For those interested in such things, there’s a fascinating video of what’s involved in starting up a steam locomotive:
A somewhat related question: What does it mean that Engine 611 is “slipping” in Ashville?
It’s like a burn-out for trains. Train people can’t get enough of it, apparently. Notice the effect at the 2:53 mark in the video. See how fast the wheels are turning? They’re slipping on the track.
The video description says it takes six to seven hours to fire the locomotive up. Six to seven hours. :eek: They must have really hated turning them off…
I have no idea. I came across it on a name search a few years ago.
They still run steam trains here in Portland during Christmas. Santa is on board, and the locomotive is decked out in lights.
Sometimes it is necessary. But it is not just a matter of time. Cooling the boiler and brick work down and then relighting it off and heating it back up ages the boiler and brick work.
I’m not sure if anyone explained this, but on these condenser locomotives, the steam went to the condenser (to be cooled back down reused) instead of being vented out the stack. Which meant they needed an alternate method to generate the draft. So condenser locomotives had steam-driven fans to provide the draft. That’s why the condenser version of the above-mentioned Class-25 has the distinctive “banjo face”.
Images of exploded locomotives are instructive for understanding just how complicated the internals of a boiler were. see item #3 in this list of historical nightmare photos for examples.
To expand on Bear’s answer, this was was done quite early in the development of steam locomotives by George Stephenson himself. Not only that, it was accidental. Steam was, indeed, originally vented to the atmosphere directly from the cylinders but people objected to the noise. Stephenson then changed the ducting into the smokebox to muffle it and – who’da thunk – it greatly improved the draft as well. Smokeboxes developed into wonderously complicated things, as this photo shows.
The tapered structure coming up from the bottom center is the blast pipe and the exhaust steam is introduced into it to shoot upward into the bell-shaped fitting coming down from the top; that’s the base of the smoke stack. The small pipe coming in from the right and wrapping around the top of the blast pipe is the blower. When a locomotive is standing still there’s no exhaust to aid the draft so the blower valve is opened to help maintain the air flow. It’s not as great as the effect the exhaust has but you’re not consuming steam as nearly as much as when you’re moving, either, so it works out. That’s why even a standing locomotive always has this hissing sound, even without the safety valve opening.
The plate in the back with the small holes is the front of the boiler; the small holes are the firetubes which convey the hot gasses from the firebox to the smokebox, heating the water in the boiler as they do so. The larger tubes with the small tubes snaking out of them are the superheaters. Steam collected from the top of the boiler contains water droplets and is at the temperature of the boiling point of water – about 360[sup]o[/sup] for a boiler at 150 psi. From the steam dome the steam is conveyed by tubes into the superheaters where it can be heated like any other gas to several hundred degrees higher than the saturated steam is.
This has several advantages among which is efficiency. In US locomotives the superheater piping is introduced into the front of the superheater tubes, runs the length of the boiler almost to the firebox, then does a 180 to exit out the front of the boiler for use. The locomotive pictured was built in New Zealand and doesn’t appear to do this; I have no idea why. The big loopy pipes are used to convey steam into and exhaust out of the cylinders.
Re: Torque at startup. For steam locomotives it isn’t zero – they could not start at all if that was the case – but it is notably lower than after it is moving. Some railroads would add a booster engine to the trailing truck of the locomotive or to the front truck of the tender to help with this, but they were not very popular. Electric motors are the opposite, maximum torque at stall. During the transition from steam to diesel-electric a common expression among railroaders was, “Steam can move more than it can start – diesel can start more than it can move.” You can overload a motor to get a train moving but can’t sustain it without overheating issues after a few minutes.
I’m curious why. Internal combustion engines have low torque at low RPM because they have a limit on how much fuel/air each piston can suck in per cycle. But steam engine pistons should be able to exert full force (steam pressure x piston area) regardless of speed. I thought booster engines were mainly for added traction (additional drive wheels), not added torque.
As an aside, it doesn’t take much to keep a stopped train stopped. Everyone’s placed pennies on tracks to be flattened, right? But if you put a penny on the track right next to the drive wheel of a stopped locomotive, it won’t be able to start: It’ll just spin in place indefinitely.
You don’t seriously think this is true , do you? Am I being woooshed??
I’ve not heard that, but I have heard that back in the steam days, a penny tucked under each of the drive wheels of a locomotive would stall it because it could not generate enough torque to lift itself that tiny amount. Having no idea whether it’s true or just another false factoid, I did not mention it in my post above.
You would think so, but a technique used to start trains back then but no longer needed was to back up a few feet – depending on the train length – to take up all the slack in the couplers, then start forward. That way you’re starting one car at a time instead of all of them at once. Experienced trainmen in the caboose would know this and brace themselves when they heard the noise of the slack running out coming at them; the caboose would start with a big jerk (No, not the engineer :)).
This was despite starting a train with the valve gear “in the corner,” that is, admitting steam to the cylinder for the entire stroke. As the speed increased the engineer would gradually “hook her up” – setting the gear so steam is admitted for less and less of the stroke. The reason for this was two-fold.
Using the maximum amount of steam this way uses up steam, and thus the water and fuel to generate it, at a truly awesome rate, making the guy in charge of buying it cry.
