Steam & Excursion > Steam Locomotives---how efficient are they?

A friend of mine and I were discussing how efficient, or inefficient, a steam locomotive really is. I realize they are a maintaince nightmare but really, how efficient are they?


steamjocky

Pretty poor actually. I don't have an engineering degree, but can tell you that a lot of heat, even on more modern locomotives, goes up the stack.
Part of the problem is the constraints given by track gauge & height limits & that 99% or better of the boilers were of the fire-tube type.

Tom

If you mean, what percentage of the heat in the fuel appeared as work at the drawbar-- in the US, simple engines rarely did much better than 6%. And that's on test, with the newest designs. Fleet average for all fuel burned by all engines on the RR probably didn't exceed 4%.

I think timz's exactly right. While I've purposely stayed away from this question due to my over-arching love of the steam locomotive, there can be no question the figures are that low.

Some special experiments have proven things could be improved, such as the Class 26 4-8-4 "Red Devil" in South Africa and others. However, even the late U.S. power likely failed to exceed 6% in regular service.

That said, I don't care. They sure as hell "hauled the mail", didn't they (what am I say, "don't they")??? :)

John

Consider that 3985 uses 50 gallons of fuel oil and 200 gallons of water in a mile, it certainly doesn't give one the impression that it's very efficient.

"Consider that 3985 uses 50 gallons of fuel oil and 200 gallons of water in a mile"

That's on the level? With how much train?

N&W ran some fuel comparison tests in 1947 with a Y6 (#2145). From Glen Lyn to Walton, overall efficiency at the drawbar varied from 6.319% using 2" x 0" coal to 6.954% using 2-1/2" x 1-1/4" coal. This section of road is generally 0.1 % to 0.2% upgrade following the New River. Average operating speed was about 20 mph with about 9300 tons.

N&W also tested a J in 1945 to determine operating efficiency gains when the boiler pressure was raised from 275 psi to 300 psi. From Roanoke to Elliston, overall efficiency at the drawbar was 5.768% with 1065 tons. This is a generally moderate upgrade section, with an average speed of about 44 mph. On Christiansburg hill (generally 1.3% upgrade), from Elliston to C-burg, the same measurement was 5.503% with 1065 tons at an average speed fo 37 mph. With 1758 tons, overall efficiency at the drawbar was 5.217% at an average speed of 24.6 mph.

There were advantages to using compounds at low speeds.

Don't have any comparable data for the Class A yet.

Ah, but the entertainment efficiency is right up around 99%, at least for me.

This is only meaningful if we have some comparison figures. How efficient is a diesel, from input BTU's to drawbar? Plenty of heat going up the stack, the radiators, and heat off the electrical gear, too. And for further comparison how efficient is a large fossil fuel power plant where they pretty much have all the room necessary.

One of the great inefficiencies on a steam locomotive is that the boiler is overfired, that is, made to produce more steam than a unit of that size can efficiently produce. To efficiently produce steam in the quantity needed would require a much larger boiler than is practical.

The mechanical efficiency of a steam locomotive is quite good, but it's the thermal efficiency that kills you. Remember that all the steam, combustion gases and smoke fuel going up the stack, which is what makes steam locomotives the dramatic machines they are, is energy going to waste. In theory, you could use a water tube boiler, with artificial draft, and a condensing steam engine to increase the efficiency, and both of these have been tried. But I fear that photo runbys would no longer attract many photographers.

As to diesel locomotives, I believe their efficiency runs in the mid-thirties.

Don Park

"As to diesel locomotives, I believe their efficiency runs in the mid-thirties."

Overall? You mean the diesel itself is in the forties?

Figures from V L Smith, Diesel D to L, 1979 Trains mag. GP38 in BTU's 33.5% 225 hp parasitic load fuel & water pumps, fans etc for 2000 HP at crankshaft. Generator effiency 95%, traction motors gears and cables 86% for 1634 HP at the rail. 2225 divides 1634 so 24.5% of BTU's for traction at the rail.

Does anyone happen to have data on a tons(coal) per hour basis? I'm curious as to how much a large loco like a Y6 would cost to operate/hour in fuel. I'm guessing CAPP coal is around $55/ton right now.

$55/ton for coal
Wonder what diesel is per ton. A gallon is about 10lbs ,
a barrel is 45 gallons?
2000 lbs /ton?
Crude @ $63/brl
$2800/ton for crude..someone please check my math.

Maybe a case can be made for steam.
If maintenance levels and employment levels could be at
what's current with diesels, maybe..
Around 1980 Withun and Rowland had a computerized
compound , onboard gasiification fro coal steam engine
called the AC3000. BN apparently were interested in placing
a 50 unit order for a higher HP 4-8-8-2 but cancelled.
part because of declining crude prices and the advent of
4000HP 3rd generation diesels. They apparently had the
fuel efficiency , emvironmental, employment , utilization
and maintenance questions dealt with. My concern was the
realtively low level 3000 HP (diesel equivalent HP), which
wouldn't have excited anyone. But the fuel cost and no electricals to maintain was a postitive.
ron

Scoopcat Wrote:
-------------------------------------------------------
> Figures from V L Smith, Diesel D to L, 1979 Trains
> mag. GP38 in BTU's 33.5% 225 hp parasitic load
> fuel & water pumps, fans etc for 2000 HP at
> crankshaft. Generator effiency 95%, traction
> motors gears and cables 86% for 1634 HP at the
> rail. 2225 divides 1634 so 24.5% of BTU's for
> traction at the rail.

That was 25 years ago. I would bet improvements have been made. In particular, 86% for "traction motors gears and cables" seems low.

During the tests cited above, the Y6 burned 8,927 lbs per hour working time with the smaller size coal to 8,197 lbs per hr working time with the larger sized coal. The purpose of the series of tests was to determine the advantage of using screened/sized coal instead of coal with a lot of fines. That's why less of the screened coal was used to move about the same tonnage over the same line. The overall efficiency at the drawbar was also higher.

Very interesting thread here.

I think dkpark hit it well on the head. Late steam had particularly good mechanical efficiency, and had steam continued this would only have improved as the use of roller or similar bearings was extended further and further into loco design.

Oh, nycman, I think the entertainment factor's closer to 99.8%.

John

"Ah, but the entertainment efficiency is right up around 99%,
at least for me."

nycman: Never has it been said better!!

For others: A gallon of diesel fuel weighs about 7 lbs.
For fuel, there are 42 gallons per barrel.

It's funny how the electric transmission is always cited the diesel's biggest drawback, as one of the major advantages any sort of "new steam" would have. True it's expensive, requires maintenance, and is a significant failure point. But it seems to me that it was and is one of the two reasons for the diesel victory (the other being quite simply the elimination of the boiler and everything that goes with it).

The electric transmission is what lets a diesel pour on full horsepower at 0 MPH when starting. It's what allows starting tractive effort which is based almost entirely on weight-on-drivers irrespective of power plant HP. It's what allowed diesel-hauled trains to do away with many/most helper districts. It comes at a price but look at what it gives you.

When I look at pictures of trains taken back in steam days, I usually see two or three locomotives. I've seen a few pictures with four steam locomotives. It's not uncommon to see a train these days with six to eight engines at the head. Why is that?
Is that why they were able to do away with a lot of the helper stations? The diesels stay with the train for the whole trip?