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Shay Trucks
Nelson Riedel Nelson@NelsonsLocomotive.com
Initial: 2/26/03 Last Revised:
06/05/2004
The starting point for the
trucks was the castings purchased from Kenneth Schroeder. The
photo below shows the castings for one of the three trucks. Not show
are the castings for the brake system which I plan to discuss in a separate
part. Note: Later, when I made the line shafts and universals I
decided to change the trucks slightly. This change is included
at the end.
The upper left two castings
are the LH Journal Boxes. The upper right two castings are the RH
Journal Boxes. The two castings in the middle of the upper row are
the Pedestals. The four castings in the bottom row are, of course, the
wheels.
The first thing I did was to machine all the castings to the correct dimensions.
The next thing was to cut, drill, thread and shape the many required flat
pieces. The final step was to assemble everything. I'm going to
concentrate on the various parts and how they all fit together in this note.
There is information on the machining and fabrication of the various parts in
the accompanying Shay Truck Machining notes.
| Side Frames: The parts for the two
side frames of one truck are shown on the right. The upper
group is for the left side frame and the lower group is for the
right side frame. The two sides are different because the drive shaft
and gears between the drive shaft and axels are on the right
side. The Journal Box castings have been machined at this
point. The
remaining parts are made from steel sheet, bar and angle
stock. The blocks that hold the bearings in the LH Journal
Boxes (upper part of photo) are machined from aluminum stock
The assembled side frames are shown below. I was a little
too close when I took these two photos which caused the bars to appear
distorted. As you will see in the later photos, those pieces
of angle are not curved. |
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| Wheels & Axels: The machined
wheels are shown in photo on the right. The right side
wheels have bevel gears attached that will mesh with pinion gears on the
line shafts. The axels were made from cold
finished steel bar. The bronze disk is an eccentric used to drive
a pump that feeds water from the tender to the boiler. This
eccentric is provided on only one axel.
The assembled axels are shown in the lower left photo and the
assembled axel - side frames are shown on the lower right.
There is a ball bearing in each Journal Box. The nuts on each
end of the axel hold the axel in the bearings. |
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Spring Planks: The trucks are sprung just like the prototype as shown in photo below. The part below the springs is the bottom spring
plank. The pedestal castings on each end are
attached to the bottom spring plank. The top spring plank is
above the springs and free to move up and down between the
pedestals. The springs push the top plank
up. There are two screws from the top plank to the bottom plank
that limit the the upward motion of the top spring
plank. One of these screws is visible to the right of the
left most two springs. The screw at the other end is partially
hidden by a spring.
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The photo on right shows the spring planks in
position on the truck. The bottom spring plank and the pedestals
are attached to the side frames The top spring plank is free to
move up and down against the springs. The locomotive frame
rests on the top spring
plank.
Note: I deviated from Kenneth's design of the
spring planks. He made the planks by welding two channels and
two flat bars together. I screwed two flat bars and a
rectangular bar together. The exterior dimensions of the two
designs are identical.
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| Braces: The photo at right shows the
completed basic truck with the eight braces between the side
frames. These braces make the truck very rigid. |
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| Left Side: This is a shot of the left side
with the journal box covers in place. The bearings on this
side are sprung with a very stiff spring. . |
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| Right Side: This is the right side of
the truck. The journal box plates cover the recess for the
line shaft and line shaft bearing. |
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This is the completed set of three trucks. 
What's missing? I decided to call
the trucks finished at this stage, clean up the workshop and move on to the
next part of the project. The following four areas will be
completed later:
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Water Pump: The water pump must be
built and installed on the middle truck. That will be done with
the rest of the feed water system.
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Pivot Block & Rollers: The connection
between the frame and trucks is via a pivot block mounted to the top spring plank.
The frame is stabilized by rollers also mounted on the top spring
plank. The pivot block and rollers will be fabricated when the
frame is constructed.
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Line Shaft and Pinion Gears: As mentioned
previously, the line shaft and pinion gears are mounted to the right
journal boxes. These will be constructed as part of the drive
shaft - universal - line shaft system.
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Brakes: The brakes are also mounted to the
trucks and are operated by a steam driven brake cylinder mounted to
the frame. I had
intended to put off the brakes until everything else had been built
and, running. However, after observing how easily the the trucks
roll, even with considerable load and recognizing that my track will
have over 5% grades, I decided brakes are a necessity. I plan to
build the brake system after the frame is finished and mounted on the
trucks.
The trucks weigh 27 pounds each at
this point. When all the missing pieces are installed, the weight
will likely increase to about 30 pounds.
| Modification: Some months after making the trucks I
added the line shafts and universals. I decided to use
a slightly larger diameter universal ring than specified by
Kenneth. This in turn caused interference with the lower tie
bar. To eliminate the interference I moved all the lower tie
bars from above the angles to below the angles as shown on the
right. I had to cut out a section of the
vertical side of the angle as seen in the photo. The tie
bars had already been drilled for a clearance hole so a nut was
required on the attachment screws. (Maybe some day I'll make
new tie bars with tapped holes.) A flat head screw is used
in locations directly under the universal rings to provide
additional clearance. |
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