The wagons discussed here appeared in the 1970s. While still retaining many of the defects of their predecessors (huge wheels, bogies a little coarse and without braking equipment, atrophied buffers), they began to look good concerning the respect of the scale: their chassis length was accurate to within 0.5 mm. So, I figured they could deserve an upgrade.
These are the following:







Here is what this lifting will consist in:
If this operation does not pose any difficulty for covered wagons, it is different for flat wagons, which are already ballasted, but not enough. My goal is to achieve the mass recommended by NEM 302, namely 0.4 g × overall length, which can be increased by 30%. This gives a mass to be reached of between 90 and 120 g approximately for an initial value ranging from 60 to 65 g, that is to say a ballast of 30 to 60 g.
The only possible difficulty is the dismantling of the roof without breakage:
The ballasts are rectangular, taken from 1.5 mm steel sheet, stuck with thin doublesided adhesive. Their width takes into account possible obstacles (reinforcements) inside the bodies.
There is very little space under the wagons, and the ballast must not be visible. There are places on either side of the 120 × 7 mm “fishbone” reinforcement, but this is not enough. By milling this reinforcement, which is removable, 1.5 mm deep and 6.5 mm wide, a central plate of 120 × 6 mm can be added. The maximum added mass is about 28 g.
Of course, if a loading is planned, the ballast can be reduced accordingly — in particular, do not install the central plate which requires a lot of work, that is what I did on the Res for which I intend a loading of ISO containers.
Wagon  Ballast  

Type  Initial mass (g) 
Resulting mass (g) ^{1} 
Length (mm) 
Width (mm) 
Mass (g) 
Habiss  60  112  173  19  39 
Iaehss  60  103  120  25  35 
Res  65  90  120  2 × 7  20 
Rloos  60  100  120  2 × 7 + 6  28 

The density of the mild steel is about 7.85 g/cm^{3}. To obtain the ballast mass, it is enough to multiply this value by the thickness, the width and the length of the ballast plate (yes, it gives its volume!), these three dimensions being expressed in cm. Example for Habiss (e = 0.15 cm, L = 17.3 cm, l = 1.9 cm):
7.85 × 0.15 × 17.3 × 1.9 ≈ 39 g