Question about "Spine cars"

Watching a unit train of containers and semi-trailers the other day, I noticed that on several articulated multiple deck spine cars, (TTX "triple 53's" to be precise) the semi trailers were actually stradling the articulation points, i.e; the wheels of the trailer were on one platform and the trailers king pin and landing gear was on another platform. Is this wise?

truman wrote:.....the semi trailers were actually stradling the articulation points, i.e; the wheels of the trailer were on one platform and the trailers king pin and landing gear was on another platform. Is this wise?

Since I frequently see semitrailers riding aboard spine cars this way, I gotta think it must not be considered “unwise” by the railroad....

A couple things to keep in mind:

1 – The “front” end of the semitrailer is supported/fastened to a 5th wheel mount – same as if it were attached to a highway tractor. The trailer is thus free to accommodate the articulation (bending) that occurs between the supporting spine car sections as the train negotiates curves.

2 – The 5th wheel mount also allows the trailer to rock left/right as the spine car platforms rock independently beneath the trailer.

So while may look odd, there’s no reason NOT to mount semitrailers spanning the articulation point.

When the articulated cars became prevelant on Conrail, we occasionally had one, with a load straddling two different platforms. We were allowed to kick them out of the train, as no manager wanted to "take the hit" on what was then, new territory. Eventually, as seen today, it was determined that the articulated connection was stong enough to survive even the roughest train handling, so it was allowed. On occasion, you would find a load straddling two cars. This was never, and still isn't allowed, due to slack movements, as well as the chance of drawbar/knuckle failure possibilities. That 5th wheel hitch is bulletproof. I have a picture, from a piggy-back wreck, of a flatcar holding a raised 5th wheel hitch, and about 6 feet of trailer, still holding onto the hitch, atop a pile of twisted cars. I also set a car out, in Allentown one night, when a passing train reported a "trailer failure" in the train. The frame had snapped, and the trailer was shaped like a "V", with the center of the trailer laying on the solid drawbar, between the cars. The sides were bulging out, and the load hadn't come out, when we set it out at the ramp.

Thanks for the input gentlemen. Wow, I never even stoppped to consider a drawbar pull apart. My concern was what would happen on a tight radius curve is the car flexes and the trailer doesn't?

truman wrote:Thanks for the input gentlemen. Wow, I never even stoppped to consider a drawbar pull apart. My concern was what would happen on a tight radius curve is the car flexes and the trailer doesn't?

What happens is not very much different than when a truck tractor + semitrailer combination negotiates a curve on a highway...

The lead spine car will pivot slightly beneath the trailer's drawpin (which is engaged to the spine car's "5th wheel" support). Simultaneously rear of the trailer will pivot a bit about it's axle(s), and it's tires will roll slightly backward on the 2nd spine car's deck.

Consider an extreme case: Theoretically a pair of spine car sections with a trailer spanning the drawbar connecting them could be at right angles to each other (a VERY sharp curve!). In this situation the trailer would assume a 45 deg orientation relative to each spine section - ie. "cutting the corner" between the two spine sections.

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As for slack action occuring at the drawbar connecting the two spine sections, the front of the trailer is rigidly connected to the leading spine car's 5th wheel support. However the trailer wheels are free to roll forward/back on the 2nd spine car's deck as drawbar slack runs in/out. ...FB

FarmallBob wrote:As for slack action occuring at the drawbar connecting the two spine sections, the front of the trailer is rigidly connected to the leading spine car's 5th wheel support. However the trailer wheels are free to roll forward/back on the 2nd spine car's deck as drawbar slack runs in/out. ...FB

That's if the air on the spring brakes has bled off. Otherwise the equalizer between the tandems will move and the axles will scuff and slide around w/ out really rolling. You could not do this w/ a tanker as the slop will stress everything.

