OK, so you think you know everything about trains? Here’s a question about passenger cars. The conductor told me that the emergency brake (that handle found hanging at each end of each passenger car) will employ all brakes on all cars on the train. Ok, but it will also trigger the release of sand from cylinders near the base of the locomotive to create friction between track and wheels.
{Personally, I thought sand acts like ball bearings, but a technically-oriented friend of mine says it acts like sandpaper in this case. He’s also a railroader, and says this was true with older trains, but was unsure about modern trains.}
All I can tell you is about freight trains, and not that much, since I was a station clerk, not a conductor, brakeman, or engineer.
Freight trains use air air pressure to control the brakes. Every rail car has hoses on each end that connect to the other cars, and to the engine. After all the cars are connected, the brakes are bled before the train is allowed to commence its trip.
Each car has a hand brake that is used to prevent rolling when stored in a yard. Usually, the brake is set on only the first car into the track, so it won’t go off the track when other cars are backed into it.
I’ve never heard of sand being used in the braking systems of locomotive engines, modern or classic. Occasionally, a commemorative passenger special powered by a steam engine would travel our lines, but I never noticed any sand bags near the engine’s wheels. If no one here knows the answer to that question, you might consult someone at a railroad museum.
John, I have noticed that electric engines have huge cylinders near the “base” running the length of the cab. I’d suspect these cylinders would be for fuel storage - if on a diesel! What would you guess these cylinders are for? (Lubrication?) It could be sand.
Sand has in the past been used by engines to provide gripping power in icy conditions when the wheels might otherwise slip. My reference for this notion is amazingly enough the Thomas the Tank Engine series. Whether they still use sand in modern locomotives is something someone would have to provide information on.
In the computer game Railroad tycoon 2 (and the first one i believe) sand is used for traction on steeper grades and must be supplied to the trians or it goes up hill very slow. I think there is some mention of snow and ice in the manual too.
also in Brooklyn, I rember driving on a road with rails running down the middle. The rails are burried in the asphalt about up to an inch above the street level due to the street settling. The road was littered with potholes, and I found I could actually drive on the rails, avioding to potholes. when the road was wet, the traction on the rails were almost nonexistant and I can see how sand would help.
Not to nitpick, but aren’t all diesel engines electric engines? It is my understanding that diesel is used to power a large electric generator, which takes up the bulk of the space inside the body of the locomotive. This electric power operates the trucks of said locomotive.
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I don’t know about using sand for dry-weather braking, but I know they carry it for snow and ice.
On the U.S. steam engines, one (or two) of the domes or bumps on top of the boiler were sand boxes. You can spot them because they have small pipes trailing down the outside of the boiler and ending between the wheels. (One dome/bump was the steam dome where I think the emergency steam let-off valve sat.)
The new diesel-electrics also carry sand, but it is up inside the body of the engine rather than suspended below.
I suspect that the placement of the sand boxes is so that the heat of the engine will keep the sand (which can accumulate moisture) from uselessly freezing just when they need it most on an icy grade.
Sand is used on most light-rail vehicles (read trolleys) and commuter rail vehicles (subway cars) in the US. It’s applied to the rail to increase traction.
The combined blessing and curse of steel wheel on steel rail technology is low friction (compared to rubber tire on asphalt). This is energy efficient, but makes stopping difficult, especially if the rail is wet or oily. (It’s hard to stop a train, you know. )
Under these conditions, sand can be applied to the rail. On the vehicles that I’ve worked on, sand is applied automatically in emergency brake. Modern vehicles also use wheel spin/slide control (think traction control and anti-lock brakes), but sand is also available, in case these aren’t enough. Of course, sand can also be used at start-up, but the grades for new mass-transit construction aren’t very steep, so it’s not as common.
My recent experience has been with light-rail and subway cars. I defer to Tom~ regarding locomotives.
The term “electric” or “diesel” refers to the energy SOURCE much like a “fossil fuel” or “nuclear” plant refers to the source. The output is electricity from a generator.
But, even if the output is the same, that does not make an electric locomotive the same (as in equivalent to) as a diesel locomotive. Their designs are quite different.
hmmmmm Jinx, be nice… after all, steam engines are powered by burning a fuel source to generate the steam, but we didn’t call them coal engines or wood engines or peat engines, now, did we?
Names are rarely consistent with rules; electric trains are trains that obtain electricity from an outside source (such as a wire); the fact diesel locomotives use the diesel to generate electricity doesn’t mean we call them electric because it just doesn’t, not because it makes sense.
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