There seems to be a missing evolutionary step in tank cars designs.
For LP gas / propane cars, did the designs really jump from the 10000 to 11000 gallon cars with underframes to 33000 gallon cars without underframes in a single step???
In the same way, did chlorine tank car designs jump from 6000 to 8000 gallon cars with underframes to 17360 gallon cars without underframes in a single step?
Railroads seem to be very much evolution driven rather than revolutionary. In the case of both the LP gas and the chlorine tank cars, it would seem like there should have been some intermediate design between the 1950s era small cars and the large cars currently on the rails, but my google fu is weak and I have not been able to find such a intermediate size car.
Do you have pictures or links for the ‘missing’ designs???
Personally I’d date the structural changes to improvement in fabrication techniques, better full-penetration welding, and better steels.
Remember that the real innovation in these cars was not allowed to persist; look up the history of ‘rail whales’. Any merely four-axled car is ‘midrange’ after that. [;)]
Railroads and modelers see tank cars through different points of view. Railroads are interested in the weight of a loaded car, instead of capacity in gallons, as most modelers are. The Official Register of Railroad Equipment which is supposed to list every car in interchange service in North America, gives the volume of tank cars in thousands of pounds. Very few list the volume in gallons-as well as with the thousands of pounds.
Due to widely differing pounds of weight per gallon of lading, we have vast numbers of different sized tank cars, dependant on gross rail loading or, how much a fully loaded car and contents can weigh and still be interchanged without restriction on the North American rail system. For a long time the universal GRL for a four axle car was 263,000 pounds. This has since been increased to 286,000 pounds for a four axle car. Nowhere is gallonage mentioned. That is the worry of the shipper and the carbuilder.
The “GATX Tank Car Manual, Fifth Edition, Feb. 1985”, published by the General American Transportation Corporation lists hundreds of commodities shipped in railroad tank cars by pounds per gallon. This will explain why a car carrying sulfuric acid will be dwarfed by one carrying the same weight in liquified petroleum gas:
Product: Common car capy. in gallons Pounds per gallon
Corn syrup 17,600 11.66
Liquified pet. gas 33,500 4.24-4.83 @-58 degrees F.
And value of any product carried by rail is by weight.
“Weight” is a stand in for mass and mass is what you want to pay for.
It has always been illogical to buy and sell liquid and gaseous fuels by volume. Solid fuels were always sold by weight. Fuel gases are priced by BTU or similar energy units which is another stand in for mass. I know natural gas appears to be priced by volume but it isn’t actually.
There were of course experiments with frameless tank cars going back even before WWI. But the modern frameless tank car pretty much followed the use of welded versus riveted tanks.
My hunch is that tank cars got larger to (try to) keep the traffic from truck competition, so maybe the missing link is to be found by looking at the size of tank trucks on the highways.
To consumers, it most certainly is. If you know of a utility using anything other than volumetric flowmeters for premise consumption, tell me about it; all the ones I have seen including the newer ‘smart’ versions all read in CCF (this being Stateside in nonmetric units) and the billing is likewise relative to that reading, not adjusted to mass.
Not that it is particularly technically difficult to build or deploy thermal mass-flowmeters, especially if they can be designed as ‘smart’ with the additional processing capability to correct for temperature and pressure variations… it’s just not the done thing.
Likewise, there are notices in every gas station here that fuel is sold by volume, uncorrected for temperature and therefore explicitly not by mass.
Now, it’s more likely that utilities making long-term contracts with gas suppliers might write provisions concerning mass-flow correction. Again if you have documentation of the details of this, I’d like to see how it is arranged and calculated. But consumer ‘price’ is determined only on volume.
Hi, that is how I would think modern Tankers evolved, thru modern design & fabrication techniques + better quality materials. I should think that T-cars are classified as Pressure-Vessels.
I looked this up in Jeff Wilson’s ‘Modern Freight Car’ book. The transition to modern T-car design began in 1954, when Union designed and built the first modern Frameless car. No. 42998, no centre-sill or running boards.
