Marklin Remotoring
The links below are for some video clips of a Marklin 8806 0-6-0 which has
been  remotored with a
6V micro motor running on a short section of Z
scale track forwards, backwards and with a stop-start.
The Marklin loco has the worm mounted direct on the shaft and the micro motor replaces the Marklin motor in
exactly the same orientation and design (just smaller).

The motor is coreless and the basket wound rotor, which has no iron core to be attracted by the permanent
magnet, means that  there is no 'cogging' or jerkiness in the rotation even down to very low speed.  Its possible
to make the motor turn at  around one rev per second, although torque at this speed is of course limited.  I
would say the that Marklin runs more  smoothly with the micro motor fitted, it certainly runs very well indeed (the
Marklin compensation is excellent).

Remotoring the Marklin loco was relatively easy compared to remotoring N scale locos.  You do not need to
use 'brute force'  to remove the original motor, the motor attachments can be removed without the use of a tool.  
The most difficult part is the lower bearing which is pressed into the chassis trapping the armature and worm
either side on the shaft..

Using some pieces of steel and a vice to support the chassis block upside down either side of the shaft &
bearing.  Use a watchmaker's hammer and a broken 0.9mm or 0.8mm drill shank (the plain part, not the drill
part) to drift the worm from the shaft which then allows the bearing to be also drifted out. This is the most 'scary'
part of the  process, but if you support the loco chassis (frame) close to the worm and use a small hammer
gently its OK.  Drifting means  to drive out with a pin and hammer.  Using too much force for this step could
break the chassis block so the important things are to support the chassis close to the bearing and use gentle
force with a small hammer.

Fit the original worm to the replacement micro motor using a shaft adapter to convert the micro motor 0.8mm
shaft to1mm which matches the Marklin worm.  Use non-permanent threadlock to hold the shaft adapter and
worm in place.  Position the motor so that the original gearing works as before and glue the replacement  
motor in place using superglue.  Solder one of the motor wires to the original pickup and the other to the
resistor and the other end of the resistor to the other pickup..

This is a cheap way to get a dead Z scale loco working, or to improve running if 'cogging' of the original motor is
a  problem.

Both motor connections are insulated from the motor can so DCC is easy (please include the dropper resistor
in series with  the motor).

The items you will need to buy from me are 6 Volt Micro Motor 6mm x 12mm with resistor, Micro motor shaft
adapter 0.8 mm to 1.0mm with resistor for Marklin locos  & please remember to add Postage & Packing (P&P)
UK ONLY OR Shipping & Handling to outside the UK. .

The following email exchange describes a possible variation to the method which should be easier if possible
on your  particular loco:

(from customer)
With your advise I was able to remove a shaft from worm gear successfully. I pulled the motor windings and
armature off of  the shaft and pushed it out of the bearing in the body. Knocked the bearing out also with a
broken drill bit. Drilled a 1mm  hole in steel plate and placed gear and shaft through hole between open jaws of
my big vise. Then hit end of shaft with a  tack/upholstery hammer and got end of the motor shaft down flush with
the end of the worm gear and then used .8mm broken  drill bit to knock it through. Really hard to get it to move
but once it started it came easily. They must be using some sort  of adhesive to hold them on the shaft.
(from Nigel Lawton)
Your experience in removing the worm from the shaft is interesting.  I did this in situ and was afraid I would
break the chassis block but the worm came off quite easily.  I did not remove the armature - it did not feel like it
would come off to me, so your experience is something I will add when corresponding with others on the topic.
The text below describes the motor and the process of re-motoring this loco.