What Multiple unit is a Mk4?

[dubscottie]

Or rather which Unit has the same construction as a Mk4.. (but shaped differently)

In the same way a class 455, 150 etc is a Mk3.

Had in another thread class 158/9..

Close. but wrong. Anyone else what to guess?

 

[ainsworth74]

I wasn't aware that there were any MUs based off of the Mk4...

 

[dubscottie]

I wasn't aware that there were any MUs based off of the Mk4...

Should be the other way round.. The Mk 4 is based on what unit..

 

[Ivo]

The Mk4 was based on the 156, was it not?

Quite a jump between a 156 and a 91 rake mind!

 

[dubscottie]

The Mk4 was based on the 156, was it not?

Quite a jump between a 156 and a 91 rake mind!

Spot on!! I thought it would take longer. well done to you!

 

[ainsworth74]

Hmm interesting, thanks for that dubscottie

 

[sprinterguy]

Hang on a minute, you could well be right, but in what way is a mark 4 based on a 156? Beyond both being products of Metro Cammell and utilising steel bodyshells, I can't see how the former was adapted from the latter:

The mark 4 carriages were a direct development of the APT-P carriage design in terms of taper profile and general carriage features, as far as I was aware that was the source of all their design lineage.

I've always viewed the 156s as the most Mk.3 like of the Mk.3 based DMUs, on account of their 23 metre carriage length. Willing to be proved wrong though.

 

[Royston Vasey]

Or rather which Unit has the same construction as a Mk4.. (but shaped differently)

In the same way a class 455, 150 etc is a Mk3.

Had in another thread class 158/9..

Close. but wrong. Anyone else what to guess?

You're basically saying that they both have an all-steel construction. Doesn't mean one is based on the other! "Shaped differently" kinda defeats your point, no?

Certainly saying the a 156 "is a Mk 4" is rather an exaggeration!!

Must try harder dubscottie! Show us more justification for your wild surmise!

 

[4SRKT]

I've always viewed the 156s as the most Mk.3 like of the Mk.3 based DMUs, on account of their 23 metre carriage length. Willing to be proved wrong though.

Indeed, especially if you look at the Irish Rail suburban mk IIIs, with hopper ventilators rather than full aircon as per normal mk III design, the resemblance is even more obvious.

http://www.flickr.com/photos/7995245@N02/3453504700/

I'm surprised more units weren't built to the mk II design. The SR carried on building units to the mk I spec for years after the mk II was standard for loco-hauled stock. I believe the only mk II units were 310s, 312s and the NIR 80 class DEMUs, still hanging on by the skin of its teeth. All attractive, comfortable and good riding sets.

 

[dubscottie]

From the October 1989 issue of Modern Railways.. (Also posted in the Mk3/Mk4 thread.. sorry)

In a Mk 3 the top-hat section verticals (the downward bits) are pressed over the long horizontals by "pressing" them.

When Met-Cam only had 6 months to develop the 156 they had to use a simpler structure as it would have taken 2 years to develop the tools to "press" sections of the structure.

They had the same time scale for the Mk4 so updated the 156 body to UIC end loadings.

On a 156 and a Mk4 only the vertical sections are continuous and short horizontal sections are used in between. This gives (unlike a Mk3) a flat surface to mount the interior. The are also thicker which gives better sound insulation. Also as the structure is simple, both BREL Crewe and BREDA of Italy (the last 32 TSO's) built Mk4 shells without expensive tools.

An interesting bit in the article was about "bodyside ripple" It was only allowed to be +/- 35mm per of metre of bodyside. It does not look like they met this going by the amount of dirt that builds up between the vertical pillars on the new Eastcoast livery!

Another point is that 2 Class 150 cars were written off when only a few years old (St Helens and Seamer). However 156490, which had much more damage (nothing was left forward of the toilet) was repaired.. Maybe due to the simplicity of its bodyshell design.

 

[O L Leigh]

Irrespective of what Modern Railways suggest, just a cursory glance at the two vehicles will tell you that they are not the same. For starters, the Mk4 has a tilt profile that the Cl156 lacks. They may have shared a number of construction techniques, but that does not make them the same. Likewise the Mk4 isn't derived in any particular way from the APT except in the sense that the IC225 concept was very similar to the APT-S.

The Mk3 based MU's really were based on the Mk3 coach, and you can see the similarities much more clearly. In fact, they just modified the Mk3 coach construction jigs in order to start turning out MU's. However, I'm not sure that it was a good idea, as I'm fairly certain that it introduced a number of weak spots into the structure that would be tested in the event of a heavy collision.

I have definately seen pics of a Cl317 driving trailer that had been in a heavy collision with a Peak during a shunting accident at Cricklewood in the 1980's and the coach had been bent forward of the leading set of passenger doors. This obviously will have compromised it's structural integrity so it was scrapped and another built with the same number. Now I believe the two Cl150 vehicles that were written off had been in collision with a bridge (St Helens) and a digger or some other heavy road vehicle (Seamer), so it's not beyond the realms of possibility that they suffered similarly heavy damage. I do recall seeing a pic in a magazine of one of these vehicles being scrapped, but I can't bring to mind enough detail to confirm the extent of damage.

O L Leigh