Do tube trains ever suffer from wheelslip?

alexl92

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I was on the tube yesterday and when departing stations on some trains, it felt very similar to when I’ve been on TPE 185s suffering wheelslip, but I wouldn’t have thought tube trains would suffer from it?
On heavy rail, it’s normally the weather conditions that cause trains to lose traction but obviously that’s not a factor underground!
Does it happen much?
 
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Horizon22

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Fairly sure the western side of the Piccadilly does. Don't forget the majority of the Underground is actually overground.
 

Darandio

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And anything underground, particularly in tunnels can often be rather damp!
 

edwin_m

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The Central Line, and possibly other lines too, have settings that can be changed on the ATP systems to assume a worse braking rate on days when adhesion is low.
 

alexl92

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Cheers! Couldn’t remember where the LU forum was. I first noticed it at Kings Cross St Pancras; can’t remember which line it was tho!
 

Bikeman78

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I was on the tube yesterday and when departing stations on some trains, it felt very similar to when I’ve been on TPE 185s suffering wheelslip, but I wouldn’t have thought tube trains would suffer from it?
On heavy rail, it’s normally the weather conditions that cause trains to lose traction but obviously that’s not a factor underground!
Does it happen much?
I recall that the A and D stock used to slip on damp autumn rails. The drivers clearly had faith in the brakes though because they usually arrived at stations quite fast, usually accompanied by the smell of burning sandite.
 

Nym

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Wheel slip or wheel slide...?

If the former, yes, there have been spesific wheel slip protection since 1973TS.
Wheel slide protection is retrofitted to 1992TS and I believe as standard from 1995TS onwards.
 

AlbertBeale

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Wheel slip or wheel slide...?

If the former, yes, there have been spesific wheel slip protection since 1973TS.
Wheel slide protection is retrofitted to 1992TS and I believe as standard from 1995TS onwards.

Can someone explain the technical difference between wheel slip and wheel slide? Thanks.
 

hexagon789

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Can someone explain the technical difference between wheel slip and wheel slide? Thanks.
I always understood that wheelslip was any form of the wheels losing grip - be it under either acceleration or under braking.

Wheelspin then refers to loss of grip under acceleration as the wheels spin faster than the speed at which the train is actually moving.

Wheelslide then refers to loss of grip under braking, where the wheels lock-up and the train effectively slides along the rails.

Wheel-slip (spinning) is upon acceleration, wheel-slide (locking) is upon braking.
I always understood wheelside to be essentially the general term for any loss of grip (adhesion), while spin and slide were specific to acceleration and deceleration respectively as I outlined above?
 

Mawkie

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Wheel slip or wheel slide...?

If the former, yes, there have been spesific wheel slip protection since 1973TS.
Wheel slide protection is retrofitted to 1992TS and I believe as standard from 1995TS onwards.
The only wheel slip protection on a 73TS is the train operator's hand returning to 'off and release' when they feel the wheelslip and back to a motoring position when there is better rail adhesion.
 

43096

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I always understood that wheelslip was any form of the wheels losing grip - be it under either acceleration or under braking.

Wheelspin then refers to loss of grip under acceleration as the wheels spin faster than the speed at which the train is actually moving.

Wheelslide then refers to loss of grip under braking, where the wheels lock-up and the train effectively slides along the rails.


I always understood wheelside to be essentially the general term for any loss of grip (adhesion), while spin and slide were specific to acceleration and deceleration respectively as I outlined above?
That's not the way I understand the terminology.

Electronic systems on trains to mitigate it are known as Wheel Slip Protection when accelerating (equivalent of a car's traction control) and Wheel Slide Protection when braking (equivalent to a car's anti-lock braking system). Confusingly, both are WSP!
 

Nym

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I always understood that wheelslip was any form of the wheels losing grip - be it under either acceleration or under braking.

Wheelspin then refers to loss of grip under acceleration as the wheels spin faster than the speed at which the train is actually moving.

Wheelslide then refers to loss of grip under braking, where the wheels lock-up and the train effectively slides along the rails.


I always understood wheelside to be essentially the general term for any loss of grip (adhesion), while spin and slide were specific to acceleration and deceleration respectively as I outlined above?
LUL define them separately.
The only wheel slip protection on a 73TS is the train operator's hand returning to 'off and release' when they feel the wheelslip and back to a motoring position when there is better rail adhesion.
73TS and D78 Stocks have Wheelslip Relays as part of the traction packages that back off the notching relays.
 

Mawkie

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LUL define them separately.

73TS and D78 Stocks have Wheelslip Relays as part of the traction packages that back off the notching relays.
Ah, that's interesting. You sound well informed, but that isn't my experience of 73s. My only experience is of the wheels slipping in the wet under acceleration without any intervention by me. How effective are the wheelslip relays?
 

ac6000cw

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General comment, not LU stock specific:

To me, wheel-slip control/prevention under power or when electric braking is something that is handled by the traction control system - be that the drivers skill or using autonomous computer controlled electronics (and all the shades in-between).

