Random question popped into my mind while listening to the Movin' on Theme, but do locomotives shift gears, like automatic transmission cars?
Steam locomotives? No. Diesel-electric? A transition from series operation to parallel operation (I think that is the move) is made when a certain speed is reached; I am not sure if this can be termed a shfting of gears.
And, speaking of gears, a certain writer of western novels thinks that steam engines have gear boxes which pop as they cool. He also thinks that they have deadman controls.
Johnny
I once rode on a Whitcomb 20 ton locomotive that actually did have a gear shifter. The engineer would shift about three times as we went along. There was no clutch in case you are wondering.
Mechanical transmission diesels, Kraus Maffai, have shifting gears. Diesel electrics do not. DC motor diesel electrics have series, series with field shunt, parallel, parallel with field shunt, four electrical connection modes of operation to insure motors and generators operate near maxium efficiency at varouis wheel and motor speeds (listed low to high). AC motor diesel electrics have motor voltage and current and frequency electronically controlled on a continuous basis, with nothing analogous to shifting gears.
Movin' on? You mean the old 1970's TV show about truckers?
Diesel Electric locomotives do have gearing between the traction motors and the axles but it doesn't work like a car or truck transmission...
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
Mr. Railman Random question popped into my mind while listening to the Movin' on Theme, but do locomotives shift gears, like automatic transmission cars?
Transmissions match the speed of the prime mover to the speed of the vehicle so that close to full HP output can be attained at any speed.
Locomotives do this electrically by having the engine drive a generator and motors powering the wheels. The "shifting" is by varying the excitation of the main generator to get the right mix of voltage and current. At low speed - low voltage, high current. At high speed - high voltage, low current.
It doesn't have discreet steps (gears) like a car transmission. It's continuous - more like a CVT transmission....
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
oltmannd Locomotives do this electrically by having the engine drive a generator and motors powering the wheels. The "shifting" is by varying the excitation of the main generator to get the right mix of voltage and current. At low speed - low voltage, high current. At high speed - high voltage, low current. It doesn't have discreet steps (gears) like a car transmission. It's continuous - more like a CVT transmission....
It is called "Transition" and it is done because the DC electric motors produce a counter voltage the faster they go. They get to point where the counter voltage won't let the motor go any faster.
Now, when you are riding the loco and it changes transition it will feel exactly like a gear change in an automobile. Sometines this change is very hard and sometimes you will barely notice it. The new EMD SD70's change down transition particularly hard and I know of one engineer who said it caused a broken knuckle in his train. This is the only time I have heard of this happening, but, I can understand why. What I don't understand is why the SD70's change transition so hard.
.
Looking only at the gears, a diesel traction motor has a pinion gear that drives a larger gear on the axle. You will see that stated as a ratio, which actually counts the teeth on each gear.
The only way to change that ratio is to dismantle the truck and physically change the gears to a set having a different ratio of teeth but the same distance between motor shaft and axle centers. It has to be done in a back shop, not in operation.
Chuck
My recollection is that on the first generation of diesel electrics transition was a manual operation. On later generations transition became a automatic function, which it remains today.
Never too old to have a happy childhood!
BigJim oltmannd Locomotives do this electrically by having the engine drive a generator and motors powering the wheels. The "shifting" is by varying the excitation of the main generator to get the right mix of voltage and current. At low speed - low voltage, high current. At high speed - high voltage, low current. It doesn't have discreet steps (gears) like a car transmission. It's continuous - more like a CVT transmission.... It is called "Transition" and it is done because the DC electric motors produce a counter voltage the faster they go. They get to point where the counter voltage won't let the motor go any faster. Now, when you are riding the loco and it changes transition it will feel exactly like a gear change in an automobile. Sometines this change is very hard and sometimes you will barely notice it. The new EMD SD70's change down transition particularly hard and I know of one engineer who said it caused a broken knuckle in his train. This is the only time I have heard of this happening, but, I can understand why. What I don't understand is why the SD70's change transition so hard.
And, if you go back to GP30s and GP35s (and SD45s), you have a bunch of stages of traction motor field shunting as well as transition. (what a disaster!)
GP40/50/60 do not have any transition or field shunting.
SD50/60/70 have generator transition which occurs at nearly full load. There are two sets of winding in the generator that can be in series or parallel. Don't know why a 70 would be worse than a 60, though.
Transition and field shunting are just an accommodation to get a bit more full HP speed range - kind of like having a two speed differential on a truck. The real "gear" work is done by the excitation system.
BaltACD My recollection is that on the first generation of diesel electrics transition was a manual operation. On later generations transition became a automatic function, which it remains today.
Manual transition remained on switchers for a while longer, sometimes "forward" transition was automatic, but "backward" was not. I suspect the reason was to save a few bucks and give the engineer a bit more control. The Reading SW1000s came with manual transition.
