|
Shay Truck Brakes
Nelson Riedel Nelson@NelsonsLocomotive.com
Initial: 4/28/03 Last Revised: 06/05/2004
Note: The truck brakes were initially grouped
with the truck pivots. Later I decided to split the brakes from the pivots
and rollers. The pivots wand rollers were then grouped with the
trucks and all the brakes system components grouped together.
I must confess that I wasn't anxious
to start machining the brake parts including:
- 33 castings
- 24 hangers
- 12 levers
- 24 clevis
- 3 anchors
- 6 beams
- 12 rods
- ~ 60 clevis pins
Kenneth specifies the finished dimensions of the castings and
most the other parts. The clevis pins however aren't
specified. After reviewing the drawings and checking over some old photos from Cass, I decided to take another
trip to Cass to check out the brakes more carefully.
(It was a good excuse to get off the leash for a couple
days.) The major difference found was that the hanger
dimensions were narrower and thicker than Kenneth specified.
The photo at right shows that the hangers which are 2"
wide and 1" thick. The hanger clevis pins are
1" diameter and use cotter pins at each end. These scale to
1/8" X 1/4" hangers and 1/8" diameter clevis
pins. The pins in the levers are similar except that
they have a head on one end.
Once I made these design changes I got more interested and the
fabrication was rewarding. ( My daughter claims that
men aren't happy unless they put their own stamp on things, like a
dog with a fire hydrant.) |
 |
The next photo shows the finished brake parts for one
truck. There is an error in the photo, only four hangers are shown while a
total of eight hangers are required per truck.
The following three photos show these parts installed on
the tender truck. If you look close you'll see that hairpin rather
than cotter pins are used at the ends of the clevis
pins. The hairpins are convenient during the
construction process. The hairpins will be replaced with standard
3/64" diameter cotter pins before the engine is actually run because
I'm afraid the hairpins may work loose and parts will fall
off.
| Park Brake: Kenneth's drawings
show how to link the two main frame trucks to the steam brake
cylinder. He doesn't show how to link the
tender truck to the steam cylinder. Because of this I
looked at the tender brake linkage last fall on a trip to
Cass. It was a bit confusing so I took some photos to enable
later recreation. Later I found these photos useless
--- I couldn't understand them.
Some time later I asked Kenneth how he linked the tender brakes
to the steam cylinder since no linkage was visible in his
photos. He explained that there is no linkage on his model;
he instead uses the tender brakes for a park brake
function. He said this is very handy on tracks where
the parking sidings are sloped. I immediately thought
this was a good idea; virtually all of my track will be
sloped. Sure seems better than a rope and anchor.
The middle and upper photos on the right show the lever I made
to control the tender park brake. The tender frame is upside
down in these photos. The lever pivot is installed on
the sloped part of a frame channel which makes the idle
orientation of the lever to be sloped downward. The
strap holds the lever up and roughly level. The slot milled
toward the front of the strap is the brake engaged
position. When the lever is in the forward position
the downward force on the lever holds the lever in the
slot.
The lower photo shows the frame correct side up and the park
brake lever connected. The lever is positioned in the
"brakes off" in the photo. The lever seems to have
enough friction to hold it in the released position.
If this loosens up I'll add a spring between the lever and
the bolster to hold the brakes off.
Note: I later modified the park brake lever and rear truck
linkage as the rear truck brakes were connected to the steam brake
cylinder. |
|
The following shows details on machining some of the brake
parts.
Brake Hangers: The following photos show
making the brake hangers. The first step was to drill the holes in
1/8" X 1/4" bar stock as shown on the left. Note the use
of a pattern to position the holes. The next step was to
group 4 hangers together using 2-56 screws as shown on the right.
The ends were then trimmed to the correct length using an
end mill as shown below on the left. The ends were then rounded
using a rounding end mill as shown on the right below. The
final step was to drill out the holes to the correct size for the clevis
pins.
Levers: The levers were fabricated using
techniques similar to that used on the hangers described above.
One difference was that the levers were held together using expansion
pins. The left photo below shows making the taper on the sides of
beam levers. Note the brass pieces used to prop up the expansion
pins on the left end. The right photo shows rounding the end
of the brake levers with a rounding end mill.
| Clevises and Anchors: The clevises and
anchors are made from 3/8" bar stock. A total
of 24 clevises and 3 anchors are required so some thought was
given to speed the process. The best choice
would be to use a 3/8" square collet in the lathe. I
don't have any square collets. Instead, I made the
fixture shown on the right and mounted it in the 4-jaw chuck. |
 |
| The first step was to drill the center of the bar stock and
cut it to the correct length. The cutoff operation is
shown on the right. |
 |
| The next step was to use a rounding end mill on the ends.
Note that seven are being machined at the same time.
The angle is aluminum. Aluminum has some give so that the
side forces are equalized insuring that each piece is held
firmly. (The ends of the 3 anchors are not rounded.) |
 |
| The next step was to make the slot in the clevis. The
slot was first rough sawed with a hacksaw. The slot was
then finished with an end mill as shown on the right. (The
anchors weren't slotted.) |
 |
| The individual clevises and anchors were then mounted again in
the fixture and tapped. |
 |
| The fixture was then used to drill the hole for the clevis pin
in the clevises and the hold down screw in the anchors as shown
on the right. |
 |
| Clevis Pins: There are 50 or 60
clevis pins required for the three trucks. The nasty
job is cross drilling the rods for the cotter pins. The
jig shown on the right made the job a lot easier. The jig
is made from brass hex stock. Steel hex stock would have
been better but I didn't have any. Square stock
could have also been used but hex can be easily mounted in the
3-jaw lathe chuck to center drill the jig. That is a
hanger clevis pin being drilled in the photo. The right hole was
drilled first and the Allen wrench inserted in the hole to hold
the pin in position. After the left hole was drilled
the jig was used to hold the rod while the excess length was
sawed off. |
 |
| This photo show drilling the single hole in a lever clevis
pin. Note the multiple holes in the jig. The holes
tend to enlarge with use and can be used to drill only about 20
holes. The jig was also used to hold the pin when
the little tip was ground off the head and the head finished
with a fine file.
Note: If I had it to do over I'd probably purchase the
clevises from Clippard. You can check out their products
at http://www.clippard.com/store/search.asp?sku=rc-
The RC-0881 looks very similar to Ken's drawings and the
smaller RC-0581 might also be usable, Note that they come
with the pins.
|
 |
This finishes the truck part of the brake
system. The linkage, steam brake cylinder and brake valve
are described in separate notes.
| 
