Leaves On The Line, a scientific explanation

[Dagworth]

This is interesting 

 

 

Andi

 

[Pandora]

Leaves on the line is far more than an adhesion issue,  it is a signalling issue,  the leaf layer electrically isolates the wheels from the track,  trains are lthen lost to the signalling system

[Northmoor]

Having worked in this technical field, I can tell you without even seeing the video that it is MUCH more to do with moisture than leaves.  It is also the case that the fact that it is a problem now and wasn't in the days of steam, has very little to do with sparks burning back the lineside growth.  It has everything to do with the acceleration and braking rates of modern trains, where in the right (or wrong) weather conditions, the braking capability can exceed the available adhesion.

[Halvarras]

17 hours ago, Pandora said:

Leaves on the line is far more than an adhesion issue,  it is a signalling issue,  the leaf layer electrically isolates the wheels from the track,  trains are lthen lost to the signalling system

 

Further to this, I have a couple of photos (not yet scanned) of brand new 158701, the first production Class 158 unit, on Swindon Stabling Point on 25/3/90 - I was very surprised to find it there. As I recall it the reason for its appearance was for an investigation into track circuit issues using the Swindon to Gloucester line, the problem stemming from a combination of the largely aluminium unit's light weight and fitting of disc brakes instead of wheel tread-scrubbing clasp brakes resulting in a build-up of insulating leaf mulch.

This could hardly have improved its braking performance either.

[Dagworth]

8 hours ago, Northmoor said:

Having worked in this technical field, I can tell you without even seeing the video that it is MUCH more to do with moisture than leaves

If you had watched the video you would have seen that that is in the video.

 

Andi

[Edwin_m]

6 hours ago, Neil Phillips said:

 

Further to this, I have a couple of photos (not yet scanned) of brand new 158701, the first production Class 158 unit, on Swindon Stabling Point on 25/3/90 - I was very surprised to find it there. As I recall it the reason for its appearance was for an investigation into track circuit issues using the Swindon to Gloucester line, the problem stemming from a combination of the largely aluminium unit's light weight and fitting of disc brakes instead of wheel tread-scrubbing clasp brakes resulting in a build-up of insulating leaf mulch.

This could hardly have improved its braking performance either.

Being a graduate trainee with BR Research and wanting to test some on-train equipment, I got a free ride on Lab 5 which was recording track geometry on the same route as part of the same investigation.  I was subsequently a little involved with:

• the Track Circuit Assister (or Actuator), which was attached to the bogie and circulated a high frequency current through the wheels and rails which was found to reduce the resistance and give detection in normal conditions.
• the TCA Interference Detector, which could detect the signal from the TCA and short the track circuit, fitted to locations where contamination was too heavy for the TCA on its own.
• the One Shot Emergency Sander, a modified fire extinguisher which could dramatically improve adhesion if operated when the train needed to stop in very poor conditions, as illustrated on a memorable early morning run with the first ECS out of Salisbury one November.  This was the forerunner of more sophisticated sanders now fitted to (I think) all multiple units.  

[Pandora]

12 hours ago, Northmoor said:

Having worked in this technical field, I can tell you without even seeing the video that it is MUCH more to do with moisture than leaves.  It is also the case that the fact that it is a problem now and wasn't in the days of steam, has very little to do with sparks burning back the lineside growth.  It has everything to do with the acceleration and braking rates of modern trains, where in the right (or wrong) weather conditions, the braking capability can exceed the available adhesion.

I've worked in the same technical field, right up front,  on  some sections of line,  in leaf fall season  you don't even have to brake to slide, just reduce power or even just  coast, the train will not roll, it will slide with the wheel's not turning at all. Leaf fall season driving that is when you really earn your pay

Edited May 23, 2021 by Pandora

[Covkid]

4 hours ago, Edwin_m said:

Being a graduate trainee with BR Research and wanting to test some on-train equipment, I got a free ride on Lab 5 which was recording track geometry on the same route as part of the same investigation.  I was subsequently a little involved with:

• the Track Circuit Assister (or Actuator), which was attached to the bogie and circulated a high frequency current through the wheels and rails which was found to reduce the resistance and give detection in normal conditions.
• the TCA Interference Detector, which could detect the signal from the TCA and short the track circuit, fitted to locations where contamination was too heavy for the TCA on its own.
• the One Shot Emergency Sander, a modified fire extinguisher which could dramatically improve adhesion if operated when the train needed to stop in very poor conditions, as illustrated on a memorable early morning run with the first ECS out of Salisbury one November.  This was the forerunner of more sophisticated sanders now fitted to (I think) all multiple units.  

 

Indeed.  One shot sanders, went to two shot sanders to the current multi shot sanders, at least on voyagers.

[Supaned]

10 hours ago, Edwin_m said:

Being a graduate trainee with BR Research and wanting to test some on-train equipment, I got a free ride on Lab 5 which was recording track geometry on the same route as part of the same investigation.  I was subsequently a little involved with:

• the Track Circuit Assister (or Actuator), which was attached to the bogie and circulated a high frequency current through the wheels and rails which was found to reduce the resistance and give detection in normal conditions.
• the TCA Interference Detector, which could detect the signal from the TCA and short the track circuit, fitted to locations where contamination was too heavy for the TCA on its own.
• the One Shot Emergency Sander, a modified fire extinguisher which could dramatically improve adhesion if operated when the train needed to stop in very poor conditions, as illustrated on a memorable early morning run with the first ECS out of Salisbury one November.  This was the forerunner of more sophisticated sanders now fitted to (I think) all multiple units.  

 

And for all of those thing, we drivers are most grateful. Those one-shot sanders have proved their worth for me on several occasions.