Re: [H0] Brake system on D&RGW 40' auto box car

Dick Dawson <dickdawson@...>


I’ve worked as an engineer in the freight car industry for over 40 years, so
let me look at your photos from that vantage point. I agree that the center
rod (the rod connecting the cylinder lever and the fulcrum lever) is at an
odd angle. The fact that the fulcrum lever (the white lever behind the
brake cylinder) has an unused hole at one end also does not make sense. I
think your suggestion that the two levers have been switched is probably
correct. If we switch the positions of the two levers and flip the black
lever, which now becomes the fulcrum lever, so that connection to the center
rod is closer to the center sill than it is now, the angularity of the
center rod will improve. While I am not familiar with this particular type
of slack adjuster, its location would be consistent with an early automatic
slack adjuster in that it is located at the same place as the series of
holes at the fulcrum lever pivot point which provided the means for manual
adjustment. The number of holes in the lever would now be correct; one for
the slack adjuster (top of the photo), one for the center rod, and one for
the top rod going to the A end truck. The white lever, now the cylinder
lever, would have four holes used for (again top-to-bottom) the hand brake
connection, the brake cylinder push rod, the center rod, and the top rod
going to the B end truck.

While the angularity of the center rod as hooked up in the photo is
excessive, center rods are not always perfectly parallel to the center line
of car in real life. Since the cylinder lever has no fixed fulcrum, the
lateral forces on it must be balanced so that it will not be pulled to one
side of the car or the other when the brakes are applied. Engineers laying
out brake rigging are careful to position the rods and levers such that the
lateral components of the forces in the brake rods connected to the cylinder
lever are essentially balanced left-to-right.

And now for some serious nitpicking. I realize that there are significant
differences in working at 3.5 mm to the foot versus 12 in. to the foot, but
I note that several important parts of the brake system are missing. First,
there is no air brake train line running between the angle cocks and
therefore no branch pipe running from the train line to the AB control
valve. Second, there is no retainer pipe running from the control valve to
the retaining valve, which at this time period would be on one of the ends
of the car. And finally, hand brake rods are typically not connected
directly to the cylinder lever, but rather are connected by means of a short
chain. Thus, when the air brakes are applied, the hand brake rod is not
pushed forward and back. Only the modeler can determine how much minute
detail he wants to include, especially for parts underneath the car where
few people will ever see it.

Dick Dawson

From: STMFC@... [mailto:STMFC@...] On Behalf Of
Roland Levin
Sent: Tuesday, November 08, 2011 3:41 PM
To: STMFC@...
Subject: RE: [STMFC] [H0] Brake systemon D&RGW 40' autoboxc ar

Thanks Gary for directing me to the handout. It's a great help for anyone
interested in modeling the underbody details. Thanks also to Richard and Tim
for the information you provided. I'm still not sure if the photos of the
brake system in the modeling notes for the kits are prototypical correct.

I took two photos of the illustrations in the modeling notes and posted them
to Photos section in the folder "Brake system Sunshine D&RGW boxcars". They
are awaiting approval. I intend to remove them as soon as this this topic is
finalized to avoid any discussions about copy right. I would appreciate if
anyone could look at them and give your comments. I suspect that the two
levers could have been mixed up and I think the angel of the center rod
looks strange. I would also appreciate if anyone could confirm that this
location of the slack adjuster is correct or at least plausible.

Best regards

Roland Levin
Stockholm, Sweden

Ämne: RE: [STMFC] [H0] Brake systemon D&RGW 40' autoboxcar

You can find an excellent handout in the file section for the group, its
called: Freight Car Underbody Detail by Gene Green. An illustration of a
slack adjustor is on page 14. It was added to the files by Doug Harding on
April 3, 2009.

Its one of my most used files! I keep it in a folder near my workshop desk.

gary laakso

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