11/04/2012, last updated
The disconnected log truck is shown in
diagram above. Recall that the objective was to make a frame
that interfaces the couplers to the standard truck. The log bunk
is a separate component that attached to the truck upper spring plank.
Drawings for individual components are in below, starting with
The basic coupler frame is made up of the two inside bars, two
outside bars and two end bars. The end bars are secured to the
other bars by 8-32 screws.
The two upper coupler plates are attached to the ends
of the inside bars with two 8-32 hex head screws per plate into
the same holes than have the 8-32 screws through the end bars from
the under side. The two lower coupler plates are attached to
the bottom ends of the inside bars with 8-32 screws running through
the upper plate, the inside bars and then the lower coupler
plate into hex nuts.
The Diagonal Braces are used on the end
of the frame opposite the foot board. One end
attaches to the inside bar using the same hex head screw that holds
the upper coupler plate to the inside bar. The other end
attaches to the outside bar using a 8-32 threaded rod though the
spacer, then the brace and then through the outside bar. The
rod is secured with hex nuts on each end. The
spacers serve as stops to limit the rotation of the log bunk.
The location of the end holes is very critical to keep the Coupler
Frame square. I drilled the holes in one end of the brace and
attached it to the Inside Bar. I then squared the frame,
clamped the brace in position and use the hole in the side bar
to spot the other hole in the brace.
The Foot Board Brackets shown in the
drawing on the right are attached to the end bar using 4-40 hex head
screws. The Foot Board is attached to the brackets with
4-40 button head screws. The Holes were drilled in the
End Bar and Foot Board first. The brackets were bent by
clamping the bar in a vise an beating the end over with a large
hammer. The brackets were then clamped in position
on the End Bar and the holes spotted using the holes in the
End Bar. Those holes were then drilled out and the brackets
attached to the End Bar. Next, the Foot Board was
clamped to the brackets and the remaining holes in the brackets
spotted using the holes in the Foot Board. The
bracket legs were marked to the correct length after the Foot Board
- Brackets & End Bar were test assembled.
A photo of an assembled coupler frame is shown
The Adapter Plates shown in the drawing are used to
attach the Coupler Frame to the truck. The plates are
secured to the truck with the threaded rods that run through the
Arch Bar Supports. The Adapter Plates are positioned above the
truck upper bar.
The Coupler Frame is secured to the
plates with a pair of 6-32 SHCS through each Side Bar on the frame.
Nyloc nuts are used on the screws. The nuts are tightened and
then backed off about 1 1/2 turn to give the truck sides freedom to
rotate slightly with respect to each other.
A photo of the Adapter Plates mounted to a truck
is shown below. Note that the Car Support Blocks are not
used on the ends of the Truck Upper Spring Plank.
The Log Bunk shown in drawing above is a
separate assembly that attaches to the center hole in the Truck Upper
Spring Plank and secured with a cotter pin or hairpin clip. The log bunk
is very similar to the log bunk used on the skeleton log cars. The
Log Bunk Components are shown in the drawings below.
|The End Posts are 5
1/2" lengths on 3/4" HRS bar stock. The upper end is
rounded on the belt/disk sander. The holes in the bottom
match holes in the Log Bunk Channel.
Center Post is 4 1/2" length of 3/4" square HRS bar stock. One
end is drilled for 8-32 screws matching hole sin the Log Bunk
Channel. The other end is turned to 1/2 " diameter and a 1/8"
hole for a cotter pin is drilled near the end. The length of
the square part of the post should be adjusted as necessary so that
the bottom of the log bunk is about 3/8" above the Coupler Frame
Side Bar. Alternately, shim washers can be used under the
shoulder of the sleeve bearing though the the Truck Upper Spring
Plank to adjust the Log Bunk height.
The wall thickness of the Log Bunk Filler Tubes is
not critical; 1/16" is satisfactory. The local supplier didn't have
the 1/16" at the time I needed them so I purchased all he had ---
1/8" wall thickness. The tubes are cut to a length such that
they are a force fit between the End Posts and Center Post.
The End Post and Center Post are attached to
the Channels first using 8-32 hex head screws and nuts.
The Tubes are then driven between the Channels and posts.
If care is taken to make the tubes the same length they will force
the posts to be perpendicular to the Channels.
Once the tubes are in place, 0.089" holes are
drilled in the tubes using the 3/32" holes in the channels as
guides. #2 drive screws are then driven into the holes.
The drive screws give the appearance of rivets and secure the Tubes
in position between the channels.
A photo of a finished bunk is shown below.
The couplers and safety chains are
described in the Couplers & Safety Chains page.
Photo above shows John Buckwalter pulling
some log cars with his narrow Gauge Shay. The first log car
is one of Ken McCauley's kits and the last two cars are my
Disconnected Log Tucks. The logs on the disconnects
are 4' lengths of 4"-5" fence posts from Tractor Supply. The
bottom two of logs are secured to the log bunks with lag screws up
through the bunks. The top logs are held in place with the chains.
Photo above shows a log chain and turnbuckle on a log car.
A 1/4" wide 5/8" deep slot was cut in the top end of the log bunk post.
A hole was also drilled for a 3/16 " clevis pin. The log
chain has 21 links per foot ---- McMaster #3593T41.
The turnbuckle, used on one side only is McMaster #30125T202.
The turnbuckle works loose with use so a 10-24 nut was added to the RH
treaded side and tightened as a lock nut.