21101

Can anyone explain how these flats occur? Surely modern trains have anti-lock brakes?

Perhaps they deliver them in a similar style to this:

Blimey, it must be a very long lorry!!

1992 stock onwards are fitted with WSP - wheel slip provention, which works like ABS in a car. You can sometimes hear it hissing away when braking in low adhesion conditions. As far as I know, no train anywhere, even if fitted with WSP is completely immune to having flats.

I am actually not 100% convinced that use of rheo braking in low adhesion conditions is actually better at proventing flats than traditional EP/Westinghouse brakes. Where as before, the brake blocks would wipe the tyres clean of any debris/water/leaf mulch/rubbish accumalted from the rail head, rheo braked trains don't get any brake block intervention until -7mph unless emergency braking is selected, which is a great way of giving yer train flats!

Of course with the A stock gone, only C stock and 1972 stock trains allow a service application of brake blocks with the westinghouse air brake.

9mph on S when air takes over. A stock series braking was faultless, no advanced train comes close. (series on power, gentle ep braking)

If A stock was 'faultless' how come about 50% of them had wheelflats at this time of the year?
The WSP on S stock seems to be keeping most of them flat free.

The only train on the Met this year I've noticed with flats is the RAT - you can hear it coming a mile off, could be the first A stock with square wheels!

If I've caught the right end of the stick he means, power controller in the Series position whilst braking gently. Not every driver does that!

I agree with t697 on this. Only a couple of seasons ago at this time of year you'd have been highlighting the units that weren't flatted rather than the few that are, and it used to take all winter to get the fleet turned back to good condition. A-stock could be made to perform really well with particularly skilled operators, whereas the S8's are much more consistent regardless of the level of operator experience.

Or is it likely to be a combination of the fact that the S Stock is driven mainly in automatic mode coupled with a more modern WSP system?

Have I used the wrong terminology? I have read several times on this forum of the S Stock operational profile (acceleration, top speed etc) being controlled by software rather than the T/Op. If this is the case surely different driving styles between T/Ops will be evened out.