I had a friend of mine ask me a question for which I did not know the answer. It also got me to thinking about something else pertaining to rail preservation. Thought I'd bring it here to RyPN. First my friends question. For many years, he lived near the Magee, Indiana crossing of the Wabash and C&O railroads. He noticed that the EMD units had to "throttle down" before they hit the diamond, then throttled up again as they crossed. In the 20 years of living there before the Wabash was abandoned and the diamond removed, he never could figure out why this was done.

What I then wondered about is how many diamonds are currently in service at railroad museums around the country and are they in regular museum service? The diamond in the attached photo is located at the Illinois Railway Museum in Union, Illinois but I don't think that the "through track" is regularly used.

So, two questions. Any answers? Thanks.

Les

Les, throttling down when crossing a diamond is a standard train handling rule on many railroads. It is to protect the traction motors when traveling over the rail gaps built into the diamond. The concern is that when the wheels bounce over the gap it will cause the brushes to bounce off of the commutators and potentially cause arcing and damage or trip a ground relay.

This is not a concern with AC traction locomotives and, at least on the railroad I worked on, this rule did not apply.

There are some newer design of diamonds where the rail is solid on the heavily used side and the cross rails are elevated up and over the main rails. Trains can proceed over the solid rails at normal speed and load but trains on the other route must proceed very slowly.

Russ is correct. In related news, I just recently read that the FRA was releasing new rules on flange bearing frog. Long common for streetcars and light rail, they have a shallow flangeway that causes the wheel to ride on the flange. This makes for a smooth ride since it doesn’t drop at the gap.

They haven’t been used for regular trains since the flange isn’t designed for that kind of load. I’m curious to see what the new rules are and how they change. Previously a frog where the flange hits was condemned.

I suspect it’s related to the diamonds and frogs like Russ mentioned, where one side “jumps” the continuous rail on the other side. I also recall experiments with flange bearing frogs, but didn’t know they’d gone past testing.

Russ -

Thanks for the diesel info. I knew somebody out there must have the answer. Appreciate your prompt reply.


Les

The same applies with trolley cars; the South Shore always shut off when approaching a crossing.

There are actually TWO crossings at IRM, the other is just across the service road (Central Ave.) from the trolley bus garage, where the lead to the lower numbered barns crosses the car line.

Remember, every turnout includes a frog, too.

Where trolley lines cross, you try to coast. An additional factor is when two lines are in different power circuits and one is insulated from the other, you have to coast on the track with the insulators to avoid an arc in the wire and jerking the motors.

In Darby PA, where SEPTA Route 11 crosses CSX's ex-B&O main track from Baltimore to Philadelphia, the CSX track is continuous and SEPTA climbs up and crosses CSX's railhead on the flange. The crossing is skewed so the trolley axles always have one wheel double-guarded. CSX doesn't pound the crossing and to the trolley it's just another flange-bearing frog.

Phil Mulligan

Flange-bearing frogs have been okay with the FRA for 15 years or so. but have been limited to 10mph on the flange-bearing side and must be designed as such. At first, they are used under special waivers, but then a general waiver. The new rules allow them without any waiver.

The frogs have been used where one way is mainline (no speed limit due to the track crossing) and the other is slower speed (branch line, short line, etc.). They really work and have proved their use. In testing, wheel flanges actually harden with use and became more resistant to wear.

If that is not enough, do a search on jump frogs. These are frogs for turnouts without a gap for the turnout side. Instead, the wheel is ramped up and over the mainline rail where the frog would normally exist. They too have been tested and are working well.

These new designs really work and can cut the costs of turnouts and track crossings due to less pounding and welding repair. With no flangeways for the turnout or slow speed side, there is less pounding from the wheels on the mainline side.

Many years ago, we had a power diamond between Union Pacific and D&RGW north of Provo that moved the rails so that there were no gaps.

On regular frogs, there is actually no restriction from the FRA on the wheel flange hitting the bottom of the flangeway. Instead, there are minimum depth and wear measurements where speeds must be reduced to 10mph, and then the frog taken out of service. It is a bit complex, but I teach the Track Safety Standards regularly through the Center for Transportation Research at the University of Tennessee. Check us out if you want the entire 4-1/2 day course.

A friend tells me that this type of diamond is designated by his Class I railroad's timetable as "OWLS". He regularly is asked by management-types "What are OWLS?". His response: "One-Way, Low Speed".

I understand that one steam operator in this area does not make "revenue" moves in one direction from their "home base" because of an OWLS in that route a few miles in that direction. I understand that the host railroad does not permit train occupancy by other than Conductor, Fireman, and Engineer (and perhaps pilot?) when traversing the OWLS.

Regards,
Bob Milhaupt

But, even standard non flange bearing frogs never leave the wheel unsupported. The reason AAR railroad wheels are twice the width of the flangeway is so the wheel is supported by the outer portion of the tread on the wing rail as the flangeway removes support near the flange. Admittedly the support isn't perfect; worn wheels cause quite a bit of rumble, but it's not like someone removed two inches of the rail running surface, which is effectively the case with a 90 degree crossing. That drop causes quite a sharp shock.

Yep - I failed to use the term OWLS when I described the diamonds. They have been called "One-Way, Low-Speed" crossing frogs. There are a lot of pictures online of them for those interested. The OWLS have become very common over the past few years as the major railroads have installed them at many of their crossings with short line railroads and branch lines.

The gaps in frogs have long been a problem, and attempts to eliminate them have included spring frogs, moveable point frogs, OWLS, Jump Frogs, and others. More are being tested at Pueblo at the test track, so expect more designs to show up.

For the record, this was specifically mentioned, with full detail as to why, in the 1945 F-unit operator's manual, and I'm sure in subsequent revisions of manuals for EMDs with DC motors.

In response to the initial question, NSRM, Carson City, NV has two diamonds in regular service. Both new in 2016, built by Harmer, 90 ASCE, both lines in each diamond are on a radius. One is dual gauge in both directions and the other is dual gauge in one direction. These replace the previous diamonds which were showing cracks in the web at the frogs.

I would post an image but my ignorance in computers prevents me from downloading images to RYPN.

Here's video of the crossing in Darby with both trolleys and a train. Note the trolleys clump across at low speed and the train glides through at track speed.

https://www.youtube.com/watch?v=iRakYWDe2tw

Yes SEPTA has catenary on the trolley line at the crossing. It's a long way between line poles.



Phil Mulligan

As far as I know the only diamond used by a museum in Oregon, Washington or British Columbia is at the BC Forest Discovery Center in Duncan, BC. This is 36" gauge.

The California State Railroad Museum has an OWLS diamond to cross the SP/UP mainline on a line that connects the old shops area to the north, and the public part of the museum to the south.