Western Railroad Discussion > Train defect detectors

I've noticed a wide range in what information is broadcast by defect detectors, even on the same railroad.  All give a milepost, most seem to give a name. Some detectors give the current temperature, others don't. Some give train speed. All give axle counts.  A few give the time. The engineer or conductor usually gives the train ID in responding. 

I'm guessing that the heritage of whoever installed the machine is a big part of what it records.  For a carrier like CSX, with a half dozen acquisitions in the past 20 years, there are a lot of heritage fixtures from different railroads in place.

I've never regularly heard crews respond to detectors (assuming no defects) outside of areas with NORAC operating rules, which doesn't apply in the west. Actually it would be interesting to see if there's any exceptions to that. Adding another variable, there's also areas on BNSF's transcon (and prove my elsewhere) in which detectors activate on defect only.

Posted from iPhone

CP makes you call out detector messages, even with no defect messages....you also have to say thank you over the radio.

Posted from Android

Railroads have an option page on each decoder's set up programming protocol. They can select any output message they want as long as there are machine sensors to provide input.

Posted from iPhone

fbe Wrote:
-------------------------------------------------------
> Railroads have an option page on each decoder's
> set up programming protocol. They can select any
> output message they want as long as there are
> machine sensors to provide input.
>
> Posted from iPhone

It's actually pretty impressive. i've seen it on a computer before. They also have a test mode where they will say everything they can.

Thanks for all the info

On the Siskiyou Line in Northern California (former SP now CORP) I know of two detectors that also give the length of the train.

cascade463 Wrote:
-------------------------------------------------------
> On the Siskiyou Line in Northern California
> (former SP now CORP) I know of two detectors that
> also give the length of the train.

That's impressive. How do they know? Are they tied into an AEI reader?

The detector records the times of the first and last axles. Speed is calculated by single wheels going over a known distance of two mechanical switches. Thus length can be calculated by the computer in the detector. The mechanical switches activated by the wheel flanges may have been replaced by something more sophisticated by now. Speed can be measured by vibrations in the rail as some crossing signals now do.

Posted from iPhone

fbe Wrote:
-------------------------------------------------------
> The detector records the times of the first and
> last axles. Speed is calculated by single wheels
> going over a known distance of two mechanical
> switches. Thus length can be calculated by the
> computer in the detector. The mechanical switches
> activated by the wheel flanges may have been
> replaced by something more sophisticated by now.
> Speed can be measured by vibrations in the rail as
> some crossing signals now do.
>
> Posted from iPhone

I understand how speed is calculated, but how train length is calculated is a cool a extra step. Taking the time at which each axle hits each switch and using speed to determine the length is more than I gave the machine credit for. Especially while calculating for different speeds over the detector for the length of the train. I know it's a simple calculation, but I'm a simple man...

Mostly the entire train passes over the detector at a steady speed. If there is acceleration or deceleration the length may not be as accurate.

Posted from iPhone

On NS, at least in central Pennsylvania, if train speed falls below about 8 mph, the machine will announce "no defects, train too slow" when the train has cleared the detector. The conductor must then drop off and the train pull by for a 10 mph roll by inspection on one side. This policy has been in effect for the last several years.  Do other railroads have this requirement? Hot box detectors came to this area in the mid 1960's and until now there had been no such policy.

fbe Wrote:
-------------------------------------------------------
> Mostly the entire train passes over the detector
> at a steady speed. If there is acceleration or
> deceleration the length may not be as accurate.

I have seen BNSF trains progress on the Transcon (like a Q LACCHI6-23A), with the car count staying the same, but the length changing.  If a train had a lot of slack bunched one time, stretched the next, that would change the length, too.

mapboy

on the UP Adams sub in WI, ex CNW, single track ABS, TWC control, detectors ID location but not direction of movement, nor speed. not much help to fans. But on UP's ex GMO/Amtrak line in IL the speed is given. very helpful obviously to railfans.

I realize they are not there for the benefit of fans, but hey it's my perspective.  I've also noticed a much more difficulty hearing them as power output may have been reduced some, esp. on CP's ex MILW Watertown sub. near where i live.

chico

cascade463 Wrote:
-------------------------------------------------------
> On the Siskiyou Line in Northern California
> (former SP now CORP) I know of two detectors that
> also give the length of the train.

Can you list locations and verify road channel?

Rob

I am bringing up this 3-year old thread because I've noticed recently that virtually all detectors on the UP in Nevada and Utah no longer report axle count, train speed and ambient temperature.  They used to do this all the time.

Has the protocol changed? Or is my new scanner somehow catching only the initial response of the detector when the headend reaches the detector location and not the follow-up response with all of the information mentioned above?



Edited 1 time(s). Last edit at 11/01/19 10:07 by chakk.

The detectors I hear make an announcement when the last car clears. They usually repeat their announcement and it is kept brief to keep the channel clear. The crew can tone the detector to have it repeat the announcement.

I don't listen enough to hear a defect ... the reports I have heard are railroad company, milepost, track number, "no defects". No car count or length.