Athearn LPG Tank Cars: "Flat Panel" Tanks Fatter than "Early" Tanks?

[tehachapifan]

My question is primarily regarding N scale but am also curious about other scales too in comparison to the prototype.

I recently discovered that the top of my N scale Athearn LPG "flat panel" tank car was sitting considerably higher than my Athearn "early" LPG tank cars. Originally thinking it had something to do with the trucks or how they are mounted, I started to examine things a bit closer and found that the trucks and their mounting seem identical between the two. It was then that I realized that the tank on the flat panel appears to have a considerably larger diameter than the early cars. I busted out my trusted calipers to find that the battery is dead, so I can't absolutely confirm this. However, this sure seems to be the case from looking at the two side-by-side. Has anyone else noticed this? Is this prototypically correct? It seems the two cars carry the same amount of product, so the larger diameter seems a bit of a head-scratcher.

[sd45elect2000]

Car capacity is different. If you have a magnifier look at a CAPY number. The cars came in a few different sizes from 25,000 to 30,000 gal.

[tehachapifan]

I don't think that's it. While it's hard to see clearly in most proto photos even with magnification, it appears the stencils on flat panels are around 148,300-149,200 for LD LMT with around 113,800 for LT WT. Whereas, the early styles cars are around 152,500 for LD LMT with around 120,500 for LT WT. So, unless I 'm figuring it wrong (possible), it appears the early cars actually have more capacity than the flat panels. Where I could be making a capacity error is with the commodity the car is (currently) set up to carry, in regard to a particular commodities weight vs. pressure. What would help is to see the water capacity stencil, which is typically way too small to be able to read from photos.

[sd45elect2000]

Usually the ends of the cars have the liquid capacity. There are a couple of other things to look for. The DOT 112 car is a pressurized car and the DOT 117 is pressurized and insulated. The insulation and the jacketing add another 8 inches or so to the tank diameter. I have a bunch of LPG cars in my yard now, I'll take some pics of them for you if you wish.

Randy

[tehachapifan]

That would be awesome! Thanks!

[nkalanaga]

"Capacity" for a tank car can be complicated, as it depends on the density of the contents.  A tank may have a higher weight capacity, but if it's made for a denser product, have a smaller volume.

[cv_acr]

That's kind of the point of the flat panel, to keep the body within AAR clearance plate diagrams on curves.

[Ed Kapuscinski]

That's kind of the point of the flat panel, to keep the body within AAR clearance plate diagrams on curves.

Chris beat me to it. This is the reason.

[tehachapifan]

That's kind of the point of the flat panel, to keep the body within AAR clearance plate diagrams on curves.

I knew the flat panel thing came to be for clearance issues, but I had either heard or assumed that the panel came to be after the earlier cars were found to have some clearance problems in or around loading/unloading facilities (where curves are probably their tightest and there are gates, etc.). Is it an absolute known fact that the panels exist because they increased the diameter of the tanks and not because of what I thought? Remember, there were some ATSF/BNSF 8-40BW's that were built with gull wing cabs and some that were not for clearance purposes. The cab on the gull wing version was not taller or bigger, AFAIK.

[Ed Kapuscinski]

I knew the flat panel thing came to be for clearance issues, but I had either heard or assumed that the panel came to be after the earlier cars were found to have some clearance problems in or around loading/unloading facilities (where curves are probably their tightest and there are gates, etc.). Is it an absolute known fact that the panels exist because they increased the diameter of the tanks and not because of what I thought? Remember, there were some ATSF/BNSF 8-40BW's that were built with gull wing cabs and some that were not for clearance purposes. The cab on the gull wing version was not taller or bigger, AFAIK.

The gull wing was actually a clearance thing, but not an AAR plate clearance thing. I believe it was to clear specific coal loaders or something like that.

[tehachapifan]

The gull wing was actually a clearance thing, but not an AAR plate clearance thing. I believe it was to clear specific coal loaders or something like that.

Right. And do we know this is not the case with the flat panels and, if so, what is the source of this info? Not trying to be argumentative but I don't want to close the case because it sounds plausible.

[pedro]

I was going to write that earlier but I couldn’t remember where I read it. Another anecdotal vote here for the flat panel existing to satisfy AAR plate requirements on the fatter tank. Someone else will have to provide hard evidence!

The ATSF gull wing cab was to clear the loadout at York Canyon mine.

[sd45elect2000]

I snapped these three this morning.

They all look to be the same size to me.

[tehachapifan]

Thanks for the photos!

Those do appear to be the same size, although the tank(s) without the flat panel appear to be what Athearn would call a "late" tank.

I guess now the question is, does an "early" tank and a "late" tank have the same tank diameter.

If so, then it would appear that all the tanks (late, early and flat panel) would be the same diameter.

[James Costello]

@tehachapifan  Back when Athearn and Walthers introduced these cars in HO, noted tank car historian Tim Frederick compiled this handy document discussing the 3 different Athearn bodystyles:

http://tankcarhomepage.railfan.net/misc/Athearn_LPG_101_v2.pdf

As mentioned previously, the flat sides are to enable the tank to stay within plate clearances.

"Insulated--insulation forces introduction of flatsides to stay within Plate C clearances"