I haven't designed that model myself. Another member of our club showed me that model and asked for a conversion for AC operation. Originally, the model was operated with center rail DC, i.e. DC on Märklin tracks. I found that this loco was a very interesting model, so I decided to documentate it, as well as the conversions I did. 

- Märklin 3084: steam loco, but without the tender

- Märklin 3098: tub-style tender

- Märklin 280270 (spare part) - pickup shoe with holdering

The pickup with its holdering is a spare part for model #3315 - it has to be installed on the first bogie of the tender.

Side view

The chassis, seen from below. The coupler between the loco and the tender doesn't have to be changed

Front view. Number plates can be ordered at firms like Kuswa, for example (http://www.kuswa.de)

The leading truck was equiped with disc wheels and snow plows

The tender was originally used for the BR38, which however had its reversing unit in the loco, and not in the tender. So there was little room in the tender, so some work became necessary to create this room.

Der Tender stammt von der BR 38, dort war das Fahrtrichtungsrelais jedoch in der Lok untergebracht und somit im Tender kein Platz dafür vorgesehen.

Deshalb mußte Abhilfe, sprich der nötige Platz und eine Befestigungsmöglichkeit geschaffen werden.

On the base plate, a new hole has to be drilled so that the reversing unit can be screwed later on	The new parts: a classical Märklin reversing unit, a plastic bush, a M2 screw , and a nut
The relais has been screwed on the base plate	The bottom side: the screw has been fixed with the nut
The tender's interior. Below the platform, about one or two holes for the wires to the motor have to be drilled	The base plate with the relais has been installed now
The tenders upper part: the struttings in the middle section have to be removed to create room for the reversing unit	In the rear and front section, the struttings are still in place, while they have alle been removed in the middle section. Their purpose is to enforce the upper part
One more view into the tender with the newly installed reversing unit
A view from the other side. It's important that the mechanical system of the reversing unit has enough room to work without any problems

A really interesting model! Certainly most model railroaders will install a decoder oder an electronic reversing unit instead of the old mechanical relais. However, this one was an conversion for a classic analog railroader. The works on the tender will be quite similar in every case.

Disclaimer: I can not be hold responsible by any damages you cause, by following my instructions. What you are doing, you are doing it at your own risk!