Could someone explain, in laymen’s terms, the idea of a geared steam locomotive please? I’ve read how they work and such. I don’t understand why they’re any better than a simple, little steam loco, or why a little steam loco couldn’t have been geared to accompli***he same thing?
Do not forget the Climax type of locos along with the others.
Logging tracks were of a temporary nature and consequently quite crudely constructed. Little grade work was done so there were numerous undulations and twists in the rail. The more rigid wheel base of a rod locomotive was just not flexible enough to traverse such track without causing too many dreailments to be feasible. There is also no way to “regear” the connection between the rods and the drivers. You can go to smaller drivers but there is a limit to that modification. The gear ratios available to the Shay, Climax and Heisler designs allowed slow speed operations of the locomotive while the cylinders were reciprocating at higher speeds. If you remember, steam engines develop their maximum horsepower when the engine is moving at higher speeds. When the rods are barely moving, the unit can stall out quite easily.
So in the end, the geared designes gave the locomotives great tracking abilities and kept the rod speeds (reduced to the wheels by gear drives) high enough to achieve the horsepower needed to get the effeciencies need to make the steam engine economical. It should be noted there were designs of rod style locomotives with two axle trucks with rod connected cylinders at each end of the locomotive that were tried. Think of a Shay with an 0-4-0 type of connection. I think the low speed of the drive rods made the design impractical in typical logging railroad speeds.
Wouldn’t it reduce the gear ratio on say, a 0-4-0 for instance, if the driving wheels were just made smaller?
I was reading about the grades these things could climb-holy cow!
One of the things that made them able to climb those big grades was that 100% of the locomotive weight was on the driving wheels. Also, the gearing down gave a small engine relatively high tractive effort (on some Shay’s, four times what the engine could achieve had it been rigidly connected).
What grades can the various steamers be able to take with little or no load?
ALL answers to your geared locomotive questions can be found here.
3 basic types
Shay, Climax, Heisler
Shays used 2 or 3 vertical cylinders mounted on the right side of the chassis. the torque from the cylinders is transfered to the drive wheels via driveshafts to bevel geared hubs on the right side of the wheels. Universal joints and expandable shafts on the drivetrains allowed for curves and rough track. These engines were very powerfull because the smaller cylinders could operate at higher pressures and higher revolutions transfering greater torque to the wheels, the bevel gearing reduced speed but transfered greater power to the axles. This is the basic principle with all geared engines.
Heisler used 2 V-mounted cylinders under the boiler which turned a driveshaft that ran centerline under the chassis to geared trucks where the bevel tranfer gear was in the mddle of the axle, not at one side like the Shay, This is also what the Climax does, however…
Climax has 2 types, the Class A and B, the Class A often resembled a flatcar with a boiler on it, which is exactly what it was with a 2 cylinder marine steam engine mounted behind the boiler with the water tank taking up the other end. The engine drives a driveshaft via a 2 speed geared transmission, the only type of geared engine to have a transmission. The Class B had two cylinders mounted more or less traditionally however at an inclined angle. The cylinders drove a flywheel like geared axle where the gearing transfered the cross chassis power 90 degrees to a centerline driveshaft and then to the bevel geared trucks.
All these engines had great ability to track across terrible track conditions and given that all axles were powered they could pull tremendous loads and climb some rather insane grades (10% being the largest I’ve heard of but I beleive the Cass RR in Virginia has some loony grades still today)
Check out the site, tons of i
I can tell you Heisler is the best geared steam engine! I run one in Freeport Illinois and let me tell you the little thing is going to be 100 in7 years and she still pulls great. Its the perfect excursion engine cause it deals with bad track a small grade ( nothing insane like 10%) and not really much in tonnage wise but back and forth 6 trips a day and it is real good on fuel and water ( even when i am being a stack rapper!) it is neat to be standing there and close your eyes on the top of our little knoll as you put the bar in the corner and pull the throttle out to its max ( well halfway is max for us) and just listen to her ROAR! Sounds like your doing 70 in a conventional steamer. Brings tears to peoples eyes ( usually due to all the cinders flying but hey you paid to ride a working steam engine not ride around on amtrak) Cant wait till next tourist season.
