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Shay Truck
Machining III
Flat Bars & Assembly
Nelson Riedel Nelson@NelsonsLocomotive.com
Initial: 2/28/03 Last Revised: 06/05/2004
The Flat Bars:
| The photo shows the assembled flat bars for one
truck. A total of 16 bars, consisting of 12 flat bars, 2
bent flat bars (side bar hangers) and 2 angles are required for
each truck. Kenneth's drawings call for Hot Rolled
Steel. I decided to use Cold Finished Steel stock for all
except the angles which are available only in HRS. The
CFS has a much smoother surface and squarer cross section.
There are a total of 9 different lengths and/or drilling
patterns in each truck. Since I was making three trucks I
decided to make a pattern for each of the 9 bar
variations. The accuracy of the lengths of the bars
and the hole patterns have a significant impact on the quality of
the finished truck so I was very critical of the patterns and in
fact redid several until I had a satisfactory set. |
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I was very concerned about my ability to fabricate
satisfactory side bar hangers ---- the part with the bends.
The hanger is made from 1/4" X 1/2" flat bar stock. The
drawings suggest that the bar be sawed halfway through at each bend
point, heated red hot at that point and then bent. This
procedure worked very well. The photo below shows the first
attempt. The bent hanger is attached the top strap
to make sure the length of the hanger is correct. (The top strap
appears to be slightly bowed in the photo. This is probably do to
positioning the camera too close to the object.) The angles on the
two sides of the strap were adjusted until they were equal.
| The drawings indicate that the gaps at
the bend points be filled by brazing. My gas welding tanks
were empty and the weather was bad so I decided to use my little
flux-core wire welder to fill the gaps. (I used a propane
burner to heat the bars for bending.) The flux
core welding made a mess but produced very strong
joints. I had to do 2 or 3 passes on each joint to get
a satisfactory buildup.. The joints were ground flat and
cleaned between each pass. The final finishing
was done with a file.
I was very relieved when I had the 6 bars shown on the right
completed. |
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The condition of the ends of the bars have a major impact on the overall
truck appearance. Sloppy ends look really bad. I'm unable to saw bars with smooth square ends and
correct lengths. What works for me is to saw the bars about
1/8" longer than required on my 14" abrasive cutoff saw ($60
from Harbor Freight) and then finish the ends to make them square and the
bars the correct length. I finished some ends in the lathe and some
in the mill. The mill is probably the quickest. I was
able to put up to about 8 bars together in the milling vise so the
operation is fairly quick. I had purchased a four fluted
doubled ended 1/2" diameter Chinese end mill from Enco for
$3.49 (probably about $5 when S&H included). I was able to
finish all the bar and spring plank ends for the three trucks using one
end of the double ended end mill. It's getting pretty dull now so
will start using the other end when I work on the frame. The
ends of the cross braces are cut at 24.5 degrees and 65.5 degrees. I
spent considerable time on my afternoon walks thinking about how to do a
good job of finishing these ends. I have a rotary table that I can
mount on the mill, but it is a big pain. It finally dawned on
me that the ends are square and at right angles with respect to the
truck side frames. It was then a simple matter to make a fixture
from scrap 1/2" angle with two holes the same distance apart as the
cross brace mounting holes in the side frames. The left photo
below show a pair of cross braces mounted to the fixture. I
rough sawed the excess length from the ends when attached to the fixture
(this allowed fairly accurate rough cuts) and then did the finish cut in
the mill as shown on the right. That's the $3.49 end mill at work.
The Spring Planks:
| Kenneth's drawings call for the spring planks to be
made by welding two channels and two flat bars together as shown on
the top right. After the welding the top and bottom are
to
be smoothed by machining or grinding. I'm not much of a
welder so that didn't seem like such a good idea to me.
I had purchased a set of Lima Locomotive Works drawings from
Kenneth so I thought I'd take a look at the
prototype. The spring plank is show on a 1923 blueprint.
