Class 57/0 Update Discussion

[TheTazman]

ohhh should not forget that we could do with some nice grubby paint jobs.

[phill70]

Thanks for confirming that

One thing that amazes me around here sometimes, is that you try to pass on some info from the horses mouth, and some people don't believe its true
Don't know why I bother sometimes.

Glyn

I wont mention the headlamps then

Good idea that

[Kromaatikse]

At least as far as the "classic" diesels are concerned, or at least the EE types, the governor and load controller are commanded through a pneumatic line, whose pressure is directly controlled by the power handle. For multiple working, this line (and some electric control signals) are fed through to the other locos. The load controller's operation is more complex but irrelevant for this discussion.

It's entirely reasonable to suppose that a pneumatic line takes some time to change pressure, in the same way as the brake pipe down the train. This will manifest as a gradual spool up of the engine RPM target (independently of it's rotating mass or turbocharger) and of the power setting for the load controller. The same goes for reducing power. It follows that the lag will increase with multiple working, just as brake response slows with a longer train.

The power handle is also connected electrically to the main traction contactor, essentially a heavy-duty relay. This only has "on" and "off" positions. The only difference between the "Off" and "Notch 1" positions on the controller is that the contactor is closed - the control air pressure remains at the idle setting. A small amount of power is transmitted in this position - reportedly enough to move a light engine gently and to compress buffers. (I don't know if contactors usually take significant time to actuate.) This does also mean that power can be cut off quickly without waiting for the control air to escape, and the engine RPM will still fall gradually in response to the control air, with no power being generated.

Shunters are a little different - the load controller does not exist, the generator field being directly controlled electrically through the handle position. The pneumatic line (which is much shorter than in a loco due to the lack of multiple working connectors) is still used to control the engine RPM. The control sequence is as follows: first movement closes the main contactor, between Notch 1 and 2 the generator field is increased at constant RPM, from 2 to 3 (a larger arc than 1 to 2) the RPM is increased at constant field, and there is a single step from 3 to 4 which adds the final field step. This arrangement presumably allows for quicker and finer control at low speed. In theory it should be possible to hear the engine working harder at the same pitch when controlling between notches 1 and 2.

The 57 is not a "classic" diesel - it has the body of a 47 but most of the internals of an EMD loco. I am rather less familiar with how their control system works, except that it has the 8-notch controller as also seen on the 66. I therefore don't know where the delays come from.

DMUs are yet another matter. From the second generation onwards, the engine control systems are usually associated with the hydraulic transmission, which mediates the input from the driving controls (which are replicated electrically down the length of the train). This is because the transmission needs to know when to fill and drain the hydraulic couplings. Recent versions also deal with the fact that there is no point in sending much fuel to the engine until the coupling is at least partly filled, thus delaying spool-up of the engine to save both fuel and wear. On older versions (including the 158s I rode every other week in the 1990s), it was usual to hear the engine rev straight up to the limiter, then a few seconds later dip slightly as the transmission filled and took the load. I suspect this is still true of Pacers at least.

On first-generation sets, the gearbox and fuel valve were controlled through electro-pneumatic valves, the electric control signals being sent through the train. EP valves are pretty slow, and it was necessary to wait several seconds for the gearbox to engage before the throttle could safely be opened. The fluid coupling between the engine and gearbox (sometimes inaccurately called a "fluid flywheel") was always kept filled, unlike a true hydraulic transmission, and simply acted as a wear-free substitute for a clutch. Some commuter sets did have simple hydraulic transmissions, eliminating gear changes and their associated delays.

[Kariban]

If you go back to WR hydraulics there were two types of transmission; the Voith type had seperate converters that emptied/filled in sequence, and the Mekrydo just had one converter and a gearbox. A fluid coupling isn't the same thing as a torque converter, though. Funny fuzzy areas...

That's rather interesting about pneumatic MU, I hadn't considered that. How detailed is RW's pass-through scripting, I wonder.

[phill70]

Kromaatikse

What is your name anyway ?