Much has been said about the geared locomotives abilities on rough track and steep grades, but where they really shined was on tight curves – pulling a string of short log buggies, they could navigate curves that would put a model railroad to shame. For that reason, some were used in dock yards and other urban areas.
dd
Wouldn’t a 0-4-0, or 0-6-0 steamer also have all it’s weight on the driving wheels?
I think it was the Baltimore and Ohio that owned one of the largest Shay type engines built and it was used as a helper on some grade in the East, possible Sand Patch or similar.
Murphy,
Sure, the 0-4-0 and 0-6-0 will have 100% weight on drivers. Each piston makes 1 push per wheel revolution. On a geared loco each cylinder makes 7, 10, 50 cycles per wheel revolution depending upon the gear ration. Go back to the steam engine effeciency, it is better at higher cycles than lower ones. There were locations where helpers were used to get trains started out of yards with heavy trains account the huge mainline locomotives could not get them started if there was even a moderate grade. Once they got out of the yard the mainline locos could wheel them along at 60 mph but their horsepower was all at the top end of the power curve. The rod connected switchers just would not have the effeciencies of the geared units. Besides the lack of pilot trucks on the switchers would make the steamers prone to derailing on the basic track loggers used.
Shays were popular with mechanics as the machinery was readily accessible. Also, the Shay ran “smoother” than the other types but allegedly “worked” on the rail on the cylinder side. It was also the more expensive.
Heislers could reach a higher top speed than the other types, and its two cylinders were larger than the others because of fewer cylinders in case of the Shay and higher gearing of the Climax.
Climaxes were the slowest of the lot, and tended to “buck” at higher speeds.
I’ve had models of all three types and still can’t decide which is my favorite over the decades.
I checked out this link. Very interesting, thanks. Trouble is, I’m still not quite getting it. For the most part, I visualize a geared steam locomotive as something like a granny-geared 4 wheel drive. They appear to be built for low speed hill climbing, on curvey rails. The sound of these things must be like a suzuki motorcycle on steroids. But…What makes them work better than a steamer on those types of lines?..Why couldn’t the same type of set-up been adapted to mainline locomotives?..Why only 2 or 3 cylenders? Why not a v-8 or something?
Thanks
A picture is worth a thousand words. See http://www.gearedsteam.com for pictures of various geared locomotives, including those not already mentioned here.
I once heard someone describe the sound of a Shay as that of a locomotive doing a whole bunch of miles per hour, while in reality just creeping along.
You’re right on just about all of your assumptions. The reason why they’re better on rough track goes to the wheelbase. On a rod engine the driving wheels have only limited up and down play, and virtually no side play, which is why some of the really long engines (x-10-x) had “blind” drivers, without flanges on some of the middle drivers, so they could take sharper curves.
Picture if you will a table with 4 pairs of legs. Now try to get all 8 legs on the ground on an uneven surface. Now try the same thing with two 4-legged tables. See the difference? That’s why a geared loco was better than a rod loco on uneven track. Now try to maneuver that table through your house, around obstacles. Try the same thing with the two smaller tables. That’s why the geared loco was better than a rod loco on curvy track. As I said, the granny gear thing is an excellent assumption. Each stroke of the cylinder of a rod loco moves the wheel one-half revolution. On a loco with 48" drivers, that’s six feet. A geared loco might have a half dozen strokes
Geared steam has been documented to have hauled usable loads up grades as much as 16%. The old saying was, A Shay can climb a tree if it can get a toe hold.
Larry: Thanks for the good explanation. If geared locomotives had good, slow speed traction, good low-speed torque, and work over tight, curvy,rough track, why didn’t any evolve into switchers?
Geared locomotives were used for switching, for example, Heisler #3 (1900 era) of the Westside Lumber Company in Tuolumne, CA. Its last decades of service on the logging railroad were to switch the yard at the mill, for which it was standard-gauged for the task. That was cheaper than buying anew a conventional switcher.
However, the vast majority of switching on “conventional railroads” was done on decent track and minimal grades, for which conventional switchers (usually 0-6-0s, and in the late steam era former road locomotives such as 2-8-0s) were cheaper and very effective for the job at hand.