It's the rail version of the AS Tronic automated manual gearbox that's common on trucks and buses so a clutch and 12 speed gearbox (actually a two speed, a three speed and a two speed in series). I doubt though that all of those speeds are used. If a clutch can handle the couple of thousand Nm of torque produced by a large truck engine, it'll deal with a train too. The system used to appear on the ZF website but not any more so I guess no customers after the Danish order.
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Why aren’t more DMUs built as DEMUs?
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It's the rail version of the AS Tronic automated manual gearbox that's common on trucks and buses so a clutch and 12 speed gearbox (actually a two speed, a three speed and a two speed in series). I doubt though that all of those speeds are used. If a clutch can handle the couple of thousand Nm of torque produced by a large truck engine, it'll deal with a train too. The system used to appear on the ZF website but not any more so I guess no customers after the Danish order.
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R
RailUK Forums
Though ZF are perfectly capable of making special parts, based on their existing catalogue, which happens often enough.
I'd assume most modern rail torque converters are of the locking type, which greatly reduces their losses as speed increases, as you effectively bypass the torque converter.
edwin_m
Veteran Member
On Sprinters (150-171) this does happen, but not until around 40mph, so they spend a lot of time heating up the fluid in the converters. It also means that over the rest of the speed range the engine is locked to the wheels, so may not be running at the most efficient speed.
D365
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I am keeping a (loose) eye on the Angel Trains Class 165/168 hybridisation project, hoping for better success than Porterbrook have had with the 769.
Bletchleyite
Veteran Member
I'd be surprised if we didn't see some sort of conversion done to the CAF DMUs at some point, plus possibly the 185s. Everything older than that will probably be ready for razor blades by the time diesel is actually banned.
The prospect of padding out the lengths with 20m Networker carriages fascinates me. Very out-of-the-box thinking.
D365
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Thankfully the Turbos are 23m carriages, so they do have a bit of extra room to play with!
superkev
Established Member
Slightly off the demu topic but what ever happened to the was two 158s converted to ZF and Voith multivspeed gearboxes a few years ago. At the time a 10% fuel saving was envisaged which would have paid for the cost of more conversions.
Thanks K
Thanks K
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Is there a thread here with more about that?
Speed43125
Member
Presentation on Chiltern / Angel Trains Hybrid Diesel and Battery Powered Trains
I'm aware of the thread at https://www.railforums.co.uk/threads/chiltern-angel-trains-hybrid-class-165-trial.169977/ but it is locked for further replies and the event starts in 90 minutes so I thought I'd better post, mods please do move this post to there and reopen the thread if appropriate...
www.railforums.co.uk
hexagon789
Veteran Member
Not sure if all twelve are used, but I got the impression they were but perhaps not.
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I have seen some pics, I'll have a look...
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They certainly go through a number of gear changes, could easily believe all 12 were used
hexagon789
Veteran Member
This video shows at least 5 though it's very possible speed doesn't get fast enough to use any higher gears on the short hop:
I have seen a reference to eight gears but it's very vague as to what it means!
Bletchleyite
Veteran Member
That sounds more like one of the more recent "solenoid controlled H-gate" type gearboxes some coaches have than an epicyclic slushbox, though there's definitely something that slips (fluid coupling or clutch) for the starting out.
hexagon789
Veteran Member
The first two gear changes seem to pass quite quickly, a matter of mere seconds
coppercapped
Established Member
The current ZF website shows two transmissions on offer suitable for railcars - the Ecolife Rail and the Ecomat Rail. The short form brochure - in German - for the Ecolife Rail shows that it is suitable for inputs of up to 2,500 newton-metre torque and 600kW (820hp). It uses a torque converter with lock-up followed by a six ratio gearbox and changes occur without loss of output torque. It claims up to 20% fuel saving but does not state to what it is being compared. My guess is that it is to a Voith 211 and such a fuel saving would seem quite feasible on stop and start journeys as one is comparing a six speed transmission with a two speed transmission which means that with the six speed it is possible for the engine to run closer to the peak of its torque-speed curve for more of the train's journey.
However, one shouldn't get too hung up over all this, modern turbocharged diesel engines have quite a flat torque speed curve over much of their operating range so their efficiency does not drop much if they are a bit away from the peak and the Voith transmission is very reliable (which is also important and has a monetary value) and fuel costs are a small proportion of railway operating costs[1].
The Ecomat Rail is smaller - its maximum input torque is 1,800 newton-metres and it is limited to four or five speeds.
[1] This won't convince some posters here who seem to want to get rid of all CO2 emissions regardless.
[2] ZF offer a range of transmissions for all sorts of uses and much use is made of modular design. If one wants a 12-speed box I'm sure they would be delighted to supply it. The question is whether the extra complexity would be covered by the fuel saving.
Edit: Point [2] added.
