Bombardier designs 125mph bi-mode for UK market

D365 · 15 Apr 2018

Sixteen powered axles vs eight obviously has its benefits.

RailUK Forums

Chester1 · 15 Apr 2018

gingertom said:
indeed. With the rest of the civilised world stringing up wires everywhere instead of resorting to bi-mode the idea might actually catch on. I mean, they can't all be wrong can they?

Bi modes are definitely a short term solution but EMUs with batteries are definitely worthwhile on routes that need to be electrified but costs have become to high. Leeds to Manchester could be 90% wired with EMUs using their batteries to get past low bridges and tunnels. It would require a linked up infrastructure and rolling stock policy though!

td97 · 15 Apr 2018

Chester1 said:
Bi modes are definitely a short term solution but EMUs with batteries are definitely worthwhile on routes that need to be electrified but costs have become to high. Leeds to Manchester could be 90% wired with EMUs using their batteries to get past low bridges and tunnels. It would require a linked up infrastructure and rolling stock policy though!

Leeds to Manchester can be 100% wired. Only since Grayling has been in office has it become too difficult to put OHLE through a Victorian tunnel.

D365 · 15 Apr 2018

td97 said:
Only since Grayling has been in office has it become too difficult to put OHLE through ~~a Victorian tunnel~~ open air.

Fixed.

Chester1 · 15 Apr 2018

td97 said:
Leeds to Manchester can be 100% wired. Only since Grayling has been in office has it become too difficult to put OHLE through a Victorian tunnel.

I know its not difficult its just been very expensive. Batteries and gaps are a reasonable compromise after the electrification debacle of the last 5 years. TPE have options for extra 397s and if CAF can put a battery in them at a sensible price then why not save the money required to raise or replace bridges and wire tunnels? If it was successful it would make wiring other lines a sensible option again. Crewe to Chester has over 30 bridges and most are listed and built 1840-60, most of the cost of electrification would be removed if no work was required on them. Much more sensible than making 125mph bi modes for 30-40 years.

James James · 15 Apr 2018

Dave1987 said:
Very much so. I’ve had old school drivers tell me that ‘back in the day’ there was no issue with wheel slip at all when you had a heavy loco with the powered wheels on it. Distributed traction is not answer to all problems even if the DFT believe it to be so.

That doesn't make much sense. Sure, locomotives are heavier. But a locomotive also has to have much higher force per wheel for the same acceleration, and hence is just as likely (if not more likely) to suffer wheelslip.

Example: hyptothetical single-car of a class 156 (both cars are similar weight, both are driven in reality), weight 35t, or just under 10t per axle, 2 axles driven -> max force that wheels can transfer = ~ 20t x coefficient of static friction between rail and wheel, and that's per 35t of train weight.

Class 91, 90tons, ~23t per axle, assuming all axles are driven it can provide a max force of 90t x coefficient of static friction.

Effectively, the class 91 can transfer 4.5x as much force as a class 156, but it might be dragging 8x40t Mk4's, so total (including loco) of 400t. That's more than 10x the weight of a single carriage in the class 156 needing accelerated, but only 4.5x max power transfer available through the wheels. Effectively, a class 156 can accelerate twice as fast as a class 91 before wheelslip occurs. (The actual power available from the motors or engines is a separate story, this is just the physics of wheelslip.)

The equations all change for e.g. heavier multiple units, or multiple units with less driven axles, etc. But it's clear locomotives don't have any clear advantage, the only scenario where they'll have an advantage is probably very short trains.

(All these numbers are approximate, and calculations are handwavy, but they're enough to prove the point.)

edwin_m · 15 Apr 2018

James James said:
That doesn't make much sense. Sure, locomotives are heavier. But a locomotive also has to have much higher force per wheel for the same acceleration, and hence is just as likely (if not more likely) to suffer wheelslip.