I have read that about three times, and I still do not really understand what you are trying to say.

The power handle is also connected electrically to the main traction contactor, essentially a heavy-duty relay. This only has "on" and "off" positions. The only difference between the "Off" and "Notch 1" positions on the controller is that the contactor is closed -

The load regulator, considering how old it is, does quite a good job.

[Kromaatikse]

If you go back to WR hydraulics there were two types of transmission; the Voith type had seperate converters that emptied/filled in sequence, and the Mekrydo just had one converter and a gearbox. A fluid coupling isn't the same thing as a torque converter, though. Funny fuzzy areas...

That's rather interesting about pneumatic MU, I hadn't considered that. How detailed is RW's pass-through scripting, I wonder.

I left out the hydraulic locomotives because that didn't really add anything to the discussion. Generally speaking, a transmission is considered "hydraulic" if it has at least one torque converter. I use "hydraulic coupling" to refer to both the torque converter and the fluid coupling that are present in modern DMU transmissions.

RW doesn't model the extra delay due to multiple-working, but then neither does it model braking delays due to the length of the train. I think the latter effect is much more important.

Kromaatikse

What is your name anyway ?

I have read that about three times, and I still do not really understand what you are trying to say.

The power handle is also connected electrically to the main traction contactor, essentially a heavy-duty relay. This only has "on" and "off" positions. The only difference between the "Off" and "Notch 1" positions on the controller is that the contactor is closed -

The load regulator, considering how old it is, does quite a good job.

The load regulator is a reasonably simple device, but it's behaviour is complex because it reacts to engine RPM, the power level setting from the pneumatic control line, the back-EMF voltage from the motors (and the allowable limits of this), and various non-idealities which always creep into any control system. As far as I have been able to find out, it varies the load on the generator so as to keep the fuel rack (which is controlled by the governor) in a set position - so the power developed varies quadratically with control position (and is independent of train speed). Then when it hits a limit switch, that means the generator voltage is at the maximum limit, so a transition (usually inserting ballast resistances into the motor fields and/or switching generator circuits into series) is triggered, which moves the operating point of the load regulator down. There is presumably another limit switch for a downward transition, which can occur under load when going uphill with a heavy train.

Nowadays the load controller is likely to be electronic rather than a mechanical device, and it might have a more complex control law, but it's still there and it does the same basic job.

The main traction contactor is simply there to break the traction circuit when the power handle is in the "Off" position - the load controller doesn't have an "Off" position. In all other positions, the traction contactor is closed and power is developed. But the first movement of the power handle doesn't yet increase the control air pressure, so the engine remains at idle RPM and the load controller selects a low power operating point. The BR manuals from the 1980s recommend using this first position (aka. Notch 1) as part of the coupling process. Most locos have three more notches (1/4, 1/2, 3/4) evenly spaced around the power quadrant for reference, but the available control is continuous and doesn't depend on them.

[Ooveecouk]

DMUs are yet another matter. From the second generation onwards, the engine control systems are usually associated with the hydraulic transmission, which mediates the input from the driving controls (which are replicated electrically down the length of the train). This is because the transmission needs to know when to fill and drain the hydraulic couplings. Recent versions also deal with the fact that there is no point in sending much fuel to the engine until the coupling is at least partly filled, thus delaying spool-up of the engine to save both fuel and wear. On older versions (including the 158s I rode every other week in the 1990s), it was usual to hear the engine rev straight up to the limiter, then a few seconds later dip slightly as the transmission filled and took the load. I suspect this is still true of Pacers at least.

Thanks, this information will come in handy when explaining our requirements to our programmer for the 156 project.