However, one shouldn't get too hung up over all this, modern turbocharged diesel engines have quite a flat torque speed curve over much of their operating range so their efficiency does not drop much if they are a bit away from the peak and the Voith transmission is very reliable (which is also important and has a monetary value) and fuel costs are a small proportion of railway operating costs[1].
The Ecomat Rail is smaller - its maximum input torque is 1,800 newton-metres and it is limited to four or five speeds.
[1] This won't convince some posters here who seem to want to get rid of all CO2 emissions regardless.
[2] ZF offer a range of transmissions for all sorts of uses and much use is made of modular design. If one wants a 12-speed box I'm sure they would be delighted to supply it. The question is whether the extra complexity would be covered by the fuel saving.
Edit: Point [2] added.
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apk55
Member
Personally I prefer the the DEMU approach.
An electric transmission effectively works as a wide range continuously variable transmission permitting the engine to deliver its rated power to the rails over a wide speed range from maybe as low as 10MPH to max speed. In addition when only part power is required the diesel engine can be run under conditions of maximum efficiency rather than the speed demanded by the gears. The simple transmission used on the class 150's was very inefficient at low speeds and at higher speeds meant that the engine had to rotate at a fixed speed irrespective of the tractive effort demand and maximum engine power could only be delivered at one speed. A multi speed gearbox improves the situation although how reliable long term they prove to be remains to be seen.
In the past an electric transmission probably cost considerably more than an equivalent mechanical transmission mainly due to the cost of making DC commutator motors and generators although now with alternators and 3 phase dives the difference would be less.
From the maintenance point of view an electric transmission system wins hands down. With only simple fixed spur gears required from the traction motor to axle and an alternator bolted to the engine crankshaft they is very little to maintain or go wrong. In contrast a mechanical system requires a complex gearbox with many clutches and gears, several rotating shafts with universal joints etc and transfer gear boxes to the axle.
As for future proofing an DEMU is much better. They could be easily converted to a EMU or BI mode by the addition of a transformer or battery or hybrid operation.
An electric transmission effectively works as a wide range continuously variable transmission permitting the engine to deliver its rated power to the rails over a wide speed range from maybe as low as 10MPH to max speed. In addition when only part power is required the diesel engine can be run under conditions of maximum efficiency rather than the speed demanded by the gears. The simple transmission used on the class 150's was very inefficient at low speeds and at higher speeds meant that the engine had to rotate at a fixed speed irrespective of the tractive effort demand and maximum engine power could only be delivered at one speed. A multi speed gearbox improves the situation although how reliable long term they prove to be remains to be seen.
In the past an electric transmission probably cost considerably more than an equivalent mechanical transmission mainly due to the cost of making DC commutator motors and generators although now with alternators and 3 phase dives the difference would be less.
From the maintenance point of view an electric transmission system wins hands down. With only simple fixed spur gears required from the traction motor to axle and an alternator bolted to the engine crankshaft they is very little to maintain or go wrong. In contrast a mechanical system requires a complex gearbox with many clutches and gears, several rotating shafts with universal joints etc and transfer gear boxes to the axle.
As for future proofing an DEMU is much better. They could be easily converted to a EMU or BI mode by the addition of a transformer or battery or hybrid operation.
supervc-10
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This is one of the things I think is so cool about the FLIRTs. TfW have ordered some diesel only ones- when it becomes worth it, slap on a panto and he presto- you've got a bi-mode!
Mordac
Established Member
Oh no you don't!
Not without high voltage traction cabling between the length of the powered bogies — which has not featured in many EMUs, nor any DEMUs.
Only if they are designed with such conversion in mind. You need somewhere to put the transformer and pantograph and you need some way of getting power from the transformer to the traction motors. Afaict the voyagers had neither and so while there was talk of conversion it never proved practical.
Is there any actual information on whether the TFW flirt DEMUs will just be FLIRT bi-modes will be designed in a way that facilities future bi-mode conversion?
apk55
Member
My own thoughts are that most DEMU designs should have passive provision for conversion to a bi mode or EMU. A typical example might be a 3 car unit. The two outer cars are designed as power cars with a diesel genset (the power packs used on the 317 would be just fine) and a single powered bogie. The center car would be a trailer but with a lowered roof section for a panograph and space underneath for a transformer even if not fitted at initial build. Provision could also be made for power cables between units together with extra control cables. The extra cost at a new build stage would be minimal.
In other cases the diesel genset could be replaced with a hybrid power pack. A much smaller diesel engine would be fitted together with a battery/ super-capacitor pack. This would be ideal for services with frequent stops. The energy storage could give a quick power boost when starting and recycle braking energy.
In other cases the diesel genset could be replaced with a hybrid power pack. A much smaller diesel engine would be fitted together with a battery/ super-capacitor pack. This would be ideal for services with frequent stops. The energy storage could give a quick power boost when starting and recycle braking energy.
ABB125
Established Member
Oh yes you do! Although it might make the train so quiet that if you're using a level crossing you might not be able to hear that it's behind you...
