Re: Two brake system modeling questions


In a message dated 12/26/2006 2:52:30 PM Eastern Standard Time,
rfederle@... writes:

Being an engineer I can tell you that all pipe sizes are referencing the
Inside Diameter with the exception of heavier walled pipe such as Schedule 80 or
above. The Brake Pipe size is generally Schedule 40 which is for moderate
pressures generally less than 150 psi.

I was going to chime in after reading all of these, (nice to have a day off
for a change). The Union Tank Car carmen where I work say that schedule 80
is all they're allowed to use for railroad brake pipes, and our mechanics on
the Morristown & Erie feel the same way. Schedule 80 Brake pipe measures just
above 1 1/2".

Release rods, also called bleed rods or bleeders by trainmen, are usually
1/2" and sometimes 3/8". One spotting feature that changed after the scope of
this list is the bend at the end. Steam-era AB rods have a 90-degree bend
with a 4-inch or longer bit of rod for the trainman to hold on to. To bleed off
a car the trainman had to pull (or push) on the rod until the brakes
released, or until the reservoir was empty. Diesel-era ABs of the many versions have
an automatic release feature where the trainman only needs to pull (or push)
on the rod for a second or two until he hears the AB valve click, and then
the AB bleeds itself off. Rods on the automatic release valves have just a
little loop at the end of the rod, providing a quick spotting feature for
trainmen who would work with both types.

That list of measurements is good. When I was more actively modeling I
measured the key rods and piping on older freight cars. After once using my own
hair for a retainer line, I concluded trying to portray the relationships in
thicknesses between the various components was more important than matching
each exact size. Using the 3/4-inch grab irons (.080 wire is perfect once
covered with paint) as a reference, since those are the most numerous and
visible on a model, the vertical brake staffs are about twice as heavy, train lines
and brake rods were between the two, retaining lines are lighter than grab
irons, etc. In an era when you couldn't trust the wire sizes in many kits
and the pre-formed ones were too thick for my tastes, I could stock the basic
stuff and not worry about what came with the kit, reusing it where its size
deemed appropriate. I built a jig and used to make my own ladders with 3/4
rungs, also largely uneeded today.

Mike Del Vecchio

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