12-axle flatcar question for the experts

[Morpar]

I am considering building a model of a depressed center, 12-axle flatcar as shown in this link:
http://southern.railfan.net/flat/cars/krl/krl300300/krl300300.html
Since this car has 6 sets of trucks, how does it turn? I can tell from the photos and diagram that it has span bolsters on each end, but how does each span bolster work with 3 trucks under it? Are the span bolsters split so that they can "bend" to go through a curve, thus allowing the pivot points of the upper deck to stay centered on the middle sets of trucks? Or is there some way of mounting the middle trucks under the span bolster that will allow them to move enough to go through curves? I have been thinking about this quite a bit tonight, and I am VERY curious what makes this car work.
To my way of thinking, these cars are going to go to industrial trackage that may have rather tight curves, so the split bolster is what I am leaning towards, as it would give the tightest turning radius. Then again, I could be full of beans!
If anyone has the scoop on these cars, please enlighten me! Thanks in advance.

[Anonymous]

I reckon a "pin" is on the middle truck. The middile truck is connected to a inner truck.

I suspect the "outer" truck is pivoted off of the middle truck. Thus: the forward truck is like a engine pilot wheels, the middle the driving wheels (on a steam engine) and the trailing truck picks up the rest of the weight.

If I confused you Im sorry, could not find words to express.

[ndbprr]

Well I've built one and it took some thinking. If you look between the trucks you will see a large bolster that all the turcks are fastened to. Don't know about any lateral motion devices. The end of the depressed section rides on a pivot on the bolster and the end sections are rigid on the bolster. I built one of the Wetsinghouse Schnabel cars. they are very sophisticated and even have hydraulic systems to move the load vertically and horizontally when clearances are tight. These trasnformer loads are quite heavy and the axles are limited to 80,000 pounds max. so you can figure the weight they can carry by multiplying the number of axles times 80,000. They are pretty hard to get to track. I finally added Athearn U joints in one end in the pivot to ease the long length and wheelbase issues.

[underworld]

The trucks are attached to a section on each end....all of the trucks pivot. Each one of those sections are attached to the main body of the car which pivots from the end sections. You will need big radius to run a car like this.

underworld

Easter Easter Easter Easter Easter!!!!!

[:D][:D][:D][:D][:D]

[ndbprr]

Not really. Mine is about 140' long and the end sections have three buckeye six wheel trucks and a four wheel truck like the prototype Westinghouse car and it will handle an 18" radius with a LOT of overhang.

[Anonymous]

I still don't understand how it is working (maybe because English isn't my language)
Can someone maybe make a quick diagram? That car is fascinating. I've got a 4-truck depressed car from Walthers but it doesn't look as good as this one [%-)]

[ndbprr]

Basically the trucks are mounted to a big square piece of steel called a bolster. The end platform is welded to one end of the bolster and the center section has a bearing on the other end.

[Anonymous]

OK guys--

Go to the following 2 locations:

http://www.kasgro.com
http://www.triarchy.com/kasgro/searchresult.asp

The first is the web site for the manufacturer/owner. You'll find the car by doing a railcar search on FD-depressed center flat car AND 340001-350000 lb capacity. This will pull up a page with the second address above. Go down to the 12 axle cars and you'll find an entry for car #s KRL 300300-300304. This is the car type in the photo. On the right is a link in blue that says A19644. Click it. That will pull up a .pdf file with a drawing of the car and relevant specs, used by prospective lessees who want to rent the car. The drawing shows truck centers of 68'-6", centered on the kingpins of the center trucks in each 3-truck set. What this means is that the three trucks on each end of the car ride on a longitudinal (oriented along the length of the car) beam called the bolster, which pivots on a kingpin which also handles the center truck. The other two truck kingpins mount through holes in the swiveling bolster beam and pivot on the beam. Because of this arrangement, the trucks on the two ends of each bolster beam swivel on the pivoting beam as though it were the car's center sill. Since the bolster beam is not the car's center sill, but it can pivot, the entire 3-truck assembly can also pivot out of line with the carbody, i.e., around a sharper curve than if all 3 trucks at each end were attached directly to the car's center sill.

