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NS 7851

Reconstruction of NS 7851


This model was was seriously damaged in the collapse of my bookshelves in the summer of 2006. I set the NS7851 aside for later inspection but it was very likely a total loss. Among this model two other models were seriously involved: the Big Boy, crushed beyond repair and the BRB. The BRB, though heavily damaged, can be rebuild. The Shay was also involved but damage was limited, though painful because I had only recently completed the project. I will repair it when I find the courage to restart a finished project.
Thankfully other models like my Climax and Y3 went out without a scratch.

In January 2007 I started reconstruction activities. The first model to undergo inspection was the NS7851. Although I considered it a total loss, I wanted to try reconstructing for the simple reason that it was a model I bought in my youth years. It is easy to buy another one, a good second hand model would cost only 70-90 euro. But emotionally this model is priceless.

Visual inspection revealed the following damage:

  • The superstructure was pushed down and was sitting lopsided to the back.
  • The rear of the engine cab bulged outward because it was pushed over obstacles belonging to the inner structure of the frame.
  • One buffer had come off.
  • On the rear both air hoses and the coupling had come off
  • Various handrails were broken
  • The cab roof was dented and torn.
  • The whistle was completely flattened, quite obviously beyond repair
  • The stack was scratched on top

Second to the visual inspection I attempted to run the model. The visual inspection was disturbing, but the running trial was seriously discouraging. A hum was all it produced no matter how much current I applied. It didn't move, not even a fraction of an inch!!

I started by disassembling the superstructure from the frame. As it turned out the bulging of the cab rear was caused by a notch on the frame. The damage proved not serious and relatively easy to repair. One problem solved.
A second running trial without the superstructure made no difference: it just wouldn't move.

After thorough inspection of the frame and after some simple tricks to get things going, I started taking the frame apart piece by piece. After every disassembly step I tried to run the motor.

I ended up with a completely disassembled frame, wheels off, rods off, cylinders and valve gear off. Only than the motor would run.

As it turned out the axle of the rear wheel set was warped. I had to exert considerable force to straighten it. Of course it is virtually impossible to bring it back into its original shape. But I tried as much as I could and dared.

I spent quite some time on requartering the wheels.

After careful reconstruction it was time to do running trails. They were satisfying. This model won't run superbly anymore unless I happen to find a replacement for the rear axle. But as it is I'm quite happy. Having made it run again is the one major step towards a successful reconstruction. The loco wasn't a total loss after all, to my great relief!!


Next I started reattaching the buffer. This has been a problem since my youth when the buffer came off after a small accident. Since then I repaired it numerous times by simply gluing it back into place. But even ACC wouldn't hold it very firmly.

And now I wanted a definitive solution.

I cut the stem and drilled a 0,7 mm hole in the center

I drilled a corresponding 0,7 mm hole in the buffer housing on the loco.

I drove a 0,7 mm brass wire into the hole in the buffer and secured it with ACC.

And mounted the renewed buffer in its housing and once again secured it with a little ACC

Next was the cab roof. As you can see only the stubs of the whistle remains. The front edge of the roof was torn and dented. The rear edge of the roof (barely visible on this photo was scratched taking away all rivets.

Fortunately I salvaged all loose parts after the collapse of my bookshelves. So I retained part of the whistle mechanism. I remodeled the whistle with a little Tamiya putty, which I drilled and pierced with a piece of 0,5 mm brass wire.

I cemented the tear in the front edge and filled the dent with putty. After hardening I drilled a 0,5 mm hole to reposition the whistle. A very small piece of styrene was used to compensate for the whistle mechanism falling a little too short.

All right it won't be like it was, but it will do, certainly after a good paint job. Remember the whistle is only 5 mm high!

Reconstructing the stack was probably the most challenging part of the job. I attached some Expoxy Putty to the stack, let it set and molded it with knife, file and sanding paper

until it suited me. During the job the putty came loose since it has only so little grip. I reattached the putty with some ACC.

Reattaching the air hoses was, let's say, a delicate job. With only just tenths of millimeters to spare to all sides I drilled a 0,5 mm hole

and inserted a short piece of brass wire.

I drilled a corresponding hole in the buffer beam, inserted the brass wire and fixed it with some ACC.

Then I cut the protruding wire flush on the inside.

There you are. Much better and in near original state.

I also applied de the brass wire technique to the steps under the drivers cab. The left one is not entirely straight but once painted black this is very inconspicuous.

The brass wire technique was also applicable to one track cleaner (is this the rigth term?), but I changed the working order a little. I first glued the cleaner back into place. After setting I drilled the hole through the glued connection

and only then inserted the brass wire to reinforce the connection.

The photo clearly shows the marginal tolerances available. Use of a drill stand in combination with a X-Y- table is absolutely essential. This is work that cannot be done by hand.


A final portrait of the reconstructed and partially repainted model