Most all American genaral scervice freight cars have 2 sets of 2 axel trucks underneath them. Why is that? Some Brittish carrages have 2 sets of 1 axel trucks. Is this because american cars are hevier than the carrages across the pond? Does it have something with the curve radius? Wouldn't it be easier for American cars to have 2 sets of 1 axel trucks? I mean, less to maintatin right?
Thanks,
Justin
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First, your picture is of a special load depressed center car, not typical of railroad cars. However, your premise of heaviness is correct. North American railroads do have a heaver loading guage, thus larger and heavier cars, thus two two axel trucks.
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Justin - just a little before your time (by about a decade) was the rude experiment with the TTOX single bogie skeleton flatcars......Gawd did I hate those switch pickin', frog hoppin' nightmares that seemed to be in the middle of about every switching derailment they called me on. (Carl, are there any left? ...I never wanted to see those empty in the middle of a moving freight train.)
As close as you get to a single bogie truck anymore are the roadrailers....
As for 3-axle cars, there are still a few of the DODX 100+ ton flatcars still out there plus others.
Plenty of span bolstered trucks out there too, like the schnabbel cars (pictured) and large tank cars ("bombs")
Justin's photo of the HD load capacity "low center carrier" is an excercise of {RR equipment} beauty. That arrangement has so many pivot points to enable it to follow almost any RR curve....
I count 14 points of pivot to allow it to follow curvatures.
Quentin
mudchicken > As close as you get to a single bogie truck anymore are the roadrailers....
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Justin,
I don't have a lot of time now, but you might want to zip over to the MODEL RAILROADER forum and see if any of the old timers can point you in the direction of a story from the late sixties about the history of freight car trucks in North America. I was a teenager then and I found it fascinating. Like Joni Mitchell says "you don't know what you've got until it's gone", but I really wish I could better remember the variety of trucks I could still see in the early sixties at Irricana, AB. It took railroads a long time to come to the standard type (or two?) we see today.
AgentKid
So shovel the coal, let this rattler roll.
"A Train is a Place Going Somewhere" CP Rail Public Timetable
"O. S. Irricana"
. . . __ . ______
This might be an easier way to find the information you were looking for.
http://www.trains.com/trn/default.aspx?c=a&id=210
Axle loads in Europe are very low, most cars can barely haul more than a road haul truck.
American railcars are upto 150 ton, with axle loads of 38 tons, nearly 20 tons more than a allowable axle load in Europe.
The 4 axle freight cars are gaining popularity in Europe too but won't weigh more than 80 to 90 tons.
Justin, if you can find a copy of George Hilton's book "American Narrow Gauge Railroads", it has a very good section on narrow gauge rolling stock evolution from 4 wheel to 8 wheel cars. American standard gauge rolling stock also seemed to evolve in a similar manner in its early years. Part of the early problem was that American railroad track (at that time) tended to be rougher and had more curves than our English counterparts. Four wheel cars just don't track as well as two truck, 8 wheel cars do under those circumstances. This was one of the reasons that English built 0-4-0 steam engines were not a big success in America at the beginning of our railroad history. Rough track and sharp curves led to the development of the 4-wheel pilot truck and four equalized drive wheels that defined the popular 4-4-0 locomotive. Admittedly, a 4 wheel locomotive has a different set of dynamics than a four wheel freight car, but some of the same problems do affect both. Nowdays, our axle loadings rule out 4 wheel cars for any application I can think of, and an 8 wheel car has the added advantages of riding smoother and tracking better than a 4 wheel car. At any rate, see if you can borrow a copy of Hilton's book from the library, I highly recommend it. You might also do some reading on early steam locomotive development.
- James
Justin - The reasons Britain stuck to 4-wheelers until quite recently are complicated, but certainly part of it was to do with curve radii on sidings. Much of Britain is very densely built up, and due to pressure of space many old factories, collieries, docks etc. had sidings with extremely tight curvatures. To serve these, British freight cars (‘goods wagon’) stayed extremely small – most wagons built up until the early 1960s had a 10’ rigid wheelbase. The air-braked standard types introduced the late 1960s (previously most British wagons were vacuum braked or unfitted) still only had 4-wheeled chassis of 18’ to 21’ or so, and even this was too large for some customers’ sidings – Ministry of Defence traffic still required a dedicated fleet of 10-footers in the early ‘90s . Also, some industrial track was lightly laid – colliery branches for example were often unable to take heavy locomotives or cars. Closure of these old sidings due to the decline of old industries and the collapse of the UK wagonload business means that large bogie wagons are now prevalent, though there are still plenty of 4-wheelers about.
