Märklin Dv 12
Dv12 is the most common diesel
engine in Finland. In years 1963-1966 68 units Sv12-engines were
manufactured (from 1977 named Dv12), numbers 2501- 2568. In years
1974 - 1984 were manufactured other 64 engines, numbers 2601 -2664.
2600-series engines had different cooling system, causing also
visual changes to the front part of the engine. In parallel to
these engines were also built in 1965 - 1972 60 engines equipped
with additional steam generator and called Sr12 (from 1976 called
also Dv12, numbers 2701 - 2760), which were slightly heavier and
the exhaust pipes were bigger on both sides of the steering cabin.
All engines are still in use.
The boggies of Dv12 are designed
by Krupp in Germany , and the same boggies are also used in german
BR215, BR216 ja BR218 diesel engines. Almost every model train
manufacturer have one of these models in the product line.
The building starts here with this
BR216-model 3374 of Märklin. It has been purchased from a
German second hand model train dealer Kurt Bothner( http://www.bothner-modelleisenbahnen.de/index.html
), price was 75,- EUR. MFX-version with sound can be done
of the BR V160 in several start sets. These are for sale in Ebay
for about 140,- euros. A list of Märklin BR 216 version is here.
The work starts with disassembling
the loco. All parts above the framework is removed and the surface
is smoothen with a file.
Br 216 is a longer loco than Dv12,
so the framework has to be shortened with 18mm. At same time four
slots are machined to the corners for the stairs. In the picture
are the short and the original framework. Also the round shape
for the speaker has to be removed as there is no room for that
in the Dv12 housing.
Another way is to machine the whole
framework yourself. I wanted to try this option and I modelled
the framework with a 3D-CAD-software (Pro/Engineer) and I machined
the framework from a brass plate. The drawing is here as PDF-format and as DXF-format. Also the 3D-model is here as IGES-files.
To fit the motor inside Dv12 is
difficult, but can be done with two tricks: the drive boggie is
rotated 180 degrees so that the field coil is located backwards
and the field coil is replaced with a narrow permanent magnet.
Now the motor fits in the cabin and the magnet can move with the
boggie inside the rear engine hood. This works at least with those
models, which have originally drum collector motor (DCM), the
large flat collector motor (LFCM) models should also be OK, but
I have not tested it. The motor modification is done with the
Märklin Set 60901 for the DCM motors and Set 60904 for the
LFCM motors. The mfx-version already inludes the permanent magnet.
When the drive boggie is turned
around, also the plastic boggie frame has to be rotated, because
the coupler is fixed to the frame. To be able to do this, two
notches have to be machined on the other end of the boggie (upper
picture) and a slot with threaded hole to the other end.
Boggies in the new framework.
The bodywork parts can be made
of 1mm aluminium sheet and DuPont CibaTool. Of course all the
parts can be cut from sheet, but for me it was easier to do the
complex form parts with a CNC –milling machine. The drawings
are here as PDF-format
and as DFX-format
for a Cad-software. 3D-models are here as IGES-files.
There are some minor differencies in dimension with the prototype
and if exact model is required, the dimensions should be checked.
The opposite walls of the cabin
are identical, so both walls are needed 2 pcs. The parts are glued
together with epoxy glue.
An assembly jig is good for aligning
and glueing the parts.
Another new way to make the body
work is using rapid prototype machine. The parts in this project
have been made with Stratasys Dimension STT.
First the holes for lamps have
to be drilled as the machine is not able to make small enough
holes.
Black paint has to be applied to
the holes to prevent the light glowing through the walls.
The parts are glued together with
zap-glue and painted with Humbrol red 19 and cream 41.
The lamps are 1,5V/15mA diameter
1,2mm from Miniatronics. Because of the low rated voltage a resistor
is needed to limit the current. There are four lights each end.
Here the lights are connected in
series in both ends, which is the best way, as the power loss
in the resistor remains low and only a 0.5W resistor is needed.
Also the wireing is rather simpel.
Here the lights are connected parallel
in both ends, which is also possible, but the power loss in the
resistor is higher and 2W resistor (hot!) is needed. Also the
wireing is more complex.
In this unit the lights are connected
so, that the lower lights are allways on and only the upper head
lights change according to the direction. There are allways six
lamps on and power loss in the resistor is about 0.75W which makes
the resistor quite hot.
The mfx-decoder is attached to
a bigger circuit board with a 21-pole connector. There is no room
for bigger circuit board, so it has to be cut a little from the
longer edges.
The board after cutting.
The decoder is in the nose part
and the speaker is placed to a low tube in the ceiling of the
cabin.
The decoder is placed permanently
to the body work and two 2-pole connectors are used for the motor
and current from the rails.
Handrails are glued to the bridge.
The bridge is painted with Revell
nr. 77.
First test run