Passenger Cars - rough riding over switches

[MP57313]

I rode the NJ Transit line to Atlantic City this afternoon. It has some fast running, but a couple of the switches were rather rough. There's a sudden side-to-side sway when the train crossed certain switches at speed.

What causes that...switch rails worn, or something in the commuter car suspension?

MP

[Anonymous]

My track guys tell me switch needs to be relined and possibly resurfaced. Side forces, from movement on the diverging route particularly, can and do cause alignment problems on switches, which can be exacerbated if the switch isn't surfaced/lined well in the first place.

[MP57313]

Thanks for the responses. The swaying occurred when the train stayed on the "main" and passed over the switches at speed (over 70 mph is my guess).

When the train took the sidings for meets there wasn't much side sway; it went rather slowly when going on to the diverging track.

[Overmod]

What kind of equipment was this?

I remember that early Amfleet equipment had a pronounced tendency to lateral float and 'dancing' in Northeast Corridor service between New Brunswick and Philadelphia; this was IIRC due to inadequate damping of the lateral *secondary* suspension. There were what seemed to be a couple of vibrational resonances that made some of the interior plastic pieces 'giggle' at times. My observation at the time was that the old PRR P-70 coaches (which were still operating on some of the 'clocker' trains at the time) were decidedly smoother-running over the same trackage, even though their trucks were not as sophisticated -- this was due principally to higher deck mass and better *tuning* of the secondary suspension. PRR was proud, I think justly, of their efforts to get the P-70 riding qualities good.

I don't remember the old RDCs on the Philly-Atlantic City line having any more than normal sway. Of course, nobody ever claimed RDCs had a particularly good ride. The new equipment probably has much better suspension in enough ways that any small 'deficits' that remain are more noticeable, and I think we should remember that when considering this issue.

Does anybody have access to track-geometry or lateral-accelerometer data for this line? It would be easy enough to measure actual accelerations using one of the laptop-based hardware/software packages for automobile performance, with appropriately-scaled and aligned sensors set up in proper locations inside the car... I would like to see measurements both at the car-floor level and at normal 'head' height (e.g. at inner-ear level...). They shouldn't be that different, but even a small abrupt roll couple might be perceived as 'sway' depending on where the car's metacenter is.

Any volunteers?

[Modelcar]

....As a bystander it generates visions of a main pushed to the side at the switch intersecting location creating a momentary side push as it passes over the slight alignment defect.

[jchnhtfd]

QUOTE: Originally posted by MP57313

Thanks for the responses. The swaying occurred when the train stayed on the "main" and passed over the switches at speed (over 70 mph is my guess).

When the train took the sidings for meets there wasn't much side sway; it went rather slowly when going on to the diverging track.

If I were still tromping around out there -- which thank goodness I don't anymore! -- I'd be very suspicious of surfacing (cross level) ... doesn't take much at 70 to create a sway in a soft-riding, light car, like the new ones.[:)]

[Junctionfan]

I have been on the Via trains and despite the LRC suspension system, going through the switches is somethimes like going over a speed bump. Don't know why it does that; I wonder if there is something wrong with the frogs or the whole switch needs to be replaced because it might be too old.

[Overmod]

I believe some of the problem is that the 'tuning' over switches is different (stiffness changes, as it does going over bridges) and this could probably be addressed by the same methods used with bridges... it's a little different because the rails aren't 'continuous beams' as they are for typical bridges, and the absolute restriction on vertical motion is greater at the region of the frog and guard.

It may also be possible that there's shock or other short-term misalignment when the wheels run over the open part of the frog, or on the sections immediately adjacent, or past the area of the 'closed' switchpoint where it feathers against the rail. Both of these are likely to be difficult areas to grind or align in service.

[Junctionfan]

I just wish sometimes that riding the train didn't feel like running a wooden roller coaster. At least Via doesn't do verticle loops.

[mudchicken]

Before I'm looking at surface, I'm looking at the back side of the frog guardrail oppposite the frog, the flangeway gap in the frog...assuming this is not a spring frog....

Can't disagree with DREPHPE, Mark or overmod either, all are valid....pleased to see that at least some folks can look beyond the rough surface side of the puzzle...[:D][:D][:D]

[Anonymous]

You wanna talk rough riding..take VIA to Nova Scotia from Quebec over the
NBEC as it felt like we decided to go off the tracks and use a old dirt road.I
was stunned as lay in the berth how rough it was.every rut in the rails was
felt.NBEC is mainly heavy freight and is upgrading as needed but man were
talking rough.

Keeps you on your toes!

David

[MP57313]

QUOTE: Originally posted by Overmod

What kind of equipment was this?

I am not that familiar with the equipment (did not look for a builder's plate) but they are straight sided cars with 3-2 seating. They look a bit like Amtrak's Horizon cars. I would think there is a captive fleet on the Atlantic City line.

[Anonymous]

Those cars are the commuter equivalent of the horizons.

MC, as usual, adds something completely and entirely useful. My people would also look at the frog. Good point!

I've ridden that line, and I suspect they need to look at realigning the tangent. That would be the part to kick out on diverging moves over time.

BTW, no offense MC, but the DREPHPE award for profoundly beautiful switch lining goes to the old Cotton Belt (not ATSF, unfortunately, although they did a very good job, too). SSW meant smooth as glass at 79. The bum award goes to the old MoP--don't try and drink coffee at speed over any of theirs, unless you are after a hot bath![:D]

[oltmannd]

NJT Comet cars have suspension similar to Amfleet. Inside journals with rubber primary suspension, coil spring secondaries. Generally, stiff primary and soft secondary suspension is the key to a smooth ride, but the rubber primaries here are almost like no suspension, so the ride is not as good as in the "days of yore".

A problem that can occur on tangent welded rail at high speeds is truck hunting. One particular cause can be the formation of a "false flange" on the wheel. Another would be that the effective taper increasing due to normal wear. Amtrak installed tread braking on the Amfleet equipment on the NEC to try to keep the wheel profile in good shape.

It takes quite a lateral jolt before you are "unsafe". Generally, anything under a 1/2 a G is OK, but that will spill your drink for sure.

On a related topic, diesel locos typically have soft primary and stiff secondary suspension to support high adhesion levels - which has led to some ride quality complaints over the years.....