tip: 3122 märklin michelin bus black “est” front...

Tip: 3122 Märklin Michelin Bus Black “EST” Front and Rear LED Lights Date: 06-07-2018, Addition 17-05-2019, Addition 16-08-2019

http://members.ozemail.com.au/~rossstew/rms/marklin.html 1

Hi All,

I did my first LokPilot 4 Micro Conversion of the Märklin 3603 Michelin Bus in 04-02-2012 for my

friend Rudolf and followed up converting all my Michelin buses in 23-05-2013. For that information

please refer to the above the above link.

I have at long last completed the LED light upgrades for all my Michelin buses 3123 Green, 3603 Green

and 3624 Red. For the red bus I had to overcome the body shell glowing and I also revised a few

techniques. For these details please refer to pages 12-15.

The 3122 Michelin bus was produced for 3 years 1992-1994

I had always intended to add a working LED head light and rear tail light but I put it into the too hard

basket at the time. Finally I have solved how to add the LED lights and I’m very pleased with the results.

For this project a lot of

thought, experimentation

and planning is required

to get the results shown

here.

The rear tail light is very

small with nearly

impossible clearances for

everything to fit and the

head light was constructed

from the original imitation

lamp

All lights operate using the F0 function on the decoder with “Rule 17” the light increases in brightness

when the locomotive moves and dims when the locomotive is stationary.

Warning: - You undertake the following modifications at your own risk.

Warning 2: - This project requires fine motor and soldering skills because of the very small parts being

used and the project requires patience to be successful.

http://members.ozemail.com.au/~rossstew/rms/pdf/lokpilot_micro_3603.pdf



Conversion of the Imitation Front Light to Working LED Light

With my success of converting Faller imitation lights to working lights for buildings and Enhancing Old

Locos with Rear Lights where LEDs were added to the raised tender lights I was confident I could

convert the front light of the Michelin bus to a working LED light.

The head light is made from clear plastic and is painted

silver as shown in the two views of the light.

With the imitation head light removed from the bus I first

filed flat the convex surface of the head light. This made it

easier to centre a 2mm drill held in a pin vice to create a

recess for a 0603 LED. I had to be very careful not to drill

too deep as the curved outline of the lamp gets smaller at

the back of the lamp. I kept testing the 0603 LED in the

hole to make sure the top surface of the LED was just

below the front surface of lamp. This would allow a clear

lens to be placed over the LED.

Drilling Holes for the Wires

Using a 0.6mm drill held in a pin vice I first drilled from the rear lamp support (see red arrow) to a depth

where the angle of the plastic changes direction.

The next drill is drilled through the front of the lamp following the direction of the lamp support (see blue

arrow). The aim is to join the two holes without breaking through the lamp support see red and blue

dashed lines above.

http://members.ozemail.com.au/~rossstew/rms/pdf/faller_imitation_lights_to_real_lights.pdf

http://members.ozemail.com.au/~rossstew/rms/pdf/loco_tail_lights.pdf

http://members.ozemail.com.au/~rossstew/rms/pdf/loco_tail_lights.pdf



Wiring, Tinting and Fitting the LED

I soldered 80mm lengths of 0.25mm enamelled wire to the LED and

used a temporary 1k current limiting resistor to test the LED works.

The 0603 white LED had a blue tinge so I used Tamiya Clear Yellow X-24 acrylic paint to warm the

LED light colour.

The LED was also too bright so I increased the current limiting resistor to 12k. This looked a much better

match to the era of the bus.

Before inserting the LED I removed the silver paint from the outside surface of the lamp and painted it

with black paint as this would prevent the lamp glowing when the LED was on. For the hole in the lamp I

painted it silver.

The LED wires were next threaded through the lamp and the LED was glued in position. A clear lens was

now glued at the front of the lamp and the edge of the lens was also painted silver.

Head Light Results

The left photo shows the head

light off.

The right photo shows the head

light on with a 12k current

limiting resistor used.



Making the Lantern Lens

As the space around the LED looked empty inside the lantern it really needed a lens for better aesthetic

looks.

To manufacture the lens I used a 1/8” brass tube with an internal diameter approximately 2.4mm. I cut the

tube to 20mm length and chamfered the end of the tube to form a sharp edge. I used the clear plastic

packaging from decoder packaging as the lens material. With the clear plastic on a cutting mat I punched

the brass tube with a hammer into the clear plastic.

To remove the lens I inserted a 2.0mm drill, blunt end into the tube (red arrow direction) and pushed the

lens carefully through the tube until I had it in my hand. Pushing the lens out at the cutting end isn’t a

good idea as it bends the lens too much.

Cutting a Slot for the Front Light Wires

The next hurdle was to find a path for the LED wires in the locomotive body.

I used a thin Dremel cutting wheel to cut the slot shown.

The slot was just wide and deep enough to allow insulation

over the copper wires and to avoid the screw mount area

for the cabin body shown by red circle.

