no…emergancy is…full service is ok to stop with… the thing with going to full service is to make sure you set your first service reduction to get an application on the the train first…then you can do as deep as you want into the air without any problems… you have to remember that full service is a brake application at service rate… the air exhosts slower out of the system then it dose in emergancy… emergancy clamps all the brakes on as hard as it can to all the cars at exactly the same time…going to full service from relese without going first service will only disable the uniform application throught the train…insted of all the brakes setting up at exacty the same time with first service…you get a brake application simmiler to the AB brake valve…where it starts to apply from the end end to there rear first… you get some slack runin…but not as bad as if you went to emgergancy…also if you go into emergancy you disable the PC switch and will lose power after 10 seconds and on many units DB. and you might be wanting them for a controlled stop… emergancy is just that…in an emergancy…and if you have to use that…odds are what is going to happen to the train behind you is the lest of your worries at that very moment in time…
"Blowing by the current record-holder—the French TGV, with a maximum operating speed of 186 mph—East Japan Railway’s Fastech 360 train will carry travelers at a top speed of 224 mph and is expected to hit speeds above 250 mph in test runs. This year East Japan Railway began testing a prototype with two uniquely shaped nose cones—at 52 feet, the longest ever—that reduce drag
The Spoilers on commercial aircraft are more to “Spoil the Lift” than as a drag measure…spoiling the lift insures that the weight will get on the wheels, so the brakes will be effective, and not lock the wheels up and slide. Notice that they are programmed to pop out as soon as there is a little weight on the wheels…it’s called a Squat switch, because it deploys the spoilers when the aircraft squats on the landing gear…it also has to be armed to actually do that properly, otherwise it would interfere with trying to take off…
On military aircraft, and on some civil aircraft, actual speed brakes are used to deploy into the “slip stream”, to create additional drag. On light civil aircraft, this is one method of slowing down a very aerodynamic aircraft quickly to get to the correct approach and landing speed, it lets you keep your speed up untill just before configuring to actually land. Otherwise, you would have to start "Coasting " well before the landing pattern…On military aircraft, speed brakes do the same thing, but it also allows (or requires) flying an approach with more power on the aircraft…retracting the speed brakes to gain more power is much quicker than the time required for the jet engine to “Spool Up” from near idle to full power…especially usefull when trying to land on a postage stamp at sea…sometimes called an Aircraft Carrier. (OK, it looks big when you’re standing on it, but try looking at it from 1000 ft up…)
Back to the high speed trains…just imagine what the maintenance requ
G’day, Y’all, Disk brakes were mentioned in a recent post. Are these ever used on freight cars? Seems like these would offer much less maintenance on wheels. The article in Model Railroader several months ago, noted that Budd advertisements boasted of much longer periods between maintenance on passenger car trucks when disk brakes were used.
On freight cars, simplicity is paramount. Freight car trucks are 3 pieces. The brake parts are mostly interchangeable. On some cars you will stencilled “AAR 18 BRAKE BEAM”. That is what the shoes attach to. Any manf. AAR 18 brake beam will fit that car. Brake shoes can be changed in about a minute, needing only a prybar. Wheelsets on freight cars can be changed out pretty quickly, just gravity holding things in place. Passenger car trucks are far more complex, so changing wheels takes more time. You also use the train air brakes more on a passenger train, keeping the train streched out to avoid slack action for the passengers, management, etc. Budd disc brakes have the advantage there.
I’ve seen them on freight cars over here, but never over there.
Disk brakes do reduce wheel wear by around 50%, but leave the wheel more succeptable to both rolling contact fatigue and contamination build up which reduces adhesion. Plus, the vehicles I’ve seen with disc brakes also have block brake handbrakes.
There are freight cars with high speed trucks and disc brakes, because they run in passenger trains - express freight cars.
What about a brake shoe that applies to the rail head instead of a wheel’s circumference? What if this shoe were several feet long? I vagely remember something about this feature in some light rail trucks.
How about this, for an even more radical idea - Such a shoe containing field coils to apply said brake by attracting to the rail.
What if these field coils worked in conjunction with a locomotive’s dynamic brakes.
What if these same coils could repel the rails to reduce wheel loading! Why go through the complexity and energy intensive magnetic levitation of a train completely from the rails, simply reduce wheel loading and friction!
Don’t rush off to the patent office just yet, it’s already been done.
Magnetic track brakes are used on trams and high speed tains for emergency braking, The theory is a brake carrier with coils and a friction surface is suspended between the wheels of a truck, When the coils are energised magnetic attraction pulls the carrier down and the friction surface contacts the rails and provides a retarding force. Currently these are only used for emergency and parking brakes because it is difficult to control the the braking rate.
Eddy current brakes use a non contact method where coils in the carrier induce currents in the rails which give a braking force. These were tried in Japan and Germany but they were found to heat the rails up too much and the induced currents in teh rails interfered with the signalling equipment.
The problem with using the DB power is that dynamic brakes produce a lot of current, I’ve seen figures as high as 700 amps per loco quoted, and that is not constant over the speed range of the train. Track brakes only work on 40 or so amps at 24 volts, so you’d need a heap of them to handle the power. Of course another difficulty is that freight cars don’t have any electricity on them to operate the equipment anyway…
Reducing the loading on the train wheels is a bad thing. You need the load to generate both the tractive effort to get the train moving and also the forces needed to guide the train along the track, especially through curves.
