What was more important in the transformation of railway motive power, at least in North America, the diesel engine or the electric transmission?

If the diesel engine had not been developed (nor the gas turbine either), would the locomotive fleet today be made of gasoline (or similar distillate) engines married to electric transmissions?

Or say the diesel engine had been developed but not the electric transmission. Would we be primarily be pulling trains with diesel power but mechanical or mek/hydro transmissions?

Or would these lackings have driven us to electrify? Or stick with steam?

I think this could shed some interesting light on our history as it did turn out.

Steve

I think they go together. There is a long history of gas-electrics, and an almost equally long history of 'heat engine' locomotives with other than electric drive. Not to mention the adaptation of steam to work with electric drive, which goes back at least to the Heilmann locomotives.

The combination of the reliability and good thermal efficiency of the diesel engine with the flexibility of the electric transmission -- and, perhaps more importantly, the development of proper governors and excitation control -- are the first half of the thing. I could also mention the protracted problems with gasoline as a railroad fuel; while it might be fair to consider how the great strides in automotive practice might have been applied to railroad-size powerplants, I think the fire danger would far outweigh any potential efficiency gains... which would still likely be short of what diesel power would accomplish at the same general level of sophistication.

The second half is the effective horsepower increase possible out of a single diesel engine without compromising reliability or economy.

Note that I consider the development of cost-effective AC electric transmission to be far more significant than all the work done up to that time with DC motors. And that the extension of higher horsepower to engines derived from 'marine' practice (notably the EMD 265H motor and GE's 6000 hp 'equivalent' went too far: there are ways to deal with the resonances and cavitation at those HP levels in a railroad locomotive, but they ain't easy, and might not be reliable enough for typical current operating conditions.

There are two interesting areas where I think 'game-changing' opportunities were lost, both of them from the late '40searly '50s: the Bowes Drive, and the use of free-piston powerplants (the great future hope of Hamilton, then Lima-Hamilton, then Baldwin-Lima-Hamilton... then GM, then periodically others... ;-} I personally think the intake-tract noise problem could have been addressed, and the issues with asynchronous bounce firing solved (especially with the advent of electronic control systems).

Free piston? Wasn't that the one where the engine only served as a gas producer for a turbine? I cannot imagine anything more ridiculous. All of the disadvantages without the benefits. I can't see how pistons, even free moving ones would make for a better source of hot gases than a turbine type compressor and ordinary combustors.

I do believe engine size will continue to grow. Eight or ten or even twelve thousand horsepower on a six or eight axle platform has no place in railway service as we know it but coupled to two, three, or four slugs (AC traction, inverters aboard the slugs, connection at the DC link level--there could be an automatic connection at the tops of the units) and impressive cost savings over multiple full locomotives could be achieved. The mother would cost only a little more than a present full locomotives. The slugs, while obviously far more costly than the junkers that are now turned into slugs, would be a fraction of the cost of a full loco. I need a patent attorney.

Steve

I would suspect that electric would have come to the forefront. I do know that the Southern Railway gave serious consideration to the electrification of the CNO&TP in the 1960s/early 70s. Electricity is the power of the future-the only question is how do we generate it?

It was the Woodward governor, which married the two into a workable system that deserves the credit. Prior to that, one had seperate throttles for the electrical side (generator excitation) and throttle (for the prime mover). It was workable, but prone to error. The Woodward Governor changed that, integrating both into a single throttle input for the engineer, taking the guess work of matching RPMs to generator excitation.

I can see you have little knowledge of the state of the art in turboshaft engine development in the '40s and early '50s... ;-}

One point of the free-piston engine is that no compressor is needed to sap a large percentage of the turbine power. Another is that the peak gas temperature is limited in ways not possible with cans -- certainly controllable to what turbine alloys could withstand even at comparatively high shp (= high gas mass flow through the turbine). Yet another is that the combustion effectiveness at part throttle/high turndown is more like that of a positive-displacement motor (which, of course, is essentially what a free-piston combustor is...)

Believe me, that many engineers wouldn't have given free-piston all the attention it's gotten over the years if straight Brayton-cycle turboshaft were more efficient.