The slot was painted black to seal the metal surface.



Routing the Lamp Wires

Using the insulation from a larger gauge wire I

threaded the enamelled copper wires through it to

provide protection from the slot and to avoid the screw mount for the cabin body.

As the cabin is articulated on the bus body I required more flexible wires to follow the same path as the

ground wire from the cabin.

The interconnection PCB is cut from an old PCB from a point motor which is very thin

and ideal for the tight fit in the cabin as shown. Using the Dremel cutting wheel I cut

through the copper foil only to provide the solder locations for the two enamelled copper

wires and the two flexible ESU wires. The PCB was super glued into place.

It is most important to locate the wires into the bottom of the recess as shown (red arrow) as the plastic

rectangle key (yellow arrow) fits into the recess. This is a very close fit but the wires have space without

being pinched or damaged.



Red Tail Light

The red tail light is positioned on the left bottom side of the bus body and is

very small. Size is a factor but the clearance of the light on the rear side to the

wheel flange is the limiting factor.

I decided to try an optic fibre solution which I hoped would be bright enough to

be able to see the red light with room lights on and to overcome the tight

clearance factor to the wheel flange.

1st Try with a Red LED

Since I had a lot of 0.4mm ultra

clear fishing line from my previous

Signal Box Project and

understanding the limitations of

using the material I decided to drill

a 0.4mm hole in the centre of the

tail light for the optic fibre which is

on powered by a red LED.

The light is difficult to see, if you

zoom in you will see it is on.

The red LED has a low light output and even though the optic

fibre is short in length I didn’t consider it was suitable for the

tail light of the Michelin bus.

A 0.4mm hole was drilled into the top of the red LED to

connect the optic fibre to the LED. I was able to do this

because of the raised moulding of the LED

2nd

Try with a White LED

A 0603 white LED has a higher light output but its size didn’t

allow me to drill the top of the LED to support the optic fibre.

This problem was overcome by super

gluing 3 layers of 0.25mm clear plastic

sheet together. The assembled layers

where then drilled with a 0.4mm drill.

The plastic was then cut to a small square

with the hole in the centre and finally

super glued to the top of the 0603 LED.

See pages 14-15 for improvements.

The tip of the optic fibre was dipped into Tamiya Clear Red X-27 acrylic paint to provide the red light

colour but also to prevent the optic fibre being pulled through the hole in the body shell.

http://members.ozemail.com.au/~rossstew/rms/pdf/signal_box_lights.pdf



The optic fibre was cut to length to allow the LED

to sit on the roof and for the insertion of the optic

fibre into the mounting hole on the top of the LED.

Using 1.5mm heat shrink tube I masked the LED

and optic fibre light without shrinking it with a

length up to the bottom of the window inserts

shown by the yellow arrow.

The heat shrink tube was squeezed between the

window inserts to hold the LED and optic fibre in

place.

Black electrical tape held the wires at the bottom

and also masked the optic fibre above the bottom of

the window insert.

The optic fibre you can see must be glued into the

moulding corner to prevent interference with the

wheel flange. I used Selleys AllFix glue for this purpose.

The light from the exposed optic fibre can hardly be noticed externally and you will notice the optic fibre

with the red LED on the previous page doesn’t illuminate the fibre all the way so the light output is poor.

Red Tail Light Results

Left photo with light off and the right photo showing the light on which can be seen when the room lights

are on.



Wheel Flange and Optic Fibre Clearance

The two views show how close the optic fibre is to the wheel flange.

Final Wiring

I mounted a small Vero board with 3 foils at

the location shown. The 12k resistor (green)

is for the front light and the 1k resistor

(blue) is for the rear light. The bottom foil is

used for making all the +pole connections

The single rolled IC pins are used as sockets

for the rear light insulated with heat shrink.

The +pole is marked with white paint.

Thin black card is used as a mask to hide the

components and wires.

At the location of the yellow arrow I cut a small

indent with a Dremel cutting disk to allow the optic

fibre space to enter the inside of the bus. The surface

was painted black to seal the metal surface.



The +Pole marked with a blue plus symbol gets its connection from the new resistor interconnection Vero

board. The other black wire is the F0 function for the LED lights wired to the new resistor interconnection

Vero board.

Finally the body shell is positioned next to the bus chassis and the rear LED is plugged into the single

sockets making sure that the +Pole marked with white paint match connectors.

The body shell can now be clipped into place making sure no wires are pinched in the process.



CV Values for the LokPilot Micro V4 Motor and lighting effects

The decoder firmware was updated using the LokProgrammer 4.7.0 software version

The only changes to the CV’s was to increase the brightness for the Head Light[1] and Rear Light[1]

Warning: Make sure you read the ESU decoder instructions before programming any CV’s

Ensure CV31=16 and CV32=0 before changing any Lighting Control Settings.

