What are the "lines" on the top of Mk3 and Mk4 coaches for?

[Egg Centric]

There's probably already a thread explaining this but I'm not sure what to search for. By "lines" I mean the parallel metal grooves on the roofs of these coaches and some derivived units. As well as clearly other trains - I'm in an Azuma (which I'm reasonably sure doesn't have the lines) in platform 4 at Doncaster typing this thread and noticed the Adelante pulling into platform 3 does have them, despite not being derived from those coaches.

I can think of a few theories:

• Styling
• Aerodynamics - either lateral stability or something very clever
• Space for wiring / air conditioning

None of these are particularly convincing though. Which is not to say that one or more of them isn't the case. I'm sure someone on here knows though!

 

[swt_passenger]

There's probably already a thread explaining this but I'm not sure what to search for. By "lines" I mean the parallel metal grooves on the roofs of these coaches and some derivived units. As well as clearly other trains - I'm in an Azuma (which I'm reasonably sure doesn't have the lines) in platform 4 at Doncaster typing this thread and noticed the Adelante pulling into platform 3 does have them, despite not being derived from those coaches.

I can think of a few theories:

• Styling
• Aerodynamics - either lateral stability or something very clever
• Space for wiring / air conditioning

None of these are particularly convincing though. Which is not to say that one or more of them isn't the case. I'm sure someone on here knows though!

Stiffness of the roof. Think about how corrugated metal sheet used in building doesn’t bend along the length.

 

[Egg Centric]

Stiffness of the roof. Think about how corrugated metal sheet used in building doesn’t bend along the length.

That makes sense. Thank you.

 

[Russel]

Stiffness of the roof. Think about how corrugated metal sheet used in building doesn’t bend along the length.

I've wondered about this myself in the past, but of course, the answer is so simple, thanks!

 

[PG]

Stiffness of the roof. Think about how corrugated metal sheet used in building doesn’t bend along the length.

In that case, how come the Class 8xx Hitachi units don't use this, or IIRC the Alsthom Class 390?

 

[Russel]

In that case, how come the Class 8xx Hitachi units don't use this, or IIRC the Alsthom Class 390?

Changes in building methods and materials over the years making the technique redundant?

 

[AM9]

In that case, how come the Class 8xx Hitachi units don't use this, or IIRC the Alsthom Class 390?

The 80x cars don't have a plain curved roof like the MKIIIs. The roof is more a flat platform to support the a/c packs and various other kit. It is fitted between the curved part of the sides which owing to its curvature is probably rigid enough to brace the roof. The 390's construction looks similar. Bear in mind that MKIII cars are just trailers.

 

[edwin_m]

80x and many other units built from the 1990s onwards are made of aluminium not steel. The bodyshell is usually extruded as a solid form rather than being made up from flat sheet fixed onto a frame like the Mk3. Thus it doesn't require any corrugations for stiffening.

It's possible to make bodyshells from aluminium sheets on a frame in the same way as the Mk3 does with steel. I think the only UK main line trains to be built that way were the two prototype Class 151s, but from what I can see on an image search they didn't have corrugated roofs. I believe the London Underground stock, also supplied by Metro-Cammell, was of similar construction. Edit: Think the PEP derivatives in classes 313, 315, 507 and 508 used this construction too.

 

[stj]

I expect as part of the spec for high speed running the Mk3 had to be stronger than a Mk2 hence the grooved roof.

 

[AndrewE]

80x and many other units built from the 1990s onwards are made of aluminium not steel. The bodyshell is usually extruded as a solid form rather than being made up from flat sheet fixed onto a frame like the Mk3. Thus it doesn't require any corrugations for stiffening.

It's possible to make bodyshells from aluminium sheets on a frame in the same way as the Mk3 does with steel. I think the only UK trains to be built that way were the two prototype Class 151s, but from what I can see on an image search they didn't have corrugated roofs. I believe the London Underground stock, also supplied by Metro-Cammell, was of similar construction.

Mk III were definitely welded-up relatively narrow aluminium extrusions, maybe a couple of feet (the bodies anyway, it was revolutionary for York works.) Mk II might have been sheet steel welded to a monocoque frame.
I very much doubt that a whole aluminium bodyshell or maybe even bodyside could be extruded in one go.
I can't remember about the roofs.

 

[43096]

Bear in mind that MKIII cars are just trailers.

There's plenty of vehicles with the ribbed roof, essentially the Mark 3 lineage of Mark 3 > 150/317-322 > 442 and the Washwood Heath development line of 156 > Mark 4 > 175/180 > 334/458/460. A lot of those are not trailers.

It should also be noted that ribbed bodysides have been used on locos elsewhere for the same reason (keeping strength up and weight down), for example East German Class 143, SLM 460s for SBB (and derivatives for BLS, Norway and Finland) and Siemens used it for its ES64F4 locos.

 

[43096]

Mk III were definitely welded-up relatively narrow aluminium extrusions, maybe a couple of feet (the bodies anyway, it was revolutionary for York works.)

