Class 319

[coloumb]

Hello all, first post. I'm not in the rail industry but I do have an interest in railways that dates back years.

I was wondering if anyone can help me with a question. I use the Thameslink line daily and have noticed that when the weather is wet, that the 319's slip like there is no tomorrow. I would think this causes considerable damage to the wheels and track, not to mention the timetable due to painfully slow starts, yet the situation seems to have gone on like this for years as far as I can tell.

I would certainly be interested to know if anyone has any comments on this?

 

[hairyhandedfool]

Welcome to the forum.

Are you refering to wheel slip (under acceleration) or wheel slide (under braking)?

Wheel slip only affects the PMS and there is a system in place to limit it, which cuts out the traction motors until the wheels stop spinning. Wheel spin is more likely to damage the track than the wheel.

Wheel slide affects all wheels and can cause flats, but again there is a system in place to reduce this, by reducing brake force to the affected axle. The slide would do more damage to the wheel, however the wheel would then cause damage to the track as it rotates.

319s also have sanding equipment on three of the four vehicles (not the PMS).

The only thing I would say is that, being quite old now, the systems take a few seconds to kick in and this can show up the unit against the newer units. I'm pretty sure other units of the same age have the similar issues.

Leaf-fall season can also have the same effect as wet rail heads, but this has been reduced over the year with the railhead treatment trains running about.

IIRC St Albans is a low adhesion area also, so there will be extra slow starts in that area.

 

[asylumxl]

I would agree St Albans is an area of poor adhesion. I usually find it particularly bad on the Up Fast line.

Not really much that can be done about it to be fair, apart from Wheel Slip Protection systems being used. Metal on metal was never going to be great for adhesion, but on the plus side has very little rolling resistance which is useful for coasting.

 

[O L Leigh]

It's a common feature of these and similar trains. They only have four driven axles, all under the same coach, so they are vulnerable to wheelslip under acceleration. Our Cl317s are the same, but the Cl315s have two motor coaches and eight driven axles so while they still slip they are not as badly affected.

Driving technique can mitigate this somewhat, but many drivers do not notch up gradually and will just give it the beans and let the WSP sort it out. Sometimes a lower power notch will result in less slipping and better acceleration as well as a smoother ride. Dropping sand can also help, but it's not always an immediate fix.

O L Leigh

 

[coloumb]

Cheers all, interesting reading. I agree St. Albans does have problems but if it's wet it can happen anywhere. It definitely wheelslip rather than spin but I take it the occasional hammering sound is caused by a flat on the wheel after a slip. I recall this used to happen on a regular basis a couple of years ago but seems to have cleared up of late. Interesting that some drivers let the WSP sort it out, but occasionally it has verged on painful the amount of time it has taken for the train to reach speed.

 

[hairyhandedfool]

Cheers all, interesting reading. I agree St. Albans does have problems but if it's wet it can happen anywhere....

Certain areas are more prone to slip/slide than others, they are called low adhesion areas and are marked in the sectional Appendix (IIRC), the reason for it is not always the same, drivers don't really need to know why though.

Obviously, if it is raining in Bedford and not St Albans for example, then Bedford would be worse.

....It definitely wheelslip rather than spin but I take it the occasional hammering sound is caused by a flat on the wheel after a slip....

Wheel slip and wheel spin are the same thing, wheel slide is under braking. The regular hammering sound will be flats caused by wheel slide.

 

[O L Leigh]

An occassional banging sound when taking power is often a good sign of the onset of wheelslip, though they usually go on to grip. We get it a lot with Cl315s, especially pulling up the hill out of Highams Park in questionable conditions. First time it happened to me while under instruction I thought we'd fallen off the road and were riding along the sleepers.

If it was a flat it would bang pretty much all the time.

O L Leigh