WHY DOES BIG BOY'S TENDER HAVE 14 WHEELS? A LOOK AT CENTIPEDE TENDERS | Railroad Economics 025

[00:00:01]I have been fortunate enough to uh just because of where I live in Ohio, I have been able to catch Big Boy, I think six times now on its uh America 250 tour.

[00:00:14]And I heard one interesting question when Big Boy was stopped in Ripley, New York, a little boy pointed and said, "Mommy, why does that thing have so many wheels?" And he wasn't pointing at the locomotive. When I turned and looked, he was pointing at the tender.

[00:00:30]And yeah, look at that thing. It has a lot of wheels, seven axles.

[00:00:36]And in my brain, I'm like, well, because of weight.

[00:00:43]And I kind of left it at that. But that that question, this was last month. I heard I heard that little boy say that. And that question kind of lingered.

[00:00:53]And I I looked it up and sort of sort of the answer is sort of, but there's more to it. My name is Mark Magna and this is Railroad Economics where we explain why the railroads do what they do and how the business really works.

[00:01:13]Today we're going to talk about not modern freight cars or anything like that. Let's we're going to talk about Big Boy's tender and why 85 years ago now, Alco, the American Locomotive Company, gave Big Boy a what what what is called a centipede tender. All those little little wheels along the tender with the nice chrome almost like hub caps.

[00:01:40]Reminds me of a Brio locomotive. But why why did they do that? And we we'll start with the obvious. Big Boy's tender is enormous. It carries 25,000 gallons of water. Originally, it also carried 28 tons of coal. Just the water weighs more than 200,000 lb. add all that coal on top of it and the tender itself, like just an empty tender, now you're looking at over 400,000 lbs rolling right behind the locomotive.

[00:02:19]That's a that's a loaded tender. the the water, the coal, the tender itself that I think it's I I think the number I came up with was actually closer to 430,000 lb, but just let's just say 400,000 400,000 lb plus to be to be safe. So, yeah, that requires a lot of wheels. But here's here's the interesting part.

[00:02:43]That still doesn't answer why Union Pacific wanted a 400,000 lb tender in the first place. Now, let's let's take a step into the the time machine.

[00:02:56]Imagine you are running Union Pacific in 1941.

[00:03:00]You just spent the equivalent of $5 million building the largest steam locomotive on Earth. Big boys, when they were delivered, they they cost the railroad about 200. But if you adjust for inflation to today, yeah, they they they would have run about 5 million, the equivalent of about 5 million.

[00:03:21]When when does that locomotive when does that massive investment when does that make money? Well, obviously when it's pulling freight, not when it is stopped taking on water or taking on coal, not when it is sitting in a terminal.

[00:03:40]Every stop costs time and time costs money. It's a cliche, but it's true. So, management gave the design engineers a very simple objective.

[00:03:55]Keep the locomotive running. That business decision immediately created an engineering problem.

[00:04:03]If you want the locomotive to travel farther between stops, you need more water. More coal, a lot more. Water weighs just over 8 lb a gallon. So 25,000 gallons, that's a little over 28,000 lb of just water.

[00:04:24]Suddenly, the engineers weren't designing just the locomotive anymore. They were designing a rolling water tower. And that's where the 14 wheels on Big Boy's tender come in. If you tried carrying all that weight on fewer axles, each axle would place dramatically more force on the railroad. More stress. More stress on the track means more maintenance means more restrictions.

[00:04:53]So the the solution could not be to carry less because then Big Boy would not have been moving. The solution was to spread the weight over more axles.

[00:05:03]But Union Pacific didn't simply stick the tender on a couple of giant trucks.

[00:05:10]Look at the yellow tenders behind Big Boy. They're just on on massive uh massive trucks. Instead, they created one of the strangest tender designs ever built. So, a couple of things worth pointing out because I know there's going to be that guy in the comments that's going to be like, "Well, actually," and that that's okay, man. I I get it. I do. Big Boy was not the first Centipede tender. Those actually started showing up around 1939 and specifically on the Union Pacific with the FEF2 and FF3 Northerns, later the Big Boys and the Challengers.

[00:05:48]Now, was Union Pacific the first adopter of a centipede tender? That's a little that's a little fuzzy and I I don't have a definitive answer. When you do a little research, a lot of people are like, "Yeah, Union Pacific was the first railroad to use centipede tenders." But all around that same time in the very late 1930s, you you see them on Boston and Maine, New York, Central, Northern Pacific. So I I I can't say that definitively, but that they were absolutely an early adopter of these centipede tenders and they ordered them that way to keep the train moving. Yeah, it it it is called a centipede tender, at least at least by us rail fans. And here's here's where this becomes very uh this enters my my domain. This enters the domain of railroad economics. The tender wasn't carrying any cargo. It was carrying inventory. Inventory that was needed to produce the transportation.

[00:06:52]Think about Amazon. Think about Walmart.

[00:06:55]Even your your local grocery store.

[00:06:58]Businesses carry inventory because running out is expensive.

[00:07:04]Union Pacific did exactly the same thing. Its inventory just happened to be water and coal. And the larger the inventory, the fewer the interruptions.

[00:07:12]The fewer the interruptions, the more productive the locomotive. The more productive the locomotive, the more freight it can move. And one more thing worth mentioning here, the tender behind Big Boy today isn't actually the one that it left the factory with. It originally belonged to Challenger 3985.

[00:07:33]I know that sounds shocking, but during the steam era, tenders were regularly swapped around as uh just another piece of operating equipment to Union Pacific.

[00:07:43]They weren't museum pieces. They were just assets, just just machinery.

[00:07:48]If another tender got the locomotive back into service faster, then that's what the locomotive would use. And interestingly, that's exactly why 4014 uses it today. So, why does the Big Boy tender have 14 wheels? Sure, because it's heavy. But it was only heavy because Union Pacific wanted to reduce stops.

[00:08:14]That business decision forced engineers to design an enormous tender.

[00:08:19]That enormous tender required seven axles. And those seven axles gave us one of the most recognizable tenders ever built.

[00:08:29]The engineers didn't wake up one morning and decide, "Wow, it would be cool if we put 14 wheels on this thing." Union Pacific's accountants, dispatchers, operating department wanted a locomotive that spent more time earning money. And the engineers that designed this thing at Alco, they simply figured out how to build it.

[00:08:52]This is an instance where the economics drove the engineering.

[00:09:01]Just a a quick reminder to everybody. Um I I understand the the business sides of things and and you know what the stock is doing and and the annual report and stuff like that. I am not some amazing railroad historian. I probably know a whole lot more than the average person, but not nearly as much as I'm sure some of you guys do. So, in my research for this video, and this is one of the videos I've had to research more than any of the others, if if I got something wrong, please let me know. Um, you know, sometimes sources say different things and and some people were adamant that the the UP was the first company to use a centipede tender, but I really couldn't verify that. I I tried. So, if I if I got something wrong, please please let me know.

[00:09:45]With that, uh, thank you so much for watching Railroad Economics. My name is Mark Magna, and if you could, uh, hit the like and subscribe or even just watch another video, that would help the channel immensely. Thank you so much, and I will see you next time.

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