Steam engine theory

[ndbprr]

One of the gripes with steam engines has alway been the pounding they give the roadbed because of the mass of the reciprocating parts. Yet the basic form of propulsion is a linear output (the piston and crosshead). Why wouldn't it be possible to have a gear mounted on the center line of each axle and a rack mounted above and below the center line that could engage the gear in a push pull fashion and eliminate the main rods, connecting rods, wheel balances and reduce dynamic augmentation? Just playing with a theory here.

[ironhorseman]

I'm not sure if I can picture what you're describing. Is this anything similar to the 3rd cylindar experiment? The 3rd cylindar was unfavorable from a maintence perspective because it was a pain to try and get to and service in the shop or anywhere. If what you're describing is anything similar to the cogs and gears of shays, well, as we all know you can't get any real speed out that.

Doing away with jointed rail and going to continuous welded rail and advances in roadbed technology/construction today's modern roadbeds could probably withstand more steam engine use than decades ago, maybe. Maintence, fuel, power are among several factors, main factors, for steams' demise. What would be an interesting idea is what steam engines would look like if they were still the predominent mode of power today. I've heard that 4-8-4s were the state-of-the-art. They were the peak in steam evolution. Would steam engines be all 4-8-4s today had they survived?

[tree68]

The constant meshing of the gears would be a real wear problem. When you consider that, at speed, you would be talking 6-8 strokes per second, the tolerances would be pretty tight and the results of a failure pretty significant.

I think there was a loco that used a steam turbine to turn the drivers (PRR?), a far better solution than anything reciprocating. That we aren't seeing more of them is an indication of their success.

For all their problems, and as complicated as they seem, the classic steam loco was simplicity itself. Even your car uses a similar technology to get around.

[Anonymous]

The Pennsy and (I think) B&O had a locomotive with four cylinders, two facing forward as usual, and the other two backward. One of the advantages of this was that the thrusts of the pistons were cancelled out (in theory). But they only built those few, and I agree with tree68--the reciprocating steam locomotive was simple, meaning it usually was better than more complex designs.

See you around the forums,
Daniel

[Anonymous]

QUOTE:
What would be an interesting idea is what steam engines would look like if they were still the predominent mode of power today

Not a day goes by that I don't think about this question...

Would we have a bunch of big boy steam engines, or would they all be streamlined, or would they all be smaller and more efficient?

It's a great way to clear your mind, much like the "tree falling in the woods" rhetorical question...... what would steam engines be like if they were still being made today?

--I suppose we'll never know.

[ndbprr]

Material knowledge and life has improved dramatically and wear problems that existed in the 40's don't even exist today. Super hard wear surcaing like tungsten carbide and Glass filled teflon packing have transformed compressor life in petrochemical plants. I would expect 5-600 psi steam and short stroke lower weight components for certain.

[AltonFan]

Another big problem with steam power is that it is labor-intensive. Moreover, repair and maintenance of steam locomotives require some rather highly-skilled (and high-priced) workers: machinists, boilermakers, pipefitters, welders, chemists, etc., and many of these special skills required far more specialized training and techniques because railroad locomotive boilers are held to much higher standards than most stationary and marine boilers. It is no coincidence that very populous countries like India and China stayed with steam for so long.

Electric traction is almost the perfect form of energy for railroading. The diesel-electric locomotive is the best compromise, allowing the flexibility of each engine generating its own power, while giving access to the benefits of electric traction. At this point, the challenge is finding a more efficient, less polluting, less expensive, but still portable, means of generating electricity.

And I say all this as someone who regrets missing the steam era.

[ndbprr]

Well I'm not so sure at this point. The materials and vibration testing methods available to day are in an entirely different class than when steam was phased out. Coupled with the knowledge available in water treatment it might be far more economical than we all seem to accept as fact. Dynamic balancing alone should allow a phenomenal reduction in rod pounding. Lightweight high strength materials would allow side rods somewhere between 10-25% the weight of what was last used. Roller bearings that are sealed would elminate lubrication and dirt issues. My original thought was if a linear motion side rod could be made functional and there is no reason why it couldn't that I can see as an engineer with a metals background t could be doable. But I'm not holding my breath either. By the way electric power is absolutely the most expensive form since converting fuel to steam loses efficiency. converting steam through a generator to make electricity or turning one with an internal combustion engine does even more so steam power would always be the most economical subject to equalizing maintenance and availablity of diesels.

[AltonFan]

QUOTE: Coupled with the knowledge available in water treatment it might be far more economical than we all seem to accept as fact.