Example: hyptothetical single-car of a class 156 (both cars are similar weight, both are driven in reality), weight 35t, or just under 10t per axle, 2 axles driven -> max force that wheels can transfer = ~ 20t x coefficient of static friction between rail and wheel, and that's per 35t of train weight.

Class 91, 90tons, ~23t per axle, assuming all axles are driven it can provide a max force of 90t x coefficient of static friction.

Effectively, the class 91 can transfer 4.5x as much force as a class 156, but it might be dragging 8x40t Mk4's, so total (including loco) of 400t. That's more than 10x the weight of a single carriage in the class 156 needing accelerated, but only 4.5x max power transfer available through the wheels. Effectively, a class 156 can accelerate twice as fast as a class 91 before wheelslip occurs. (The actual power available from the motors or engines is a separate story, this is just the physics of wheelslip.)

The equations all change for e.g. heavier multiple units, or multiple units with less driven axles, etc. But it's clear locomotives don't have any clear advantage, the only scenario where they'll have an advantage is probably very short trains.

(All these numbers are approximate, and calculations are handwavy, but they're enough to prove the point.)

All this is true, but there are are couple of factors that make a difference. For example:

An old loco has more weight on each axle which may help break through rail contamination that reduces adhesion.
Older trains have a less smooth ride, with the wheel sometimes "hunting" to and fro across the rail, which helps to clean both.
Tread brakes on older stock also clean the contamination off the wheel.

The situation also changes at higher speeds. Acceleration equals force divided by mass but force equals power divided speed, so above a certain speed the train is using full power and the acceleration drops as speed increases. Resistance to motion also reduces acceleration and increases with speed.

w1bbl3 · 16 Apr 2018

Chester1 said:
If it was successful it would make wiring other lines a sensible option again. Crewe to Chester has over 30 bridges and most are listed and built 1840-60, most of the cost of electrification would be removed if no work was required on them. Much more sensible than making 125mph bi modes for 30-40 years.

The slight problem is that GWML electrification has struggled with cost vs budget on the "easy" plain line bits and far less so on tunnel and bridges which mostly appear to have been completed on time. Any kind of avoid tunnels / bridges strategy would probably still see them wired but as neutral sections to avoid raising a lowering the pan multiple times per journey.

I can see applications where batteries rather than diesel self power make a lot of sense particularly for services where the core route is electrified but the service extends on to a short branch which wouldn't be economic to wire even before the current mess. However it shouldn't be forgotten that batteries are heavy and have a limited life before replacement, over the very long term wiring may still be more cost effective.

Chester1 · 16 Apr 2018

w1bbl3 said:
The slight problem is that GWML electrification has struggled with cost vs budget on the "easy" plain line bits and far less so on tunnel and bridges which mostly appear to have been completed on time. Any kind of avoid tunnels / bridges strategy would probably still see them wired but as neutral sections to avoid raising a lowering the pan multiple times per journey.

I can see applications where batteries rather than diesel self power make a lot of sense particularly for services where the core route is electrified but the service extends on to a short branch which wouldn't be economic to wire even before the current mess. However it shouldn't be forgotten that batteries are heavy and have a limited life before replacement, over the very long term wiring may still be more cost effective.

Batteries limited life makes them expensive but could be very useful while their capacity continues to grow meaning that each time they are replaced the off wires range increases. I think the main application for EMU batteries will probably be by ToCs like Northern when the sprinters need replacing. When services are very intertwined a whole fleet makes sense to minimise time off the wires. Neutral sections and batteries for intercity services have different economics though.

mpthomson · 16 Apr 2018

td97 said:
Leeds to Manchester can be 100% wired. Only since Grayling has been in office has it become too difficult to put OHLE through a Victorian tunnel.

Should actually say only since Network Rail has shown itself to be entirely incapable of delivering electrification on time or on budget due to woeful project management skills.... etc It's public money that they're wasting and it can't continue in that manner. That's why the projects were curtailed. I'm sure that at some point Leeds/Manchester will be wired, there's just no money for it at the moment.

