Alan's Shay
Initial: 11/02/08 Last Revised:11/07/2008

Alan of Chelmsford, Essex, UK built the  7 1/4" gauge 'B' class Shay locomotive show above and was kind enough to share the following photos.  The text and captions are Alan's words.  The locomotive specifications are at the end of the page.  Alan may be contacted at

The outline is based on the early 1900's style, of a loco of about 65 ton size. The model weighs about 300 lbs dry. It uses a conventional copper loco style boiler, coal fired, with 4 radiant type superheaters, and rated at 100psi.  It steams well and I've done over 50 miles with it so far.

The 3 cylinder engine uses piston valves, (not quite correct for period), but I wanted an engine that would rev freely, which it does, light engine it will do over 10 mph. Cylinders are 1 3/8" bore by 1 1/2" stroke, using alloy pistons with cast iron rings.

I've fitted a steam brake system for the rear truck and vacuum brakes for the front one to be compatible with braking systems on most UK club passenger stock. The driving truck I use also acts as a coupling converter between the buckeye couplers (from your Railroad Warehouse Co.) and UK style buffers and drawhook & chain.

The loco is essentially all my own design, based on information wherever I could find it, including your site which I found quite useful. Castings, apart from the wheels, were produced by a local foundry from patterns that I made. 

Engine side view of loco and driving truck, July 2008

Front view, it’s No. 4 as ‘4’ is easy to mill out! The small rectangular box on right hand footplate is battery box for headlamp, steam turbo generator a job for this winter!

Non engine side, before headlamp fitted.

Me playing trains at a private railway in Norfolk, the trucks, 18 in all, are not mine. May 2008

General view of engine. The top and end engine cover plate yet to be made. Not sure whether I will lag the cylinders, such nice castings!

Some engine details. The chrome valve at top centre is the engine regulator (throttle) valve, which is on the ‘hot’ end of the superheater. Below it is the cylinders lubricator. The air tank to the right is used as the vacuum reservoir for the vacuum brake system. The brass cylinders in front of the cylinder blocks are steam operated drain cocks which double up as pressure relief valves in case of water carry over. (A bad driver who lets the boiler water level get too high!)

Close up of valve gear bits. Eccentrics are mild steel, straps are gunmetal (bronze).

Engine on test stand, Nov 2006. Used for initial steam tests to check out before painting. Would easily buzz round to over 1200rpm.

Rear view of engine during construction. Middle copper pipe is steam inlet, other two are exhaust, yet to be piped together. Elbow on lower right is for exhaust dump valve for initial engine condensate. Plumbing is mostly 15mm domestic fittings, silver soldered. (15 mm is UK standard). Main engine fixing studs to chassis can be seen on bedplate casting

Drive gear side of front truck.

Sprung axlebox side of rear truck. Note bolster suspension spring just visible, one of 3 each end. Brass pipe is train vacuum pipe, black lead is from bicycle speedo sensor.

Another view of rear truck, shows somewhat dirty brake shoes and brake beam.

A truck during construction, Dec 2005. The circular bit in the middle houses the thrust race, which then bolts to a heavy plate to span the chassis rails.

Detail of truck and pinion bearing casting, showing fabricated universal joint yoke

Steam brake cylinder and drive shaft details. Cylinder bore is 1 inch.

Front drive shaft assembly, and above it the vacuum brake actuating cylinder with pull rod. Cylinder is 2 ½” bore. Typical vacuum “pressure” is 15 inches mercury.

Inside the smokebox. The hexagon at the bottom is the engine exhaust jet, which is changeable to suit driving conditions, the concentric tube in the middle is the steam blower jet. To the right is the vacuum ejector steam exhaust and behind that the superheater hot and wet steam headers with the steam outlet union and pipe.

General view of smokebox and door. The US style door fixing dogs are dummy, the door number plate has a screw thread extension which fits into the hole in the central bar. The larger door aperture means the whole superheater assembly can be removed through the smokebox.

Drivers eye view of cab controls. The layout has been designed for ease of operation rather than authenticity, not that I have much information on the full size anyway.
Controls, from upper left, whistle valve, vacuum ejector, boiler pressure and vacuum gauges, in front of which is the steam draincocks control and stop valve, steam brakes stop valve, injector steam and Wier pump valve. Hiding behind the regulator valve control is the steam manifold pressure gauge, and below are the vacuum and steam brake application levers. The handbrake handwheel is on the left.

Cab during construction. The removable roof section join can be seen. The roof is laminated up from three sheets of thin plywood to hold it’s curved shape.

Wier pump and clack, steam vacuum ejector, injector clack and stop valve and Wier pump lubricator pot. The Wier pump wasn’t made for this engine, it is probably a bit over scale, it was made some years ago from commercial castings as a fill-in project. It works well though, nice to have when the injector plays up.

This is the engine bedplate casting ex foundry and the bearing housing blocks.  Making the coreboxes for this was a bit of a nightmare, but the end result was worth it.

