Can anyone explain hows a three cylinder locomotive worked?
You know about 2-cyl engines -- right? In the US, if you're standing on the right side of the engine and the crankpins are at 3 o'clock, so the piston on that side is all the way forward, then the piston in the left cylinder will be midway along its stroke and the left crankpins will be at 12 o'clock. Two-cylinder engines always have the cranks 90 degrees apart.
A theoretically lovely idea: have three cylinders, with two on the outside, 120 degrees apart, and a third one on the engine's centerline, driving a crank on one of the axles. Might be the same axle as is driven by the outside cylinders, but in the US the center cylinder usually drove the axle ahead of the axle driven by the outside cylinders.
In the US, the centerline third cylinder almost always drove the second or third driver axle, so its axis had to be inclined so its rod stayed above the driver axle(s) ahead of its crank. So its crank wasn't 120 degrees from the outside cranks. (9-1/2 degrees of inclination on SP and UP three-cyl engines, as I recall.)
Adams1 Can anyone explain hows a three cylinder locomotive worked?
Another variant:
Ed
Google 'Swiss drive' for an explanation about 120-degree motion being inherently in balance. In practice you might see a locomotive phased differently as all three cylinders will be double-acting; Smith compounds, in particular, had the outside-cylinder rods and gear quartered for 'normal' balance and the middle cylinder at an appropriate angle to them.
Actuating the valves on that center cylinder could be interesting, particularly if the inside main rod acted on a driver pair in second or even third position with the crank webs occupying a substantial part of the space between the frames. Hence you see the Holcroft and Gresley 'conjugated' gear, which derives the motion for the center valve from the motion of the outside valves and typical valve gear, and in either lever or whip-shaft form is entirely forward of the cylinder casting (or indeed of the structure of a cast engine bed).
In practice several factors conspired to introduce progressive lost motion and slop in this gear, and (for example on some of the UP 'Nine' 4-12-2s it was replaced with a whole third set of radial valve gear on one side.
Overmod, And how many people own an HO, N or O Scale Indiana Harbor Belt Class U4a - the world's largest 0-8-0, designed to push endless strings of cars over the hunp? Three cylinders (Gresley Valve Gear) - and it had a tender truck booster, too! (And, yes, I own one)
Gresley conjugated valve gear - Wikipedia
IHB+0-8-0+Switcher.jpg (998×521) (ogaugerr.com)
I have one in HO and one in O that isn't built (but not with the motorizing kit). I had one years ago that I rebuilt into a 4-8-4...
Easily the greatest of the 0-8-0s, although there were 'certain' 2-8-0s that were in its league...
I don't remember it as a hump locomotive, though; wasn't it transfer power for long heavy cuts?
BEAUSABRE Overmod, And how many people own an HO, N or O Scale Indiana Harbor Belt Class U4a - the world's largest 0-8-0, designed to push endless strings of cars over the hunp? Three cylinders (Gresley Valve Gear) - and it had a tender truck booster, too! (And, yes, I own one)
Me, too.
Lookin' like practically EVERYONE's got one. Or more.
IHB had at least one hump yard. Something had to do the pushing.
DPM's write-up with the U-4a photograph implied that they also worked heavy transfer runs. IHB had humps at both Gibson and Blue Island.
The German S 3/6 Pacific has four cylinders and theres one in the railway musem at Nordlingen that is active for excursions and one in the Deutsches Museum in Munich. The Brits used a lot of 3 cylinder locos, too.
Alco pushed the three-cylinder concept hard in the 1920's and had some good points concerning the same, but the overwhelming majority of railroads didn't want anything to do with it. They just didn't want the maintenance headaches of a third cylinder.
Three-cylinder engines in the US tended to be simple.
Four-cylinder tended to be compound (articulateds are NOT in this conversation).
Leaving out Shays, I expect there were a lot more of the latter than the former.
My favorites of the 4-cylinder locos are the SP&S Atlantics. Atlantics tend to be either graceful, or not. These were not.
They bought 10, that were delivered in 1909. They were simpled in 1923/4.
Here's a picture of one pulling train 6 (I think). You can tell it's not a compound anymore, because the counterweight on the front drivers is in the normal location. It was placed in a very weird spot on the compounds (see Santa Fe, below).
Here's a 4-cylinder Santa Fe 4-4-2:
It, too, has that counterweight in the "funny" position, as you can see.
Showing a bit more enthusiasm than SP&S, Santa Fe had 172 of them, in 7 classes.
I suspect all the 4-cylinder compounds were scrapped or simpled before the first of the three-cylinder locos was produced. Hope not--I like them.
