Modelcar cordon Although the weight of a RR car falls on the center plate of the truck bolster (the part that goes from side to side), there are two additional supporting bearings, one on either side of the bolster about half way from the center to the end. These bearings have clearances that enable the car body to rock slightly from side to side and enable the trucks to rock a bit with the irregularities of the track. Is there any attempt to design any real "bearing surface" to these contact spots that support the rail car side to side.....?
cordon Although the weight of a RR car falls on the center plate of the truck bolster (the part that goes from side to side), there are two additional supporting bearings, one on either side of the bolster about half way from the center to the end. These bearings have clearances that enable the car body to rock slightly from side to side and enable the trucks to rock a bit with the irregularities of the track.
Although the weight of a RR car falls on the center plate of the truck bolster (the part that goes from side to side), there are two additional supporting bearings, one on either side of the bolster about half way from the center to the end. These bearings have clearances that enable the car body to rock slightly from side to side and enable the trucks to rock a bit with the irregularities of the track.
Is there any attempt to design any real "bearing surface" to these contact spots that support the rail car side to side.....?
Because the center bearing is so small of a support point in relation to the ten-foot-width of the car, the side bearings are needed to keep the car from tipping over when it begins to rock side to side. When the car is not rocking or is standing still on level track, the side bearings carry no load. When the car rocks far enough to one side, the side bearing on that side will be momentarily loaded. The side bearings are actually crude roller bearings set to travel parallel with the track in order to accommodate the truck pivot, should it happen to pivot when the bearing is loaded.
henry6 There were problems with several TTX cars not because of trucks but because of length of drawbar...when coupled to regular cars, drawbars were too short and there were derailments.
There were problems with several TTX cars not because of trucks but because of length of drawbar...when coupled to regular cars, drawbars were too short and there were derailments.
If I remember right, if you squeezed an empty one in a curve, it had a tendency to pop off.
The TTOX and TTUX were different by the type of "truck" they had. One had one of UIC European design and the other was a simpler, more "North American" design. There was some mod program along the way that converted one kind to the other for some reason that escapes me...
I always wondered why they just didn't run a solid train of them in some dedicated lanes, say NJ to Chicago. Would have gotten around most of the drawbacks. Perhaps the dawn of double stacks changed the economic equation.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Bucyrus Because the center bearing is so small of a support point in relation to the ten-foot-width of the car, the side bearings are needed to keep the car from tipping over when it begins to rock side to side. When the car is not rocking or is standing still on level track, the side bearings carry no load. When the car rocks far enough to one side, the side bearing on that side will be momentarily loaded. The side bearings are actually crude roller bearings set to travel parallel with the track in order to accommodate the truck pivot, should it happen to pivot when the bearing is loaded. The side bearings could be made to carry load in conjunction with the center bearing, but for the truck to properly equalize the loading to the wheels, the bolster needs to have the weight applied to its center, so it can act like a lever with the center load point being the fulcrum. Then the wheels and side frames can move up and down independent of each other by rocking the bolster like a lever, thus allowing the bolster to distribute the load equally to each side frame while allowing them to adjust to track irregularities
The side bearings could be made to carry load in conjunction with the center bearing, but for the truck to properly equalize the loading to the wheels, the bolster needs to have the weight applied to its center, so it can act like a lever with the center load point being the fulcrum. Then the wheels and side frames can move up and down independent of each other by rocking the bolster like a lever, thus allowing the bolster to distribute the load equally to each side frame while allowing them to adjust to track irregularities
Sure that makes sense....I wondered if perhaps that area was just the two surfaces rubbing against each other as load was applied but did wonder about going into curves if the car body was loaded one side or the other causing friction and trying to restrict the truck from rotating on it's "pin". The Crude roller makes sense.
Quentin
Kootenay Central Four-Wheel Container and TOFC Flats, CPR & GMD. This Link illustrates a short-lived series of 4-wheel Flats built by locomotive builder GMD of London, Ontario. http://www.trainweb.org/oldtimetrains/intermodal.html By the mid-Sixties they were in the weeds at Sortin Yard, Montreal, along with lines of Lidgerwood gons and their plows, post-war salt-corroded reefers,double-door automobile boxes and the like. Bound for Scrap, rather than glory.
This Link illustrates a short-lived series of 4-wheel Flats built by locomotive builder GMD of London, Ontario.
http://www.trainweb.org/oldtimetrains/intermodal.html
By the mid-Sixties they were in the weeds at Sortin Yard, Montreal, along with lines of Lidgerwood gons and their plows, post-war salt-corroded reefers,double-door automobile boxes and the like.
Bound for Scrap, rather than glory.
That's an interesting link. Appears to largely track the pair of articles by F. H. Howard in Trains a long time ago, but I do recall that they performed fine even under extreme loads and rough tracks. See:
What I really appreciate, though, is the photo of the side-loaders about 2/3 of the way down that page. If I recall correctly, those were called or made by a company named "Streadman" -= I've not seen that one before. Thanks for sharing.
- Paul North.
There are also constant contact side bearings, which take up some of the slop inherent with the normal side bearings, giving longer service life and faster possible speeds.
One manufacturer here: http://www.minerent.com/ccsb.asp. I'm sure there are others.