The trunk guide casting ex foundry. The bit sticking out to the right fixes to a plate bolted to the top face of the chassis rail and thus takes the weight of the engine. The trunk guide bore is circular on my design.

Cylinder block casting ex foundry. The cast in portway between the power cylinder and valve bobbin cylinder is just visible. Side and rear lugs are machining aids.

The chassis in primer. Front is to the right. Note the substantial engine mounting plate.

My driving truck from the underside. This is a commercial model which I modified for the buckeye coupler from the standard buffers and drawhook. The plastic pipe conveys vacuum to any carriages pulled.



Mainline gauge model, i.e. 1/8 scale.
Based on Lima “B” Class Shay, of about 65 tons, of early 1900’s
Overall size, 65” long, 14.5” wide and 20” high.
Dry weight is about 280 lbs, ( ~ 300 lbs working).
Project was started in May 2005, engine first run, without cab etc, in July 2007.
Model is not quite complete, needs domes, bell, pinion guards etc etc.

Aim was to produce a loco which would travel easily at 5 to 6 mph and thus be suitable for passenger hauling on Club tracks. (That is real, not scale speed).
The overall size and weight had to be compatible with my estate car.
It is thus my own design, based on information from books and the Web, mostly USA based sites.
Was designed to be easy to operate and maintain, as far as possible.
Designed on a PC with a 2D CAD system, “Turbocad” v4.
Some attention was paid to lubrication methods, and replaceable bearing bushes.
Design of individual parts was made compatible with my machining facilities.
Note that the design is in metric dimensions, I have quoted inches here when convenient.

Copper boiler, coal fired, of conventional locomotive type, 100 psi rated.
Barrel 6” diameter, 17” long, firegrate 6” x 4.5”.
16 fluetubes and 4 super heater flues with stainless steel radiant type elements.
- I had the boiler made professionally.
Water feed is by rear truck mounted axle pump, injector or Wier pump.

3 cylinder, piston valve, Stephenson’s valve gear.
Scaled from full size 11” bore by 12” stroke engine, ie 36mm x 38mm.
Pistons are aluminium alloy with two cast iron rings.
Piston valve bore is 18mm, using 3 part stainless steel bobbins with cast iron rings.
The 3 throw crankshaft is of built up construction, Loctite(603) and pinned, with case hardened big end journals. The 3/4” diameter shaft runs in bronze bearings, the centre ones being split.
The central eccentric pair is also split.
All the engine casings are to my design, cast by a local commercial foundry in spheroidal graphite iron, (a ductile grade and beautiful to machine!).
Note: I am aware that all the early engines were slide valve, but I wanted a loco that would not be an unwelcome slowcoach on the track, so I designed an engine that would rev freely. It needs ~800rpm do travel at 6mph (model velocity), which it does comfortably.
I understand some early locos were re-engined if they got damaged.

Based on the early bar frame design.
Bar frame section 14 x 5mm black bar, 12 x 3mm for top braces, bottom angles 12 x 12 x 3mm.
Wheel diameter 116mm, (~ 4.5”). These are commercial front bogie wheel castings for a 7 ¼” Gauge “King” class GWR 4-6-2 locomotive!
Gear ratio is 1.75:1, a bit lower than most Shays, (it also made the pinion manufacture a bit easier). Gears are 35T and 20T, which I cut myself.
I made the patterns for the truck castings, cast as for engine parts.
The axles run in two-row self aligning ball bearings on the gear side, and a standard sealed ball race on the other end in the sprung axle box, both 12mm bore.
The pinion shaft runs in porous bronze bearing bushes.
The truck pivots on a ball thrust race (slightly preloaded) with limit stops to prevent damage to the universal joints etc in the case of a derailment.
Universal joints and sliding shafts much as Mr Shay designed them, shafts are ½” square, sockets are two pieces of bright steel angle silver soldered together.
Cast iron brakes shoes on both trucks, chassis mounted vacuum actuator for front truck, (to be compatible with most UK passenger stock), steam power cylinder for the rear truck coupled with screw down cab handbrake.

Main rails 20 x 40 mm hot rolled channel (single piece) with substantial plate and channel drag boxes for the “Railroad Warehouse” couplers, (very nice), and one channel frame stretcher.
The truck pivot bearing housing plate bolts to the side channels to allow easy removal of a truck without any other loco dismantling.
Oak buffer beams of 26 x 40mm section complete the chassis.

Outline based on the early loco type, with typical Shay features.
Designed to lift off after removal of securing nuts to cab floorplate for easy maintenance access to cab pipework and controls.
Removable cab roof section for ease of driving.
All timber construction in fine grained pine,(ex 1970’s window frame!)
Timber has been varnished, I have no idea what the full size did, but it looks nice!
Front windows hinge open, side windows slide, both with hardwood frames and Perspex panes.
The internal arrangement of controls has been made to make driving as comfortable as possible.

Water tank
Outline based on the early loco type, with typical Shay rivet patterns.
Standard construction of sheet and small section angle, riveted together.
Sides fixed to floorplate to make a removable sub assembly.
Capacity nearly two gallons (UK).







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