Simply, why don;t they exist anymore and what was the “benefit” of them?
Most of the center-cab switch engines were a design outcome of a solution to cooling, electrical, and control problems when it was necessary to put two prime movers into the locomotive in order to generate enough horsepower to fulfill the performance goals of the locomotive. The low hood of the switch engine – a requirement so the enginemen could better see men on the ground, cuts of cars, positions of switches, etc., meant the only place to put a the cooling fan and radiator location big enough to cool the engine, was the far end of the hood. Placing the radiators above the engine with top-mounted cooling fans, as would be required if the engines were both in the same hood (there would be only one free end available), made the hood too high for visibility over it. Also, the center-cab design placed the generator ends of both engines against the cab, which made it convenient for electrical controls and cabling. All this saved cost, too.
The goal of this type of locomotive was high tractive effort in a single unit, which had some agreement labor issues as well. The high cost and compromises necessary for such a unit made them unattractive to most railroads, and once it was realized that two M.U.'d switch engines were a lot more economical and versatile to operate, the center cab had no future. The center-cab was almost exclusively a market idea of the minority builders who were striving desperately to differentiate themselves from EMD and Alco.
I can’t think of any significant benefits to the center cab from a maintenance or operating perspective, but lots of drawbacks.
RWM
Not what I was hoping to hear (rather hear the truth, but was hoping maybe there was a some use so I could make a center cab road switcher), but it makes a lot of sense.
Well there were little tiny centercab switchers, and huge centercab road switchers. Baldwin’s centercabs were basically two full size road-switchers put back-to-back with only one cab. In the early diesel days, the RR employee unions tried to maintain the steam-era work rule of one crew per locomotive, so theoretically if a railroad used an A-B set of F units, they’d have to have two crews on duty. (That’s why in the early days railroads would take say an A-B-B-A set of F’s and give them all the same number with a letter suffix, so they could list them as being one locomotive.)
In the late forties Baldwin attacked the problem by putting two engines together with one cab in the middle. It worked OK but was awfully big. The railroad I grew up with, the Minneapolis, Northfield and Southern, had some, but they were too big for the branch I grew up on so I never saw them in action.
From algomacentral.railfan.net:
Perhaps it helps to think of center cab switchers not as variants of end cab diesels, but rather as continuations of what was being done with electric locomotives. Place a cab at the end of the engine and either the engine has to be turned (time and expense, and sometimes simply not possible as with the big transfer diesels) or there have to be cabs at both ends (an expense, but common with some electrics and a handful of diesels). The classic old fashioned steeple cab electrics were a solution to this, so for GE to use a similar idea for its small diesels was a common sense solution
Even the famous PRR GG1 is, in a sense, a center cab locomotive, although not in the same way that we are talking about because the engineer was more or less trapped in his side.
A center cab diesel switcher such as the GE 44 tonner also tends to place the greatest weight over the trucks.
And by the way plenty of old 44 tonners are still laboring away at industries and grain elevators and such.
Dave Nelson
Hi Railway Man ,
If I’m not mistaken, Brookfield Locomotive does make centercabs and they’re fairly large loco’s, not just mining and small industrial equipment. Connecticut DOT/ Metro North is receiving Pass/Road loco’s from them. I had a magazine with some of thier loco diagrams in it, but I apoligize, I can’t remember what or where it is.
Den.
I find it hard to believe any locomotive builder built centercab diesel locomotives because it was a convention left over from electric locomotives, particularly since there were plenty of end-cab electric locomotives built in the same era for railways like GN, MILW, N&W, NH, and VGN. Small electric switch engines were often built with a center cab because the builder was trying to get the equipment onto a very short frame and needed room at each end to install the traction-motor blower and switch gear above each bogie, and didn’t want to elevate the cab above this equipment on one end, particularly since electric centercab switch engines were often height-constrained by low trolley wire.
There is no good reason or common-sense reason to put a cab in the middle of a diesel switch engine other than when forced to by the dual-engine layout, but plenty of reasons not to do it, namely cost of construction and cost of maintenance, reduced visibility for the engineer, reduced ventilation, hotter operating conditions, more smoke in the cab, etc. I’m sure there were builders who when forced into this layout attempted to market it as “safety” or “equal visibility both ways” but these are weak arguments.
The GE small diesel-electric locomotives, which used twin Caterpillar, Cummins, Buda, or Cooper-Bessemer engines (and probably some other engine makers I have forgotten about), had the same issue with providing cooling and control convenience as the larger switch engines, thus the center-cab. I’m not aware of any center-cab diesel-electric switch engine with one of its hoods empty; they were both occupied by a diesel engine in every one I’ve seen except the C-415. I recall an article discussing why the C-415 had such a strange layout but I cannot why Alco chose to do this – can someone provide them here?
Brookfield is essentially a custom builder – they never have had more than a handful of locomotives built in a year. I don&#
I have always thought that the principal reason for the small-center-cab-diesel/electric switcher was that it could employ two, readily-available-and-conventional-low-horsepower engines and their cooling systems so the cost of a 360-to-400-horsepower locomotive could be minimized. A secondary reason was that it provided excellent visibility in either direction, an attribute very useful in the switching environment.
The Whitcomb 44-ton loco was the most handsome of the breed, and the GE 45-ton side-rod model (with only two of four axles with traction motors) the most animated because of its side rods.
I invite different opinions.
Mark
The GE 45-tonner:
http://www.northeast.railfan.net/images/tr_pstd170.jpg
The Whitcomb 44-tonner:
http://www.northeast.railfan.net/images/ri367.jpg
Whitcomb also had a side-rodded 45-tonner. Davenport (and likely other manufacturers) also had center-cab diesels in the 44- and 45-tonner range. You can see lots of other photos of small diesel locomotives at the northeast.railfan.net website.