Mike WSOR engineer | HO scale since 1988 | Visit our club www.WCGandyDancers.com
jchnhtfd In a two axle car, however, all twist has to be accomodated in spring deflection. This means, inevitably, that the low wheels, at diagonally opposite corners, will be (relatively speaking) unloaded and prone to derailment.
Not being familiar w/ 2 axle suspension practice "across the pond", I just figured that the cars incorporated cross equalization on one of the axles. 0-4-0 switchers usually had the front axle cross equalized and the back axle sprung to the frame from the journal boxes to provide a 3 point suspension. It seems to me that I've seen American bobber cabooses designed this way also, using leaf springs on one axle connected to a cross equalization bar and simple coil springs above the journal boxes on the other axle. Of course, on a freight car with a higher center of gravity (when loaded) cross equalization could lead to instability. Certainly, unequalized two axle cars will act just as described in a "twist" scenario.
jchnhtfdThe flexibility, incidentally, also explains the better ride...
Flexiblity of a two truck, four axle car vs a 2 axle car is only part of the reason that the ride is better. The other part is the equalization between the axles on each truck. For instance, if a two axle car is traveling down the track and hits a 1" high bump (unreasonable, I know, but bear with me for the sake of argument) each end of the car will jump up 1" as each axle hits the bump. But when a two truck, four axle car hits the same 1" bump, each end of the car will make two 1/2" jumps as each axle hits the bump. The same thing happens when each car hits a kink in the track, causing it to jump sideways. Equalization is one of the main reasons a two truck, four axle car rides smoother than a two axle car. I'll bet that the multiple truck high capacity cars such as the one in Justin's picture almost float down the track!
- James
oltmanndI always wondered why they just didn't run a solid train of them in some dedicated lanes, say NJ to Chicago. Would have gotten around most of the drawbacks. Perhaps the dawn of double stacks changed the economic equation.
The Milwaukee Road used solid sets of the Four-Runners for their Sprint Train service from Chicago to St. Paul. The cars were stenciled to keep them in that service.
So when did 2 axle Bobber cabooses get outlawed? I've read conflicking dates.
beaulieu The Milwaukee Road used solid sets of the Four-Runners for their Sprint Train service from Chicago to St. Paul. The cars were stenciled to keep them in that service.
Did they have any unusual derailment problems with them? I never heard of a Sprint Train wreck. But again, just because I never heard of it, doesn't mean it didn't happen.
CShaveRR Here's a question for somebody who has a better understanding of physics than I. I've seen heavy-duty flat cars with pairs of six-wheel trucks at each end, and with three four-wheel trucks at each end. I would assume that, with wheels and bearings of the same size, both types would have the same gross rail load. What would be the advantages of one over the other--economy for the six-wheel trucks (think about how they'd be attached to the carbody) and curvability for the added four-wheel trucks? .
Here's a question for somebody who has a better understanding of physics than I. I've seen heavy-duty flat cars with pairs of six-wheel trucks at each end, and with three four-wheel trucks at each end. I would assume that, with wheels and bearings of the same size, both types would have the same gross rail load. What would be the advantages of one over the other--economy for the six-wheel trucks (think about how they'd be attached to the carbody) and curvability for the added four-wheel trucks? .
I have no real knowlege, but will make a semi educated guess. Assuming the bearing size is the same, the weight limit would be the same. The advantage of the 6 wheel truck would be the simplicity of the suspension. See the discussions that follow the original post. However, 6 wheel trucks are odd ducks at the local car shop. Total cost on the new car is probably more too due to lack of volume in sales. The advantage of the 4 wheel truck is standardization. A 100T truck is a 100T truck is a 100T truck. The car mfg can buy a standard truck 'off the shelf'. If one goes bad the local rip track can slip a replacement under the car in no time. The 4 wheel truck rig may have a slight advantage in minimum curve.
Phil
Timber Head Eastern Railroad "THE Railroad Through the Sierras"
Carl and Phil,
This is an issue my father talked about once. Only we were discussing depressed centre flats with two four wheel trucks at each end. CP used to operate them up until the 70"s I think, and my father said they did there job exactly as advertised when they were loaded. But deadheading them to their next job was a real problem.
If you think of an empty flat car as having eight points of contact with the rail, the tare weight per wheel is spread out eight ways. But on a sixteen wheel car, the not much heavier tare weight is distributed among sixteen contact points. This greatly reduced weight per wheel made them incredibly derailment prone going over switch frogs. It became necessary to move them in the slowest wayfreights available, which meant very time consuming trips to their next job. He also said it wasn't unknown for serviceable cars to be hauled as bad order cars behind the caboose. He said train crews just hated to be stuck with one of those empties.
Phil is right of course that the car manufacturers want to reduce their costs and the purchasing railways didn't realize at the time this would be a problem. I presume that cars like the one pictured at the start of this thread have much more sophisticated suspensions to alleviate this problem. I had hoped to hear Carl's take on this issue for a while, but it seems he has the same questions I had.
AgentKid
So shovel the coal, let this rattler roll.
"A Train is a Place Going Somewhere" CP Rail Public Timetable
"O. S. Irricana"
. . . __ . ______
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