DarloRich
Veteran Member
perhaps rail grinding has reduce the prevalence of this?
Which post does this comment refer to please?perhaps rail grinding has reduce the prevalence of this?
Which post does this comment refer to please?
A huge chunk of the underground section of the Central line (worst is between Liverpool Street & Stratford), and the Jubilee line between Bond Street & Baker Street.
perhaps rail grinding has reduce the prevalence of this?
My thoughts too on why the section between Hoylake and West Kirby had it, I did read that much of this line had originally been laid on sea shingle. I wonder if such a formation leads to track flexing and causes corrugations, or if it was purely resonance from the substructure.one theory was resonance in the earth below the formation, possibly very ancient rotted vegetation - alternatively inadequate compacting during construction.
Isn't there an actual phenomena known as "roaring rails" where the top of the rail head develops small ridges that causes the roar; or have I dreamt it? A bit of a mystery, but something to do with the local soil or trackbed characteristics perhaps? Move the rail to a different location and the ridges rub out and the noise stops. Put new rail down in the original location, and the ridges develop again.
Rail grinding would remove the ridges, at least temporarily.
I think there is. I think that the different (hollow) sound that I heard on the SR EMUs was down to the wheels. They seemed to be lighter in construction like pre-nationalisation wheels, as was used on the class 404s (Nelsons). The 4-SUBs and even the 4-EPBs also had a similar sound, yet the few examples of non-corridor EMUs with the 3-faceted ends (2-BILs) that were still running sounded more like rollerskates with quieter wheels. Of course, after the BIG/CIG/VEC fleets were rolled out, these trains were fitted with B4 bogies so their sound wasn't very different to most other late MK1 & 2 rolling stock. The REPs of course had a much heavier sound.Is there also a component of rail noise that is down to wheel profile or bogie type - would that also exacerbate things in bad areas? In terms of hauled stock think of the difference between a Mk2 on B4s versus a Mk3 on BT10s even on fault-free track.
There was an article in, I think, the Railway Gazette some years ago by a staff member of Plasser & Theurer in Austria giving a review of technical and scientific investigations into the cause of 'rail roar'.[1] I can no longer remember the details but it was certainly concerned with resonance leading to the effect you describe. There was a mention of 'pinned frequencies' where the combination of rail clip spacing, the stiffness of the rail pad between rail and sleeper, the vibrational characteristics of the rail itself, the ballast and rail bed generally gave rise to some preferred frequencies of vibration in the rail head. The wheels then hammered the high spots which work hardened the rail at those points.That's about how I remember it ( from yonks ago ) - a barely educated guess would be something related to resonance ( which yeah, would be trackbed related ) resulting in uneven wear over very short distances, and then that snowballing as it's both already uneven and synchronised with whatever is resonating. Might be also related to how the rail is clipped, in that case?
But that was a barely educated guess - probably papers at the RSSB about it somewhere.