Shay Reversing Gear
Nelson Riedel Nelson@NelsonsLocomotive.com
Initial: 9/23/03 Last
The reversing gear is another one of those pieces I've been putting off. The reason for the postponement was that I wanted
to duplicate the prototype, especially the sector plates with a lot
of teeth but didn't have good photos or dimensions
from the prototype. Reverse gears of several shays
photographed and measured on a visit to Cass in September 2003. There
are several variations of reversing gears including steam powered
reversing gears on some of the larger shays.
The Cass No 10 reversing lever moves through an arc of a little
50 degrees (measured by holding a protractor on the front view photo above).
The reverse shaft on my shay engine rotates 32 degrees. Kenneth
specified an arm on the reversing gear longer than the Johnson bar lever
thus reducing the 32 degrees to a bit less than 30 degrees at the reversing
gear handle. I think
the reason that Cass No 10 lever moves about 50 degrees while the
angle on my Shay is closer to 30 degrees is that the the link levers are longer on
my shay than on Cass No 10.
I wanted a bit more lever motion so I could have a few more of
those neat teeth so I decided on a total lever motion of about 40
degrees. The arm and Johnson bar lever lengths will be adjusted
as necessary to make things work out.
Cass 10 has 2 sector plates (the curved pieces with the teeth).
There is a heavy vertical bar welded to one of the sector plates which is
further steadied with the thin rectangular plate. I decided to
copy Kozo Hiraoka's design and use only one sector plate with the other set
of teeth cut in the stand, a vertical plate running down to the
|Stand & Sector Plate: 12 gauge
material was selected for the stand and sector plate. I started
with a 3" wide by 3.5" high piece for the stand and
screwed a smaller piece for the sector plate to it as shown on the
right. The hole
is centered and 3/4" from the bottom and tapped
1/4"-28. There is a aluminum spacer plate
sandwiched between the sector plate and stand to permit turning
the inside of the sector pate without marking the stand.
Those are 4-40 screws holding the pieces together.
|A long 1/4-28 bolt was chucked in the lathe and the stand screwed
on the bolt. A washer and nut were added to secure the plates.
The outside was then turned to 2.5" radius as shown on the
|The inside was turned to 2.125". The sector plate was too
wide at this point but I decided to cut the teeth and then finish
the turning (maybe a premonition).
|The lathe chuck (with the stand and sector plate still attached) was
transferred to an adaptor on the rotary table. The
rotary table was then mounted on the lathe/mill table and a 1/16"
wide slitting saw mounted in the milling head.
The plan was to use a 2.5 degree pitch and cut the teeth 0.70"
deep. That proved too close spacing so I went to 3 degrees
cut the teeth twice as deep ---- planning to remove the extra 0.070"
later. When doing the second set I found the
the chuck wasn't tightened on the rotary table and it had rotated some
screwing up the pattern --- so it was a third attempt with the teeth 0.21" deep.
Sure was glad I had the extra width on the sector plate.
|This is how things looked after the 0.14" excess tooth length
|The chuck with the plates was than moved back to the lathe and
0.14" turned off the outer edge (the part on each side of the
teeth) to match up with the teeth. Next, the sides were
trimmed to match the gear teeth and new holes drilled to hold the
sector plate to the stand. This shows the finished stand and sector plate with dimensions.
|This shows all the parts of the stand. The two spacers ( 0.128" long)
were cut from 1/4" rod. The base and bearing were cut from 1/4" bar
stock. The initial plan was to solder the
stand to the base but 4-40 screws into the edge of the base proved
to be sufficient.
|Handle: The photo on the right shows the various
parts of the handle system. The handle was made from 1/8" X
3/6" CFS bar. It is 6.5" long from the
center of the 1/4" axel hole at the bottom to the tip.
The spring retainer was cut from 1/8" X 1/4"
bar. It has a hole to allow the 1/16" rod on the latch to
slide through and the latch to move up and down. The
screwed to the handle(#1 brass screws), silver soldered and then the screw heads
The latch was cut from 3/8" CFS bar stock. The rod out the
top is 1/16" retained by a drop of Loctite.
The spring is from the
scrap box --- OD < 1/8", ID > 1/16".
The lift bar was cut from 1/8" X 1/4" CFS bar stock.
The trigger was cut from 1/4" X 1/2" CFS bar stock
|The assembled handle mounted in the stand is shown on the right. The
latch block is screwed to the handle with 1-72 button head screws
--- left over from the tanks.
