When you see a car labeled as 70 ton, is this the load capacity for that particular car?
I have several Intermountain 70 ton flat cars for use in a military train. I’m trying to figure out how many tanks one flat would be capable of hauling. The tank in question is a 1950s era M48. Wikipedia lists the weight of an M48 as 49.6 tons. Two tanks would be 99.2 tons. So a 70 ton flat should only carry one M48 if I understand ton designations correctly.
Look at the data on the car side. Load limit weight minus light weight is the amount of weight the car can carry.
And if your model is similar to one of these, http://www.ttx.com/Equipment/listingtype/special-equipped-fleet/chain-tie-down.aspx, the text with the photo gives capacity.
I believe this is mistaken. Cars in the 50’s were often stenciled with (nominal) Capacity, load limit, and light weight. The Capacity and load limit were usually fairly close. The light weight was primarily there so that when a loaded car was weighed, they could subtract the light weight and know how much the load weighed.
EXAMPLE: Let’s say you have a 3-bay hopper car labeled as a 70 ton car. It might be stenciled Capy 140,000, Ld Lmt 141,200, Lt Wt 58,800. Now if this car is riding on a pair of trucks capable of 100 tons (combined, 50 tons each), that would equate to 200,000 pounds. Subtract the light (empty) weight to arrive at the maximum load (load limit) this car would be rated to carry.
If repairs are done on the car, it should be reweighed and re-stenciled with its new empty weight, and load limit adjusted accordingly.
Brad
I would say usually yes. IIRC axle loadings are limited to 80,000 # per axle. Theoreticaly.a four axle car could.carry 320,000 # or 160 tons. It would impossible for a car to carry.160 tons of.marmallows as it would require a very large car. Other materials are vary dense so a weight limit is reached before volume.
Well, maybe, but this is the way it was just described in the November MR.
Well, this would be getting into Cooper’s load rating for bridges, and truck capacities. Today, modern roller bearing trucks typically come in 70-, 100-, and 125-ton varieties. But another consideration is the rail and track they will be operating on. Sure, a mainline track might handle a (fully loaded) 125 ton truck easily, but what about that ancient spur with that 90-pound rail? That kind of load could very well break a rail. Besides, even if a particular car was equipped with 125 ton trucks (example - the “shared” trucks on articulated intermodal cars), it could be loading 125,000 pounds per axle. Clearly the track and and bridges will need to be able to support this kind of load.
Simply swapping trucks under a particular car wouldn’t automatically increase the weight capacity. The frame, crossmembers, bolsters, floor, etc., are all designed for a given capacity. Sure, it might handle an occasional minor overload, but a 70 ton car carrying a 100 ton load runs the risk of suffering a catastrophic failure while en-route.
Here’s a good example:
Brad
Matt.
One tank for each car would be prototypical. If the tanks are scale then two would be too long for a typical 50s era flat. If there is any overhang on the ends that would be over the coupler then an idler flat would be used. If I remember the M48 had a 70mm gun that stuck out several feet over the back with the travel lock closed. I loaded many an M60a1E5 tanks on rail cars and it was one per car even if it was rated for the tonnage of 2. Blocking was under each end of the tracks that were lagged to the decks. Also tie downs were wire rope cables with turn buckles. No chains. Make sure the gun tubes are end plugged and locked down and the hatches are closed and dogged. Don’t forget the DO NOT HUMP signs on each side of every car. I see wat too many models missing those signs.
Pete
Thanks for all the info.
Pete,
Yes the M48’s are scale, 1/87 Roco tanks.
I can fit two tanks per flat if the turrets are reversed. And you are right that the 90mm sticks out over the back. But I like the way they look as one per flat …and there’s the weight issue [;)]
Once I get the tanks painted and decaled, I’ll work on the wheel (track) blocks and tie downs. Thanks for mentioning wire rope instead of chain.
Here’s one tank per flat, and the flat car data:
Hmm [^o)]
If my math is right (using LD LMT - LT WT), the cars capacity in lbs is 87,800. And if the load is in the center the capacity is even less at 50,600. So I don’t think these flats can handle an M48, which I think weighs 99,200 lbs.
But if I just go with the LD LMT, I’m fine with one tank per flat…even in the center of the car,
Where did you come up with the 50,600?
Anyway, looking up M48 tank weight in Google it appears that there are differences in opinion as to what the weight actually is. See:
http://www.militaryfactory.com/armor/detail.asp?armor_id=29
http://afvdb.50megs.com/usa/m48patton.html
I would also suspect that the weights given are the combat weight, which would include fuel and ammunition. I don’t think the tanks would be shipped “ready to run”.
For a 70 ton car, the number following LD.LMT. is determined by subtracting the LT.WT. from 210,000, an arbitrary value (for 50 and 55 ton cars, that number would be 169,000 and for 40 ton cars, 136,000). Your nominal 70-ton flatcar is good for just over 74 tons, as indicated by the LD.LMT. It doesn’t matter if the trucks are rated for more, the car is not designed to carry more.
The only exception to this is if the car’s owner has reduced the LD.LMT. because of structural limitations or other reasons. In these cases, the total of the LT.WT. and LD.LMT. would not equal the arbitrary number for that car, and the restriction would be indicated by a star symbol to the left of LD.LMT., as shown on the 40 ton car below:
Only the car’s owner may change the LD.LMT.