My wife and I spotted several examples of truck trailers spanning two TOFC flats the past several days. A couple things we noticed:

1 – Trailers thus carried were aboard only “twinned” 88(?) ft TOFC flats – ie. pairs of 4-axle cars semipermanently coupled with a solid drawbar. Observed no trailers spanning conventionally coupled TOFC flats, nor spanning articulation points on 3x or 5x TOFC spine cars. (Note: I presume a drawbar connection such as this eliminates any kind of draft cushioning between the connected cars. Thus any relative movement of the two railcars beneath the trailer should be almost non-existant.)

2 – Every example we saw had (3) 53’ trailers loaded aboard a "twinned" set 88 ft. flats. Makes sense I guess since 3 trailers thus loaded increases the carrying capacity of the twinned car set by 50%. (Otherwise only a single 53’ trailer can be carried aboard each 88 ft car...)

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wis bang wrote:

FarmallBob wrote:As for slack action occuring at the drawbar connecting the two spine sections, the front of the trailer is rigidly connected to the leading spine car's 5th wheel support. However the trailer wheels are free to roll forward/back on the 2nd spine car's deck as drawbar slack runs in/out. ...FB

That's if the air on the spring brakes has bled off. Otherwise the equalizer between the tandems will move and the axles will scuff and slide around w/ out really rolling. You could not do this w/ a tanker as the slop will stress everything.

Since about the late '60's, all OTR truck trailers’ parking brakes are required to be spring-applied – ie. full system air pressure is required in the trailer "emergency" air line to release the trailer brakes. Thus if the trailer parking brakes are not already applied, they will be the instant the tractor’s air lines service and emergency lines are disconnected from the trailer.

And therefore any fore/aft movement while loaded aboard a flatcar(s) can only be accommodated by “scrubbing” of the trailer tires on the deck, as the trailer parking brakes will be fully set at all times.

Bob, you are correct regarding the solid drawbars, between permanently connected cars. The slack in a drawbar (a true drawbar, not coupler) is measured in fractions of an inch. If the wear becomes excessive, they are bushed, or replaced. I've never seen a parted drawbar, but broken drawbars on coupler assemblies, are somewhat regular, in occurence. As mentioned, IF we encountered a load spanning two cars across a coupler, it was kicked out of the consist. You wont see containers spanning cars, only trailers. The pivoting ability of the 5th wheel, makes this articulation possible, without forcing the trailer off the cars, in crossovers, or around tight curves.

truman wrote:Watching a unit train of containers and semi-trailers the other day, I noticed that on several articulated multiple deck spine cars, (TTX "triple 53's" to be precise) the semi trailers were actually stradling the articulation points, i.e; the wheels of the trailer were on one platform and the trailers king pin and landing gear was on another platform. Is this wise?

Trailers spanning the articulation joint on spine cars? Never seen it....ever. This is a very common occurrence, however, on drawbar-connected "Long-Runner/Triple-53" or "Triple-57'" TOFC flat cars. But spine cars? I can't come up with a reason for loading a spine car this way as it would render the platform that the hitch is actually sitting on as totally useless. There are 2-28'/1-57' spine cars that have a hitch on both ends of each platforms for 2-28' trailers to sit back-to-back on a single platform. Still, nothing spans over the articulation joint. Could this be what was seen? I would love someone to prove me wrong on this, but I don't think they can without photo-manipualtion!

MLEmodels wrote: Trailers spanning the articulation joint on spine cars? Never seen it....ever. This is a very common occurrence, however, on drawbar-connected "Long-Runner/Triple-53" or "Triple-57'" TOFC flat cars. But spine cars? I can't come up with a reason for loading a spine car this way as it would render the platform that the hitch is actually sitting on as totally useless. There are 2-28'/1-57' spine cars that have a hitch on both ends of each platforms for 2-28' trailers to sit back-to-back on a single platform. Still, nothing spans over the articulation joint. Could this be what was seen? I would love someone to prove me wrong on this, but I don't think they can without photo-manipualtion!

Agreed. I have only seen this on the Long Runner cars. Never on spine cars.

Here's a shot of a trailer spanning a "twinned" (drawbar connected) pair of TOFC flats, passing thru CP382 on the CSX Chicago Line at 59 mph:

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Yup. Maybe not the exact same car model, but thats what I saw. thanks Bob.