Definitely? Why, then, do Mark 3 bodyshells go the brown colour of rust when they oxidize?

 

[randyrippley]

Definitely? Why, then, do Mark 3 bodyshells go the brown colour of rust when they oxidize?

Because the mk3 body is steel
The PEP bodies were aluminium

There's plenty of vehicles with the ribbed roof, essentially the Mark 3 lineage of Mark 3 > 150/317-322 > 442 and the Washwood Heath development line of 156 > Mark 4 > 175/180 > 334/458/460. A lot of those are not trailers.

It should also be noted that ribbed bodysides have been used on locos elsewhere for the same reason (keeping strength up and weight down), for example East German Class 143, SLM 460s for SBB (and derivatives for BLS, Norway and Finland) and Siemens used it for its ES64F4 locos.

Corrugated body panels date back to 1930s German aircraft and Citroen vans

 

[superalbs]

There's plenty of vehicles with the ribbed roof, essentially the Mark 3 lineage of Mark 3 > 150/317-322 > 442 and the Washwood Heath development line of 156 > Mark 4 > 175/180 > 334/458/460. A lot of those are not trailers.

It should also be noted that ribbed bodysides have been used on locos elsewhere for the same reason (keeping strength up and weight down), for example East German Class 143, SLM 460s for SBB (and derivatives for BLS, Norway and Finland) and Siemens used it for its ES64F4 locos.

And perhaps most commonly, they're used on just about every carriage in the former Soviet Union.

In that case, how come the Class 8xx Hitachi units don't use this, or IIRC the Alsthom Class 390?

I believe the 390s actually do!

 

[randyrippley]

Mk III were definitely welded-up relatively narrow aluminium extrusions, maybe a couple of feet (the bodies anyway, it was revolutionary for York works.) Mk II might have been sheet steel welded to a monocoque frame.
I very much doubt that a whole aluminium bodyshell or maybe even bodyside could be extruded in one go.
I can't remember about the roofs.

Alusuisse / Lonza have had the technology to extrude full-length aluminium body panels for at least 30 years

 

[43096]

Because the mk3 body is steel

I'm well aware of that. Hence my question to the OP that Mark 3s were "definitely" aluminium.

 

[edwin_m]

Mk III were definitely welded-up relatively narrow aluminium extrusions, maybe a couple of feet (the bodies anyway, it was revolutionary for York works.) Mk II might have been sheet steel welded to a monocoque frame.
I very much doubt that a whole aluminium bodyshell or maybe even bodyside could be extruded in one go.
I can't remember about the roofs.

You are right that extruded aluminium construction produces "planks" that are assembled up into the bodyshell, not the whole bodyshell in one go. As a variation, Turbostars and Electrostars are bolted together instead.

However, the Mk3 is definitely constructed of steel sheeting welded to a framework.

 

[AndrewE]

Alusuisse / Lonza have had the technology to extrude full-length aluminium body panels for at least 30 years

Of course they do, but even whole body panels? I was surprised to read

The bodyshell is usually extruded as a solid form rather than being made up from flat sheet fixed onto a frame like the Mk3. Thus it doesn't require any corrugations for stiffening.

as I really couldn't believe a whole body shell being extruded at once. Of course it wasn't!

By coincidence, Greg whatnot was just being shown "in the factory" at Derby. The EMU coach floor was made up of half a dozen longitudinal "planks," each one extruded in one go as I had understood. They were then welded along their length. It implied the roof was similar. I hadn't realised the bodyside panels were just huckbolted in between the floor and roof, as I was under the impression that bodysides were made up using long extrusions in the same way.
Maybe I got "Mk 3 -derived" EMUs and Mk 3 coaches mixed up and thought that both were made from longitudinal strips. ("Strips" meaning complex hollow carefully-designed sections.)

 

[BRX]

It should also be noted that ribbed bodysides have been used on locos elsewhere for the same reason (keeping strength up and weight down), for example East German Class 143, SLM 460s for SBB (and derivatives for BLS, Norway and Finland) and Siemens used it for its ES64F4 locos.

And of course, class 66s & 67s

 

[fgwrich]

A pair of poor photos showing the insides of a Mk3 roof prior to scrapping. You can just about make out the ribs before you see the air con ducts.

 

[Egg Centric]

Must admit my "mental image" when I look at them is already slightly different with this new knowledge. A bit like when you know about the arrow in the FedEx logo. You cannot unsee it. I now see corrugation not lines!

Almost wish I hadn't ask. I'd been seeing those lines since a hornby train set at pre prep!

 

[KevinTurvey]

If I remember correctly the floor 'panelling' on the mK2 and possibly the Mk3 were also ribbed as well as the roof to provide stiffness and strength, the Mk2 floor panels were prone to corrosion and very difficult to repair which is why there are so few (relatively) preserved.

 

[DelW]

Maybe I got "Mk 3 -derived" EMUs and Mk 3 coaches mixed up and thought that both were made from longitudinal strips. ("Strips" meaning complex hollow carefully-designed sections.)

