TDM Locos

[TomJ93]

Ok, i'm not too clued up on things like this (as this question will probably prove) but now the 67s have TDM could you top and tail some MKIIIs with say a 90 at one end and a 67 on the other. For example when it is under the wires and the 67 is leading use it to control the 90 on the rear?

Thanks for satisfying my curiosity

 

[Hydro]

No, the 67's have a limited form of TDM that doesn't control the engine. It was used in conjunction with a Propelling Control Vehicle in shunt moves when on mail trains. Basically the train was propelled by the 67 using a man in the PCV to send power requests (in set increments) down the TDM to a Propelling Advisory Control System (PACS) unit in the 67's cab, and the driver responded to the PACS using the throttle. RES 47/7's used the same system. This was only used for low speed shunting.

AC locos had full TDM that allowed full control of the locomotive remotely from a DVT or DBSO. 67's using DVT's have the DVT converted to AAR multiple working.

 

[TomJ93]

But the 67s that Chiltern use? DVTs have full control over them.

From what I gather from your post an 87 could act as a DVT for a 90?

 

[ainsworth74]

But the 67s that Chiltern use? DVTs have full control over them.

As Hydro said the DVT's that work with 67s have a different control system to that used by other AC locomotives. The two are incompatible with each other hence why a 67 couldn't control a 90 or vice versa.

 

[Hydro]

But the 67s that Chiltern use? DVTs have full control over them.

The DVT's are converted to the multiple working system that the 67 uses, AAR. As far as I know, any TDM loco can work with any other TDM loco, regardless of type. 86's have worked with 90's (standard convention is to have the 86 leading, as the 90's non-tap changer controls can overload the 86 by applying power too quickly). I don't know if the TDM system will work with one loco shut down and controlling the rear one.

 

[TomJ93]

Ok thanks guys

I was just thinking it would be a great idea but then again if it was possible BR would have done it.

 

[ainsworth74]

I was just thinking it would be a great idea but then again if it was possible BR would have done it.

They would have struggled to do it with 67s seeing as they didn't arrive until 3 years or so after BR ceased to exist

 

[TomJ93]

I meant diesels in general Having a 47 and an 87 on an XC service would have been useful.

 

[ainsworth74]

I meant diesels in general

I thought you did but was just being sure

 

[hairyhandedfool]

BR did do it!

Eight HST power cars had TDM equipment fitted to work with Class 91s, when the equipment was no longer needed on the power cars it was removed.

 

[captainbigun]

But the 67s that Chiltern use? DVTs have full control over them.

From what I gather from your post an 87 could act as a DVT for a 90?

No, 86/87 have to be applying traction themselves in order for TE demand to be sent through the TDM as the current feedback sets the TE demand. 89/90/91 work the other way, the TE is taken directly from the traction electronics based on the position of the power controller.

As has been posted above, 67s use AAR. The only non-AC class fitted with TDM is the HST.

 

[Nym]

class 47?

 

[Hydro]

47/7's had the same deal as the Class 67. The Scotrail push/pull ones, IIRC, had unique TDM system only suitable for the early DBSO's.

 

[ChrisCooper]

I imagine the reason EWS decided to modify their DVT to run with AAR and not modify 67s for TDM was that it allowed any AAR fitted loco (i.e any 67, 66 or 59) to run with their train, instead of having just a small pool of 67s available. The only real issue is having to through wire the coaches, but oviously it's not too bad. Probably more reliable than TDM too as it suffers from using the RCH cables, which afterall are a pre-grouping design meant to control the lights, not a loco. The same was done for the W&S and Chiltern sets.

 

[captainbigun]

Lack of spare TDM equipment would have been the main driver. The AAR modifications to the DVT are a lot simpler than adding TDM to a loco.

The shove duffs used a much simpler Brush multi-working system.

 

[jopsuk]

then there's the southern region multiple working system- as far as I'm aware the fitted 31s could be used to push even when in formation with 4VEPs on the 3rd rail, not just with the 4TCs off it? 73s as far as i know have the same system?

 

[Hydro]

That's my understanding too, an EMU could multi with an SR fitted loco with both powering. 33/1's and 73's had the system.

Our 73's have adaptor multi cables that allow the SR multi system to be wired through the coaches Blue Star cabling to have two ED's push/pull on electric.

 

[Rhydgaled]

The only non-AC class fitted with TDM is the HST.

class 47?

