Leaf blowing trains.

[Bald Rick]

I must admit, I agree with Need2. What you have probably experienced is where the TMS and the brake modules can adjust the blending. I have a brake graph somewhere that shows where the blending adjusts.

very possibly - it definitely wasn’t only tread brakes, but then it definitely sounded like something On the wheel tread during braking (from 100mph!).

 

[43066]

Fair enough.
Can’t see the benefits though.

Scrubbing the wheels clean, so better braking and better traction for getting away from stations.

Don’t 700s apply a small amount of brake pressure even when the regen is active? Everything I’ve driven equipped with rheostatic or regen brakes still registers half a bar on the brake cylinder when braking from any speed.

 

[furnessvale]

Scrubbing the wheels clean, so better braking and better traction for getting away from stations.

Don’t 700s apply a small amount of brake pressure even when the regen is active? Everything I drive equipped with rheostatic or regen brakes still registers half a bar on the brake cylinder when braking from any speed.

Correct. Wheel conditioning to remove crud from the treads.

Over the years, several attempts have been made to completely remove tread braking in favour of discs, rheostat, whatever, but if the tread is dirty, you are wasting your time.

 

[skyhigh]

Over the years, several attempts have been made to completely remove tread braking in favour of discs, rheostat, whatever, but if the tread is dirty, you are wasting your time.

I can't comment on anything else, but at least 170s, 333s, 195s and 331s don't have any form of tread brake (and only some 158s have the scrubbers).

 

[43066]

I can't comment on anything else, but at least 170s, 333s, 195s and 331s don't have any form of tread brake (and only some 158s have the scrubbers).

AFAIK, other than 700s, nothing built after 156s(?) has tread brakes.

A lot built before them also had disc brakes only, eg HSTs, 315s, 455s etc.

 

[Need2]

Scrubbing the wheels clean, so better braking and better traction for getting away from stations.

Don’t 700s apply a small amount of brake pressure even when the regen is active? Everything I’ve driven equipped with rheostatic or regen brakes still registers half a bar on the brake cylinder when braking from any speed.

It may keep the wheel tread clean and stop any build up of crud, but that’s only half the trains wheels.
My point is that if the treads ARE clean then They will not help braking whatsoever in low adhesion slides as they only come into use at a low speed.

 

[43066]

It may keep the wheel tread clean and stop any build up of crud, but that’s only half the trains wheels.
My point is that if the treads ARE clean then They will not help braking whatsoever in low adhesion slides as they only come into use at a low speed.

I see your point.

Since they’re acting on the motored wheels there’s still the benefit of better traction making getting away easier. I reckon I lose more time starting than stopping during leaf fall.

 

[Need2]

I see your point.

Since they’re acting on the motored wheels there’s still the benefit of better traction making getting away easier. I reckon I lose more time starting than stopping during leaf fall.

You still get the same pulling away problems, the white sanding light comes on a certain parts of the route quite often and that is obviously after stopping If they did much use then I can’t see it.

 

[ComUtoR]

You still get the same pulling away problems, the white sanding light comes on a certain parts of the route quite often and that is obviously after stopping If they did much use then I can’t see it.

The white sanding light acts differently when braking and accelerating.

 

[skyhigh]

The white sanding light acts differently when braking and accelerating.

Interested to know, purely as a comparison to our 195s. The sander/WSP light will illuminate under braking when WSP activity is detected and sand will be applied automatically. Under power, the light will again illuminate when loss of traction detected but sand won't be deployed unless the driver presses the button (and the button doesn't illuminate to show sand is being deployed, it just continues to flash if the wheels are still slipping). Is that similar to how it works on a 700?

 

[Need2]

Interested to know, purely as a comparison to our 195s. The sander/WSP light will illuminate under braking when WSP activity is detected and sand will be applied automatically. Under power, the light will again illuminate when loss of traction detected but sand won't be deployed unless the driver presses the button (and the button doesn't illuminate to show sand is being deployed, it just continues to flash if the wheels are still slipping). Is that similar to how it works on a 700?

Exactly the same.
In a way proving that friction tread brakes (on 700’s at least) do not improve braking (wheel slide) or wheel slip.

 

[niggill617@gma]

There were all sorts of ideas on adhesion, and the related problem of detection by track circuits, throughout my time at British Rail Research and successors (1987-2006). A big one that hasn't been mentioned is bringing back sanders, which are now fitted to many multiple unit classes.

"Knorr-Bremse are also able to offer a system whereby the brake unit will control the dynamic brake during WSP. It gives signals to the local traction control unit for each car / bogie / axle to reduce or hold the dynamic brake effort in parallel with the signals it uses to control the pneumatic valves to change the brake cylinder pressure during wheel slide. Such a system eliminates the conflict that can occur between a traction and a friction brake WSP system. Knorr-Bremse have also produced blending systems that monitor the dynamic brake effort during wheel slide and if the reduction in this force exceeds set criteria (as the traction system attempts to control the slide), it will redistribute this effort onto the other trailer axles in the braking network and reduce the dynamic brake demand to a lower level. 5.2.3 Auxiliary tread brakes Auxiliary Tread Brakes (ATB) have been fitted to a limited number of disc braked vehicles and are thought to aid track circuit operation by cleaning and roughening the wheel treads. Their ability to improve low adhesion is considered small as they act only to clean and roughen the wheel treads and not the railhead where most of the contamination is to be found."

The above is from The Adhesion Working Group Manual. I didn't know dynamic brakes could have anti-skid functionality, I believed reversion to friction brakes was the solution, during adhesion issues. I have read that double variable rate sanders are very efficient.