And the whole shebang goes down with any failure in the prime mover -- or the consist has to be broken up with the road slugs redistributed to other consists ... where, not coincidentally, they wouldn't be needed because other consists would already have a full contingent of useful slugs.

Sadly enough, there is already a prime mover capable of reliable power over 8000 HP from a single block. It's a Fairbanks-Morse... and IIRC the company owning the rights, since it also has the ex-Alco 251 tech, won't let the OP engine be adapted for locomotive service.

Bigger than that: you run into packaging problems, then you run into cooling problems; then you run into pollution problems; then you run into engine-longevity issues. Developing high horsepower out of a cast block causes ultrasonic vibrations at points in the casting, which causes cavitation wear in the coolant. There's an empirical 'sweet spot' for engine size somewhere in that 4500 HP range, where economies of scale for the powerplant are high, but deleterious effects aren't manifest -- not coincidentally, this matches what can be run through six axles' worth of AC drive.

Turning to a different way to accomplish the concentration, installing multiple 'power modules' onto one frame (like a genset locomotive on steroids), with road slugs or MATEs giving the extra axles, isn't really a good idea either (with the possible exception of 'married pairs' (or triplets) where the operating cabs are on the slug/battery carrier, for reduction of NVH). There's a point at which distributing the engines across the consist gives better flexibility and all that -- see how Mr. Dilworth set things up.

Note that the current scam in 125-mph-plus passenger locomotives (which is the only place high power density really pays) is to use the moral equivalent of Paxman Valentas -- in the case of Siemens, a somewhat-sensible Cummins QSK, in the case of Progress/EMD a rather loony 1800-rpm C15. These might already be 'too far' for the expected longevity of railroad 'power by the hour' quality guarantees...

"Sadly enough, there is already a prime mover capable of reliable power over 8000 HP from a single block. It's a Fairbanks-Morse... and IIRC the company owning the rights, since it "

Has FM-Alco actually sold any 251's for locomotive service?

@Overmod: Thanks for the interesting info about free piston engines. Must read up on them.

The objection to concentrating so much HP into one power plant could also be applied to the unit reduction that has taken place since the days of the FT. At this point, the limitation isn't too much HP concentrated in one machine for reliability's sake but that we're probably reached the limits of adhesion and TE. Much higher HP in a single unit might be good for passenger but not for freight. The cost savings for single power generating units at each point (leading and DP positions) will be too huge to be ignored. Make them reliable enough and breakdowns will be seldom enough that it won't override this.

@David: I think you are overstating the importance of the Woodward or any governor which simply operates the fuel racks (or throttle on a gasoline engine) to maintain a constant engine speed under different loads. Typically what that speed is varies among the control notches. I think what you're after was an invention primarily by GE's Hermann Lemp which was a clever arrangement of field windings of either the traction generator or in some cases an auxilliary which automatically balanced things out to fully load the engine to just the right amount for different engine speeds.

That's what eliminated the separate engine throttle & generator field controls back in the gas/electric era. With Lemp's system, even if the engineer did have direct control of the engine throttle, the system still properly loads the generator to match the engine's capability.

There is some discussion of this in Nov. 1966 TRAINS ("Where Would Dieselization Be Without GE?" but a better explanation is in RYPN contributor David Hamley's article in Jan. 1974 TRAINS ("How it all began--3 / How to Control an Engine of Limited Power").

if the diesel engine (gas also) never developed, and include this with automotive gas cars,
we would see first a stronger interurban network, more streetcars, steam locomotives might have transitioned to steam turbine or switch to overhead electric nationwide.
Automobiles probably would still be about with electric versions, but we would see more intimate connectivity with railroads instead of cars.
Or else we would go to propane powered engines. But thruout the 20's on theres been many experimental engine versions.

You have to consider today the fuel crunch we are looking on towards alternative fuels, and one day someday the hand may be forced on us to make some changes, we're trying to find new fuel by fracking, do alternate fuel creation and so on.

You forget, the fuel rack is only one of the items controlled by a Woodward governor. It also controls generator excitation, via the load regulator.

Jeff

Consider when a nation doesn't have oil. And it can't depend on imports, or for strategic reasons refuses to. The answer to that question is all over Europe. What you get is electrification. Europe was electrifying even before the diesel came along, but when it did, they kept electrifying. So there is your answer: the electric transmission.