Are there end-of-train devices that allow the engineer to apply the brakes from the rear of the train, in addition to all the usual functions of such devices. Thaf is apply and release with or without simultaneously at the front.
Most End of Train Devices today are two way ETD’s that permit the Engineer to initiate a Emergency brake application from the ETD, by triggering it with a radio signal. This type of ETD is required be used in terrirories that have a greater than 1% grade that exceeds 3 miles in length for trains that exceed 4000 tons.
No matter where the application starts from, it applies throughout the whole train. It never applies throughout the train simultaneously. Instead, the application propagates from car to car, starting from the point or origin. In the “emergency” phase, it propagates much faster than in a service application.
The above is why such a device is useful. But would a more refined device that allows full brake control be a help in train handling? For example, in makiing a 30 pound reduction on encountering a downgrade, after more than half the train is over the summit, I might wish to make a 15 pound reduction simultaniously from the rear to keep the slack stretched. The full 30 pound reduction will reach the rear of course, but meanwhile the 15 pound reduction propogatting from the rear should smooth the ride for the rear cars.
It coujld be abused, of course, which could pull drawbard. But so does lots of bad handling on heavy freight trains.
Dave,
The more refined device that you mention would be ECP brakes. They are controlled by wire, as opposed to being controlled pneumatically with a function built into the conventional air brake system. Therefore the application of ECP brakes is simultaneous rather than propagating from one car to the next over a period of time.
The functionality of what you are describing is very close to the function that I have detailed in my concept for a safe oil train thread. That concept relies on the functionality of ECP brakes, but it adds control function beyond what is currently being done with ECP brake systems being designed and tested.
In my concept, that added control function is to make application of the brakes is divided in response to a derailment in order to keep the train stretched. This is very similar to what you are describing in dividing the application into differing levels of braking force.
I think that such an engineer-initiated brake application system is available now, but it comes with a locomotive attached. I think a DP application can be done to stretch the slack, if necessary. I hope an engineer will quickly correct me if I’m wrong.
Can’t speak to the two way EOTDs - ours just hang on the coupler and flash…
That said - a point of order: A “first service” brake application is a ~six pound reduction. Full service is going to put you in “equalization,” and at about a 26 pound reduction.
Any reduction in the brakeline below a 26 pound reduction will have no further effect on the brakes - they’re on as hard as they will ever be (via air).
So that 30 lb reduction is going drag the train to a stop…
Thanks for the correction. I should have said an eight pound reduction at the head-end and a four pound reducion at the rear.
Air brake operations on the DP always follow the lead engine. There isn’t any separate control function for the automatic or independent brakes. Only the throttle and dynamics can be operated independently of the lead engine. About all you can do is reduce the throttle on the rear end. I do that sometimes when I feel (sometimes literally) that the DP isn’t responding as fast as it should when I want to notch down.
I would guess an EOT could be made to make a gradual air brake reduction instead of an all or nothing emergency dump, but to release from the rear you would need an air source. Adding a compressor, something to power the compressor and reservoir to an EOT would make it awfully heavy.
Jeff
A brake pipe reduction travels about 900 ft/sec and it takes about 5-10 sec for the brakes to set up. It takes about 9 sec for the reduction to travel the length of an 8000 ft train. How long will it take the engineer between when he sets up the brake reduction on the head end and when he makes the reduction on the rear end? How long will it take him to finish making the head end reduction, then change over to the control operating the EOT and make the reduction on the rear? If the process takes more than 6-7 secs, then by the time he can set the brakes on the rear, the head end induced reduction will have begun on the rear.
With a DP, since the reductions mirror each other, the reduction on the head end is virtually instaneous with start of the reduction from the rear end. Since the variable reduction would only be desired at specific times, and would differe in the pressure reduction, it sounds like it would have to be manually set.
Considering it takes almost as long for the brakes to actually set as it takes for the brake pipe reduction to reach the rear of the train, so even if the transmission was immediate, by the time the small reduction was made the large reduction would have begun.
Would the few seconds the lower reduction would be applied before the higher reduction started really be useful for train handling?
DaveH,
" … the brake pipe signal travels from the front to the back of the train at a rate of about 500–600 feet per second for service braking and about 930 feet per second for emergency braking …"
You may want to recalculate your figures.
Understood. A compressor or a very huge airtank with valves that would be recharged when the brakes are in release from the front, neither very practical.
A brake pipe reduction travels about 500-600 ft/sec and it takes about 5-10 sec for the brakes to set up. It takes about 15 sec for the reduction to travel the length of an 8000 ft train. How long will it take the engineer between when he sets up the brake reduction on the head end and when he makes the reduction on the rear end? How long will it take him to finish making the head end reduction, then change over to the control operating the EOT and make the reduction on the rear?
With a DP, since the reductions mirror each other, the reduction on the head end is virtually instaneous with start of the reduction from the rear end. Since the variable reduction would only be desired at specific times, and would differe in the pressure reduction, it sounds like it would have to be manually set.
Considering it takes almost as long for the brakes to actually set as it takes for the brake pipe reduction to reach the rear of the train, so even if the transmission was immediate, by the time the small reduction was made the large reduction would have begun.
Obviously the sooner the braking begins the quicker the train reduces speed, but that’s not the discussion, its whether making a small reduction on the rear before the main reduction occurs helps train handling. Is 14 seconds or less significant?
Ideally, the controls would set up for simultanous application. Still far less expensive than conversion to electric control of braking. There could be a control set up with “off – 1/4 —1/2—3/4—Full”.
Doesn’t CN have air brake repeater cars that can also be used as a EOT (or SBU in their local parlance, I believe)?
There seem to be two varieties of CN Distributed Braking Cars.
One type is boxcars:
http://www.railpictures.net/viewphoto.php?id=424763&nseq=2
http://www.railpictures.net/viewphoto.php?id=424764&nseq=1
The other is well cars:
The CNSU container looks as if it can be loaded on the rear of any container train and hooked up for the purpose.
a
Looks like they use 3 sets of truck marker lights for the rear marker. Strange.
Canada begat Justin Bieber so nothing would surprise me
LMAO. [(-D][(-D]