Episode 49: From Class 55 to the G7 (3)

In the two previous parts, →the idea for the conversion to the G7 was presented, as well as →the first partial steps for the boiler and cab. Today, the focus is now on the running gear, the associated linkages and the cylinders with the Lentz valve control:

The Chassis

The new leveling compounds

A perhaps small, but nevertheless striking difference to the BR55 are the balance weights. These are together with the spokes and the hub from one and the same casting. To adjust the geometry of the counterweight, I milled 0.5mm off the counterweight. This was quite tricky. In case of carelessness, there is definitely a risk of something jamming and breaking the casting. That would have been a bit of a disaster, of course, but fortunately everything went well.

For the two wheels with the driving rod connection, it was a bit more difficult still, because a considerable part of the counterweight had to be removed. After that, there was a lot of air where spokes actually belong. So non-bearing spokes were molded from plastic. This restored the appearance. This has no significant effect on stability. All gaps and gaps are filled and sanded before the paint is applied. Actually a huge job only for other leveling compounds… but if you are enthusiastic about details, there is no turning back 😉

Control linkage

The original control linkage before the conversion: On the left, you can clearly see the black cylinder flange for the valve control rod. This area was then converted to the Lentz version. Another modification is the swingarm (center of the picture). In the original BR55, the compression position “center” is fixed, so actually no ride is possible 😉

Here now the rebuilt version, not yet treated in color. The valve lever has been moved over the cylinder. For this purpose, the feedback lever (center of the picture) was extended towards the top. On the swingarm (one picture further), the pivot point has now moved slightly upwards from the center of the swingarm, so maybe 50% compression. On the one hand, this corresponds to a realistic setting for “ride”. On the other hand, the Lentz valve levers are actually moved back and forth while driving and do not just stand still. This, together with the good visibility due to the raised boiler, makes for a great visual impression.


In the style of other old locomotives, the undercarriage and rods were kept completely in red. Only the joints and lubrication points were colored in gray. The cylinders are kept in the same RAL 6020 dull matt as the boiler:

The Cylinders

Changes in dimensions

It’s simple: core, de-saw, widen, add on, fill, sand and paint. But see for yourself:

The Lentz valvecontrol

The Lentz valve control is currently only reproduced with a simple brass tube above the cylinder. The four nozzles pointing upwards are still missing. Perhaps there will be another 3D printed part for this later.


Now a few impressions of the assembly after finished coloring:

This →is continued with part 4.

Thanks for reading, yours

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