[holzroller]

Refurbished 37's were given electronic load regulators. With classical diesels, including refurbished 37's you had to put the controller to the on position before you could take power, so you couldn't go from 0 to full power. If you tried you got nothing at all. Contactors react pretty quickly, if they tripped on 20's or 37's (no2 end) you got a loud bang and a big flash. You also had at least 3 weak fields stages on most classic diesels to deal with the back emf, a simple way of thinking of these is as an electrical equivelant to gears. Occasionally Eastfield would dump a 37 on us that had faulty weak fields, like driving around in first gear, and you could forget about running at your booked speed. The air supply from the throttle controlled the fuel rack on the diesel engine, the more fuel, obviously the more horsepower, the load regulator adjusted excitation in the main generator in order to match the output of the generator to the horsepower output of the diesel. In the event that the output requested was too high, breakers tripped and the engine was put back to idling. On some loco's you then had to press a button to reset, others you waited a few seconds before re-opening the throttle. On the class 47 it was possible to start a heavier load than you could pull, your amps would remain in the yellow area for too long and you would burn out your generator. Deltics were also notorious for being easy to trip, probably because they were at the then limits of technology. If you are really interested in the technicallities then look for British Railways Diesel Traction Manual For Enginemen, you can still pick these up if you are lucky, I got mine from an old dirver who was training me. There are various other publications as well

[vbomber]

The 57 is currently the best out there in my opinion, however we are using a SIMULATOR so for me the vigilance device aka dsd pedal is the only thing that would polish this product off, oovee please set the benchmark and roll this out , there is a hst and 166 by DJB that has a version of a vigilance device and I only drive hst,s using the DJB it really adds that extra bit of realism which a SIMULATOR should have.

Good luck for the year ahead I look forward to using more of your products, 2011 the year that rail works sets the benchmark?

[styckx]

It's really neat to watch the evolution of modeling. From the first time we could open a window, to the first opening doors on the chinese locos, to train length and opening vents on the Class 57, to the animated brakes and cab of epicness on the Russian TEM2. There was more evolution in between all this but I'd go on forever.

I imagine in 5 years we'll be able to cook in a buffet car and get docked points for burning the biscuits.

[LeeEAS]

NAMEPLATES.

That is the only thing I think is missing from the Freightliner 57s, other than that I can't fault them!

I was disappointed to see they were missed out, here's 007 as an example: http://davidmulligan.fotopic.net/p14092907.html

[wolly1380]

Kromaatikse

What is your name anyway ?

I have read that about three times, and I still do not really understand what you are trying to say.

The power handle is also connected electrically to the main traction contactor, essentially a heavy-duty relay. This only has "on" and "off" positions. The only difference between the "Off" and "Notch 1" positions on the controller is that the contactor is closed -

The load regulator, considering how old it is, does quite a good job.

I thought the power handle was pneumatically connected to the governor is this true?
Oh the class 57/0 I can't see any refinement's this needs maybe a little work on the model around the front windscreens they need to be a little larger towards the roof line.

[Wikkus]

I thought the power handle was pneumatically connected to the governor is this true?

Have a read back through the last two or three pages, Jon, as there's a lot of info in there, specifically, that *some* are but others are not As to the 57, there's not been any confirmation as to how it actually works, hehe.

Rgds, Rik.

[Wikkus]

The 57 is currently the best out there in my opinion, however we are using a SIMULATOR so for me the vigilance device aka dsd pedal is the only thing that would polish this product off, oovee please set the benchmark and roll this out , there is a hst and 166 by DJB that has a version of a vigilance device and I only drive hst,s using the DJB it really adds that extra bit of realism which a SIMULATOR should have.

That's as may be, but Zane did say a couple of pages ago that there wasn't a vigilance device on the 57, so...

Rgds, Rik.

[Ooveecouk]

The 57 is currently the best out there in my opinion, however we are using a SIMULATOR so for me the vigilance device aka dsd pedal is the only thing that would polish this product off, oovee please set the benchmark and roll this out , there is a hst and 166 by DJB that has a version of a vigilance device and I only drive hst,s using the DJB it really adds that extra bit of realism which a SIMULATOR should have.

That's as may be, but Zane did say a couple of pages ago that there wasn't a vigilance device on the 57, so...

Rgds, Rik.

There is a vigilance device on the real one but no on our simulator version yet. There isn't a DRA though on either, which is what I said IIRC.
Cheers
Z