Nelson Riedel, Nelson@NelsonsLocomotive.com
1/14/2003, last updated 06/05/2004
The following shows the various parts of the engine for the Shay
|Rough Castings: I started with
the set of castings shown on the right that were purchased from
Kenneth Schroeder. The gray castings are cast iron
and the bronze colored ones are indeed bronze
castings. The cylinder castings are at the top with
steam chests (the boxes). As you can see, it's a three
cylinder engine. The long narrow pieces are the crosshead
guides. The little pedestals are the valve stem
guides. The three smaller bronze casting are the valves
and the six larger thin bronze castings are the eccentric straps
that drive the valves. The big casting with the three
arches is the crankcase.
|Lower Engine: The lower engine parts are
shown on the right. The crankcase has been machined.
It's dark because it was given an acid bath and then sprayed
with WD40 just before the photo was taken. The eight
bronze pieces are the split main bearings machined from bronze
rod. The four rectangles are caps machined from steel
stock that hold the bearings in place. The crankshaft is
made from precision ground stainless steel rod and stainless
flat bar stock. The webs are pinned in place with
stainless taper pins. The stainless disks are the
eccentrics that drive the valves.
The next photo shows the bottom of the assembled lower engine with
the crankshaft, bearings and bearing caps and eccentrics all in position.
This next photo shows the top view of the lower engine. The aluminum
block on the left is a handle to turn the crankshaft. The
two larger aluminum blocks hold the engine upright and off the
table. These three aluminum blocks are used only for engine assembly
and test and will be removed when the engine is mounted to the
|Cylinders & Associated Parts:
The parts for one of the three cylinders are shown on the
right. Sorry that the photo is a little dark. I
tried making the background lighter but the stainless parts then
became hard to see.
The machined cylinder is in the upper left with the upper and
lower heads and the green head gaskets. The machined
crosshead guide is shown below the cylinder.
The two piston rings are shown on the upper right.
These are made from cast iron and were purchased completely
machined. The piston and piston rod were machined from
stainless steel stock. The brass disk near the
bottom of the piston rod is a packing gland that is mounted in
the lower head to seal around the piston rod by pressing against
graphite impregnated yarn.
The parts below the piston rod are the crosshead machined from
bronze stock and the connecting rod & connecting rod pin
machined from stainless steel stock
The rod bearing machined from bronze stock and the stainless
strap are in the lower
Valve Components: The valve systems requires many small
carefully machined parts. These parts for one cylinder are
shown below. The part in the upper left is the steam chest casting
that mounts to the side of the cylinder casting. The
stainless steel steam chest cover is to the right of the steam chest. The
brass part with little ball is the snifter valve that mounts in the top
of the steam chest. The larger brass piece is the valve stem
packing gland which mounts in the lower side of the steam chest.
The machined valve stem guide casting is below the stem chest.
little straps screw to the top of the guide to retain the valve stem in
the guide. The stainless steel reverse shaft bearing block is in the lower left corner. Both the valve stem guide and
the reverse shaft bearing block mount to the cross head
The bronze block below the steam chest cover is the valve. The
hex brass part below the valve is the valve adjusting nut.
The stainless steel and bronze valve stem is to the left of the
The large bronze parts on the right are the machined eccentric
straps. The links blades fabricated from stainless steel
stock are shown are in the upper right.
The flat part with the curved slot in the center of the photo is the reversing link fabricated from stainless steel
stock. The parts below the reversing link are used in the
reversing link assembly. These were machined from bronze and
stainless steel stock. Machining the curved slot in the
reversing link and a matching curve on one of the bronze parts shown below
the link was challenging for this amateur machinist using fairly
primitive equipment. I got it right on the second attempt.
Note: Ken specified cold rolled steel for
most the engine parts such as the connecting
rods, heads, steam chest cover, link blades, etc. I chose to use
304 stainless steel for all these parts
in an attempt to improve the finished appearance. This was
probably a mistake since the 304 is really tough. It's going to be cold rolled steel for the trucks.