On a more serious note, I like the "powerpack" concept because, for example, you could replace the diesel one with hydrogen. Note also the coincidence that Network Rail recommends hydrogen power on the Norfolk/Suffolk local routes, currently operated by trains with a diesel powerpack...
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Am I missing something here, how does the current get to the motors at the moment? I would assume all you're doing is replacing the diesel gensets with a transformer and associated equipment and hence voltage/current would be similar in either case.
edwin_m
Veteran Member
The FLIRT units must have the relevant cabling to get the power from the diesel module to the motors. 80x have them too, for the opposite reason of getting the power from the transformer car to the motors in the rest of the train (though I think they can also transfer power in diesel mode). But 22x units don't, which was one of the reasons why conversion of these to bi-mode proved too difficult. In those units the engine on each car can only power the motors on the same car.
I think that even on the 80x, the power from each engine only goes to traction motors on the same vehicle, 22x style, with a parallel bus between vehicles for 25kV only. FLIRTs and 769 are the exception I think in terms of engines feeding traction motors 'remotely'
coppercapped
Established Member
All true, but I would suggest that in the case of railcars rather than locomotives the advantages are more theoretical than actual. In the following I am not trying to score points, but trying to point out that engineering design is a question of balancing priorities.
Modern ac drives are very effective in utilising to the maximum the adhesion available between wheel and rail, which is very important for locomotives pulling heavy loads. This is not a situation faced by most multiple units on urban or inter-urban services although it may be more of an issue for very high powered units used on high speed (around 125mph and more) services. For diesel engines up to 750/800bhp used in railcars ultimate adhesion is not such an issue.
Automatic gearboxes and the associated transmissions of the sizes used in medium powered railcars are used in their tens of thousands world-wide in heavy lorries, buses and off-road equipment. They benefit from long development experience and the advantages of mass production; they are efficient, they have to be. As a result of these large volumes they are also very competitive both in first cost and on-going maintenance costs - they are as close to 'fit-and-forget' as is reasonably possible.
One of the factors affecting track access charges is the unsprung mass of the wheelset and drive components. Even though an ac motor is shorter and lighter than a dc machine of the same power if the motor drives the axle through a simple spur gear then a proportion of the motor's mass is carried directly by the axle, so contributing to the unsprung mass. The unsprung mass may be minimised by mounting the motor on either the bogie, which complicates the final drive, or on the body in which case the drive layout is the same as a mechanical system.
The fuel consumption benefits of a multi-gear mechanical transmission compared to an electric transmission depend on the duty cycle, but in any event are not large as traction diesel engines have quite a flat torque-speed curve so the specific fuel consumption will increase only slightly if the engine is running off its 'sweet spot'. There is a considerable difference in fuel consumption between a simple two-speed hydrokinetic transmission such as the Voith 211 when used in stop-start traffic and a modern multi-ratio mechanical drive or a modern electric drive. This has been recognised and Voith now offer the 4 speed DIWA drive - based on that used in buses - for railcars. It can cope with input power up to some 430bhp.
As to 'future proofing' a diesel (hydro)mechanical transmission: there is no fundamental reason why an electric motor cannot later either be added to a (hydro)mechanical transmission, giving a bi-mode, or replace the diesel engine entirely. The trick is to make the space under the coach floor flexible and to a large extent this has already happened with the latest designs of diesel trains, all the major components now being mounted on rafts which can be easily removed for maintenance or component repair. This is a step change from designs of only a couple of decades ago whereby the major bits of gubbins were fixed individually to the body.
There may well be advantages in using DEMUs in future, but I maintain that they are not so significant as you suggest.
edwin_m
Veteran Member
While there is a lot of validity in your post, I would point out that with the move to hybrids and EVs (or indeed hydrogen vehicles), automotive is gradually moving to electric transmissions too. The advent of mass market electric transmissions of a similar rating to the mechanical ones could be a game changer for rail multiple units.
Many hybrids still retain mechanical transmissions and place the motor flywheel side of the transmission, particularly the larger vehicles. "Through the road hybrids" aren't overly common although it's an easy way to provide hybrid and (basic) 4WD alongside pure electric driving capability by putting an EDU on the rear axle and leaving the front as a relatively normal front wheel drive system - JLR's smaller plug in hybrids and PSA's plug ins do this I believe.
Also I'm not quite sure what you mean by electric transmissions - where cars are electrically driven, they tend to use EDUs - a motor directly into a differential via a single gear pair to increase the torque/slow the motor. I don't know how relevant those will be to rail transmissions other than potential savings that could generally be made to the motors themselves. Certainly doesn't strike me as much that could carry over to Rail
edwin_m
Veteran Member
By electric transmission I'm meaning a system like in a diesel-electric train, where the engine generates electricity that turns a motor with no mechanical connection between the engine and the wheels, obviously with some electronics and probably a battery to hybridise it. Like with a DEMU, the end of the system nearest the wheels is then identical to a pure electric vehicle.
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