If that's still confusing, think of the apparatus as a long steerable 6-axle truck, where the first 2 axles steer as an independent unit, the next two do the same, and the third do as well. That means that the entire six axle assembly can swivel under the car, and each of the 3 trucks can also swivel individually. This lets the entire 6-axle truck assembly (needed to spread the 350000 lb/175 ton weight of the load), which has a wheelbase approximately 5 times longer than a single truck, track around a conventional curve that otherwise would be an impossibly sharp curve for the car.

Schnabel cars and some larger/more sophisticated FD's work the same way, except they also have hydraulic controls that let an on-board operator shift the entire carbody to one side or the other on the bolster beam kingpin, to allow the long car and oversize load to clear obstacles on the side of the car, like buildings or other trains passing on a curve. Needless to say, these cars do NOT usually move loaded at high speeds.

Hope this is clear. If not, shoot back a post and I'll try again.[:D]

[Anonymous]

drephpe,
So what you are saying in very plain terms is the following. Take an I-beam, attach truck to the front of it, one in the middle and one in the other end. All trucks can freely rotate, while I-beam itself doesn't have any pivoting points? And so this car rides on a pair of these I-beams at each end? Right?

[Anonymous]

Dimastep--

I tried to find a link to a top-down drawing of the 3-truck assembly, but was unsuccessful.

You're almost there. But the I-beam can also pivot. Think about the front engine of a UP Big Boy or other articulated steam locomotive. It's a 4-8-8-4, where the front cylinders and 8 drivers are called the front engine, and the rear 8 drivers and cylinders are the rear engine. The locomotive is NOT on a single rigid frame--if it were it could never go around many main line curves, it's so long--instead, there are two frames-one rigid and one that swivels, connected by a pin in the middle so the locomotive can "bend". The front set of driving wheels and the lead truck are on a separate, swiveling frame (the "I-beam") that pivots on a pin attached to the rigid frame of the rest of the locomotive near the trailing front engine driver, so that the whole front engine--drivers, cylinders, lead truck and pilot (the "4-8" of the 4-8-8-4), can swing out to the side on a curve. Now, lengthen the frame to the rear, put a truck where the drivers are (right at the pin) in place of the drivers and add another truck at the back of the swiveling frame, and you'll have what is under one end of this car.

Based on what I see in the Kasgro drawing, on this car the I-beam pivots on the same kingpin as the center truck. This means going into a sharp curve, the I-beam pivots like the front of the Big Boy and the leading truck on the I-beam swings out to one side of the car AND pivots in the direction of the curve (like the lead truck on the Big Boy). Since the I-beam pivots in the middle, when this happens the trailing truck on the I-beam swings out to the other side of the car AND ALSO pivots in the direction of the curve. The middle truck just pivots in the direction of the curve, as does the I-beam. The same thing happens in reverse on the other end of the car. This is a double articulation that lets this very long car with lots of wheels to distribute the weight go around a comparatively sharp curve, in the same fashion as the Big Boy. The I-beam and lead truck swing to the side into the curve just like the front of the Big Boy.

Let me know if this doesn't help and I'll try again.

[Anonymous]

Like Athearn Auto-Max? In that case I can't imagine how the I-beam pivons and still stayes strong to distribute some weight to the end trucks. How it doesn't crack at the pivot point.
I mean, imagine Auto-Max and you press really hard on the center where two half-cars join. Then all weight goes to the center truck. You see what I am saying?

[Anonymous]

Dimastep--

If you make the I-beam too small or the wrong shape, it will break at the pivot point. But the car's design engineers take that into account and design the beam so that the weight is spread among the 3 trucks attached to it, in much the same way as a bridge distributes the weight of a load among all its structural members. The design also includes safety factors that work to spread the car's weight evenly across the 3 trucks by building a far stronger beam than is necessary to simply handle the load. When this is done properly, the beam will not break until beyond the end of its useful life or unless it is subjected to some extraordinary set of forces (like you would have in a derailment or if the car were greatly overloaded and subjected to unsafe speeds on very rough track).

