Similarities with 158's and Mk4 Stock

[najaB]

Just like Bombardier Electro/Turbostars I believe. Over the years many posters have wrongly described them as having a 'tilt profile' as well; AIUI they are also shaped that way to stay in gauge after major suspension failure.

To be fair, they do have a 'tilt profile' just not for deliberate tilt!

 

[randyrippley]

Mk4 uses a sectional/modular build technique similar to the 153/155 units, though not using Leyland parts.
Intended to be easily adapted to other carriage lengths, but never actually used
as other designs proved cheaper for MU production.
Also the long term Mk4 rigidity was always suspect due to the sectional build

 

[edwin_m]

Would the train actually tilt after loss of an airbag? I would imagine the airbags either side would be linked so that the opposite one would deflate to keep it level.

 

[tomuk]

Mk4 uses a sectional/modular build technique similar to the 153/155 units, though not using Leyland parts.
Intended to be easily adapted to other carriage lengths, but never actually used
as other designs proved cheaper for MU production.
Also the long term Mk4 rigidity was always suspect due to the sectional build

The Mk4 is nothing like a 155/153 it is of a welded steel construction.

The 153/155 like the 142s are made from pressed steel sections riveted together. (Based on the panels used on the Leyland National bus.)

The 156 and Mk4 structure is a cheaper version of the Mk3 structure.

In the Mk3 the horizontal and vertical 'ribs' that lie behind the skin are continuous pieces of steel made with special tooling to allow them to overlap each other and be welded to the skin.

Metro Cammell saved the cost of the special tooling and instead just welded the ribs together from separate pieces. This allowed the 156 and Mk4 shells to be made by multiple outside contractors.

 

[Rick1984]

According to Wikipedia

The Class 158 and Class 159 diesel multiple units, although superficially similar, are not based on the Mark 4 bodyshell: the Mark 4 is derived from the Class 156

 

[Paul180]

They were a nuisance, people got in the way.

They still are on SWT Cl 158/159 people refuse to sit up when people want to alight and board

 

[danielnez1]

I was reading a old issue of a rail mag (can't remember which one) from 1989 and they had a feature about the design of the 158 and they mentioned that the design was derived from the Mk3 coach design.

A IEEE publication (N.B. may be limited access) by two Metro-Cammell employees states:

The bodyshell of the Mk IV passenger vehicles and the Driving Van Trailers is of conventional construction based upon the lightweight shell developed by Metro-Cammell for the British Rail Class 156 Diesel Multiple Units.

 

[randyrippley]

Metro Cammell saved the cost of the special tooling and instead just welded the ribs together from separate pieces. This allowed the 156 and Mk4 shells to be made by multiple outside contractors.

So I'm right -the Mk4 was built to a sectional design, the main difference being that welds replaced rivits in assembling the sections.The key point is the welded ribs are a potential weak spot and have lessened rigidity over a Mk3

 

[edwin_m]

I was reading a old issue of a rail mag (can't remember which one) from 1989 and they had a feature about the design of the 158 and they mentioned that the design was derived from the Mk3 coach design.

Classes 317 to 322 and 455 were certainly derived from the Mk3 coach, made shorter and a bit wider with different doors and windows but the same basic structure. Class 158 was totally different being built out of welded aluminium rather than steel.

 

[danielnez1]

Classes 317 to 322 and 455 were certainly derived from the Mk3 coach, made shorter and a bit wider with different doors and windows but the same basic structure. Class 158 was totally different being built out of welded aluminium rather than steel.

For something to be derived from a predecessor it doesn’t need to share all of its characteristics. Granted they are constructed using different materials, but that doesn’t necessary mean every design aspect of the MK3 had to be tossed away.

 

[edwin_m]

For something to be derived from a predecessor it doesn’t need to share all of its characteristics. Granted they are constructed using different materials, but that doesn’t necessary mean every design aspect of the MK3 had to be tossed away.

Well no, they still kept the basic dimensions and mechanicals. But the bodyshell is otherwise totally different in design and construction, the bogies are totally different, the doors are totally different...

 

[tomuk]

So I'm right -the Mk4 was built to a sectional design, the main difference being that welds replaced rivits in assembling the sections.The key point is the welded ribs are a potential weak spot and have lessened rigidity over a Mk3

Well not really. The Leyland based designs are assembled from separate steel pressings. The pressings form each window bay and in theory you could assemble as long a body as you wanted by just riveting on more pressings.

You can see the 'joins' in the pictures below.

Leyland National JHJ 150V by yoshieboy, on Flickr

Class 142: 142002 Manchester Victoria by emdjt42, on Flickr

153 307 by Hugh Llewelyn, on Flickr

On a BREL Mk3s or Metro Cammell 156/Mk4/175? the bodies are assembled from sheets and lengths of steel the sizes of which are purely down to what can be handled at the factory.

I suppose the correct description is to say the Leyland designs are modular and the Mk3 and Mk4 are not.

 

[tomuk]

Well no, they still kept the basic dimensions and mechanicals. But the bodyshell is otherwise totally different in design and construction, the bogies are totally different, the doors are totally different...

I agree and in actual fact they don't share the same dimensions either. The 158 is not the same size as either a Mk3 coach or a Mk3 based DMU/EMU.

I would suggest that if BREL had won the contract for the Mk4s that they might well have been aluminium construction like the 158s.

I believe the 158 construction was based on work done on the APT-P which was also made of aluminium extrusions. This design refined then into the Networkers, Electrotars and Aventras.