Not sure - there’s all sorts of HTML junk showing, almost as if it’s copying and pasting the whole web page into the reply when you hit the “quote” button - which web browser do you use ?
If you want to do it manually, put the word “quote” (without the ") inside square backets at the start of the text block you want to appear as a quote, and then “/quote” (without the ") inside square backets at the end of the block. Do the same thing using “url” to create hyperlinks.
Tony
(the quoted part of this message was created by hitting the ‘quote’ button instead of the ‘reply’ button)
Looks like you’re using HTML tags instead of “forum code” tags. As was mentioned, the forum code uses the square brackets instead of the “less than” and “greater than” signs. Aside from that, many of the tags are similar in concept, if not syntax.
If you go back into your quoted post and make those replacements, you should see most everything turn out right.
At low speeds your max braking rate will be limited by wheel slide. At high speed, wheel slide will also be a limiting factor, and the consequences of wheel slide are more severe. Also, it had generally been believed that adhesion goes down at high speed – hence the original high-speed trains being MU – but wheel slip control has modified that restriction, hence locomotives on high-speed trains. The main limiting factor at high speed then will be heat dissipation – have you seen the pictures of those huge multi-rotor disks on TGV axles?
I like the example of the Boeing 777 landing distance. While the 777 has rubber tires and reverse thrust, the brakes on an airplane have stricter heat dissipation constraints as they have to be light so the airplane doesn’t carry extra weight in flight. On the other hand, high maintenance is accepted in airline operations in terms of frequent replacement of brakes, and on some military aircraft with very high landing speeds – B-58 Hustler, English Electric Lightning – brakes that had to be replaced every few landings were accepted. But while the details of whether the jetliner actually compares with the TGV need more work, it gives a very good engineering ballpark estimate of what kind of stopping distance to expect.
The heavy braking for a TGV isn’t just a matter of safety, it is also a matter of keeping the schedule. If you brake at too leisurely a pace, you spend less time at your high cruising speed and your overall trip time will increase. While they say jackrabbit starts and stops waste gas in your car, they do save some time – the wild cab ride effect.
I have no idea what train handling manual you are talking about, but, go tell whoever wrote it they might as well shove it where the sun doesn’t shine. TOTAL BS!!!
Sounds like something out of Nick’s train handling book!
csx98,
You of all people should know that is not the way brakes work! If it did, you would be picking up brake beams and other assorted parts all over the place.
To the others,
All of this 2 -2 1/2 mile stopping distance is basically a bunch of hogwash thrown around a campfire at night. Sounds impressive, but that’s all it is, a bunch of talk.
Grades will effect stopping distances as much as anything. Ascending grades will shorten and descending grades will lengthen stopping distances. Snow can really effect stopping distances, but that is out of the normal range of this conversation.
csx/98 is right about one thing, I can’t stress enough how important the proper use of the “first service” brake application is! Let me say that one more time, I can’t stress enough how important the proper use of the “first service” brake application is! The first service brake application takes all of the slack out of the brake mechanism putting the brake shoes against the wheels and getting them heated up. This effects any further applications to the point that one pound could make you or stop you.
I mis-spoke, I should have said, the use of train air brake to control speed is discouraged. Throttle modulation, and dymanic braking are the preferred method of speed control.
And I really can’t tell the Senior Road Foreman of Engines to shove it, and not find myself in an investigation. Especially, now that we have Mr. Tony “I want to fire everyone” Ingram and his cabul of rules facists over here, instead of over there.
I know what he is trying to say, but, written that way it is still pretty stupid. Being that you can’t use but so many axles of D/B to begin with, how does he expect you to control the train going downhill when the D/B won’t hold it?
Let me try. Contrary to popular opinion, the problem isn’t the weight. The problem is that the maximum braking force the hopper car can generate is set so that the wheels don’t slide when it’s empty.
An analogy. If you are riding on a bike and you stop from 20 mph or so by dragging your feet, you can probably get stopped in pretty short order. But, try to stopping your car from 20 mph by dragging your feet… Same braking force - much greater inertia, so much longer stopping distances.
If the weight difference between a loaded and empty frt car is not too great, then the difference between loaded and empty stopping distances isn’t too great. The same goes if you are dealing with trains that have mixture of loads and empties. But with unit trains, the difference can be extreme and the push for greater loaded capacity and lower tare wts only makes matters worse.
But you can fit load-sensitive brakes to get round the loaded/empty brake force problem (as described in the ‘Empty/Load Sensors’ section here http://www.railway-technical.com/brake2.html )
Most RRs no longer have a Caboose on them, they have a End of Train device or a (EOT) on the Engines there is a device mounted near the Radio called a Head End device or (HTD) these are another means to stop the train other than Emergency Braking and Engineer Reduced Braking. HTDs & EOTs set the Brakes from the rear of the train rather than front to rear. This means shortens the stopping distance.[tup]
What would make you think that? Why would you think that a train going into emergency from the rear would stop any quicker than one going into emergency from the head end? Do you have any idea of the how much higher the percentage of breaking in two would be if the train went into emergency from the rear rather than the head end?
Have you ever operated an EOT? Do you have any idea how long it takes for them to react? I would imagine that you would think, as I at first did, that as soon as you flip the switch the rear of the train goes into emergency. That is not always the case.
The purpose of the EOT is not to put the train in emergency to stop any quicker, the purpose of the EOT is to put the train in emergency in case of a trainline blockage. In other words, in the name of safety.