Wayne
Look to the left of the data photo where it says CTR LD LMT 111700. So 111,700 - 61,100 = 50,600
I suspect there is a center load limit because the load weight is not distributed over the trucks if it is in the center of the car.
Wayne,
Thanks for the load limit info. So it looks like my flats are good to go for the military train.
Ah, I didn’t read the fine print!
If anyone is interested, I’m going for a Camp Irwin look for the desert section of the layout. I was inspired by this film clip, and I even have a similar convoy bus model on the to paint list:
Okay, I confess to being confused. In the November issue of MR in the information desk section Jim Hediger states that load limit is the empty weight of the car plus the maximum load it can carry without exceeding its rated wheel and axle capacity.
In the following link, http://www.bouldercreekengineering.com/scale_ops3.php, which seems to give a pretty good explanation of the whole thing, they define load limit as the maximum net weight permitted based on axle and journal limits. They further state that if gross weight minus light weight is greater than the load limit, the rail car is overloaded and unsafe. If my understanding is correct, this means that the maximum load the car can carry is equal to load limit minus light weight. I think this agrees with what Jim said.
If I look at the following site, http://www.icrr.net/terms.htm, they define load limit as the maximum load in pounds which the car is designed to carry. This seems to agree with Wayne’s definition, unless the maximum load the car is designed to carry really includes the car structure.
So, who can give us the real definition?
By the way, according to Jim’s article, the capacity data line “was deemed unnecessary” and was eliminated from the lettering standards in 1990. Unless they changed the meaning of the terms, that capacity line doesn’t really enter into how much a car can carry.
I believe SW Chief is mistaken. You do NOT deduct the light weight of the car from the load limit. You deduct the light weight from the maximum weight (usually not stenciled) to arrive at the load limit.
As a trucker, this carries directly over from my profession. Road trailers are designed to carry only so much weight (as my previously linked photo shows). Maximum weight in the U.S. (without special permits) is 80,000 pounds. Now lets say my tractor weighs 17,500. The maximum legal weight for my trailer is 62,500. The builders plate clearly states the maximum gross weight for the trailer is 65,000 pounds. This IS NOT the weight of the load! This is the combined weight of the load and the trailer. Since the trailer is roughly 10,000 pounds, I can legally haul 52,500 pounds without being overweight. The trailer can legally and safely haul 55,000 pounds, without being overloaded as per the builders plate. If my tractor weighed 15,000 pounds, I would be within the 80,000 pound limit.
I believe SW Chief is mixing up maximum gross weight with load limit. Gross weight is the total combined weight of car, load, trucks, air in the reservoirs, tie downs, tarps, snow on the roof … EVERYTHING. It’s the weight you will see when the car is weighed. This is the number you deduct the light weight from to determine load limit.
If my trailer was to receive repairs, the gross weight limit would be unchanged, but my load limit would probably change, due to the trailer weighing more/less. Rail cars are the same, in fact, they have to be reweighed and restenciled after being repaired, to reflect the new light weight and recalculated load limit.
Brad
Don’t confuse load limit with the center load limit stencil. The center load limit is designed for a small area of the center of the deck. Such as a bridging bolster or cradle such as this. http://www.rgspemkt.com/215-P1.html The tanks tracks spread the weight over a large area where a large percentage of the deck would be used.
Load limit is typically 3% higher than capacity. Always load to capacity and this limit gives a little leeway for unforeseen things like rain and ice accumulation. The car pictured shows 140,000 lb capacity but can safely handle for a short time 148,900 lbs.
Pete
As I stated previously, the LD.LMT. is determined by subtracting the LT.WT. from an arbitrary number which is based on the car’s nominal capacity. I’m not sure who determined what those arbitrary numbers should be (ICC, FRA, AAR?) but that’s the way which it was done at least well into the diesel era. I can’t say for certain if it’s still in effect or has been superseded by another method.
As far as I know, there’s no time limit on the amount allowed by the LD.LMT. [swg]
Wayne
The load limit (tonnage) is what counts…The power desk and train crew must know the tonnage of the train.Also the load limit must be followed according to Federal rules and regulations.This is why cars are weigh…
Here’s how the prototype sums it up for their customers.I will use boxcars.
http://www.csx.com/index.cfm/customers/equipment/railroad-equipment/#boxcar_specs
http://bnsf.com/customers/pdf/50ftF_BoxcarDiagram.pdf
http://www.uprr.com/customers/equip-resources/cartypes/boxcars.shtml
Sorry Dr. Wayne, but unless there has been a change as you say, I cannot agree with you. I have a couple color guide books which clearly show the weight data. In just about every case, the value shown on the capacity line is less than the value shown on the load limit line. I don’t see any way where the light weight subtracted from the capacity number can end up being larger than the capacity number.
Looking at the PC book for example, many of the cars are shown to have the same capacity of 154,000 pounds. I suspect that this is the number you are calling arbitrary. Maybe these are the so called 70 ton cars. Looking at some 2-bay covered hoppers, all with a capacity of 154,000 pounds, I see light weights of 53,700, 51,900, 55,600, and 55,400. The corresponding load limits shown are 166,300, 168,100, 165,400, and 154,600.
I think I’d agree that the capacity data is arbitrary, but I am not convinced that it has much to do with the cars actual load limit.