Dented Carriages?

johnnychips

Established Member
Joined
19 Nov 2011
Messages
2,990
Location
Sheffield
Every morning on Sheffield station, as I am waiting for my train, I see the XC HST come in. The carriages seem ‘dented’ with some undulations above the window line, not smooth as you would expect. The paint is unbroken and I am not supposing for one moment there is any problem with the structural integrity. I know these are old trains, but how would they have acquired these smooth dents? I wonder if anybody has noticed anything similar on other rolling stock?

Edit: I did try to take a picture, but my bionic I-phone camera doesn’t pick them out.
 
Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R

RailUK Forums

Bletchleyite

Veteran Member
Joined
20 Oct 2014
Messages
69,212
Location
"Marston Vale mafia"
I guess it's just distortion of the outer skin caused by heat etc. For some reason this is much more commonly seen on European coaches than UK ones. No safety issue, as it's not the skin that gives the body its strength, it's the structural members underneath it.
 

Killingworth

Established Member
Joined
30 May 2018
Messages
3,090
Location
Sheffield
Every morning on Sheffield station, as I am waiting for my train, I see the XC HST come in. The carriages seem ‘dented’ with some undulations above the window line, not smooth as you would expect. The paint is unbroken and I am not supposing for one moment there is any problem with the structural integrity. I know these are old trains, but how would they have acquired these smooth dents? I wonder if anybody has noticed anything similar on other rolling stock?
The recently withdrawn EMR/LNER units were too. In this picture from Sheffield the ripples are accentuated by the ineffectiveness of the carriage washing equipment!

20201203_072710 (3).jpg
 

158747

Member
Joined
5 Aug 2010
Messages
271
Location
Trowbridge
I guess it's just distortion of the outer skin caused by heat etc. For some reason this is much more commonly seen on European coaches than UK ones. No safety issue, as it's not the skin that gives the body its strength, it's the structural members underneath it.
Mk3 coaches are monocoque construction, where the outer skin is welded to the inner framework, the combined strength of these two elements are what give vehicles of this type of construction their strength.
 

edwin_m

Veteran Member
Joined
21 Apr 2013
Messages
21,561
Location
Nottingham
It seems to be characteristic of Mk3 and other coaches with thin steel skins welded to an underlying structure. It's not seen in aluminum stock.
 

Domh245

Established Member
Joined
6 Apr 2013
Messages
8,022
Location
nowhere
It seems to be characteristic of Mk3 and other coaches with thin steel skins welded to an underlying structure. It's not seen in aluminum stock.

I think I'm right in saying that all aluminium stock has been extruded sections, so there's a lot more rigidity and uniformity in the section. I suspect a train with a thin, rolled aluminium skin might have the same sort of ripple-y texture?
 

Bletchleyite

Veteran Member
Joined
20 Oct 2014
Messages
69,212
Location
"Marston Vale mafia"
It seems to be characteristic of Mk3 and other coaches with thin steel skins welded to an underlying structure. It's not seen in aluminum stock.

I guess it occurs because the skin expands/contracts at a different rate to the structural members. You also don't get it on cars, because there aren't separate structural members and skin, it's all one thing (and shaped for rigidity rather than flat).
 

DB

Guest
Joined
18 Nov 2009
Messages
5,036
I think I'm right in saying that all aluminium stock has been extruded sections, so there's a lot more rigidity and uniformity in the section. I suspect a train with a thin, rolled aluminium skin might have the same sort of ripple-y texture?

So far as I know they are all extruded sections welded together - doubt if it would be possible to construct trains of aluminium using a skeleton frame and skin, as with steel, due to the different properties of the materials.

The ripple effect described is particular noticeable on the mk4s, and certain colours really show it up. When East Coast started repainting the sets the first few were done in a metallic silver, which made it really noticeable. They then switched to grey, which didn't make it as obvious.
 

Railengineer

Member
Joined
19 Nov 2013
Messages
112
The Mk 3's had bodyside undulations when they were built. This was caused by the heat from welding as others have said above. The reason it is more obvious now is because 'back in the old days' they were ironed out using filler (Isopon) in the BR works before painting. These days they CBA to do it and it costs too much in time and money.
 

tomuk

Member
Joined
15 May 2010
Messages
254
So far as I know they are all extruded sections welded together - doubt if it would be possible to construct trains of aluminium using a skeleton frame and skin, as with steel, due to the different properties of the materials.

The ripple effect described is particular noticeable on the mk4s, and certain colours really show it up. When East Coast started repainting the sets the first few were done in a metallic silver, which made it really noticeable. They then switched to grey, which didn't make it as obvious.
It is more noticeable on the Mk4s because their structure required more welding when built. More heat the worse it gets. When Metro Cammell designed the Mk4s (and 156s before) they used a design that needed less expensive tooling. The horizontal and vertical strengtheners/ribs butt up rather then overlap. This made the bodyshells cheaper to make and allowed multiple outside contractors to build them. It does mean the finish isn't as good as a Mk3 and they are slightly weaker.
 

edwin_m

Veteran Member
Joined
21 Apr 2013
Messages
21,561
Location
Nottingham
It is more noticeable on the Mk4s because their structure required more welding when built. More heat the worse it gets. When Metro Cammell designed the Mk4s (and 156s before) they used a design that needed less expensive tooling. The horizontal and vertical strengtheners/ribs butt up rather then overlap. This made the bodyshells cheaper to make and allowed multiple outside contractors to build them. It does mean the finish isn't as good as a Mk3 and they are slightly weaker.
Although wasn't the weakness counteracted by using thicker structural members? Resulting in slightly less interior space.
 

Top