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

[tehachapifan]

@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.

Really great resource, thanks!

According to this document, the "OD", which I'm guessing means overall diameter, of the "early" car is 120.4" and the OD of the "flat panel" is 127.6". Definitely bigger and, if the bottom of each tank sits at the same level, I would assume the top of the flat panel would have to be 7.3" higher than the early tank. That seems about right looking at my models coupled together.

Assuming this document is error free, I believe the case can be considered closed.... although it doesn't explain why the pic above of the two tanks coupled appear to be the same size (the document also lists the "late" style with an OD of 120.4"). Maybe the wedge angle of the photo is somehow hiding the size differences.

[wazzou]

Really great resource, thanks!

According to this document, the "OD", which I'm guessing means overall diameter

Outside Diameter, I believe.  ID would be Inside Diameter.

[tehachapifan]

Outside Diameter, I believe.  ID would be Inside Diameter.

I flipped a coin on it being outside or overall.

For anyone interested, I got the calipers working again and measured the diameter of the two tanks and compared it to the measurements in the above link. The "early" tank comes in at 0.7580" or 121.28 scale inches (prototype is 120.4") and the "flat panel" is 0.7920" or 126.72 scale inches (prototype is 127.6"). I got these by multiplying x 160. If there's a more precise formula, please let me know.

[jagged ben]

... I got these by multiplying x 160. If there's a more precise formula, please let me know.

Nope.  By definition you can't calculate scale anymore precisly than by using the scale factor.

N scale does have some nice coincidences, like that 1/16th of an inch is 10 N scale inches, 3/8" is 5 N scale ft, 3/4" of an inch is 10 N scale ft.  But you don't need to know any of that to multiply thousandths by 160.