Set the brightness value first to a low setting before turning the lights on. There should only be 12Volts

DC across the solder pads indicated by the blue + and black - shown above. This voltage was measured

on the original decoder and should be maintained so the bulbs which are in series don’t burn out.

The final results were well worth the effort.

Bonus Time The bonus file 3122.zip (151Kb) contains the following listed files

3122.yra 3123.yra 3624.yra

The file 3122_470_micro.esux can be used as a starting point for a locomotive conversion similar to this

loco. This file overrides any CV values in the table above. It can only be used with LokProgrammer 4.7.0

and above.

Motor Settings [Index:0 (CV31=0, CV32=0)

CV# Name Range New Default

1 Primary Address 1-127 94 3

2 Start Voltage 1-255 3 3

3 Acceleration 0-255 24 32

4 Deceleration 0-255 16 24

5 Maximum Speed 0-255 71 255

6 Medium Speed 0-255 25 88

52 Load Control Parameter “K low speed” 0-255 41 15

53 Control Reference Voltage 0-255 140 140

54 Load Control Parameter “K” 0-255 36 50

55 Load Control Parameter “I” 0-255 37 100

66 Forward Trim (1x Voltage) 0-255 128

95 Reverse Trim (1x Voltage) 0-255 128

Function Control Settings [Index:4096 (CV31=16, CV32=0)

Function

Output

Mode Select Brightness 0-31 Special Function

CV# Value CV# Value CV# Value

Head Light[1] 259 2 262 20 263 132

Rear Light[1] 267 2 270 20 271 136

http://members.ozemail.com.au/~rossstew/rms/files/3122.zip



Märklin Box

I obtained this loco from a friend in Germany and it never came with a box to store the locomotive in.

The locomotive had the plastic storage insert and I stored it in a plastic bag to seal it from dust.

Last week while helping out a Märklin friend he asked if I could make use of a spare Märklin locomotive

box, it was a perfect fit for my Michelin bus.

The box came with a sleeve without a window and no insert. I used Gel super glue to glue a thin plastic

window made from packaging and printed three labels which were glued onto the box with PVA glue.

The plastic insert for the locomotive was the correct size for the box so now the locomotive is protected

from dust and provides physical protection.

This is the label printed on the box.



3123 Green, 3603 Green and 3624 Red Michelin Buses

The 3123 (large roof tank) is on the left and the 3603 (small roof tank) is on the right.



3624 Red Body Shell Glow

After I had added the rear LED light to the bus I noticed that there was a hot spot on the body where the

LED was mounted see yellow circle.

I tried to overcome this problem by adding black electrical tape under the LED which worked but there

were still further body shell glowing problems which I discovered when I turned the room lights off.

With the coach lights on, the entire body shell glowed in the dark through the roof and side walls. The

rear light also glowed at the yellow line. It was clear that I had to mask the translucent body shell to get

acceptable lighting.

I painted the roof and side walls with black flat

acrylic paint, it required two coats of paint to mask

the body shell. You will also notice that the window

frames are not painted.

Caution: - The window inserts are a very tight fit to

remove and replace and this task should be done with

extreme care to avoid breakages.

To help mount the optic fibre to the LED I revised my method by punching 0.4mm thick clear plastic the

same size as the lantern lens see page 4. Two pieces of circular plastic were carefully glued together with

super glue then drilled through the centre with a 0.4mm drill.

Finally the circular assembly was super glued to the top of the 0603 LED then painted with flat black

acrylic paint as shown above. This method was easier than my first attempt cutting with a sharp knife and

the heat shrink was a better fit over the optic fibre mount.



Improve Optic Fibre Clearance to Wheel Flange

Using a Dremel 108 - 0.8mm engraving

cutter or similar I carefully milled a shallow

grove in the corner of the body shell to

improve the optic fibre clearance to the wheel

flange. Use the cutter with extreme care. I

then painted the grove with flat black acrylic

paint as shown.

The optic fibre was cut to length to allow the LED to sit on the roof and for the insertion of the optic fibre

into the mounting hole on the top of the LED. The 1.5mm heat shrink tube is then pushed onto the optic

fibre mount. Note the small piece of electrical tape under the LED light assembly.

The heat shrink tube was squeezed between the window inserts to hold the LED and optic fibre in place.

The optic fibre must be glued into the moulding corner grove with PVA glue to prevent interference with

the wheel flange. I clamped the optic fibre into position (yellow arrow) until the glue had set.

Black electrical tape held the wires at the bottom and also masked the optic fibre above the bottom of the

window insert.

Please note that the green Michelin buses didn’t require a body shell paint mask.

Resistor Masking

As mentioned on page 8 I constructed thin black card masks to

hide the components and wires.

The size is 18mm W x 9mm H x 5mm D



Final Photos

The animation of the lights can be seen on the Tips page for this article.

As always enjoy your model trains.

tip: 3122 märklin michelin bus black “est” front...

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