Certainly a small, simple 4-wheeler is cheaper to build and maintain than a large car, but obviously you need more of them to carry the same load, which ends up costing more overall. Also 4-wheelers can have undesirable ride characteristics, as a result of which they usually have a relatively low speed limit, even on good track. On poor track, or if poorly maintained or unevenly loaded, they can (as Mudchicken points out) be prone to derailment.
Keith
As others mentioned, having a pair of trucks helps greatly on rough track, perhaps more critical for frontier railroading. Single axles transmit any irregularities directly to the carbody, as I found riding a fairly modern DMU in Britain some years ago. Over here, cross-overs would jerk the Turbotrain enough that it was recommended that passengers remain seated in station terminal approaches. In both cases, light weight also contributed to the roughness.
One of the controlling factors in car capacity is bearing capacity. This can be increased by increasing the size of the bearing (axle diameter or width) or by increasing the number of bearings. One of the reasons for having additional axles on heavy-duty flatcars, like the one you pictured, is bearing capacity for the ultra-heavy loads. The other is axle loading on the railroad structure itself.
North America, because it went to 4-axle freight cars very early, based its practice on large capacity cars. For small shipments the local wayfreight would usually carry an LCL (less-than-carload) boxcar and small shipments would be loaded/unloaded at various stations. This business was quite labor intensive, since shipments would get exchanged between cars at major terminals to be forwarded on towards their ultimate destination. The railroads here conceded the "retail" freight business to trucks a long time ago.
In Britain small shipments would match the small cars rather better. The small cars had other advantages. It was not uncommon to have very short turntables (barely long enough to fit the wheelbase of the wagon) on a siding. Cars could be turned 90 degrees and pushed immediately into the industry or warehouse. This saves an incredible amount of space in a country where space is at a premium, and the same procedure could occur inside the building. Manpower was quite adequate to push the cars. As in North America, though, the small shipments were very vulnerable to road competition and have mostly left the rails. What freight is left mostly uses cars equipped with a pair of two-axle trucks.
John
According to the ORER, the car in the picture, KRL 16450, is actually just a depressed center flatcar (FD), not a Schnabel (LS).
Amazingly, the October 2007 ORER does list 274 of the TTOX cars. Perhaps they keep them around as bad examples.
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Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
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Mudchicken,It is indeed a common knowledge that those front-runner cars were a PITA. I wonder though, why were they in use for so long, why was there not a trial in one particular corridor to make sure these cars will indeed work? So much money wasted on those derailments cleanup!
Rode talgos in Spain over the same routes with both two single axels on each car and a two axel boggie between cars. The two axel 4 wheel boggie rode much better IMHO. That was the time I converted from the idea of single axel cars for the US system.
CShaveRRHere'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
Can someone describe how a car with three four-wheel trucks at each end would be suspended....? Where would the pivot points be....?
Would one truck be located with a pivot pin....and the other two be suspended with a frame across them {pivot in center}, and each truck pivoted from that frame.....?
{Actually, thinking about that last thought....don't think that would work either}
The Talgo's don't really even have single axles, each wheel is in a half axle.
The Axle does not continue under the car.
Don't forget some of the stack platforms, or five packs (five platform sets), share two axel trucks, too. It is therefor: platform one and five have one and a half trucks each while the other three platforms share each truck inbetween so that there may be only 6 trucks instead of 10..
So how do the Brits handle containers? It sounds like a daunting task for a railroad that has small freight cars and tight radius curves.
Mike
Mudchicken,
I have a model of that pice of junk! I hate it. I saw a thing on Rail Pictures.net of one. The one and only comment was, "Glad one got saved." Also the bogies don't pivot. What idiot designed that... Oh I forgot TTX.
Quintion,
I think the pivot point is in the center of the middle wheelset on each end of the car. Also, the wheels axels I mean dont continue under the car. It is suspended by something. maby a bar with roller bearings that the 1/2 axel fits into? Anyway, the "wheels" can turn indapendantly of each other. This is what makes it so easy to go around curves with this car.
That car I just found on the internet. I decided to post it. That same compnay, Red N' Ready I think, has a massive car that has a hugh depression in it. I will look for pics.
