D365
Veteran Member
- Joined
- 29 Jun 2012
- Messages
- 11,498
Sixteen powered axles vs eight obviously has its benefits.
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?
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.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!
Only since Grayling has been in office has it become too difficult to put OHLE througha Victorian tunnelopen air.
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.
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.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.
All this is true, but there are are couple of factors that make a difference. For example: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.)
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.
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...
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.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.
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.
Then again, the Night Riviera isn't any normal, seated train.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.