The first problem is how to get the shell off.

I have owned several of these over the years and some are very difficult to get in to, others come apart easily. It seems to depend on how well the body shell is glued together in the factory.

You will find some coffee-stirrers or match-sticks useful.

There are 3 "lugs" on the frame, 2 on the left side, 1 on the right (assuming the long-hood is front and you are looking from the cab forward).

Carefully insert a screwdriver in between the motor-block and the side frames. As you lever the sideframes apart, insert a coffee-stirrer or match-stick in the gap to stop it closing up. The chassis can be a tight fit but take your time and you can gently lever it out of the body.

Due to the construction of the chassis block it is not possible to convert it to 16.5mm gauge so it is necessary to find a replacement. The large cutaway on the left of the frame is so that the cab is kept completely empty. If you don't use the Bachmann chassis described below, the replacement chassis might obscure part of the cab.

Your replacement chassis will need:

• Wheelbase of 60mm +/- 1mm
• Wheel diameter of 19mm +/- 1mm
• It doesn't matter if there are intermediate wheels as these can be removed
• The chassis cannot be longer than 87mm - but that doesn't mean you can't saw the ends off to make it 87mm

The Bachmann Branch Lines (British) 00-scale, Great Western 8750 class Pannier tank has a wheel size and wheelbase which is an almost perfect match for the Tm 2/2 if you remove the centre set of wheels. This is a nice little loco and almost seems a shame to throw the body away. Catalogue number 32.201, 32.202, etc., available on-line from a number of UK model shops.

The chassis is only gear-driven to the rear axle, the coupling rods transferring the drive to the other wheels. However, as the chassis is hidden, this is not really a problem as none of the rods are visible once the model is on the track.

Before you start cutting the loco to pieces, verify that all is well and that it runs OK. You will not be able to claim a replacement if it is defective after you have cut it apart.   To remove the body, lever-out the coupler pockets with a small screwdriver. This will reveal two screws, one behind each buffer beam. Remove these and the body will simply lift off.

After taking the body off, remove the small metal weight under the circuit board (already done in this view). This will fit in under the cab keeping the inside clear.

Then pull off the backhead detail, which is still in place to the left of the motor in this view.

This is the "point of no return", after this, the modifications to the chassis are not reversible!

To Bachmann's credit, the model has jointed coupling rods - which is awkward for us, we cannot just remove the centre set of wheels otherwise there would be no way to transfer the drive to the other set.

Firstly remove the crank pins from the middle set of wheels.

Then remove the keeper-plate from the bottom and drop out the centre set of wheels.

Using a pair of wire cutters, cut off the rim of the wheel. Clean up the resulting crank with a file. This is not visible in the finished model so you do not need to be too tidy.

Using a pair of side cutters (such as Zuron rail cutters), remove all the extra detail from the chassis and keeper-plate and the current-collectors that rubbed on the centre set of wheels.

Reassemble the chassis and you should have something that looks like this.

Using side cutters, remove the original centre-buffer couplers. Then, using a razor-saw, and the edge of the coupler opening as a guide, saw through the bodywork.

Cut right through the old backplate of the coupler (A in the picture) and the bodyshell (B in the picture) down to the level of the coupler opening (arrow in picture).

Cutting a square bottom to these openings is difficult. Fortunately we need to attach a couple of pads of Plasticard for fixing the chassis to so finesse is not critical.

These pads need to be about 1mm thick (approx. 40 thou) and 11mm square to fit in the bottom of the openings.

Dry-fit the pads and fit the chassis in place to ensure that everything is level. You may have to do a small amount of filing or trimming to get it to fit.

Using either thin pieces of Plasticard or filing, adjust the height of the end of the chassis so that it is in line with the brace across the chassis - as in the view to the left.

The exact height is not critical, but ensure that the chassis is level, otherwise the loco won't sit level on the track.

You can also see in this view that the rods and cranks are easily clear of the inside of the body shell.

Once the glue has dried thoroughly (at least overnight), drill the new Plasticard pads for the screws that held the original body on the Bachmann chassis.

About all that is needed now is to screw the chassis in place and fit the couplers of your choice. I found that Kadee #5s were at the right height if fitted to the bottom of the buffer beam. I used some 40 thou Plasticard to fill in the opening in the existing buffer beam and made a "platform" to fit the coupler to on the bottom.

The original Bachmann loco had extra weight in the body, and during the conversion the ballast weight from the chassis was also discarded so the loco is rather light. Fortunately, there is plenty of space inside the body to fit some extra weight.

For comparison, here is a Fleischmann Magic Train Deutz diesel alongside the finished conversion.

The Schöma loco is much larger, although it has to be said that the Deutz loco is a model of a small prototype.