Valve Operation: The valve design is
both simple and effective. The next photo shows the cylinder mounted to crosshead guide with
the lower head sandwiched in-between. The lower end of the
piston rod is screwed into the top of the bronze
crosshead. The upper part of the connecting rod is shown
fitting into the lower end of the crosshead.
I'm holding the valve with the recess in the underside
visible. The valve moves up and down against the flat
machined surface of the cylinder side. The steam chest
bolts to this side of the cylinder. The steam chest is
connected to the boiler via the throttle (valve) so that the
interior of the steam chest contains uder pressure. (The
steam chest contains steam ---- novel)
The center slot on the machined side of
the cylinder cylinder connects to the exhaust port
on the right side of the photo. The upper slot
connects to the very top of the cylinder (the cylinder inside
the casting) and the lower slot
connects to the very bottom of the cylinder. The
valve moves up and down over the slots to control the input of
steam from the steam chest to the cylinder and the outlet of steam
from the cylinder to the exhaust.
Assume the piston is at the top of the cylinder and the
valve is near the lower extreme of it's motion. In this position the recess in the valve will be over both the
middle and lower slots permitting steam to pass from the lower
part of the cylinder out the lower slot, through the valve
recess and into the middle slot and on out the exhaust
port. At the same time the upper slot is starting to
be uncovered permitting steam from the interior of the steam
chest to go through the upper slot into the top of the
cylinder and push the piston down. As the piston moves
down, the crankshaft rotates and the eccentric will first push
the valve down to fully uncover the upper slot and then up so
that when the piston reaches the bottom of the cylinder
the the valve will have moved to near it's upper extreme
closing off the upper slot from the steam in the steam chest and
opening the upper slot to the exhaust. At the same time
the lower slot will start to be uncovered to let steam enter
the lower part of the cylinder and push the piston back
up. One of the neat things about a steam
engine is that is that the piston is powered in both directions.
|The photo on right shows the cylinder with the
steam chest attached and the steam chest cover removed to expose the
valve. The upper head is visible as is the snifter valve
at the top of the steam chest. The valve stem packing
gland is at the bottom of the steam chest. The steam
inlet header bolts to the right outside of the steam
chest. Steam enters the steam chest from the header
via the hole barely visible in the right side of the steam
The valve is pushed up and down by the valve stem. The
long nut on the valve stem provides for adjusting the valve
position such that operation is the same for both the up and
down stroke. (Valve timing is adjusted by rotating the
eccentrics on the crankshaft.) The little
screw in the adjusting nut prevents the nut from moving after
the adjustment has been
The valve is shown near the lower extreme position with the
upper slot fully open. This valve position corresponds to a piston moving down and near the middle of the
||These two photos show the view the front
end of the engine. In the left photo the reverse lever is
in the position for reverse where the valve for the #1 cylinder
is driven by the second eccentric. In the
photo on the right the reverse lever is set for the forward
direction and the first eccentric drives the #1 cylinder
|Side view of engine: Recall that the Shay
engine on the right side of the locomotive.
This photo show the outer side of the engine. The rod across the front controls the
reversing of the engine. There will a lever attached
to the left end of the rod which will in turn connects to a long
reversing lever in the cab.
|Rear side of engine: The is the rear side
of the engine that is next to the locomotive frame and
boiler. The upper copper pipe is the inlet
header. This header has a valve and air line fitting off
the photo to the left. These fittings permit engine
operation with compressed air. When the engine is
mounted to the locomotive this header will be cut near the left most
cylinder and a steam supply pipe connected at that point.
The lower copper pipe is the exhaust header which will
connect to the exhaust pipe that takes the exhaust steam to the
smokestack via the smokebox at the front of the engine.
The engine as shown here weighs 27 pounds.
The engine has been operated a couple hours on compressed air and
runs very smoothly. It will rotate on as little as 2 or 3 psi
pressure. Being an engineer, I was compelled to do a quick
power calculation that indicated a power in the 0.5 to 1 HP seems
possible. I am now faced with the overwhelming urge to build
apparatus to actually measure the power. That should best be
postponed till next winter if I'm going to have anything running this