Bachmann LMS 10000/1: Fitting Wheelsets

Wheelset diagram The diagram shows the arrangement of the wheelsets. Plain-ended axles of 2mm diameter are required: pin-pointed ends should be removed.

The diagram shows stub axles. An alternative, which we have not tried ourselves but has been done successfully by others, is to open out the gear muffs to 2mm diameter and use full-width axles. Obviously then the option of 'split frame' pickup is lost.

In the following we refer to 'outer', 'centre' and 'inner' axles. On each bogie, the outer axle is that nearest the coupling end. The inner axle is at the end of the bogie towards the middle of the loco, with the remaining centre axle being the one in between. On the Bearing Carriers (1) and Subframe Mainframes (8) the inner axles are indicated by a single half-etched dot, the outer axles by two half-etched dots (see the Bearing Carriers instructions for a full explanation of the marking system).

Dismantle the Bachmann OO wheelsets. Recover the final drive gear muffs and the axle bearings, noting, on the four inner and outer axles, that the bearings have two grooves, the outer, narrower of which engaged with the brass pickup strips. Discard the wheels and axles.

To ease the wheelsets apart without undue distortion of the central plastic gear muffs, ease the tapered jaws of a small pair of pliers over the axles, between the backs of the wheels and the bearings.

Bachmann Bearings Take the eight inner and outer Bachmann axle bearings, and remove the pickup flange and groove from each. Note that the remaining grooves are not as wide as those on the bearings for the centre axles.

The grooves and flanges can be filed away by placing the bearing over the ends of one of the OO stub axles held in a pin chuck, and working the bearing against the face of a file, using the pin chuck and axle as a holder.

The 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 train to the axles.

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

We found that the tapered end of a 2.3mm cutting broach was about 2.1mm diameter so used that to cut half way through the bearing from each side, finishing off with a smooth broach. Not a technique for the purist, perhaps, but adequate for our purpose. Alternatively, using a lathe, we have simply drilled through the bearings.

Allocate pairs of the Bachmann axle bearings to pairs of the kit's Bearing Carriers: the wider, centre bearings to the centre carriers (no axle id dots), the narrower inner/outer axle bearings to the carriers for the outer axles (two dots), and the inner axle (one dot).

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

Collect together the Drive Unit, brass bogie Subframe, Bearing Carriers and Bachmann axle bearings for the bogie. You will also need three full-width, 2mm diameter, axles.

Taking the axles one at a time, slide on to each axle one of a pair of Bearing Carriers, the pair of 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 Subframe and the Bachmann drive unit. The 'four-wheeled' part of the drive unit goes towards the outer (i.e. coupling) end of the bogie, driving the centre and outer axles, with the socket for the cardan shaft facing the inner end of the bogie.

Testing movement of 4-wheel drive unit Take the centre and outer 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 If you are having three driven axles, remove the drive unit from the subframe and clip the third, inner, axle into place. Replace the drive unit in the subframe, now engaging all six of the bearing carriers into their slots. Holding the 'four-wheeled' part of the drive unit such that the tops of all four of its bearing carriers are level with the top of the subframe sides, check that the third axle has at least ±0.5mm of vertical travel. If this is not the case, check for free movement of the individual carriers in their slots and then, if required, open out the Bachmann bearings a little more, on this axle only, up to a maximum of 2.3mm.

That concludes the test. Unclip the axles from the Drive Unit and put them to one side, ensuring that each axle bearing is kept with its respective Bearing Carrier.

We now assemble one of the outer wheelsets to check for lateral play.

If using the Branchlines stub-axle conversion kit in P4, you may find it necessary to reduce the width of the plastic gear muff, very slightly, to get the correct back-to-back measurement. We found that the best way to do this, to avoid distortion and retain squareness, was to file the end of the muff with it placed over the plain end of a 1.4mm drill held in a pin chuck, similarly to the way we reduced the width of the idler gears.

Take the Bearing Carriers and axle bearings for one of the 'two dot' outer axles and assemble them with the gear muff, axle(s) and wheels to the correct back-to-back measurement. Test fit the axle in its slot in its bogie subframe to determine the amount of lateral play. There should be just 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 necessary, dismantle the wheelset and fit full- and half-thickness 2mm washers (supplied on the fret) between the bearing carriers and wheels, until this condition is met. If there is insufficient play, even with no washers fitted, reduce the inner width of the wheel bosses accordingly.

Record the washer configuration you arrived at. If you had to reduce the inner wheel bosses, repeat the operation on the remaining wheels. Take off an extra 0.5mm on the wheels for the two centre axles, subject to not going beyond the line of the inner wheel rim.

Now we can assemble the remaining wheelsets.

Assemble the inner wheelset, inserting washers as for the outer wheelset.

Assemble the centre wheelset. This wheelset will have no, or fewer, washers, to allow sideplay. In P4, with gauge widening, ±0.5mm is enough, ±0.75mm plenty.

Test fit each inner and outer axle in its slot to confirm that the correct number of spacing washers has been fitted. The fit should be sufficiently loose to allow the axles to spin freely in the bearings, and the bearings should move freely up and down in the axle slots. Particularly with EM wheels, you might need to file a small amount from the outside edges of the subframe stretchers to fit within the back-to-back of the wheels.

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

That completes the assembly of the wheelsets.