Moreover, the ports for admitting and exhausting steam to the cylinder are only so big. If you’ve got, say 200 psi in the boiler and push the pistonhead back with steam for its entire travel length, when it comes time to reverse direction you’ve got 200 pounds on the one side and pretty close to 200 on the other and have to literally push it through the port to move the piston.
Much better is to adjust the valve gear so it admits steam to the cylinder for only part of the stroke and let the steam expand to move the piston. That way when it’s time to reverse the piston’s direction you have 200 psi on one side and (ideally) atmospheric on the other. The locomotive isn’t so musclebound and the stockholders will cheer at the reduced fuel costs.
Here is a Very Large locomotive somewhere in Nebraska running at 70+ mph. You’ll notice that while it isn’t exactly stealthy, you’re not hearing the barking chuff of a locomotive dragging a train upgrade. The cutoff has been adjusted to perhaps 10% and the throttle opened just enough to overcome wind and rolling resistance to maintain speed. If you back up to 3:30 or so you’ll hear 844 actually working a bit as it accelerates and climbs what passes for uphill in Nebraska.
No a steam engine produces max torque when starting, but minimun horsepower. When a engine is stopped full steam pressure can be admitted to the cylinder for the majority of the stroke. At full speed with full load the steam is admitted for a shorter part of the stroke. The reasoning behind a penny being able to keep an engine from moving is not lack of torque but lack of traction. The idea is the engine will not have enough traction to lift the weight of the engine up and over the penny. Me I believe the drive wheel will suck the penny under the wheel and spit it out the other side and the move on.
Moving the Johnson bar from one “corner” to the opposite corner will change the direction of the engine. The Johnson bar controls the Stevenson links on the engine and is put in the "corner to produce max torque. If the engineer then opens the throttle to fast the wheels will spin. So it is slow and easy.
The timeing of the inlet and exhaoust valves are determined by the Stevenson links. For Max torque the inlet valve will open near TDC and close about I believe around 2/3 down the stroke. The exhaust valve will open before BDC (sorry I have forgotten by how much maybe just shy of 1/3 from BDC.) And it will close just before TDC. By linking the engine in and out efficiency can be obtained. With the engine fully Linked in the inlet valve opens before TDC and is open shorter. About 1/3 of a stork or less. The exhaust valve will open just before BDC and close before TDC.
So on start up with the engine linked out there is more pressure in the cylinder when the exhaust valve is opened, more noise. When running at speed linked in there is less pressure when valve opens. Less noise. If the train starts up a hill and slows down. The engineer will have to link the enigine out for more power.
Linking an engine in and out is all about improving fuel and water efficiency. Fuel cost money, water has a volume and weight. use less and nees less. simple.
The slacking of the trains couples is to require less traction to start the engine. I have seen diesel engines do the same.
Dang it. The words “valve gear” in my post were supposed to include the link to the Wiki page on the subject. There were all kinds of valve gear over the years for railroads. As Wiki puts it, “Valve gear was a fertile field of invention, with probably several hundred variations devised over the years. However, only a small number of these saw any widespread use.” As the name implies, Stephenson gear was earlier and popular until around 1900 with Walschaerts being more popular after that, again, on the railroads. If you’re truly a snipe you’re probably more familiar with Stephenson because it never really fell out of favor in marine applications so long as reciprocating engines lasted.
Some years ago I was a passenger on Delta Queen and was delighted to find they allowed passengers in the engineroom so long as they were just cruising and not busy working their way to a pier or something. Instantly as I came down the ladder I was like, “Oh, wow! Stephenson link!”
“You know this stuff?”
“Book knowledge only,” and explained the love of railroads connection, ending with, “I’m more used to something about an eighth this size, simple instead of compound, and not being worried about condensers.”
Likewise, when I toured below decks on Hornet the docent, a retired engineering officer, mentioned feeding the superheated steam back into the saturated side and I said, “Huh. On railroads once the steam’s been superheated they don’t let it come anywhere nearthe water surface again before they use it once and throw it away.” This led to a fifteen minute discussion about the merits of fire tube vs. water tube boilers, compound vs. simple, and why railroads rejected condensers that I’m sure was boring a hell to the rest of the poor souls on the tour.
I’ve seen diesels back the slack out of four or five cars before starting a train but not the whole train, like I mentioned with steam.
I have a training model of a steam engine. It is on a flat board. It was designed as a learning aid. My Dad used it to better understand the actions of the valves and the Stevenson links on a marine engine. He was studying for the Unlimited 3rd Assistant Engineers test given then by the Comerance Department. You can use the model to see what happens when linking in or out.
I use to like to watch the making up of trains in the Watsonville rail yard. you could hear them put the slack in the trains and then pull the slack out when going forward. Some of those freight trains ended up being around 100 cars.
While in New Orleans my wife and I took a river trip. I spent 90% of the time in the engine area. Double expansion condensing engines. Had a good conservation with the fireman/oiler. Engines small enough did not require a licensed engineer, which surprised me. He was only certified. It was an interesting trip. Wife was a little upset that I did not spend much time with her on the romatic river trip.
Wife <-> Steam engine = no contest
My knowledge of the penny holding a train comes from my uncle, who used to hang out at railyards a lot, and was quite the prankster in his younger days. He’d actually done it.
And what you really need is a wife who also wants to spend time with the steam engine.
Hard to find.
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