So, all four cylinders are lined up laterally across the front? And the two high-pressure ones have rods to cranks on an axle under the boiler. Or are the low-pressure ones the inner ones? Hard to tell which are which.
Still in training.
Lithonia OperatorSo, all four cylinders are lined up laterally across the front?
That was the case with European four cylinder locomotives. Here in the US the Vauclain compound four cylinder locomotives had the cylinders stacked, for lack of a better term, two per side, high pressure on the top, low pressure on the bottom. Most of the time anyway.
It should be noted that when the "superheat" process was invented it killed the compounding concept here in the US which made American railroaders very happy, those compound locomotives were a pain to maintain.
It goes without saying we're leaving out the Mallet type locomotives, a whole 'nother animal.
Lithonia Operator So, all four cylinders are lined up laterally across the front? And the two high-pressure ones have rods to cranks on an axle under the boiler. Or are the low-pressure ones the inner ones? Hard to tell which are which.
Yup. I'm sure the inside cylinders were the high pressure, because of space constriction.
What is quite interesting is that this design was "fully" balanced.
Oh, yeah. I was trying to find a picture of the cylinder layout of the above, but found THIS instead:
That "thing" is a booster engine. A 4-4-0 woulda been the American answer, but in Bavaria, we do things better!
There were two 'Vauclain compounds': the type with the common crosshead and valve, usually with HP above LP except where space didn't permit; and the later balanced type with four cylinders abreast (which I recall as also having only two valves and complicated passages)
One of the more famous configurations was the de Glehn compound, now called by courtesy de Glehn - du Bousquet, which usually has the HP to the sides, driving on the normal main, and the LP with their greater reciprocating mass side by side in the middle, ahead of the HP, a bit like Woodard's Central Machinery Support.
Cole compounds, the Alco contender in the years before the Schmidt superheated changed the game, were also a line-abreast arrangement.
For completeness we should add tandem compounds, terrifying in normal reciprocating locomotive practice but just fine in steeple compound motors like the Willans high-speed engine, and the somewhat inexplicable Plancher system (I encourage someone to explain the actual point of it to me...) There is also the Shaw, a casualty of increasing 'hog' size but interesting for high-speed reciprocating locomotive design.
There is a tandem compound engine in the stern-wheeler towboat on display at Keokuk, Iowa.
Lithonia Operatorall four cylinders are lined up laterally across the front?
In the US, inside cyl on 4-cyl engines usually drove the second axle, so inside cyl were usually inclined. There were a few exceptions -- some UP 4-4-2s and one class of SFe 4-6-2s come to mind. They drove the second axle with horizontal cylinders, which meant the inside rods had to banjo around the leading driving axle.
Baldwin built the SP&S (and matching GN) compound Atlantics. I'm looking at a builder's photo of the GN engine, and you can see the cylinder caps for the high pressure cylinders. They are horizontal, and set inward from the low pressure cylinders. The valves are mounted higher, and inwards.
The HP cylinders drove the front axle--very straightforward, though it seems the rods would be kinda short.
The LP drove the rear axle.
Baldwin also built the Santa Fe engines. The layout was roughly similar to the above engines, but ALL the cylinders drove on the front axle. I'm looking at a drawing for the cylinder casting, and it matches my description above.
7j43kin Bavaria, we do things better!
Well, German machinists aren't shy about showing off how good they are!
Flintlock76 7j43k in Bavaria, we do things better! Well, German machinists aren't shy about showing off how good they are!
7j43k in Bavaria, we do things better!
When I started work in a machine shop, my boss was Austrian (took over from a German, who was retiring). He wasn't a show off, but he was VERY good. And a very nice guy.
He said, in Austria, when he worked there as a machinist, he would go to work wearing a suit and carry a briefcase, then change for work, and etc.
He said it was common practice.
Here, he wore mostly slacks and a sports shirt. Sometimes, if we poked him enough, he'd do some real machine work again. Then he'd put on a shop apron over his clothes.
Our shop, by the way, was spotless. The lighting was excellent. The tools were in top shape.
At the Deutsches Museum in Munich, there are three complete machine shops. One is from about 1900 with all vintage lathes, kerosene lighting and so forth. One is from the 1960s-1970s and one is ultra-modern with CNC equipment and other modern items. When I was there about 5 years ago, there were about 6 men, all middle aged working in the 1960s shop. I suppose that was the equipment that they were most familiar and comfortable with.
Our community is FREE to join. To participate you must either login or register for an account.