This is a 4mm scale Chassis for the Lancashire and Yorkshire Railway (L&YR) Class 28 Mogul Experiment Locomotive in 00 gauge.
Due to the large wheelbase, this is reliably suitable for 3rd radius curves and greater. Test builds show that the assembled chassis will sometimes go around 2nd radius curves and points (small Hornby types) but not always. Springing will help but this chassis is primaraly designed to be built fixed, a different version designed for brass Hornblock springing is in the pipeline for the future.
The chassis is designed fixed but cut outs above the axles holes and 'half etched' vertical lines are cut out to guide your saw blade should you wish to add fully sprung brass Horn-blocks from another company. 1/8th / 3mm Brass 'Top Hat' Bearings need to be added by simply pushing them in and gluing them in position with Super Glue. A 1/8th Reamer or Taper Reamer may need to be rotated gently by finger pressure to get the best working clearance for the axles. If so, do it a little at a time and keep checking. You will also need some 5' 6" wheels for the Mogul Experiment. Suitable 22mm diameter wheels are available from several vendors. To fit the chassis to the body the rear simply slots in at an angle. The front is fixed via a screw or bolt that taps easily by simply screwing it in under pressure. A nut can be glued in place inside the Smoke-Box Saddle if desired. For the Mogul Experiment the Pony Truck swivels on the same pivot as the fixing hole so when the Chassis to Body retaining bolt is in position, as long as it isn't forced tight the Pony turns freely. Several Pony Wheel sizes can be used depending upon how far up you screw the retaining bolt and 2mm brass bearings can also be added for an optional consideration. 12-13mm wheels are reccomended for the Pony.
The Brake Rodding is sprue joined on the chassis top along with the Guard Irons, these are to be cut off and glued in position relative to the rake pads and wheels. Suitable coupling rods are available in Raw Brass from the SCC page. Wheels, Axles, Crank Pins, Motor, Gearbox and Brake Pipes are left to your preference and alternative sourcing.
General note: Once the chassis is built and working you may need to file/shave a small amount of material from under loco body for the coupling rods due to the running plate needing to be printed thicker than a scale reality. On some models sometimes the inside edge of the splahsers need a small amount shaving away too (moreso in P4). A few passes with a brass brush in a mini drill makes this a 2 second job though.
For wheels, axles, crankpins etc
Alan Gibson is a great resource
...as is Markits
For Motors and Gearboxes, High Level are recommended.
For the L&YR Class 28 and Mogul Experiment, to allow your model to be motorised without having to hack away at the underside of the firebox or boiler as is common with many of kits depending what parts you use, a 'Roadrunner Compact +' Gearbox and a 1220 Mashima Motor from High Level will fit nicely, although it is rather small and may lack power if the trains are too long. If using this combination the gearbox sides will need to be packed width ways with plasticard or similar, these components were used in the research and development trial builds.
EDIT: Future builds have shown that a London Road Models GB4 Single stage Motor Mount (Gearbox) fits better, is cheaper and quicker to build. As with all loco kits the choice is entirely yours though.
For crank pins, hand rail rod/wire and pillars, washers, bearings and other small sundry items Mainly Trains is a good website to visit.
But of course you can use whatever suits your needs and preference best,
the above has been typed out to hopefully aid you should you be new to kit building. The advantage of these 3D printed kits is 90% of the work is done for you, both on the body and the chassis.