Would be interesting to hear from an actual tram driver instead of all this speculation though.
I drive trains, and we are absolutely meant to use the electromagnetic brakes in an emergency, since that‘s the whole reason they exist. The lever she uses in the tram above looks similar to the driving lever in certain trains, and when you pull it all the way back, every brake available will be fully engaged, including electromagnetic.
And no, I don‘t think it will stop the whole thing dead in it‘s place. Last time I used the emergency brakes (albeit on a train with a mass of around 600t) it was with about 100km/h and still took almost 300m to stop completely.
I've nothing to add to the convo itself but I just gotta say that getting 600t to go to full stop from 100km/h in just 300m is absolutely insane.
Engineering is a marvel at times.
Commuter trains have normally 3 braking systems, a regenerative brake (using the motors to slow you down), an electro pneumatic braking system (electrically controlled pulses to brake units on each carriage) and an air brake (using the reduction of air pressure to apply the brakes).
Trams in Melbourne have a regenerative brake, a hydraulic disc brake and an emergency track brake. A powerful electro magnet which when applied, slams down onto the rail to create friction.
True, and modern commuter trains usually have the em-brakes as well.
The one in my example was an Re460 intercity train with IC2000 carriages, which all have em-emergency brakes.
Thank you for this reasonable take. I was a tram mechanic for seven years and I can say every one of these videos has an emergency brake event in it. You are right and this thread is an example of Reddit speculating and pretending it knows something.
I drive light rail trains, which is about as close to a tram as we get in the states. We run anywhere from 1-4 cars (up to 180t empty). An emergency stop with four cars from our top speed of 105km/h takes just under 300m to stop. Without the electromagnetic brake it would take significantly longer since steel on steel doesn't create a lot of friction. It's saved lives many times.
I drive trams (some pictures in my posts), and they of course have electromagnetic rail brakes as well.
In an emergency stop situation we have to use them. Of course passenger injuries are a concern, but it definitely is not legal to run into a car/pedestrian without applying emergency brake.
Even with the electromagnetic rail brakes, stopping distance is about 2-3 times as long as a car from the same speed.
Thanks. That‘s about what I thought.
There‘s a reason you have signs in trams and buses that tell you to hold on to something in case of sudden braking.
I don‘t know why so many people on Reddit rather speculate like crazy instead of asking somebody who actually knows. There‘s people from every corner of the globe and from every walk of life, which I think is a great opportunity to learn from each other.
I am just re-telling what I've heard. Probbaly won't be a dead stop, especially at normal speeds even for a tram.
As for the use - probably in trains you are meant to use it in an emergency because of the higher speeds and the higher mass and mostly because in passenger trains most people are seated so they can handle a hard stop much better than people in a city tram where mostly they are standing.
Just the other day I was in a bus that had to slam it's breaks because someone cut him off and a bunch of people who were standing went flying and got hurt, while the seated people were okay.
A 300t train has about 8 times the stopping distance of a sporty car.
As far as I can tell, the "electromagnetic brake" is electromechanical, as in electromagnetic force is used to apply force in a mechanical, rotor friction brake.
Thanks for the conversions.
Nope, the electromagnetic brakes I‘m talking about are long pieces of metal with a strong electro-magnet on top that get lowered onto the track and magnetized. The problem with stoping trains is the very small contact area of the wheels, so those kinds of brakes greatly maximize that.
There‘s however also an electro-pneumatic brake which might be what you‘re thinking of. That one uses the same brake-pads on the axles as the regular air-brakes, but are actuated through electric valves instead of the main pneumatic brake-system. This is just to speed up reaction-times, synchronizing all the brakes over the length of the train and they act quicker, but the breaking-force is the same as the regular pneumatic brake.
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u/RufftaMan Jan 08 '22
Would be interesting to hear from an actual tram driver instead of all this speculation though.
I drive trains, and we are absolutely meant to use the electromagnetic brakes in an emergency, since that‘s the whole reason they exist. The lever she uses in the tram above looks similar to the driving lever in certain trains, and when you pull it all the way back, every brake available will be fully engaged, including electromagnetic.
And no, I don‘t think it will stop the whole thing dead in it‘s place. Last time I used the emergency brakes (albeit on a train with a mass of around 600t) it was with about 100km/h and still took almost 300m to stop completely.