Mark
RM:
I’m not sure what makes these reasons weak versus the other reasons you gave. Every design has a handful of desirable features and a handful of bad ones. You need to look at the design as a whole, not as one attribute that might be more important to somebody.
I would think that for an engine intended for light shortline use as well as switching, having the cab in the middle would be a useful safety feature. You can’t always turn engines.
The small center-cab diesels were and are most useful in industrial settings (particularly private railroads) where the number of cars to be moved at one time is low and the distances short.
Common carriers used them mostly on branchlines and shortlines where track and bridges had low weight-bearing ability and the traffic was light. Recent decades saw the abandonment or upgrade of these lines, so either no or more powerful locomotives are required now. They were also used to switch industrial areas with tight curves and clearances, particularly in urban settings. But most of that activity has dried up, and where it still exists, the railroads use their now-nearly-obsolete conventional locomotives. Some of the center-cabs ended up as railroad shop switchers at the end of their useful careers.
The small center-cab locos were not often used for regular yard switching because they didn’t have sufficient power. Horsepower needs were normally 1,000 or more for such service.
Mark
Having had to make million-dollar decisions on locomotive questions, I’ve developed some biases, it’s true: I don’t like anything that’s expensive to maintain, if I have an alternative.
The safety value of a center-cab locomotive for grade-crossing collisions is nil because on the type of line these are used on speeds are very slow. The typical center-cab switch engine cannot operate at much above 20 mph, and at speeds in excess of 20 mph the bogies typicallly used on this type of locomotive begin damaging the truck as well as making the ride quality impossible. The standard end-cab switch engine is not significantly more unsafe than the center-cab at low speeds in grade-crossing collisions – should they even occur because speeds are low.
You’re correct that visibility on the center-cab is equal both ways. I would call it equally bad. At least on an end-cab switch engine the visibility one way is excellent, and the other way it is not substantially worse than what the center-cab has to offer. In a yard application the idea is to orient the locomotive so that the cab is facing the yard and the nose the lead, so the engineer has the best possible view of the
I don’t know what era you’re modeling but they were widespread in light industrial and light short-line applications through the 1970s. While their employment has declined significantly since then, there are still many out and about. The “center cab” feature is not the cause of why it’s used on one line or not another line, it’s merely a characteristic of the type. In other words, a railroad did not go out and say “I need a center-cab!” It went out and said, “For this much switching, and this much mileage, and this much revenue, what’s the least engine I can purchase and make it work?” And the low-cost answer for low-density industrial and short line operations was often the GE center-cab, or the competitive offering from Whitcomb. That they were center-cab vs. end-cab was pretty much irrelevant to the railroad or industry.
RWM
So am I the only person that noticed the MN&S Baldwin is missing it center axle on each truck? I wonder what was up with that?
This one was gonna be a more modern engine.
No, but I did. [:D]
I was hoping to get some unbiased data, as I did. so now I;ll tell you what I;m wanting. For grins of it, I was looking at making a GP60 center cab. Why? It looks cool. But I was wondering of the basis of the Center Cab idea to determine if it would even be useful. The 60 was gonna be used by Northern Enterprises ( A free-lance car/engine rebuilder) as a shuttle taking coaches to Amtrak stations to be taken to their private owners, a back and forth taking supplies from the mainline down the branch to the faciity, and to tote around a set of cranes for hoisting old wrecks and taking them back. But from what it sounds like, a standard engine would be better.
Your imagination ran riot. This is sometimes a good thing, but not in this instance, I think. Yeah, a standard engine would be much better. A “normal”, prototype-based center-cab would be good.
Mark
Since this is about US prototypes, I’ve held off, but here are a few thoughts:
After experimenting with a few one-off and small-run diesel-electrics, Japan’s National Railways standardized on a twin-engined B-B center-cab diesel-hydraulic, class DD13, and built them by the hundreds. They were used to replace 2-6-0s (and their tank variants) in yard switching and branchline service. On the road, they were rated at 70kph - track speed for most of the JNR’s locos.
The next step was the DD51, a B-2-B design (yes, there was a non-powered truck in the center of a rigid frame!) with two 1100hp prime movers. Intended to supplant steam in fast passenger and freight service, it was rated at 100kph - not too shabby for narrow gauge.
The DD13 has seemingly faded into oblivion, but DD51s are in operation today, some of them built since 2000.
Chuck (modeling Central Japan in September, 1964)
Chuck, the choice of a B-2-B wheel arrangement baffles me. It seems that the only purpose of the non-powered axles would be to reduce the axle loading on the track (as well as tractive effort.) Why not reduce the weight of the locomotive, or was there a desire for high-horsepower versus tractive effort? For this western-trained mind, a A-1-A+A-1-A, a 1-B+B-1, or a 2-B+B would be much more logical. Can you explain? And how about a picture?
Mark
The UP has a Gen-Set switcher, UPY 2005, that is a center cab design. Looks similiar to the old Alco C-415 type at first glance.
Jeff
Mark, you aren’t the only one scratching his head about this one. I never have heard a good excuse reason for the dead axles in the center. The Japanese rail network had/has several classes of Bo-Bo-Bo electrics, and at least one oddball with a Bo-1-Bo arrangement.
Try this link for photos:
http://www.jtrains.com/trainmodels.asp
Run down the menu for the various classes. The photos are almost all N scale (1:150) models, but they will give you the idea.
Chuck (modeling Central Japan in September, 1964)