Eyersey468
Established Member
- Joined
- 14 Sep 2018
- Messages
- 2,135
How do tread brakes work?
All EMUs have discs from at least class 313 onwards. I think some of the older AC units did too, but pretty sure the DC slam-door units didn't.
Class 700s have tread brakes too.
As I believe all the new aventuras aswell?.
Do tread brakes have any advantage over discs when there is leaf slime or other stuff leading to low adhesion? Does the tread brake have a cleaning action on the wheel surface?
Do tread brakes have any advantage over discs when there is leaf slime or other stuff leading to low adhesion? Does the tread brake have a cleaning action on the wheel surface?
Not sure about the last sentence.Yes, they do clean the wheels, but disc brakes provide a higher more consistent level of braking particularly at higher speeds.
In poor rail conditions while the tread brakes may be less inclined to lock-up the wheels, the disc brake will always at least match if not still exceed the braking performance of the tread brake.
Not sure about the last sentence.
HST power cars have both disc and tread brakes.IMO, the best compromise is disc braking with tread conditioning blocks operating at, say 10psi.
Class 700s have tread brakes too.
Yes, I believe they couldn't find room for the disc brakes on the powered axles. Something like a 700 will use a lot of electric braking, so the friction brakes get an easier life although they still have to be specified for the full braking load in case of a failure in the electrics.Only on the driven wheels I think. Definitely not all wheels though.
Only on the driven wheels I think. Definitely not all wheels though.
Yes, I believe they couldn't find room for the disc brakes on the powered axles. Something like a 700 will use a lot of electric braking, so the friction brakes get an easier life although they still have to be specified for the full braking load in case of a failure in the electrics.
From what I gather the new 745/755 fleet from Stadler have disc brakes but also a form of brush to clear the wheel itself preventing the build up of leaf mulch.
The outer axles on class 345 have no brakes at all.
Most likely. Not been on the course yet so only getting hear say.Scrubber blocks?
Designed to make up for the fact that disc braked trains when braking don't clean the wheels in the same way that tread brakes trains do.
I understand that, but does it take into account poor TREAD condition, which scrubbing blocks can eliminate, rather than dirty rails?If your maximum braking rate is 9%g with disc brakes and 7%g with tread but railhead conditions are so poor that a brake rate of say only 1%g can be supported then you will get 1%g deceleration with either type of brake. Modern WSP-equipment will typically give the disc-brake the edge even in poor conditions.
That's how I understand it anyway.
I understand that, but does it take into account poor TREAD condition, which scrubbing blocks can eliminate, rather than dirty rails?
Is that even allowed? Does it not have an inboard axle-mounted disc brake then?
Yes. I believe that 158's are fitted with discs and treads. (the treads were retrofitted later after their first autumn in Yorkshire resulted in 156 158 hybrid sets being formed.)Do tread brakes have any advantage over discs when there is leaf slime or other stuff leading to low adhesion? Does the tread brake have a cleaning action on the wheel surface?