There was an interesting story in Trains some years back about some early E units where the entire consist made transition automatically at nearly the same exact speed, creating quite a jolt as the power came back on and the slack ran back out. It was solved by detuning each end of each locomotive so that each truck would make transition at a slightly different speed.
tomikawaTT Looking only at the gears, a diesel traction motor has a pinion gear that drives a larger gear on the axle. You will see that stated as a ratio, which actually counts the teeth on each gear. The only way to change that ratio is to dismantle the truck and physically change the gears to a set having a different ratio of teeth but the same distance between motor shaft and axle centers. It has to be done in a back shop, not in operation. Chuck
I know that passenger diesels have different gearing ratios than freight units for higher speeds.In some cases freight railroads have regeared units for specialized high speed service. Good examples were UP's "Fast Forties" which were SD40-2s geared for high speed (over 80 MPH) service on the Transcontinental mainline..
carnej1 tomikawaTT Looking only at the gears, a diesel traction motor has a pinion gear that drives a larger gear on the axle. You will see that stated as a ratio, which actually counts the teeth on each gear. The only way to change that ratio is to dismantle the truck and physically change the gears to a set having a different ratio of teeth but the same distance between motor shaft and axle centers. It has to be done in a back shop, not in operation. Chuck I know that passenger diesels have different gearing ratios than freight units for higher speeds.In some cases freight railroads have regeared units for specialized high speed service. Good examples were UP's "Fast Forties" which were SD40-2s geared for high speed (over 80 MPH) service on the Transcontinental mainline..
The analog would be the gear ratio of the differential of a car.
I've heard full forward of the Johnson bar in a steam locomotive refered to a "full forward gear", and full back referred to as "full rearward gear." Why I don't know, there's no gears involved, unless this is modern terminology reflecting everyones familiarity with the automobile.
Firelock76 I've heard full forward of the Johnson bar in a steam locomotive refered to a "full forward gear", and full back referred to as "full rearward gear." Why I don't know, there's no gears involved, unless this is modern terminology reflecting everyones familiarity with the automobile.
Probably because it operates what is called Valve Gear.
dBigJim Firelock76 I've heard full forward of the Johnson bar in a steam locomotive refered to a "full forward gear", and full back referred to as "full rearward gear." Why I don't know, there's no gears involved, unless this is modern terminology reflecting everyones familiarity with the automobile. Probably because it operates what is called Valve Gear. And the varying degrees of the Johnson Bar affected the valve timing of the pistons - in a internal combustion engine it would be referred to as 'variable valve timing'.
BigJim Firelock76 I've heard full forward of the Johnson bar in a steam locomotive refered to a "full forward gear", and full back referred to as "full rearward gear." Why I don't know, there's no gears involved, unless this is modern terminology reflecting everyones familiarity with the automobile. Probably because it operates what is called Valve Gear.
And the varying degrees of the Johnson Bar affected the valve timing of the pistons - in a internal combustion engine it would be referred to as 'variable valve timing'.
BigJim It is called "Transition" and it is done because the DC electric motors produce a counter voltage the faster they go. They get to point where the counter voltage won't let the motor go any faster.
A couple of points:
AC motors also have a "counter voltage" (AKA back EMF) that increases with speed, a permanent magnet synchronous motor coupled with a voltmeter will make a respectable tachometer. This is why the AC drives for traction motors are variable voltage as well as variable frequency.
The counter voltage on the DC motor represents the conversion of electrical to mechanical energy (or vice versa when the motor is acting as a generator), where the amount of power converted is "counter voltage" times the current. For a constant power drive, such as the Lemp system, the current is inversely proportional to the voltage.
- Erik
"Valve gear", OK that makes sense. Thanks!
"Gear" that you bring to enable you to do something....sleeping bag, canteen, rifle to get your deer, camera, tripod, memory card to take photos,..... rods, levers cranks, to permit steam input and output from locomotive engine's cylinders.....
"Gear" that consists of machined ridges and gaps that interlock and serve to transmit energy by moving when a rotating gear engages another. Traction-motor or rack-and-pinion?
About gears: DC motor-ed locomotives could have gears allowing 100 mph or 55 mph maximum speed; same motors=same starting tractive effort with similar weight on drivers.
There's a "critter" here in Central Ca. that has a 1930's floorshift from an automobile transmission.
The KM hydraulics on SP that I worked used gears to reverse but acceleration used movement of fluid from torque converter to "another stage different range" torque converter; three of them.
Previous revalations about transition open a lot of subjects.
SP's SDP-45's were rewired to lock in parallel circuits on starting, 'cause the amount of time for transition to occur somewhere around 23 to 26 mph was too much of the running time between stations....when they succeeded the FM Trainmasters.
SP's Alco's were modified to make engine loading and turbo-smoke more agreeable.
Other subjects from other subjects....go
,
GM and Westinghouse DC motors had a variety of gear ratios. For those sets, the total number of teeth added up to 77. Here are some pretty standard ratios:
65:12 Top speed about 50 MPH. Switching, heavy freight.
62:15 Popular freight ratio. Top speed about 65MPH
60:17 Fast freight or mountain passenger (Think SP FP7s on the "City") Top speed 70-75 MPH
58:19 Dual-service freight/passenger. Top speed 80-85MPH.
