3D drawing screenshots from SolidWorks
For such a small class they have a very varied construction – only the prototype No. 1 has a single motor (with 4-speed gearbox & reverse gearbox) driving both axles on a single bogie.
All the others have 2 motors. 2 to 7 only have a gearbox for one motor as before, the 2nd motor drives the second bogie via one axle only, both motors have a reverse gearbox. 8 to 17 have a separate gearbox & reverse gearbox for each motor, but this time driving all axles. 18 & the GWR built angular versions (diagrams A, A.1 & A.2) are similar but replace the spur drive with bevel drives which enables the deletion of the reverse gearbox, Reverse is achieved by moving the bevels on the nearest axle. From 18 onwards the motor & gearbox were lower so they fitted under the floor. This enabled the motors to be mounted opposite each other. Previous ones had the floor & seats raised over the motors & radiators. Fortunately the mechanism is fully hidden behind the valances on numbers 1 to 17 so can be ignored by modellers. It is of course fully visible on numbers 18 to 38.
17 & 34 were express parcels. 35 to 38 were twin units.
18 was an oddball mixture of the early streamline type shape with shallow valances & a large luggage compartment – half way to becoming the GWR angular ones.
2, 3 & 4 were the only ones fitted with buffets, they also had 2 lavatories. 10, 11 & 12 had one lavatory. 5 to 17 had sliding doors.
Not surprisingly, with all those variations, the internal layouts & seating also varied. The most common forms – numbers 5-9 & 13-16 had 20 seat units (counting 2 per-side, back-to-back and 3 per-side back-to-back as single units of each) of 13 different types, usually just varying in width & height.
The model has servo operated sliding doors with the luggage doors sliding in opposite directions using levers that are geared together. The doors are operated individually so need 4 channels plus 2 more for speed and direction. My R/C system copes with this but conventional R/C requires 6 channels. This model does not have couplings as per the full size version.
It comes complete with motor, speed control and 3 Li-Ion cells (other cell types can be used).
Russell J. H. A Pictorial Record of Great Western Engines OPC Out of Print
Judge C. The History of the GW AEC Diesel Railcars Noodle Books
Preserved locos 4 at Swindon Steam Museum, 20 at Kent & East sussex Railway, 22 at Didcot