However, it was not approved by the Interstate Commerse Commission until 1961 and that could account for why T-car design suddenly revved-up, the designs were there, but not fully in use?
It is worth noting that cars with Aluminium Tanks still have Centre-sills, also Co2 & Cryogenic liquid cars.
It must be good to design RR cars because as time moved on, you see how the designs were rationalised for quicker, cheaper production in the need to remain competetive on price, maintain AAR standards, but still deliver the shipper’s goods. Paul
Gasoline and diesel fuel is definitely sold by volume (gallons in the US, litres in Canada).
My natural gas utility bill for home heating is in fact also measured in cubic metres (Canada). I assume that’s calculated at a standard pressure and that’s how it’s represented on the bill.
On the other hand I filled up my propane tank for my barbeque on the weekend and was charged for 11 pounds of LPG.
The ORER I have here absolutely lists both gallons and weight capacity in the table for tank cars - just as for other types of cars it lists cubic foot capacity as well as weight.
Yes, gross weight is the limiting design factor which is why cars designed for specific commodities range so much in size from 14K gallon sulphuric acid tanks to 33K compressed LP gas tanks in order to stay in the weight limit for a loaded car. (Which you basically stated as much - just reinforcing.)
That’s because volume doesn’t work for what is basically a gas liquefied under pressure. Flow meter won’t work; tank is opaque and irregular so can’t be calibrated like labware; external ‘liquid crystal’ level gauges aren’t accurate. So the more sensible alternative, weight, is used… because it’s easy just to purge the tank, plop it on a scale, and fill by display.
Airplane fuel is critical, so it gets carefully measured … by weight. You could do that with your car, too; it’s how they tell how much old newspaper or whatever you brought to recycling in your pickup bed. But it isn’t cost-effective to put automobile scales at every pump, and watch for scams…
… and of course differential weighing of an instrumented section of your natural-gas line to gauge the amount of mass passing at typical gas admission pressure, then integrating over time for a billing period is… not exactly practical…
Gasoline and diesel are sold on temperature corrected volume. In Canada that’s as if the delivery temperature were to be 15C.
So, fuel is sold by mass. The consumer just doesn’t realize that because the “measured” and displayed numbers always look the same. The actual physical volume of fuel delivered changes.
If there was anything produced in mass numbers between these steps, I cannot find anything about those cars.
It makes sense that the jump could have been that large is the change from 50 ton loads to 70-100 ton loads took place the same time the heavy underframe was removed.
If so, they would have increased the total capacity of the freight car at the same time the “dead weight” of the car was decreased.
Sad indeed. You read all of my posts with almost obsessive concentration.
Perhaps if you would quote me in context.
I am not wrong because I change my mind when new information comes my way. Before that I am, of course, always corrct in what I say. In the case of expression of opinion correctness is irrelevant.
The majority of consumers are happily unaware of the fact that they are charged for volumes of fuel not actually delivered. Good thing too as charging by actual as measured delivered volume would be dishonest. Gives you a whole new perspective in those old gas pumps which really did deliver by uncorrected messured volume. On a really hot day your fuel economy would seem very poor. Not any longer, a gallon of gas is really a gallon, er, by mass (6 lbs according to Wikipedia).
CNG isn’t shipped by rail as far as I know. If it were the loaded tank cars would not be very heavy apart from the robust construction required. Mind you, CNG would provide quite a bit of structural support for cylindrical tanks with domed ends. About 1/5 the “weight” of an oil tank load (at 200 to 250 bar). Keeping it cold enough is tricky when using rail transport.
This excuse for repeatedly and purposefully posting inaccurate information is no longer funny, if it ever was. This expression of yours has run its course with this audience and needs to be retired.
Your now blunt accusation is not supported by the facts.
In addition, by making this totally unwarranted personal attack you reveal an obsessive attention to my posts, which is incomprehensible under the circumstances. I suggest you desist. I will do the same for you.