Whereas wheel-slide control/prevention under friction braking is handled by the braking control system (human or otherwise).

A possible dictionary definition of slipping is "lose one's footing and slide unintentionally for a short distance" versus sliding which is "move smoothly along a surface while maintaining continuous contact with it" i.e. a longer term event.
 

trebor79

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Judging by the marks on the railhead you can see at tube stations, the answer to the OP question is "Yes".
 

rebmcr

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Judging by the marks on the railhead you can see at tube stations, the answer to the OP question is "Yes".
That's more likely to be corrugation within the metal, caused by the pressure of acceleration forces (specifically when the wheels are adhering properly).

It's more apparent on some ATO lines that lack randomisation, as the consistent behaviour concentrates the forces in quite narrow locations.
 

Lewlew

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Judging by the square wheels I had on my train the other day then it's a very much "Yes!".
 

trebor79

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That's more likely to be corrugation within the metal, caused by the pressure of acceleration forces (specifically when the wheels are adhering properly).

It's more apparent on some ATO lines that lack randomisation, as the consistent behaviour concentrates the forces in quite narrow locations.
If you look on the Bakerloo and Piccadilly lines in particular, you will see the patches on the railhead where the metal has momentarily melted and then solidified. You see them on heavy rail too.
 

southern442

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I've only ever experienced it on the Central Line to my memory. Might that say more about the train's ability to cope with adhesion issues than anything else?
 

Lewlew

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I've only ever experienced it on the Central Line to my memory. Might that say more about the train's ability to cope with adhesion issues than anything else?
It's more to do with ATO than the actual train braking.

The ATO system counts wheel revolutions so it knows exactly where it is between stations and signals (and other things). When the train comes into a station and the ATO starts braking, if there is any slight wheel slip or slide (caused by the smallest bit of rain) then the ATO loses count of the revolutions and doesn't know exactly where it is so it will apply the emergency brake and stop the train quite harshly. The driver then puts it into manual and moves into the platform.

Leyton westbound was always a problem. Coming into the platform and also shortly after leaving and heading down the slope into the tunnel.

When driving in manual, the train brakes quite well but the ATO has access to more braking capacity than a driver does in manual (I forgot what the actual rates are).
 

southern442

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The ATO system counts wheel revolutions so it knows exactly where it is between stations and signals (and other things). When the train comes into a station and the ATO starts braking, if there is any slight wheel slip or slide (caused by the smallest bit of rain) then the ATO loses count of the revolutions and doesn't know exactly where it is so it will apply the emergency brake and stop the train quite harshly. The driver then puts it into manual and moves into the platform.
Does the ATO do anything if there is wheelslip whilst accelerating?
 

rebmcr

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I've only ever experienced it on the Central Line to my memory. Might that say more about the train's ability to cope with adhesion issues than anything else?
I've seen it a fair amount on S Stock in the rain, on the then-manual section between West Ham and Bow (both ways).
 

Daniel

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Does the ATO do anything if there is wheelslip whilst accelerating?

Yes, emergency brakes the train generally, because as Lewlew mentioned, the system loses count of wheel revolutions - or to look at it another way, the number of revolutions suggests the train has travelled further than the system expects - so the train is halted as a precaution. It is common therefore in excessive weather events for trains to be driven in manual in open sections to mitigate against this. Controllers can, however, adjust the brake rate on outside sections, to reduce harsh acceleration and braking, during leafall season for example.
 

Dstock7080

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On the sub-surface CBTC we’ve been told that as axle counters aren’t the primary method of train locating that the system will detect a train slipping/sliding and automatically inform other trains in the area to moderate the braking/acceleration rate and instigate automatic sanding if required
 

rebmcr

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On the sub-surface CBTC we’ve been told that as axle counters aren’t the primary method of train locating that the system will detect a train slipping/sliding and automatically inform other trains in the area to moderate the braking/acceleration rate and instigate automatic sanding if required
Smart!
 

Mawkie

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On D Stock they worked, 3-4secs of wheelspin followed by motor cutout then reapplying power- without driver intervention
I had the opportunity to test the 73TS wheelspin technology tonight (!) - to be honest, I have never allowed my wheels to spin for that long before taking action myself - and indeed they did seem to gain adhesion after a fashion without intervention.

I don't believe I will adapt my usual low rail adhesion driving technique though as I seem to be able to prevent the wheelslip better than the tech.
 

Bald Rick

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On the sub-surface CBTC we’ve been told that as axle counters aren’t the primary method of train locating that the system will detect a train slipping/sliding and automatically inform other trains in the area to moderate the braking/acceleration rate and instigate automatic sanding if required

I saw a presentation explaining how that system was developed on the eastern side of the Central line .... a 7-8 years ago. It was interfaced with rain radar data too.
 

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