Wheelsets assembled and in nominal position

I'm using Slaters wheels that are supplied in a flat-pack form that contains a pair of wheels complete with axle and wheel retaining (countersunk Allen) screws. Driving wheel packs also include crankpin 12BA screws, bushes, washers and nuts; these are contained in a plastic tray sealed with Selotape. Also, in the above photo are the tools required at this stage. These are a modelling knife with the ubiquitous acute angle blade, a small flat file and an Allen key. The file is needed to 'clean-up' the square ends of the axle; a snug fit is required for the wheels, not too tight as the wheels can be on and off quite a few times before completion of the model.

Before assembling wheels on the axles it is necessary to remove the small moulding excess close to the rim. In the above photo the small excess can be seen at 9 o'clock on the back of the right-hand wheel; it has been removed with a sharp (modelling) knife on the left-hand wheel - see nominal 3 o'clock position. The axle with retaining screws and the items constituting the crankpins, are on the left in the photo. Here's the Slaters GA drawing...

... and here's the assembly underway:-

From the left in the above photo, crankpin components, wheel with crankpin assembled, and axle fitted to one wheel. Note the 12BA nut holds the steel washer and brass top-hat bearing solid on the wheel; the bearing surfaces for the motion rods being the combination of the steel washer under the nut and the brass top-hat. For the coupling rods, the top-hats have to be reduced in length, to the thickness of the rods plus working clearance. The centre wheels require a further top-hat bearing for the connecting rod, again reduced in length to the thickness of the rod plus working clearance.

'Here's one I made earlier' - it belongs to my model of 34064 and is virtually identical as far as the principal components are concerned

Here's the starter for 10, the etches: chassis frames, motion rods, bogie fames, and parts to form the cylinders and motion brackets.

Note in the above photo the tools employed at this stage, namely a pair of small (and sharp) side-cutters and a small flat file. The side-cutters are used to carefully separate the various parts, and the file used to remove the excess metal at the attachment points.

Here's some more views of 34064's chassis, with 34008's frames alongside:-

Before assembling the basic chassis, more decisions were required, these are as follows.

• Electric Motor & Gearbox unit. From previous experience, I've chosen to use the same unit as in the two Bulleid Pacifics I've built i.e. a Crailcrest motor and MSC 14:1 2-stage gearbox. These are particularly bulky power units and, in O-gauge, there's not many locos that afford the room; Air-Smoothed Bulleids being one of the notable exceptions. The performance from these units is really first class in terms of low-speed running and pulling power, as well as a very respectable top speed, again with an amazing amount of power. I haven't come across a better power unit, for O-gauge!

• Driven axle. The real issue here is whether the chassis is to be compensated. From personal experience, I've found compensation on locos to be a luxury that can be dispensed with, in the name of free-running. However, 3 rigid axles affords far from satisfactory running, mainly due to poor electrical pick up - never much more than 3 (out of 6) wheels in electrical contact with the rails, at any one time. The overall performance of my 34064 is a powerful reason for me duplicating its drive and electrical pick-up arrangement - see later.

• Electrical pick up. On my previous Bulleids this has been a bit of an afterthought, so for 34008 I thought I'd plan ahead and use Slater's plunger pickups.

The motor position is an over-riding consideration - everything has to fit around it

The above photo shows one frame marked-up with the position of the gearbox and the rim of the driving wheels. Also marked are the positions for the plunger pickups. Whilst the positions appear very close to the edge of the wheel, it has to be born in mind that the rims have a Vee insert for the (electrically dead) centre moulding, to prevent rotational slippage - see back of the wheel rim at 6 o'clock, above. The above photo also shows markings above and below the centre axle bearing (etched) hole; when the holes are opened-out to the markings, 1.5-2mm of movement is provided for the centre axle's bearings. This movement allows a minimum of 4 wheels to be in (electrical) contact with the rails. A slight downward springing will be provided for the centre axle to ensure (electrical) contact of the wheels; importantly it will overcome any tendency of the spring plunger pickups to lift the wheels. Finally, note the business end of a reamer used to ease the holes in the frame for the brass top-hat axle bearings and the axle bearings themselves.

All that remains is to drill pilot holes for the plunger pickups; I've elected to include an optional position for the centre driving wheel, as I shall be fitting additional stiffening to the chassis in the area of the gearbox. Note an Engineer's Clamp used to stiffen the two frames, which are bolted together, whilst the holes are drilled using a mini-drill.

Constructions continues on separate pages - see 'Quick Links' at top of page