I was able to scan part of that blueprint and
"process" the image to get the lower part of the sketch on the
right. Note that they welded the 3/8" plates on
the top and bottom to get smooth surfaces. Kenneth must be complimented
on a design that very closely approximates the prototype
profile from
readily available stock. |
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In spite of the nice profile of the welded channels/flat
bars I decided to use CFS stock to make my spring planks. The top and
bottom are 1/8" X 1 1/2" flat bars and the center part is a
3/4" X 1" bar. The rough cut stock for one top
and one bottom spring plank are shown on the right. Update:
Some time after I finished the trucks, I visited Mike Mihalyi who is
building a pair of Shays. He used a different spring plank
design based on Ken's earlier drawings. He used a pair of 1" X
1/2" X 1/8" channels instead of the 3/4" X 1" solid
bars I used. He screwed the 1/8" X 1 1/2" bars to the top
and bottom of these channels. This is like the Lima drawing without
the two 6"-15 1/2" channels on the inside. If I make
another Shay I'll use that design. The
next step was to locate and drill a 1/2' hole in each piece. (This
is
the hole that provides access to the lower screw in the pivot
block.) A bolt though this hole was used to hold everything
together and aligned while other holes are drilled for flat head
screws to hold everything together.
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| The ends were finished to the correct dimensions
after everything was screwed together. The photo on
the right shows finishing the right end of the bottom spring
plank. The notch provides clearance for the line
shaft. In this case most of the material was removed for the
notch by sawing. The end mill provided the final finished
surface. That's the $3.49 end mill at work. The socket
head cap screw is in the hole that will later be used for one of
the screws that limits the upward motion of the top spring
plank. |
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| The bottom of the pedestals are attached to the top
of the bottom spring plank. Rather than marking off and
drilling both the pedestal and spring plank and hoping they fit
together, I drilled the holes in the bottom spring plank and
then used it as a template to drill the pedestal as shown in the
photo. This
enabled the pedestals to be positioned and all dimensions verified
before the castings were drilled. This operation worked very
well.
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| Once the pedestals were mounted on the bottom
spring plank, it was possible to finish the ends of the top spring
plank including the slot that rides in the pedestal rib. The
photo at right shows milling the slot. And, that's not the
$3.49 end mill. That's a single ended 5/16" end mill
which cost $1.99. The slot is about 3/8" wide. Two cuts
were required. The mill height was adjusted slightly
above the centerline of the spring plank. After a first cut, the
spring plank was turned over and a second cut taken. This
technique assured that the slot centerline was on the spring
plank centerline. |
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| The top of the bottom spring plank and the bottom of
the top spring plank each require 12 spot faces for the
springs. The spot faces are 1/2" diameter and
1/16" deep. I used a counter bore with the pilot
removed to do the facing and used a drilling template as sown on
the right to to position the spots. The same template was
used on all six spring planks to make sure the spot faces on each
end of the springs lined up. I chose a counter bore
because the smooth sides wouldn't cut the template. If I had it to do
over I'd probably try to use that $3.49 end mill --- the
counter bore cost more than
$10. |
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The finished pieces of the two spring planks for one truck are
shown on the right. The spring planks were disassembled to
remove the burrs from the machined edges and holes.
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| That's the cleaned and assembled pair of spring
planks. I was really pleased with these. |
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| This shows the the springs in position |
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| There are a pair of screws between the two spring
planks that limit the separation of the two planks so that the
springs are retained even with no external pressure. |
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| I was very concerned that the journal boxes be
assembled in the side frames such that the axel holes are
perpendicular to the side frames and the axels have the correct
spacing and are positioned correctly with respect to the spring
planks. To this end I made the assembly jig shown on the
right. It has two axels with the
correct separation and held parallel by the bars welded between
them. This photo shows positioning the lower angle on the RH
Journal Boxes to mark the Journal Box mounting holes. The previously marked mounting hole centers
were very close to those found by this technique so the jig might
be overkill. |
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In this photo the jig is being used to hold
everything together for drilling the mounting holes in the top of
the journal boxes.
The end result was three trucks that are square and rigid and
operate extremely smoothly. |
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| All the patterns, templates, jigs, etc used to
fabricate the trucks are shown on the right. This
technique requires extra material but allows one to spend
extra energy on the pattern and then duplicate the pattern
quickly.
It's on to the frame next. |
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