A family tree

BREL: Mk3 > Mk3 EMU Mk1 (455/317) > Mk3 DMU (150) > Mk3 EMU Mk2 (319/320/321/322)

Met Cam: 156 > Mk4 > Coradia/Juniper (170, 334, 458 etc)

BREL: ATP-P > 158 > Networker (465/165 etc) > Turbostar (168, 170, 172) > Electrostar (375, 377, 387) > Aventra (345, 710)

 

[edwin_m]

I believe the 158 construction was based on work done on the APT-P which was also made of aluminium extrusions. This design refined then into the Networkers, Electrotars and Aventras.

Up until the Networkers they used welded extrusions, but the Electrostars (Turbostars too), and I believe the Aventras also, have the roof, floor and sides attached to each other by large bolts. Welding aluminium is tricker than welding steel and there was some concern after accidents (including Ladbroke Grove I think) that the bodies were splitting along the welds because the heat had weakened the metal. I don't know if that was their reason to change though.

 

[dubscottie]

Up until the Networkers they used welded extrusions, but the Electrostars (Turbostars too), and I believe the Aventras also, have the roof, floor and sides attached to each other by large bolts. Welding aluminium is tricker than welding steel and there was some concern after accidents (including Ladbroke Grove I think) that the bodies were splitting along the welds because the heat had weakened the metal. I don't know if that was their reason to change though.

After Ladbroke Grove there was real concerns about the strength of the 168/170 etc to the point that some wanted Adtranz to put a bodyshell through a car style crash test.

If a welded body split (OK it was hit head on by another train going at over 100 mph) what chance would a bolted one have.

Also the Mk4 is not sectional. The steel members run the coach length and a Mk4 is as strong as a Mk3.

 

[tomuk]

After Ladbroke Grove there was real concerns about the strength of the 168/170 etc to the point that some wanted Adtranz to put a bodyshell through a car style crash test.

If a welded body split (OK it was hit head on by another train going at over 100 mph) what chance would a bolted one have.

Also the Mk4 is not sectional. The steel members run the coach length and a Mk4 is as strong as a Mk3.

The Mk4s are about 6 tonnes heavier than the equivalent Mk3 this is partly down to the SIG bogies but also the extra metal/welding required to keep the strength the same as Mk3 despite the simpler construction.

Overall crashworthiness has improved through the BREL/Adtranz/Bombardier line.

On the 158 aluminium extrusions are single skined and welded together.

Whereas the Networkers and early Electro/Turbostars the extrusions are double skinned. The amount of welding has also increased on the later electrostars and Aventra.

 

[edwin_m]

If a welded body split (OK it was hit head on by another train going at over 100 mph) what chance would a bolted one have.

Depends on how many bolts you use and how large they are. Unlike a weld, if it isn't strong enough the design can be changed to add some more.

Agree it wouldn't have made much difference at Labroke Grove. Great Heck shows that a traditional steel welded structure suffers a similar fate in a similar situation.

 

[MK Tom]

I agree and in actual fact they don't share the same dimensions either. The 158 is not the same size as either a Mk3 coach or a Mk3 based DMU/EMU.

I would suggest that if BREL had won the contract for the Mk4s that they might well have been aluminium construction like the 158s.

I believe the 158 construction was based on work done on the APT-P which was also made of aluminium extrusions. This design refined then into the Networkers, Electrotars and Aventras.

A family tree

BREL: Mk3 > Mk3 EMU Mk1 (455/317) > Mk3 DMU (150) > Mk3 EMU Mk2 (319/320/321/322)

Met Cam: 156 > Mk4 > Coradia/Juniper (175, 334, 458 etc)

BREL: APT-P > 158 > Networker (465/165 etc) > Turbostar (168, 170, 172) > Electrostar (375, 377, 387) > Aventra (345, 710)

Does this essentially mean the 180 is a Mark 4 based unit? The 175/180 bodyshell looks and feels like a Mark 3, but is obviously structurally different. I guess that's the result of not having the tilt profile - the 175/180 body is what a non-tilt mark 4 would've looked like.

I suppose there's nothing in the Met Cam lineage before the 156, back to the 101? I know they built stuff for overseas - it'd be interesting to see what fills that gap. Obviously they built the 151s, then following the failure of that designed the 156 to feel like a souped up 150.

 

[edwin_m]

I suppose there's nothing in the Met Cam lineage before the 156, back to the 101? I know they built stuff for overseas - it'd be interesting to see what fills that gap. Obviously they built the 151s, then following the failure of that designed the 156 to feel like a souped up 150.

The 101s had some similarities with the roughtly contemporary Met-Camm Pullman stock - window style and depth in particular. I don't know if this is also true of the body structure itself. Any resemblence to the 156 over 20 year later would be purely coincidental.

 

[bgstrowger]

Does this essentially mean the 180 is a Mark 4 based unit? The 175/180 bodyshell looks and feels like a Mark 3, but is obviously structurally different. I guess that's the result of not having the tilt profile - the 175/180 body is what a non-tilt mark 4 would've looked like.

The Class 175/180 bodyshell bares some similarities to the Nightstar stock, which in turn is based on the Mk4 but with a non-tilt profile.

For the electric Coradias, I think their lineage is based more on the GEC Networkers.

 

[danielnez1]

Well no, they still kept the basic dimensions and mechanicals. But the bodyshell is otherwise totally different in design and construction, the bogies are totally different, the doors are totally different...

Just like how the MK3 based DMU/EMU have shorter bodies, different bogies and doors. Go figure.