47/7's had the same deal as the Class 67. The Scotrail push/pull ones, IIRC, had unique TDM system only suitable for the early DBSO's.

The Scotrail 47/7s may have not had the same TDM as 90s, 91s etc. but it was still proper TDM was it not? I that case the Class 43 (IC125 Power Cars) and Scotrail 47/7s are the only non-AC classess that have been fitted with some form of TDM or another. If you can put one sort of TDM in a 47, I can't see why the other type of TDM (the version in the 91s and 43s) couldn't be installed in a batch of 47s to allow them to work with DVTs and the DBSOs (which of course would have had to be modified to work with AC locos for London - Norwich).

 

[captainbigun]

I have to confess I don't know much about the Brush multiworking kit, however it wasn't TDM. TDM uses 8 bits to for TE demand, it's translating between that and the power control on a diesel that requires additional complex electronics.

What's the point in fitting 47s? There's not much call for a 95mph push/pull loco, let alone enough spare TDM equipment to fit them anyway.

Fitting TDM to a DBSO is not comparable to fitting it to a loco.

 

[Rhydgaled]

What's the point in fitting 47s? There's not much call for a 95mph push/pull loco, let alone enough spare TDM equipment to fit them anyway.

Fitting TDM to a DBSO is not comparable to fitting it to a loco.

6 spare DBSOs, a bunch of stored class 47s 20ish mark 2 coaches that will be languishing at Canton from December (most are already) and a dire need for 158s to relieve overcrowed services on the Cambrian line and/or provide a much needed express service from Carmarthen/Fishguard to Cardiff.

 

[route:oxford]

This has always confused me a little.

What is the difference between the method of two locos operating whilst connected immediately together and at opposite ends of a rake of coaches?

 

[jopsuk]

For a start, the coaches need some way of transmitting the signal.

this has a good summary of the different Multiple Working systems

 

[route:oxford]

For a start, the coaches need some way of transmitting the signal.

this has a good summary of the different Multiple Working systems

So essentially, it's as easy as building two converter units and running cat5 cable units through each coach.

 

[Nym]

Kinda, kinda not, Packet Data Communication wouldn't really be appropriate for multiple working systems, unless it was a continus tcp stream, but if packets droped it would be disasterous (potentially)

 

[Hydro]

This has always confused me a little.

What is the difference between the method of two locos operating whilst connected immediately together and at opposite ends of a rake of coaches?

Coupled together they are in multiple. At each end, they are also in multiple but the method is known as push/pull. Push pull requires the coaches to be through wired for the control system, and the same is true for propelling using a DBSO or DVT. In the case of Blue Star, you need a 27 way multiple working cable to transmit the electrical signals, and a control air pipe. For TDM, you need TDM cabling. Originally the TDM signals actually went through the lighting circuits of Mark 3 coaches, but these were unreliable and dedicated cables had to be installed.

 

[ChrisCooper]

Coupled together they are in multiple. At each end, they are also in multiple but the method is known as push/pull. Push pull requires the coaches to be through wired for the control system, and the same is true for propelling using a DBSO or DVT. In the case of Blue Star, you need a 27 way multiple working cable to transmit the electrical signals, and a control air pipe. For TDM, you need TDM cabling. Originally the TDM signals actually went through the lighting circuits of Mark 3 coaches, but these were unreliable and dedicated cables had to be installed.

They still go through the lighting cables on the Mk3s and it still causes some reliability issues. Only the Mk4s have dedicated cables for TDM.

 

[Hydro]

I always thought they were re-wired. You learn something new every day!

 

[captainbigun]

You must have a robust communications system, you can't have the odd instruction going missing. If your TDM deconfigures then the brakes go on, it has to be that way.

The Mk2s and Mk3s use the RCH cabling which originally serviced the lighting control and PA. TDM was added on top, that in itself doesn't cause a problem, but the odd dodgy lighting inverter, some water in a junction box and it soon goes to pot. The jumpers and associated circuits have to be maintained to a better standard than originally intended as they now form a critical part of the train interface.

The error of this way was seen in time for the Mk4s (and infact MK3 DVTs too) to carry dedicated through wiring (though this also carried the FDM for the door control) and UIC connectors. Both are much more suited to the job.

As it happens ethernet buses are now finding their way on to our trains. The Siemens Class 380s use an industrial ethernet bus for the control communication. Massive savings on cabling and interfacing but a lot more complex to implement safely.