I'm going to try again and find a drawing or photo I can post to help you get the concept.

[Anonymous]

OK--here's a Schnabel site that will give you at least an idea of how you spread a lot of weight among a lot of trucks by articulating what are called "span bolsters" (the official name for the I-beam we're talking about here) and make a VERY flexible car (much more flexible than the FD being discussed here--look at the bend and overhang!):

http://home.att.net/~Berliner-Ultrasonics/rrschnab.html#schndiag

[Anonymous]

drephpe, thanks for your help! I can easily imagine how they make 8-truckcar working as similar techniques are used on trucks to haul heavy loads, and I've seen those. It is when the number of trucks is 3 that it confused me. Well, I'll take your word for it as you version does make sense to me [:)]

[Anonymous]

Look at the Schnabel car. The bolster on the FD is most likely similar--independent beams on a single kingpin at the center truck (you can only put 2 trucks on one span bolster and still get flexibility). Either that or the drawing is wrong and they're pivoting on the center-most (to the car) truck, which would allow a single span bolster with the middle truck and the end-most truck adjacent to the coupler on the same beam. I bet an inquiry to the manufacturer (word it and approach it in a very professional manner) would get you the specific answer for that car.

Multi-truck cars are fascinating and, as you correctly note, are somewhat similar to mulitaxle bogies on OTR heavy-haul trucks/trailers.

Glad to help.

[tomd81]

Let me try to illustrate how the two span bolsters are used to support flat car. See the attached diagram.



Span bolster 2 is connected to the flat car and also span bolster 1. This way the weight of the flat car is spread over all six axles.

Tom

Visit my schnabel and large car web pages at
http://www.garlic.com/~tomd

[Morpar]

Tom,
Great picture, and it matches at least one of the TTX cars on your site (I use it a lot actually), but is that the same for the KRL (Kasgro) cars? Looking at the photos you have, the photos I have, and the diagram from your site, I don't see where there is room under the car for 2 span bolsters on each end. All the data seems to point to 1 of 3 choices.
1. The span bolster is the length of all 3 sets of trucks, 2 of the trucks pivot normally, and the third has a different "mounting" that will allow it to move laterally in a curve. Baldwin did something similar when they built an experimental turbine (shown in the back of MR's Diesel Locomotive Cyclopedia). Instead of span bolsters between them, the outboard trucks could just move around more than normal.
2. My thought on this is that the span bolsters meet and pivot over the middle truck. In your picture above, remove most of the blue bolster to the left of the middle truck and locate the point the car pivots on over the middle truck, perhaps even using a long pin that serves as both car and truck pivot. Now have both bolsters on the same horizontal plane, using a "lap joint" over the middle truck. This would seem to offer all of the flexibity advantages, while keeping the car's deck height down.
3. The currently unknown to me. This is what things usually are!
Thanks to all who have responded. I still hope to get a little more clarification on these cars.

[raillee]

hi drephpe,how it pass curves safely? can you give us a pic of it?

[7j43k]

With the subject car, it appears there is, on each end, a single bolster spanning three trucks--not typical for multi-truck cars.

The center truck must have lateral motion (as opposed to a kingpin).  This is because the center truck must move "sideways" in a curve.  For example, if a typical two-trucked car goes around a curve, the center of the car will be shifted towards the inside of the curve--if there were a truck there, it would have to have lateral motion to account for this.  The same happens with this span bolster.

Of interest, also, is how the vertical load is equalized.  Typically, it's done in a manner illustrated by Tom's picture above.  But, with this system, each bolster can only have two pivot points "below" and one "above".  My guess is that with the three-truck bolster system, they are letting the equalization be done entirely by the springing.  In a sense, this is not equalization, as the point of equalization is also to keep the wheel loading "equal".  Here, the load on the wheels, and on the track, is going to vary.  I suspect that the designers felt that the variance would not be a problem.  Also of note is that this car will have a lower tare weight compared to a more typically designed car, since the bolster system can be simpler.

 

Ed