The class 455 EMUs have steel bodies based on the mk3 design, but when they were built BR had surplus ex class 508 trailers, which had aluminium bodies based on the PEP prototype design.

A sub-group of the 455s had one of these trailers included in each set, meaning that they have three steel mk3 type coaches and one aluminium PEP type coach. The difference in profile between the two designs is very clear when you see one of these hybrid units.

 

[edwin_m]

The class 455 EMUs have steel bodies based on the mk3 design, but when they were built BR had surplus ex class 508 trailers, which had aluminium bodies based on the PEP prototype design.

A sub-group of the 455s had one of these trailers included in each set, meaning that they have three steel mk3 type coaches and one aluminium PEP type coach. The difference in profile between the two designs is very clear when you see one of these hybrid units.

I've edited my previous post to mention the PEP-derived classes.

 

[100andthirty]

Of course they do, but even whole body panels? I was surprised to read

as I really couldn't believe a whole body shell being extruded at once. Of course it wasn't!

By coincidence, Greg whatnot was just being shown "in the factory" at Derby. The EMU coach floor was made up of half a dozen longitudinal "planks," each one extruded in one go as I had understood. They were then welded along their length. It implied the roof was similar. I hadn't realised the bodyside panels were just huckbolted in between the floor and roof, as I was under the impression that bodysides were made up using long extrusions in the same way.
Maybe I got "Mk 3 -derived" EMUs and Mk 3 coaches mixed up and thought that both were made from longitudinal strips. ("Strips" meaning complex hollow carefully-designed sections.)

All over the world, aluminium vehicles are constructed using long aluminium planks. Floors and roofs are usually constructed as seen on the Greg Wallace programme.

Huckbolts are a different matter. Huckbolting is, as far as I know, unique to Derby though a lot of cars have been built this way; Electrostars, Turbostars, Aventras, 2009 tube stock, and S stock. Everyone else welds the sides to the roofs and floors, and only starts assembly of components when they've got a complete bodyshell.

Pretty much all suppliers build sides in modules between doors, meaning they are a lot shorter than the roof and floor modules. Some suppliers weld those side modules and cut out the window apertures after welding. As an example, a class 345 Aventra has eight side modules - four per side, though an intercity car, such as a class 80X, with end doors would only have two side modules - one each side.

 

[ac6000cw]

There's plenty of vehicles with the ribbed roof, essentially the Mark 3 lineage of Mark 3 > 150/317-322 > 442 and the Washwood Heath development line of 156 > Mark 4 > 175/180 > 334/458/460. A lot of those are not trailers.

It should also be noted that ribbed bodysides have been used on locos elsewhere for the same reason (keeping strength up and weight down), for example East German Class 143, SLM 460s for SBB (and derivatives for BLS, Norway and Finland) and Siemens used it for its ES64F4 locos.

And of course, class 66s & 67s

...and the 59s.

Corrugated body panels date back to 1930s German aircraft and Citroen vans

...and 1930s trains.

The 1934 US Budd-built Pioneer Zephyr lightweight streamliner train used corrugated/ribbed stainless steel, welded using Budd's proprietary 'Shotweld' process. That was followed by thousands of mainline and subway cars built by Budd over the next 40 years or so, including many built in other countries by various Budd licensee's. The Amtrak 'Amfleet' cars are still in regular use (photo from Wikipedia):

<p>
By &lt;a href="//commons.wikimedia.org/wiki/User:Pi.1415926535" title="User:Pi.1415926535"&gt;Pi.1415926535&lt;/a&gt; - &lt;span class="int-own-work" lang="en"&gt;Own work&lt;/span&gt;, CC BY-SA 3.0, Link

 

[BRX]

Those Amfleet coaches are slightly banana shaped (ends are slightly lower than middle) - I wonder if that's intentional to allow for deflection when loaded, or something that develops after years of use.

 

[ac6000cw]

I wonder if that's intentional to allow for deflection when loaded

AFAIK, yes it's intentional, for the reason you stated. I think it's normal practice for long rail vehicles, as they are basically beams supported near the ends.

I have seen freight vehicles in the US with noticeable 'banana shaped' sags, presumably due to having spent many years carrying heavy loads in the middle of the vehicle e.g. 44 year old, 65ft 'gondola' PC 592006 near Altoona, PA:

 

[AM9]

Those Amfleet coaches are slightly banana shaped (ends are slightly lower than middle) - I wonder if that's intentional to allow for deflection when loaded, or something that develops after years of use.

Iswn't that like the class 153 units that have developed a sag between the bogies?

 

[ac6000cw]

Iswn't that like the class 153 units that have developed a sag between the bogies?

BRX was saying that the Amfleet cars are bowed upwards in the middle (look carefully at the rear car in the photo). The 153's (and the freight car in my photo above) have developed downward sags in the middle.

I've read descriptions of diesel loco construction, where the underframes are designed to have a small upwards bow in the middle when built. Then after the heavy diesel engine and alternator are fitted and with a full fuel tank etc. the underframe becomes more-or-less flat (or slightly bowed upwards, to allow for a bit of sag over time).