2-8-2 - THE BUILD

[doctorwayne]

I think that the term "injector" is somewhat confusing, as it implies that it "injects" water directly into the boiler. Actually, an injector is a pump of sorts, with no moving parts, where steam is mixed with the water. This moves it, under pressure, from the injector to the boiler, via the check valve. The check valve's purpose is to allow the water to enter the boiler, but prevent the water and/or steam that's already in the boiler from escaping.
Check valve placement can vary, with some locos using a dual top feed-type, fed from either two injectors or from an injector and a feed water heater. Some locos used a single-feed top-mounted check valve for only the water from the fwh, with a separate, side-mounted check valve (usually on the engineer's side of the boiler) for water from the injector.
Other locos used two side-mounted check valves, usually one on each side of the boiler. One would be fed by an injector, while the other could be supplied by another injector or by a fwh.

This loco has a dual-feed, top-mounted check valve, with water supplied by two "lifting" injectors located inside the cab:


This loco has side-mounted check valves, both supplied by non-lifting injectors located beneath the cab. You can trace the water line from the vertical horn-like gizmo beneath the cab to the check valve. The other pipe, running from the un-shrouded turret, is the steam supply line to operate the injector:


...and this one also has two side-mounted check valves, but both are supplied by lifting injectors mounted on the sides of the boiler, just ahead of the cab. Steam is supplied by a pipe from the turret (inside the cab) and its admission to the injector is via rods operated by the fireman. The longer pipe beneath the cab is the water supply from the tender, while the shorter pipe is an overflow:


If you're not going to install a feedwater heater, you need to use both injectors. If you plan on using a fwh, use the injector only on the engineer's side of the loco.
With either set-up, you'll still need check valves, either two side-mounted single feed ones, or a single-feed top mounted one, along with a side-mounted one, or a dual feed top-mounted one.

Thanks for the kind appraisal of the 4807. The brake shoes were part of the original locomotive, a Bachmann USRA Light Mountain. Precision Scale offers brake shoes and hangers in plastic or brass (plastic creates less hassles with shorts, while brass is easier to affix securely (soldered), but makes it more difficult to maintain clearances for electrical purposes.

Wayne