Got it Carl.....That sounds like an expensive suspension and geometry.
bubbajustin Quintion, I think the pivot point is in the center of the middle wheelset on each end of the car. Also, the wheels axels I mean dont continue under the car. It is suspended by something. maby a bar with roller bearings that the 1/2 axel fits into? Anyway, the "wheels" can turn indapendantly of each other. This is what makes it so easy to go around curves with this car.
Justin.....I understand how the pivots are placed on the good looking HD car photo you posted, I was asking how the suspension was configured on one Carl had noted.
But on the car in the photo Justin, you will find the axles do continue to the other wheel. Those "trucks" are similar to any 4-wheel truck. Bolsters are involved to get pivots placed properly. Hence, in my opinion, it could negogtiate rather sharp RR curves.
m sharp So how do the Brits handle containers? It sounds like a daunting task for a railroad that has small freight cars and tight radius curves. Mike
Container terminals are modern facilities which were designed from the outset to handle large cars, so there is no problem with tight curves. British intermodal traffic employs spine cars and wells similar to North American practice, except of course the loading gauge is much smaller, so double-stacking and TOFC are not possible - the well cars are used to handle Hi-Cube containers which would be out of gauge on a spine car.
This is in reference to the TTOX/TTUX two axle TOFC flatcars produced in the 1980's. They held only one trailer each. Which was a good thing.
bubbajustin Mudchicken, I have a model of that pice of junk! I hate it. I saw a thing on Rail Pictures.net of one. The one and only comment was, "Glad one got saved." Also the bogies don't pivot. What idiot designed that... Oh I forgot TTX.
These cars had several potential advantages. The first being that they were built to handle only one trailer. The then standard two trailer TOFC flatcar was a very bad result of Federal government rate regulation.
The regulators attempted to "cost out" rail movements by basically adding up all the railroad's cost by category, i.e. switching, then dividing by the number of CARLOADS. This was obviously not good and came from a study never designed or intended to cost out individual shipments. When trailers came along the regulatory cost per trailer for many things was the same as the regulatory cost for a carload if the flatcar only carried one trailer. This often placed this imaginary cost above the competing truck charge. Since the regulators wouldn't allow rail rates below this imaginary number, one flatcar per trailer this made TOFC rates non-competititve with trucking.
A solution was a longer flatcar that could carry two trailers. This met no marketing or operating need and did not reduce overall intermodal system costs significantly in any real way. But it dealt with the imaginary costing done by the regulators and allowed TOFC rates to become truck competitive. The 89', two trailer, flatcar had some derailment problems of its own and proved a real problem when highway trailers grew longer. It handled two 40' trailers just fine. It could be modified to handle twin 45' trailers although mechanical people resisted this due to the fact that the two 45' trailers had a combined length longer than the flatcar. Their resistance was not founded in any real problems with handling two 45's per car. It was just basically resistance to change.
The cars handling two 45's had to be loaded/unloaded at a mechanized terminal. This lead to the closing of circus ramps. (More ramps were closed than should have been.) When trailers grew longer than 45', well...I won't go there. I'll just leave it at the fact that the 89', two trailer, TOFC flatcar was a response to bad regulation and not any real need.
When the regulation went away, so did the need for the two trailer flatcar. The TTOX/TTUX cars were a result. A railroad no long needed to "mate" trailer shipments in pairs of two. You could move exactly the number of platforms you needed on each thain. They were also very light weight, less than 12 tons IIRC. Since many rail costs do relate back to weight this actually did reduce cost.
The TTOX/TTUX cars were a good idea that aparently didn't work out all that well. If you will only accept things that are certain to be raging successes, you're never going to do anything.
I hadn't heard of any extraordinary derailment problems with them, but just because I didn't hear about it doesn't mean it wasn't so. An increased tendancy to dereail may have helped doom them, I don't know about that. But I do know that they were TOFC only cars in an intermodal system that was rapidly changing to containers. They also were built to handle 48' trailers and as those were replaced with 53's the cars became virtually useless.
.
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.
Two comments on the Trains article referenced way back on Page 1.
Popular lore is that Timken began calling journal bearings "friction bearings" in the early 1950s when they first started to produce tapered roller bearings for railroad use. Another term for journal bearings is "oil film" bearings. Roller bearings for RR use became feasible only after the development of high strength steel that would stand up under the heavy loadings presented by RR work. Another advance seldom mentioned is the development of seals that keep lubricants in and water/dirt out. AFAIK we didn't have such seals in commercial quantities in 1950.
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.
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.....?
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