European Railroad Discussion > Brake Question - new Question

Was discussion in TO http://www.trainorders.com/discussion/read.php?17,3751336 eventually is not constructive? What has a TED to do with the train length?

When the engineer is actuating the brake he releases air from the brake line. This pressure lowering goes through the train after a time depending from the train length it will reach the train end. This time will be a little longer in long trains than in short trains. This is not what the engineer is interested so.

The TED is device which indicates that the train line is working proper through the whole train to the end and only indicated on the manometer in the cab and that the train line is not interrupted by closed cocks as happened on the Cahoon accident.

This check is not installed in European trains.

Correct?????????????

Erwin from Austria

I was hoping some "experts" might respond to this but so far not. I would agree with your comments, and I think that technically you are correct, train length should not matter in deciding to use the FRED (Flashing Rear End Device)or TED as you call it. Maybe it is just a good added safety indicator with a longer train since so much more distance has to be covered with the air supply, but that's just an option chosen (required) in the U.S.

Here is a good question, and I assume this is the case in Europe as it is here, but do freight trains do a air pressure check before departure? Here in the U.S., a person (second crew member, yard man, etc.) will perform an air pressure check on the rear end of the train, before departure. I assume this is also a reason for having the FRED at the back of the train so the person can read the air pressure.

Isn't the difference due to the fact that in the US the single pipe barke system is used? The European two pipe sytem gives much faster responses, and an immediate application of the brake of either pipe fails.
Again, I am sure some expert can tell us!

spflow Wrote:
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> Isn't the difference due to the fact that in the
> US the single pipe barke system is used? The
> European two pipe sytem gives much faster
> responses, and an immediate application of the
> brake of either pipe fails.
> Again, I am sure some expert can tell us!

The air signal down the brake pipe is going to propagate at a speed near the speed of sound as determined by the air pressure in the brake pipe. But to that you must also consider friction in the air pipe into the speed, which can be significant when you consider the brake hoses between cars are on the center line, while the brake piping on the car frequently is routed around the perimeter of the car. Every fitting and pipe elbow adds friction. Now the signal transmitted via radio to the EOT travels at close to the speed of light. The EOT can only initiate an Emergency brake application, not a lesser service application. If however instead of an EOT the train has a Distributed Power  Locomotive on the rear, then the Engineer can initiate any type of brake application very nearly simultaneously from both ends of the train. If DPU locomotives are spaced throughout the train even faster applications are possible. 

A two brake pipe installation allows for a graduated release of the train brakes, but offers nothing to the speed of brake application. Electronically Controlled Pneumatic Brakes (ECP) offers the Graduated Release Ability of a 2-pipe brake system with the much faster application speed of electric signal propagation.