In parts of the West, farmers, cities, Indian reservations, state governments, and the Federal governement are all fighting for available water. Water treatment, shipment, and stops are costs the railroads were and remain glad to do without.

QUOTE: By the way electric power is absolutely the most expensive form since converting fuel to steam loses efficiency. converting steam through a generator to make electricity or turning one with an internal combustion engine does even more so steam power would always be the most economical subject to equalizing maintenance and availablity of diesels.

But electric traction offers a variety of advantages, regardless of the efficiency of generating electric. Ease and simplicity of control, multi-unit lash-ups under the control of one crew, and dynamic braking come quickly to mind. If traffic density makes overhead catenary economically feasible, then all the issues and costs of electric generation can be sloughed off on the firms that generate electric.

(I never really got into the numbers, but from what i understand, the steam locomotive engine was notorious for its limited thermal efficiency. Trying to conquer this drove the development of compunding, articulation, and superheating.)

And remember, the whole package has to fit in a space only so high, wide, and long, and heavy, and has to negotiate existing right of way, including tunnels, bridges, service areas, parallel tracks, and the capacity of the track itself.

Finally, the environmental regulators are now setting their sights on the diesel-electric locomotive engine, which by some reports, is a major source of air pollution. I can see some very real public relations problems from having what amounts to a furnace on wheels riding the mainlines of America, even if steam power is able to produce less, and less noisome, exhaust.

[ndbprr]

But that isn't the whole cost on Electric engines. First you need the catenary which is now in excess of $1,000,000 per mile for mainline operations plus the generating stations adn the maintenance. There is a reason no one including the PRR or its following owners has extended the electrification. When the whole energy picture was dirt cheap it made sense. It can't and won't be done now.

[CSSHEGEWISCH]

Robert La Massena wrote an article for TRAINS in 1974 with some proposals for a four-cylinder compound rigid-wheelbase locomotive with outside and inside connecting rods and poppet valves. The design was based on novel combinations of proven steam technology available at the end of the steam era (roughly 1948). What made it interesting was the lack of experimental technology in the proposal.

[AltonFan]

QUOTE: But that isn't the whole cost on Electric engines. First you need the catenary which is now in excess of $1,000,000 per mile for mainline operations plus the generating stations adn the maintenance. There is a reason no one including the PRR or its following owners has extended the electrification. When the whole energy picture was dirt cheap it made sense. It can't and won't be done now.

You will note that I said:

QUOTE: If traffic density makes overhead catenary economically feasible, then all the issues and costs of electric generation can be sloughed off on the firms that generate electric.

There are only a few places in North America where this situation prevails.

The point is, electric transmission is nearly the perfect way to drive a locomotive. Catenary and third rail power transmission are usually too expensive and or inconvenient for railroad use, so any future developments in motive power are likely to be in finding new ways for locomotives to generate or otherwise acquire electricty.

In an old issue of the RLHS Bulletin, there is an article on why the ACE-3000 project disappeared. One of the points mentioned was that EMD and GE went to the railroads sponsoring the project and told them that if they were interested in alternatives to the diesel, the railroads should leave the R&D to the locomotive builders.

[ndbprr]

OK but that is my point (and I'm not arguing here just making sure we understand each other). Traffic density has been in decline for 50 years. The only reason some lines are as busy today as they were is because other lines have been shut down. Even the corridor handles about 25% of what it did in the PRR days and with the volume the PRR had they decided it was uneconomical to continue the program. I just don't see any way to get the traffic required to justify electric engines, catenary or the maintenance required.

[foamer4000]

Who is going to invest billions of dollars to reinvent obsolite technolgy? The thermal efficiency for Union Pacific #3985 is 08.0%. Yes Eight percent. How many times can electricity be converted to get down to 8% efficiency? Don't forget that the railroad can't get enough crew trained now, how will they do it when the demand grows ten fold to maintain steam locomotives? Railroads could not afford steam engines in 1950 and they can not afford them now. Failed diesel-hydralic tests in North America is proof that American heavy haul railroading is too tough for a mechanical transmission.
Foam on

[ndbprr]

If you read the articles from the era both SP and D&RGW gave the mechanical transmission very high marks on the Krauss Mafei engines saying it was trouble free. Reason they didn't continue was the oddball factor ina fleet of diesel electric engines You can't compare 3985 to what could be done today any more than if you used a 1942 car as the basis to justify fuel consumption, power or any feature of a modern car.