the DF7B’s only illuminate with the main cab light on at the same time which somewhat reduces the effect.  


Some of the notable details include brass air horns, metal window visors and windbreakers, brass windshield wipers, metal uncoupling rods with painted handles, wire pneumatic lines, separate engine room access door handles (lots of them!), brass etched factory plates, separate fuel lines & filler cap, etched metal footsteps, brass roof ladders and one of the coolest things yet - floating dynamic brake vents above the fan (and yes, DCC users will enjoy watching these things operate - see electronics).  


The bogies are predominantly assembled with plastic parts and have an amazing amount of detail and include full traction motors, sanding equipment, brake cylinders, full brake rigging, wheel guards and traction booster arms with working linkages. Primary and secondary suspension components are separate brass springs. There are even small labels on the dampeners. For those who like to run trains at night, all this detail is shown off with two LED lights per bogie, per side. Wheels are chemically darkened metal with painted red face and white rims as per standard Chinese practice. 


Paint work is stunning, typical of all ChangMing/Charming products with a nice matt finish. All liveries are evenly applied and there are subtle variations between each road number. Edges between the colors is razor sharp. The lettering is just as good, crisp, sharp and clear - probably better than the prototypes! All the small labels and characters are perfectly legible, even the tiny characters on the builders plates. Cab door handles are painted silver, battery box handles red, fuel filler cap is silver and the list goes on. ChangMing have a habit of providing us with this level of detail and the DF7B's are no exception.  


Optional parts vary between road numbers, however they all include the couplers, draft gear and air hoses. The draft gear must be inserted in the holes on the coupler mount before the coupler/coupler box slides inside. This is a bit tricky as the holes on the frame are a fraction too small for lugs on the part. More details about the couplers is below under 'coupler conversion'. ChangMing have also provided four air hoses. Most DF7B's I have seen out in the wild, usually only have one hose to the right of the coupler, however the tap is present on the other side. This is probably a good for owners of the ChangMing DF7B’s as they will undoubtedly break if one attempts to install them without first drilling the hole a fraction bigger (or filing the air hose end down a bit). Other detail parts 'may' include chains for the handrails or decorative cab plates which are attached with a small piece of two sided tape already in place - just peel the backing tape off and apply (highly recommended to use tweezers for this as the adhesive is very strong) – note I haven’t installed the large cab side brass plates on my DF7B 3020 at the time of this review, but they can be seen in the photo under the ‘packaging’ section of this review.



The DF7B's come with a huge range of features for DCC/Sound/Smoke users. I have not tested the DC version of these models. The sound comes from a 21pin ESU Loksound v5.0 DCC decorder. Sounds are all very high quality and very clear. The sound suite includes two air horns, dynamic brake noise, engine prime and start up, brake squeal, flange squeal, a range of voices, coupler noise, oil pump, compressor and cab door noise. The dynamic brake sound is linked to the two working dynamic brake fans which spin fast enough to send a blow of air up through the floating slats above creating a rippling effect. Aurora models were the first to employ this design, but ChangMing have perfected it and is now a standard feature on their recent/applicable locomotives. The smoke units work well and there are two exhaust ports. The smoke is synchronised to the engine speed via a small turbine fan inside the smoke unit which pumps out more smoke up when powering up and on start up. The effect is very good and there is enough fluid to keep you going for a while. Note that extended use will eventually leave an oil stain on the roof and I don't recommend using them for extended periods of time as ChangMing's previous releases have occasionally developed faults. Being that the body shell is plastic and previous ChangMing smoke units have seem disastrous results, I only trust them enough to run for a few minutes at a time. To apply the fluid, I hold the locomotive on the side and line up the needle applicator on the bottle into the exhaust ports before righting it and allowing a couple of drops to fall in. There is no need to squeeze the bottle, it should flow out on its own accord. Over filling may cause the turbine to come off the motor shaft leading to overheating and subsequent sad feelings.   


The lighting effects are very nice. DCC users (maybe DC?) will enjoy the following:

  • Main headlights (directional)

  • White marker lights (directional) and red marker lights (manually set)

  • Ditch lights (directional) - dual and single lens type as seen in photo above)

  • Bogie lights

  • Number board lights

  • Cab light and instrument gauge lights (in conjunction with each other)



My DF7B's are all excellent runners and perform quietly and smoothly through the speed range, although there is an occasional slight hiccup at very slow speeds. This is partially due to the design of the way the drive wheels (all of them) are connected via shafts and universal joints, in a similar way most brass locomotives are built. Electrical pickup is taken from all wheels and they are fitted with power storage, which eliminates stalling for a brief period of time over dirty or insulated track.  They have a good weight of 580 grams which should be enough for a train of well over 25 freight cars on level track.



If you ever feel the need to take one of these things apart, you can do so by removing the couplers once installed (that in itself should be enough to deter people from doing so), then taking out the four small screws hidden under the wheels at the far ends of the locomotive. The general arrangement of the guts has the decoder just behind the cab, smoke unit under the exhausts, dynamic brake fans under the... dynamic brake fans and the speakers are buried in the fuel tank.

Coupler Conversion

As mentioned under the ‘packaging’ section of the review, ChangMing have sent the models out with the couplers to be installed by the owner. It's fairly straight-forward, however there are a couple of points that should be mentioned. Firstly, I highly recommend working on these models upside down (the model, not you) and this can be done safely by supporting it in the plastic cradle which comes with the model.

The draft gear/pilot assembly should be installed first and this is going to be the most difficult part of the operation. The lugs on this piece are a fraction to large for the holes in the frame, so if yours doesn't fit in fairly easily, I would suggest to file the holes out very slightly with a file, sharp knife or similar. I found just by scraping away some of the paint from inside the mounting holes was enough, but others will need a little more persuasion. Don't be concerned if you file the holes a tiny bit too much that it will drop out, as you will see the entire lot will be held in with a screw. Once you've got this in, pop the provided coupler (scale head metal knuckle type with whiskers) or coupler of your choice into the coupler box ensuring the flat plate is on the bottom, then slide it in from the front of the pilot. Once this is in, the screw must be fastened from underneath. If your coupler isn't quite lying flat, it is possible the draft gear piece isn't all the way in, however this can often be corrected by tightening the screw to force it into place.


The next complicated part to this is you will notice a cross member piece blocking the screw hole and there are two ways of getting around this obstacle. For me, I found inserting the screw partially until it meets the obstruction, then gently prying it away with some needle nose tweezers before screwing it in the rest of the way, was enough. If you don't feel comfortable doing it this way, the cross member can actually be removed (again be very careful) by prying it off towards the lead wheel. I prefer the first option as the plastic is fairly forgiving and putting the cross member piece back in place is more trouble than I care to expose myself to. When you have it all together, you can attempt to couple to a wagon and then realise you've put the coupler in upside down and repeat the process all over again. 

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