Track twist faults!

[Dale1995]

Can anybody help with what causes twist faults?

 

[edwin_m]

Uneven settlement below the track?

 

[alex17595]

Voids below sleepers due to them being packed incorrectly or the ballast being washed away.

 

[O L Leigh]

Twist faults with what? Track or rail vehicles?

O L Leigh

 

[miikey]

Dipped joints/welds, voiding sleepers, poor condition of ballast, poor drainage leading to poor foundations.
The list is endless.

 

[83G/84D]

Sounds like they are pretty self explanatory but can someone who knows about these things explain what a twist fault is please?

I noticed some markings trackside today indicating twist faults and was wondering.

 

[edwin_m]

It's when one rail rises relative to the other at too great a rate, usually measured over a 3m or 10m (?) length to correspond roughly with the length of a bogie or a wagon inner wheelbase. It can lead to "wheel unloading" when the rail under one wheel of a four-wheel wagon or bogie is significantly lower than under the others, so the springs have to be much more extended to keep that wheel on the rail. Combined with faulty springs or poor weight distribution this can cause that wheel to jump off the track. There have been several derailments in recent years where twist is at least partly to blame.

 

[83G/84D]

Thanks for the explanation.

 

[gimmea50anyday]

The same phenomenon caused the derailment that led to the destruction of DP2 at Thirsk in 1967. The harrogate to Northallerton line had already been closed, but in order to provide a diversionary route for ECML services had to be reopened in haste. Fortunately demolition hadnt yet started. Oh the irony!!!

 

[Henna55]

does anyone know the O.A.S.I.S way to work out a twist fault? Iv completely forgot how to it! I have an exam coming up and I’m pretty sure it will be in there somewhere!

Thanks

 

[Boodiggy]

does anyone know the O.A.S.I.S way to work out a twist fault? Iv completely forgot how to it! I have an exam coming up and I’m pretty sure it will be in there somewhere!

Thanks

OPPOSITE ADD SAME IS SUBTRACT.

 

[Henna55]

Yea I know that part. But how do you get it to the 1:500 or 1:340 part? The sum after opposite add same is subtract

 

[Boodiggy]

To work out the gradient simply divide 3000 (Twist measured over 3m) by the twist value.
So a 15 mm twist would be 1:200.

Is that what you mean?

 

[Boodiggy]

To work out the gradient simply divide 3000 (Twist measured over 3m) by the twist value.
So a 15 mm twist would be 1:200.

Is that what you mean?

OASIS is a bit different, as it tells you how to work out a twist on either one or both rails.

 

[Henna55]

OASIS is a bit different, as it tells you how to work out a twist on either one or both rails.

Yea so if I had a reading of 7mm and then 8mm on opposite leg that would give me 15mm divide that by 3000 would give me 1:200 but if them reading were on same leg it would be 1:3000 is that rite?

 

[Henna55]

No sorry I have thatvthe wrong way round!

Edited it so it’s correct

 

[Boodiggy]

No sorry I have thatvthe wrong way round!

Edited it so it’s correct

All you are looking for is 15mm difference over 3m. It will be harder to locate in a transition but as long as you can identify a 15mm change of cross level over 3m the rest comes with experience

 

[Henna55]

All you are looking for is 15mm difference over 3m. It will be harder to locate in a transition but as long as you can identify a 15mm change of cross level over 3m the rest comes with experience

Thanks for help mate, appreciate it.

 

[Boodiggy]

No probs...