Fitting Wheelsets

Four 2mm diameter plain-ended axles are required. Pin-pointed ends should be removed. If you are using ready-assembled wheelsets it will be necessary to remove one of the wheels from the axle.

For discussion on the possible choices of wheels, see the Wheels and Axles section of the Technical Description page on the website.

Dismantle the four Bachmann wheelsets. Recover the four final drive gears and the eight axle bearings. Discard the wheels and axles.

The eight Bachmann axle bearings need to be opened out to accommodate differential movements of the axles in the suspension whilst at the same time holding the drive gears in mesh and transmitting the tractive forces from the drive unit to the axles.

Open out the internal diameters of each of the eight Bachmann axle bearings from 2.0 to about 2.1mm.

Hold each bearing in a chuck and drill through with a 2.1mm drill. Lubricating the drill, e.g. with paraffin, will help.

The following operations check the differential movement between the drive train and the bogie subframe. Repeat them for each bogie in turn.

Find the brass bogie subframe and bearing carriers for the bogie.

Taking the new axles one at a time, and with regard to the identification marks on the bearing carriers and subframes, slide on to each axle a bearing carrier, two Bachmann axle bearings and the second bearing carrier. Note that the ears at the tops of the bearing carriers face outwards towards the ends of the axle.

Orientate the brass bogie subframe and the Bachmann drive unit. The socket for the cardan shaft should face towards the inner end of the bogie.

Take the axles and clip them in to the drive unit using the Bachmann bearings. Fit the drive unit into the subframe, engaging the four bearing carriers into the slots in the subframe. Holding the drive unit with one hand and the subframe with the other, check that the drive unit can move freely up and down relative to the subframe with the carriers sliding in their slots. At rest the tops of the carriers will be level with the tops of the subframes. The suspension is designed to deflect ±0.5mm, so the free movement needs to be maintained both when the base of the drive unit is parallel with the base of the subframe, and when one axle is raised up to 1mm with respect to the other. If there is any binding when the units are parallel, check the movement of individual carriers in their slots and correct as necessary. If there is binding when one axle is raised, open out the Bachmann axle bearings just a fraction more, up to a maximum of 2.3mm.

Test fit of Drive Train in Subframe This is a similar test being performed on a six-wheel drive unit.

That concludes the test. Unclip the axles from the drive train and store them in their respective containers.

We now use one of the axles, still with its bearing carriers fitted, to check for lateral play. Full- and half-etched 2mm spacing washers, provided on the fret, can be used to adjust the amount of play. If you are using ready assembled wheelsets and have one wheel already fitted to each axle, you will need to vary the operations slightly to suit.

If you wish to set your first trial fit by measurement, the design nominal minimum distance between the inside faces of wheel bosses is 16.8mm. The exact dimension on your particular bogie may differ slightly from that value.

Take one of the axles with its bearing carriers. Fit the wheels to the axle to the correct back-to-back measurement. Test fit the wheelset, with its carriers slotted in to the bogie subframe, to determine the amount of lateral play. There should be just a little; enough to allow the wheelset to tilt such that the wheel on one side is raised about 1mm with respect to that on the other. If there is too much play, dismantle the wheelset and fit 2mm washers between the wheels and bearing carriers until the condition is met. If there is insufficient play, reduce the inner width of the wheel bosses accordingly.

Record the washer configuration you arrived at and dismantle the wheelset. If you had to reduce the inner wheel bosses, repeat the operation on the remaining wheels.

Now we can fit the Bachmann gears to the new axles and assemble the wheelsets. Do the following for each axle.

If you have one wheel already fitted to the axle, slide on the required number of washers adjacent to that wheel, then the bearing carrier (ears facing the wheel), then a Bachmann drive bearing.

Fit one of the Bachmann final drive gears into position centrally on each driven axle. The gear should be a tight fit on to the axle, sufficient to transmit drive forces without slipping.

Slide the Bachmann bearings, then the bearing carriers, then any washers required, on to the axle.

Fit the wheels to the axle to the correct back-to-back measurement. If you are using the 'American' pickup system make sure that the insulated wheel is adjacent to the carrier for the insulated side of the bogie.

Test fit each axle in its slot to confirm that it moves freely up and down and has a suitable amount of lateral play.

Lubricate the bearings with a light machine oil and ensure that the oil is taken in to all the axle-bearing interfaces.

Completed Bachmann wheelset That completes the assembly of the wheelsets. The photo here shows a similar completed wheelset in place in a bogie subframe.