Theoretical Design For A New DMU For Portsmouth-Cardiff Services

[whole diary]

[eightf48544]

The problem is that any underfloor DMU^▸ (Diesel Multiple Unit) is going to be rubbish.

To get the higher acceleration and top speed you want you've got to cart around a larger/heavier/noiser lump of metal.

Electrification is the only answer then loco hauled Mark 3s or if you must have units 442?s. Although I liked the Clactons in original form. Rode well and accelerated and braked so well that GE timed them to do 60 mph start stop sprints over relatively short distances. You could stand in an intermediate cab watching the speedo you'd be doing 60 at the platform end. I've got a photo taken without flash on slow film of the speedo rock steady on 90.

[devon_metro]

Nono!!!

Tilt stock is built to tilt within the standard loading guage so as long as a train fits the standard loading guage it could thereoetically be any shape!!

[John R]

The problem is that any underfloor DMU^▸ (Diesel Multiple Unit) is going to be rubbish.

To get the higher acceleration and top speed you want you've got to cart around a larger/heavier/noiser lump of metal.

Electrification is the only answer then loco hauled Mark 3s or if you must have units 442?s. Although I liked the Clactons in original form. Rode well and accelerated and braked so well that GE timed them to do 60 mph start stop sprints over relatively short distances. You could stand in an intermediate cab watching the speedo you'd be doing 60 at the platform end. I've got a photo taken without flash on slow film of the speedo rock steady on 90.

Given where we are, even the provision of decent underfloor dmu's is likely to be a) a dramatic improvement and b) a fairly amazing turnaround. Anything else is just pie in the sky.   

[swlines]

I remember reading some stuff about clearance between tilting and non tilting stock to prevent scrapes.

Don't quote me on it by the way - it may not be true.....

Erm, right. What planet do you live on by the way? I hear Venus is quite good at this time of year.

Oh and one question, how the hell do you know that 172s will have a better acceleration to 100mph when you have NEVER BEEN ON ONE???

The problem is that any underfloor DMU^▸ (Diesel Multiple Unit) is going to be rubbish.

To get the higher acceleration and top speed you want you've got to cart around a larger/heavier/noiser lump of metal.

Loco haulage is not the solution for Portsmouth Cardiff, not to mention low turnaround times, loco release times to allow run-around, and the amazing reputation of being very slow at accelerating it's really a no-go zone.

[Btline]

Calm down SWLs^▸ (South Wales Line)!!!

*LM^▸ (London Midland - recent franchise) told me in an email that the 172s would have better acceleration (and I have seen somewhere on the interweb the same).

*I live on Earth- that's why I travel on Britains rail network (although the person who wrote what I read might be that figure from Mars).

*Loco hauled stock would only be temporary, until LM 150s/new build some.

[swlines]

Of course LM^▸ (London Midland - recent franchise) would say they accelerate faster ... it's called PR^▸ (Public Relations)! I highly doubt the acceleration time to 100mph will differ much from a 170 in all honesty. And even then, I'd say Cardiff to Portsmouth would benefit way more with acceleration on par with a 185.

[Btline]

LM^▸ (London Midland - recent franchise) would not introduce stock onto the snow hill lines with worse performance! The Snow Hill lines are already congested. It would be mad - they would save the cash and refresh the 150s!!!

[swlines]

Of course 172s will accelerate faster than 150s - we're talking about speeds against 170s here...

[Shazz]

How about build a batch of locos similar to 43's and borrow some of the few hundred mk2's hanging around?

Refurb them to a high standard. Job done.

[swlines]

Acceleration would be too slow to meet the paths - including the allowances for slack time.

[tramway]

As posted elsewhere something along these lines. NZ Mk II's refurbishment and diesel hauled

http://en.wikipedia.org/wiki/Image:38522796_59f6c38d59.jpg

How about Cl 67's re-geared for 90/100MPH should have adequate acceleration, with a DVT^‡(resolve) at 'tother end.

[swlines]

Shortage of DVTs^‡(resolve) - none are wired for through working with class 67s so there would have to be very expensive mods made (WSMR^▸ (Wrexham, Shropshire and Marylebone Railway) have done these).

[eightf48544]

This debate should actually be moved to the case for electrification.

To get the acceleration and top speed required is going to need around 15hp per ton just for traction plus a another 25hp say for A/C and other auxilaries.

That means something like the Voyager.

15hp per ton is a doddle with EMUs^▸ (Electric Multiple Unit), but not with a "cheap" DMU^▸ (Diesel Multiple Unit) which will require 550 HP engine per 35 ton (max weight) coach. Can the manufactures actually build  a 15HP per ton beast and meet the crumple zone and other crash requirements at 35 tons or less.

[qwerty]

Of course 172s will accelerate faster than 150s - we're talking about speeds against 170s here...

Guys, bear in mind that 170's are 100 mph units and as such are slower off the mark than 75mph units. It's all in the gearing.

If the 172's for the Snow Hill lines are modern inner suburban 75 mph units then I expect they will go like a rocket up to 45 mph whereas the longer legged 170's will catch up at higher speeds.

As a rule of thumb a good 150 will be doing 60 ish one minute from rest. I've not timed it but the drivers vigilence device goes off after a minute  and I'm ususally doing around 60 by the first time it goes off.

I've not driven a 170, but a friend who was at Central Trains reckoned they took an age to accelarate.

[tramway]

Thought struck me last night prompted by 8f^s posts regarding typical power requirements, and a possible solution that may also remove the generally disliked underfloor power on current multiple unit designs. Clearly we are also unlikely to see electrification on the route for a considerable number of years but would like to see acceleration rates comparable with electric traction.

There is already considerable interest in hybrid traction as the conversion of the 43 by Hitachi is demonstrating, there must be potential for this technology in this scenario.

Take as a starting point a basic Voyager and install the hybrid element in one end and distribute electric traction to every car. Internal layout will be a continued debate but I think the concept will be workable in the very near future. This solution is on the basis that a large part of 1 car would be dedicated to power generation and the batteries therefore through corridor connection would be redundant, making 5 car sets. If you can get the power density for the unit to be underslung then this would allow 4 car units and through corridors.