Class 50 Freight Operations Trial - one of the most signature shortsighted BR decision?

[Davexoc]

39 minutes ago, seraphim said:

The EMD Super Series wheelslip control system was groundbreaking; the key was the recognition that optimum adhesion was achieved by the wheel rotating slightly faster than "true ground speed". There was debate about what the ideal "creep %" was - between 5 and 10% seemed to be the best.

 

I remember the first 59 to visit OC, the EMD guy explained that basically it had 7 speedos, one on each wheelset and the radar one for actual speed. You want max power at 10MPH, turn all the axles at 11MPH and away you go. The engine blocks mind you harked back to 1938 IIRC, but were by this time supercharged with a viscous coupling to disconnect that once the turbocharger was spinning nicely.

 

I guess the BR equivalent to the creep system was trialled on 58050 - the 'sepex' one? Or was that not as advanced?

[The Stationmaster]

14 hours ago, Davexoc said:

 

I remember the first 59 to visit OC, the EMD guy explained that basically it had 7 speedos, one on each wheelset and the radar one for actual speed. You want max power at 10MPH, turn all the axles at 11MPH and away you go. The engine blocks mind you harked back to 1938 IIRC, but were by this time supercharged with a viscous coupling to disconnect that once the turbocharger was spinning nicely.

 

I guess the BR equivalent to the creep system was trialled on 58050 - the 'sepex' one? Or was that not as advanced?

I think the real BR equivalent would have been the Class 60 which had some sort of adhesion control although I don't know anything about it.  It certainly didn't impress Yeoman's although in their case it was being compared with the GM system which was already operational and they were also highly, and rightly, impressed by EMD's customer support and spares supply situation which put the entire UK industry to shame.

 

EMD could supply smaller spares immediately which in the case of Britain meant that anything up to, and including one ton in weight would be shipped by air freight and this meant it could be collected from LHR the day after it had been ordered.  Traction motors would take bit longer but could still be air-freighted.  Technical queries normally gota reply by return of fax/telex message.   

[seraphim]

I pressed "send" last night, and then realised I forgot to mention the key technical innovation which enabled Creep, which was the doppler radar. Traditional wheelslips worked by comparing axles - such as the "current balance/imbalance" system discussed above. The problem is that such systems don't detect all-axles slips. To allow creep, the control system must know "true ground speed", which - by definition - cannot be measured by a traditional axle-based speed probe. Hence the use of doppler radar to achieve this. 

 

Class 60 basically pinched the Super Series idea, although Brush argued that they took the concept and improved it. Cynics would say "made over-complex and unreliable". I couldn't possibly comment.

 

The spec for Class 60 stated that it had to acheive 500kN tractive effort (the equivalent for Class 59 was 509kN). I was on the Class 60 project at the time, and there was dancing in the streets on the day that the first loco got to that magic number recorded by the Test Car.

 

Answering a couple of other points made. The SEPEX control scheme, as trialled on 58050 and then incorporated on Class 90 (and probably 91, unsure, never worked on them) seperated the circuits for traction motor armature from motor fields; a traditional "series wound" motor had the field in series with the armature (hence the name). This meant that one can control the motor and the armature currents (basically) as one variable. SEPEX allowed independent control of field and armature current, and hence - in theory - improved ability to control slips.

 

As an aside, Class 90 was SEPEX and had Doppler radar from new; the radar was disconnected very shortly after, as it was unrealiable and there were concerns about axle strain - basically, one wheel slipping but the wheel on the other no slipping, leading to "winding up" an axle - by very small amounts, but nonetheless a Bad Thing. The redundant radar housing was an evil head-bang hazard with painful memories.

 

It's slightly unfair to describe the engine in a Class 59 (the EMD645) as harking back to 1938; the EMD engine is an evolution, in the same way that one of the 1980s GEC Ruston engines was an evolution of the engines fitted to 10000/10001. That said, it you stripped down a Class 66 engine, a Class 59 engine and a WW2-era 567 engine, you'd be hard-pressed to tell them apart.

 

The supercharger is driven by an over-running clutch; once the engine gets to "fast enough", the clutch disengages and it becomes a turbocharger. This is necessary because, as a two-stroke engine, the EMD needs to be pressure scavenged. The clutch is what makes the distinctive metallic ringing noise on a Class 66.

[45125]

1 hour ago, seraphim said:

I pressed "send" last night, and then realised I forgot to mention the key technical innovation which enabled Creep, which was the doppler radar. Traditional wheelslips worked by comparing axles - such as the "current balance/imbalance" system discussed above. The problem is that such systems don't detect all-axles slips. To allow creep, the control system must know "true ground speed", which - by definition - cannot be measured by a traditional axle-based speed probe. Hence the use of doppler radar to achieve this. 

 

Class 60 basically pinched the Super Series idea, although Brush argued that they took the concept and improved it. Cynics would say "made over-complex and unreliable". I couldn't possibly comment.

 

The spec for Class 60 stated that it had to acheive 500kN tractive effort (the equivalent for Class 59 was 509kN). I was on the Class 60 project at the time, and there was dancing in the streets on the day that the first loco got to that magic number recorded by the Test Car.

 

Answering a couple of other points made. The SEPEX control scheme, as trialled on 58050 and then incorporated on Class 90 (and probably 91, unsure, never worked on them) seperated the circuits for traction motor armature from motor fields; a traditional "series wound" motor had the field in series with the armature (hence the name). This meant that one can control the motor and the armature currents (basically) as one variable. SEPEX allowed independent control of field and armature current, and hence - in theory - improved ability to control slips.

 

As an aside, Class 90 was SEPEX and had Doppler radar from new; the radar was disconnected very shortly after, as it was unrealiable and there were concerns about axle strain - basically, one wheel slipping but the wheel on the other no slipping, leading to "winding up" an axle - by very small amounts, but nonetheless a Bad Thing. The redundant radar housing was an evil head-bang hazard with painful memories.

 

It's slightly unfair to describe the engine in a Class 59 (the EMD645) as harking back to 1938; the EMD engine is an evolution, in the same way that one of the 1980s GEC Ruston engines was an evolution of the engines fitted to 10000/10001. That said, it you stripped down a Class 66 engine, a Class 59 engine and a WW2-era 567 engine, you'd be hard-pressed to tell them apart.

 

The supercharger is driven by an over-running clutch; once the engine gets to "fast enough", the clutch disengages and it becomes a turbocharger. This is necessary because, as a two-stroke engine, the EMD needs to be pressure scavenged. The clutch is what makes the distinctive metallic ringing noise on a Class 66.

If I remember correctly the doppler on the 60 had to be moved, this was due to it been able detected the movement of passing trains. The doppler didn't like certain things like snow and steel decked bridges. Can remember examining some down loads off a 60 and you could see all sorts weird things under those conditions. It was quite interesting watching a 60s wheels when creep was active, you could see the wheels twitching.

 

 

The 90 and 91 are very similar to one another in the way the T/Ms are controlled.