56:21 Passenger mid-high speed (Santa Fe F3s/F7s) top speed 102MPH
55:22 High speed pasenger. Mostly found on E-units
The GE motors from the same era have corresponding speed ratios, but not the easy 77-tooth count. The only one I can remember off the top of my head is 74:18 for freight engines (about 65 MPH)
For a time in the 1960s and 70s SP stenciled the ratio on truck frames.
Transition is also part of Electric streetcar, MU and locomotive operation.
rcdrye Transition is also part of Electric streetcar, MU and locomotive operation.
"Transition" on DC streetcars, MU's and locomotives was the speed control, running in series-parallel on a four motor unit would give half the speed of full parallel, with field shunting used to give higher speeds. The resistors used for starting were not intended for use longer than 30 seconds to a few minutes at a time. Transition pretty much disappeared when chopper controls became practical.
Perhaps the ultimate in electric locomotive transition were the Milwaukee Bipolars which could operate with all 12 motors in series, 2 sets of 6 motors in series, 3 sets of 4 motors in series or 4 sets of three motors in series, along with field shunting.
efftenxrfe "Gear" that you bring to enable you to do something....sleeping bag, canteen, rifle to get your deer, camera, tripod, memory card to take photos,..... rods, levers cranks, to permit steam input and output from locomotive engine's cylinders..... "Gear" that consists of machined ridges and gaps that interlock and serve to transmit energy by moving when a rotating gear engages another. Traction-motor or rack-and-pinion?
Homonyms is, I think, the word we need here. Two words that sound the same and in this case have the same spelling but have different meanings.
There are gears in an automobile transmission. There is also Walschaerts valve gear. They are quite different.
John WR efftenxrfe "Gear" that you bring to enable you to do something....sleeping bag, canteen, rifle to get your deer, camera, tripod, memory card to take photos,..... rods, levers cranks, to permit steam input and output from locomotive engine's cylinders..... "Gear" that consists of machined ridges and gaps that interlock and serve to transmit energy by moving when a rotating gear engages another. Traction-motor or rack-and-pinion? Homonyms is, I think, the word we need here. Two words that sound the same and in this case have the same spelling but have different meanings. There are gears in an automobile transmission. There is also Walschaerts valve gear. They are quite different.
Of course a Shay locomotive uses both types of gear(s): Steam valve gear (Stephenson, IINM) as well as transmission gears (albeit quite different than an automobile)...
Carney,
What's this "Stephenson" stuff. Adlai Stephenson was a guy who ran for US President. No one named Stephenson ever had anything to to with trains. Don't you know anything about railroads?
John WR Carney, What's this "Stephenson" stuff. Adlai Stephenson was a guy who ran for US President. No one named Stephenson ever had anything to to with trains. Don't you know anything about railroads?
One should be careful about opening one's mouth wide enough that a foot can be inserted.
George Stephenson
and his son
Robert Stephenson
John WR Carney, Adlai Stephenson was a guy who ran for US President.
Adlai Stephenson was a guy who ran for US President.
Adlai Stevenson also served a term as governor of Illinois and was the US Ambassador to the United Nations at the time of the Cuban missile crisis.
Hit this link and read the descriptions:
http://www.steamlocomotive.com/appliances/valvegear.php
.....I'm sure I was being kidded as you know what Walschaerts refers to...
Beaulieu,
Everyone knows that the steam locomotive was invented in the U S of A by....well, his name escapes me at the moment. But he sure wasn't no fancy schmancy British guy. That Wiki article is a forgery. Are you sure you didn't just make it up?
Next thing you'll be telling me Americans didn't invent canals either.
John
John WR Beaulieu, Everyone knows that the steam locomotive was invented in the U S of A by....well, his name escapes me at the moment. But he sure wasn't no fancy schmancy British guy. That Wiki article is a forgery. Are you sure you didn't just make it up? Next thing you'll be telling me Americans didn't invent canals either. John
Everyone knows the Martians invented canals..
I had thought that anyone who knew the history of steam locomotives knew of Stephenson valve gear (which was invented by William Howe, the head pattern-maker of the Robert Stephenson Locomotive Works; Mr. Howe did not realize the great value of his design, and sold it to Mr. Stephenson for twenty guineas (if you do not know what a monetary guinea is--whereas a pound sterling was twenty shillings, a guinea was twenty-one shillings--, your education has been neglected), who obtained the patent for the gear about 1842).
In 1844, Egide Walshaert, the foreman at the Belgium State Railway shops at Brussels, patented his valve gear. However, his design was used mainly in Belgium, despite its advantage over the Stephenson gear (it is entirely outside the wheels, and is thus easier to work with), and it was not until about 1897 when it began to be used extensively in the construction of locomotives in America.
In 1912, William Sherman Brown, a locomotive engineer of the Southern Railway, patented the Southern valve gear, and it was used extensively on Southern locomotives.
The above information (except the value of a guinea) comes from the 1922 edition of The Locomotive Up To Date.
Our community is FREE to join. To participate you must either login or register for an account.