D365 · 16 Apr 2018

mpthomson said:
Should actually say only since Network Rail has shown itself to be entirely incapable of delivering electrification on time or on budget due to woeful project management skills...

So instead we choose to forget the lessons learned from GWEp, allow the supply chain to collapse and therefore go through all the pain again in 15-20 years?

Charlie Smythe · 17 Jan 2019

About adhesive weight and wheel slip. The DfT loves distributed traction but does it actually work? If you have 120 tonnes of adhesive weight on a Co-Co loco then you 20 tonnes per axle right? What is the difference between that and 4 coaches with one powered bogies each giving 120 tonnes on 8 axles. You still have 120 tonnes of adhesive weight so surely it wouldn't make a difference.

Spartacus · 17 Jan 2019

Didn’t Audi answer this one?

Jozhua · 17 Jan 2019

I really hope these bi-modes or other trains are cascaded down to XC because they've needed it for a long time. I started using that route around 5/6 years ago, and at that point it was severely overcrowded on almost every trip! Can't believe the DFT hasn't done anything about it, but they probably are unaware of it as it only exists in the mysterious realm beyond London...

Are Cross Country HSTs compatible with accessibility 2020? The interiors seem newer and not heard of plans to replace them...

59CosG95 · 17 Jan 2019

Jozhua said:
I really hope these bi-modes or other trains are cascaded down to XC because they've needed it for a long time. I started using that route around 5/6 years ago, and at that point it was severely overcrowded on almost every trip! Can't believe the DFT hasn't done anything about it, but they probably are unaware of it as it only exists in the mysterious realm beyond London...

Are Cross Country HSTs compatible with accessibility 2020? The interiors seem newer and not heard of plans to replace them...

They are indeed being made PRM compliant as we speak; one 7-car rake (XC03) has had sliding doors (similar to ScotRail's HST fleet & GWR's HST GTi fleet) fitted. Doors excluded, they were already equipped with disabled spaces/toilets.

Bletchleyite · 18 Jan 2019

59CosG95 said:
They are indeed being made PRM compliant as we speak; one 7-car rake (XC03) has had sliding doors (similar to ScotRail's HST fleet & GWR's HST GTi fleet) fitted. Doors excluded, they were already equipped with disabled spaces/toilets.

The doors are not required for PRM compliance, they are mainly a safety upgrade. Though you would I think need to provide additional staff to operate them on behalf of PRM passengers if you did retain slamdoors.

Townsend Hook · 18 Jan 2019

Bletchleyite said:
The doors are not required for PRM compliance, they are mainly a safety upgrade. Though you would I think need to provide additional staff to operate them on behalf of PRM passengers if you did retain slamdoors.

AIUI The GWR ‘Night Riveria’ stock has received a derogation from the requirement to fit PRM-complaint doors on the grounds that there are sufficient staff to operate them on behalf of passengers. Obviously that isn’t going to be practical on pretty much any normal, seated train.

59CosG95 · 18 Jan 2019

Townsend Hook said:
AIUI The GWR ‘Night Riveria’ stock has received a derogation from the requirement to fit PRM-complaint doors on the grounds that there are sufficient staff to operate them on behalf of passengers. Obviously that isn’t going to be practical on pretty much any normal, seated train.

Then again, the Night Riviera isn't any normal, seated train.

Townsend Hook · 18 Jan 2019

59CosG95 said:
Then again, the Night Riviera isn't any normal, seated train.

Precisely my point.

Bombardier designs 125mph bi-mode for UK market

D365

Veteran Member

RailUK Forums

Chester1

Established Member

td97

Established Member

D365

Veteran Member

Chester1

Established Member

James James

Member

edwin_m

Veteran Member

w1bbl3

Member

Chester1

Established Member

mpthomson

Member

D365

Veteran Member

Charlie Smythe

Member

Spartacus

Established Member

Jozhua

Established Member

59CosG95

Established Member

Bletchleyite

Veteran Member

Townsend Hook

Member

59CosG95

Established Member

Townsend Hook

Member