passenger car operation and diaphragm question

Discussion in 'Passenger Equipment' started by skyraider, Mar 29, 2023.

  1. skyraider

    skyraider Member

    Recently I found a set of old Balboa brass full length passenger cars. They are painted for a road which ran close to the area I model, so I bought them (six brass cars, new in the original boxes; factory painted and lighted). They are somewhat crude by today's standards but the total price was $310, including shipping and tax.

    After putting window tinting in all of the windows to hide the lack of a car interior, I unfortunately discovered a problem on the layout: I inadvertently built an S turn. Most of the mainline is 34" radius, but this one spot has a short 34" left turn followed by a #6 right hand switch. The reverse portion (curved portion of the switch) is the mainline; the straight goes to the industry siding. As a result, I'm concerned about operations.

    Close coupling may be out of the question. So I'm considering diaphragms. Does anyone have any experience with them? I've never installed any on passenger cars and want to avoid problems if possible.

    Thanks in advance.
  2. geep07

    geep07 Member

    Went on Google and typed in "passenger car diaphragms review"
    This came up on You Tube.

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  3. skyraider

    skyraider Member

    Thanks, John. I've got a call in to American Limited to see which diaphragm might be compatible with Balboa cars. From what I understand, most of the parts of the American Limited kits are delrin, which is difficult to paint and almost impossible to glue. Maybe this video will clear up some things.
  4. skyraider

    skyraider Member

    The American Limited diaphragms that were tested in the video only scored 6 / 10 on the reviewer's scale. There were several noteworthy issues. Thanks for that video!!
  5. kenmc

    kenmc KenMc Supporter

    I can tell you from experience that long passenger cars don't like S curves, and diaphragms make the problem worse. They also object to sudden curvature changes (eg, straight to curved track) without at least a modicum of gradual spiral transition. Try out your cars without diaphragms and see what combinations work or don't. Then try with diaphragms the same. "Soft" diaphragms may be forgiving enough to exert little side pressure in curves. I cut a fold out of some old (brand?) rubber ones and had pretty good success. Otherwise, sometimes gluing a clear plate across the diaphragm opening may let them slip against each other and not catch. You have minimally acceptable track radius (34 inch minimum from my experience), but it may be worthwhile to explore re-laying your S curve.

    There are two ways to learn in model railroading and in life: From your own mistakes, or from others'. The latter is far preferable.

    Ken McElreath
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  6. gstout

    gstout Member Supporter

    Try them and see what happens. You might get lucky.

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  7. geep07

    geep07 Member

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  8. skyraider

    skyraider Member

    As I said, there was one mental faux pas on the layout--the S curve created by the short 34" curve followed by the #6 switch that curved back the opposite direction. If I had it to do over, I would probably do it differently. At the time, passenger cars weren't even on my radar, and have only become of interest during the last four months or so. The current track plan was the only way I could see at the time to accomplish a double industry siding and have the mainline end up where it needed to be where it met a liftout. It's still the only way that I can see to accomplish the industry, which is pretty pivotal to this layout. As we all know, layouts are compromises, and sometimes you have to sacrifice.

    At this point the sacrifice is the coupling distance between the passenger cars. 34" is also what I consider to be the minimum, in spite of numerous manufacturers who claim 24" for their passenger cars. When I look at the cars on the 34" radius they don't look as good as I'd like.

    Thanks to all of you for the input!!! It definitely gives me something to think about. One other "creative solution" I'm playing with is some sort of custom made drawbar system. The obvious issue with that is getting the cars on and off of the track. Once my staging yard is complete, that may be a realistic answer.
  9. mark

    mark Staff Member Staff Member


    You may find these resources helpful regarding diaphragms.

    Tony Thompson in California is a regular blogger touching on a large and diverse array of topics related to prototype (largely Southern Pacific), modeling and operation issues. He posts regularly every 3 days. Most blog posts incorporate links to prior related posts. This is a site well worth monitoring on a regular basis.

    Please see his blog site Modeling the SP -

    A quick search of his site for "diaphragms" resulted in multiple hits. Prior posts include addressing both standard and full carbody diaphragms.

    Please see the following posts -

    Model Railroader magazine also has another good but short article. It is very similar to how a local modeler, Chuck Hitchcock, handled diaphragms on his former large, multiple passenger train, operating railroad, The Argentine District. Most of his through passenger trains set out and picked up mail/express/baggage cars on the head in and sleepers, coaches and diners on the rear. Originating and terminating trains were built from or sent to the post office, commissary and coach yard tracks.

    The one change (improvement) was to use a solid clear plastic outer diaphragm surface. This provided a totally smooth surface between adjoining diaphragms. For uncoupling at the Argentine Passenger station he used stragetically placed electromagnets. As a back up he had a couple of "L" shaped wire in a wood handle tools to grab the trip wire to open the knuckle on Kadee couplers.

    Please see are bellows-like connections that enclose the space,if they keep cars from coupling and uncoupling.

    Hope this helps.


    Last edited: Mar 29, 2023
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  10. skyraider

    skyraider Member

    Thanks, Mark. Tony Thompson's site is one I follow regularly. He has given me several ideas for flat car loads, etc. I'll look at his stuff on diaphragms.


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