Re: Sprung Trucks


proto48er
 

The following discussion is "O" scale only, because I have never had
any HO.

Couplers:
I obsessed over the scale coupler problem for years in "O" scale -
did not like the appearance of Kadees at all, but did not like the
plastic or brass dummy couplers common to "O" because, although they
looked good, they did not operate - you had to pick the car up to
uncouple.

PSC made some "operating" couplers in brass kit form, but they did
not operate reliably and were hard to build up. PFM also made some
nice looking brass couplers which operated well and reliably, but
they were discontinued (I think - could not ever locate more of
them). They had spring-operated knuckles. I had experimented with
early Clouser couplers - a nice scale appearance (actually a
traction coupler or an early type D coupler), but they were hard to
assemble when first brought out by Bill Clouser in the late 1960's.
The castings were rough - it took me about one hour to assemble one
pair of them with tedious filing. This cleanup had to be done,
otherwise, they would not operate.

Then, in the mid-1980's, Chicagoland Hobbies in Chicago had some
Clouser couplers that were very nicely cast, not rough castings like
the 1969 Clousers. It only took 10 minutes to assemble a pair, and
the operation was superior. I was sold on them on the spot!
Contacted Clouser and bought 400 pair (in "O" scale, things have a
very bad habit of disappearing when the manufacturer decides to
discontinue them - you have to get them while you can). Best money
I ever spent!! They operate flawlessly, but do not uncouple
automatically - you have to use a wand or install (and MAINTAIN)
operating cut levers. Cut levers work great on passenger cars with
diaphragms.

Draft Gear:
The next problem was what draft gear to use. I created a design
similar to a Waugh draft gear on the prototype, and used it as a
draft gear/coupler centering device. It is built up from brass,
only uses a single spring, and consists of 7 parts. It is simple
and durable. In "O" scale, part of the function of the draft gear
is to protect your expensive brass car from damage occasioned by a
sudden stop - like running the loco into a dead block with a heavy
train. My draft gear consists of two channels, each 1/2" long, with
the outer one being 1/4" X 1/4" in size, and the other being smaller
so as to fit snugly inside the first. This smaller channel has two
slots cut straight across it, and two small pieces of flat 0.050"
brass fit in them, but are just short of touching the walls of the
outer channel. A spring is placed between the brass pieces to press
them against the sides of the two slots. A bent 0.030" brass strip
C forms a yoke which slides over and under the spring/brass piece
assembly. At the end of this yoke, a hole is drilled to mount the
coupler.

First, here's how it works: When you push the coupler into the
striker plate, the shank pushes up against the front brass piece,
which, in turn, pushes the spring. The first brass piece moves
inward until it hits the other side of the front slot. If you make
the slot so that this motion is a scale 2-3/4", you will duplicate
the prototype travel of a standard freight car draft gear of the
1940's. If you pull on the coupler, the brass yoke pulls the rear
brass piece forward until it hits the front of the rear slot. There
is a mild centering action with this setup - the spring resting
length is longer than the two brass pieces installed in the slots,
so there is pressure on the coupler shank if it is done correctly.
The coupler shank has to be cut off square and the pivot hole
drilled precisely the correct distance from the cut off end for good
centering action without any slack.

This is designed to be used with scale striker plates of various
designs. The striker plates are soldered on the end sills first.
Then the coupler/brass yoke/spring/two pieces of brass are assembled
next. The larger channel is soldered to the floor of the car.
Then, the smaller channel with the two slots is placed upside down
in the larger channel, with the one brass piece in each slot. The
inner channel is moveable at this point, so it can be adjusted to
provide the 3" of clearance between the horn of the coupler and the
front of the striker plate. Then the channels are spot soldered
together. It took longer to write this than it does to finish one
freight car.

How do you make the striker plates?? Make them out of styrene for
your specific car, then have them sacrificially cast in brass! If
you are really anal, you can also cast the outer channel with dummy
details of the prototype draft gear, but you will have to mill it
smooth or the brass pieces inside will not slide correctly.

The result is a true prototype action draft gear! It is really neat
to see the cars bunch up slack on the downhill, and strech it out on
the uphill grade. The prototype draft gear acts the same way - it
resists the coupler shank being pushed in for a travel of 2-3/4",
then sets up solid. Same action when the coupler is pulled out.

The Clouser coupler is now available from Norm Buckhart (see the
Proto:48 website) and is as nice as the ones I am using. He has the
Clouser patterns and has them cast at Valley Brass & Bronze, so they
are excellent. The couplers do have a smaller shank (4" X 5") than
the prototype.

This coupler problem bothered me for a long time, but I am OK with
the above solution. The key design parameters are the spring
dimensions and spring constant, and the ability to slide one channel
inside the other so that you can accurately position the coupler
from the striker plate easily. A. T. Kott

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