The prototype uses clevis pins with cotter pins. The
clevis would have to be about 1/16" diameter --- too small to drill a
hole for a cotter. Instead, 1/16" roll pins were used for
the clevis pins. The outer holes --- those in the trigger and
the lower end of the lift bar were drilled 0.70" to allow free
movement with the pins a tight fit in the inner
|Arm Johnson Lever & Link: The last parts are the
arm, the Johnson bar lever and the link between the arm and lever. One
thing that had troubled me was that the link had to have two degrees
of freedom like a ball joint or universal. The
link used on Cass 10 is shown on the right. Note
the ball joints on each end of the link.
|Arm & Ball Joint: This photo shows the partially
completed arm and a ball joint.
The ball joint is from McMaster-Carr - part # 60645 K 611.
It has a 1/8" hole and 6/32 shank. I had ordered two, one
with RH thread and the other LH thread. The one with LH thread
was shipped from another warehouse and hadn't arrived when this
photo was taken. I also obtained a 6-32 LH thread tap.
The plan is to make a coupling threaded LH in one end and RH in the
One ball joint will be screwed into each end and the link length adjusted by
turning the coupling.
That is the partially fabricated arm in the photo The
end is made from 1/8" X 3/8" CFS bar stock that was heated
and bent in a U shape. The main part of the arm is also
made from 1/8" X 3/8" stock and silver soldered into a
shallow 1/8" wide slot milled in the end of the U shaped
piece. The arm was then ground and filed to make it
somewhat tapered and the sides of the U shaped end thinned to about
3/32" The arm was left extra long during the
fabrication to make handling easier. The last step was to
drill the 1/4" axel hole and then cut off the end.
I used a somewhat shorter arm than specified by Ken --- 1.75"
between the centerlines.
|Completed Reversing Gear: The arm and handle are
silver soldered to the 1/4" diameter axel.
The color of the photo is weird --- incandescent lamps.
|Link with Arm and Johnson Bar Lever: The Johnson
bar lever is 2.25" between the center lines. With this length
about 95% of the available rotation of the reverse shaft is used at the
extremes of the reverse lever. This is by design --- I didn't want to force
the reverse shaft to the stops.
is made from 5/16" hex stock. I'm going to remake it with
1/4" stock to cut the size slightly (didn't have 1/4"
stock). A lock nut is
required on one end --- a standard nut on the RH threaded
ball joint. The screws through the ball joints are turned
1/8" diameter from 3/16" hex stainless stock.
The ends are turned down to 0.112" and threaded 4-40. Double
nuts will be used on the ends to lock them in place as
on the prototype.
|Finished Reversing Gear with Link: The ball
joints on the link permit considerable flexibility in the position
of the reversing gear. I'm going to select the position
after the boiler is in place.
|Update - Different Mounting Arrangement: I've got to
the point of figuring out where to locate all the
controls. Earlier I'd planned to mount the reversing
lever fairly close to the side of the cab. I'm now trying to
fit in the steam brake valve, the reversing gear and the throttle
lever, all of which are located near the engineer. Locating the three
controls as close as possible to the position in the prototype seems
to work the best.
A platform is built around the reversing gear on Cass 5.
The platform covers the arm and link and makes a flat surface to
mount the engineer's chair. The photo on right shows the platform to
be 18" high (I used the original photo and enlarged it to read
the tape measure).
|This photo shows the platform to be about 35" wide and the lever
to be located about 30" from the cab wall.
The stand for the reversing gear I'd made was too high
and the arm and handle were located too close together. After
fooling around with the possibilities I decided to make a different
base, mount the base about 1" below the floor and move the arm away from the lever.
Dropping the base below the floor leaves most the space under the
platform empty. That might be a good place to
mount the atomizer regulator. I'm also going to test an igniter
of the type used in a gas grill to see if it will work to relight
the burner if it should go out. If the igniter works,
the button part could also be mounted under the
platform. The atomizer pressure gauge would
work nicely in place of the engineer's seat. (That piezoelectric
igniter didn't work out. An electronic igniter did work and
the push button switch for that igniter was mounted in this
area.. See ElectricalI
|This photo shows the new base made from 1/4' thick angle. The inside corner was squared on the mill.
A longer axel was used separating the lever from the
handle. One quarter inch was cut off the bottom of the
stand because the stand is on top the bottom leg of the base
rather than beside the base. The stand was secured to the
sort leg of the angle with 4-40 screws. The short leg of the
angle fits between the flanges on the frame I beam and is secured
with a couple 8-32 screws.
|This photo shows the reverse gear mounted to the
frame. The gray piece of plywood is a model of the
boiler backhead with the throttle lever. There is ample clearance
between the reverse and throttle levers. The steam
brake valve will mount above the rear cylinder. The
steam brake lever will be above the reverse lever and below the
The bottom leg of the angle is wider and longer than
needed. There will be some pipes running in this area and the
angle might be a useful anchor point so I decided to postpone
reducing the size of that bottom leg.