Prototype for everything corner.

[montyburns56]

Sarah Siddons Northwood 1972 by Trainsandtravel

 

 

[Titan]

On 31/08/2021 at 23:23, melmerby said:

Wikipedia states that they were needed due to the lighter weight of the diesel locos compared to the steam they replaced.

Really? The Peak has way more weight on it's driving wheels than an 8F or 9F.

Crappy brakes more like

 

All diesels that hauled passenger trains had to have crappy brakes.  If they used enough brake force to take full advantage of the available adhesion the tyres would overheat when trying to stop from 90mph plus. Not so much a problem for steam locos that had much bigger wheels and generally lower speeds. Hence when diesels haul passenger trains it is the coaches that help stop the locomotive.  However when hauling fitted freight, the diesel loco brakes were usually still a bit better than the wagons they were hauling, especially if it was partly fitted.  This was the reason for the passenger/freight brake changeover switch on diesel locos.  On passenger workings to avoid snatch, the train brakes would come on before the loco brakes, and for freight it was vice versa.  This is the reason that most diesel locos were restricted to 60mph light engine, and also a minimum number of coaches in tow if they were allowed to run at their top speed - I think for 100mph Deltics had to have at least six coaches behind them to provide adequate brake force, with a progressive limit on top speed the fewer coaches you had.

[russ p]

2 hours ago, montyburns56 said:

 

I've found a better picture of it. I wonder if anyone has ever modelled it?

 

 

By Graeme Phillips

 

Has the 120 been modified or was there a variant with a massive van?

[Mark Saunders]

6 hours ago, ianmacc said:

Looks like a lamp…

 

Assume the grain hopper is a barrier vehicle of some type?

Go for the simple answer, there for loading with grain as they were the largest hoppers that could get around the tight curves!

[ianmacc]

6 minutes ago, russ p said:

 

Has the 120 been modified or was there a variant with a massive van?

It was a modification to remove the standard accommodation in favour of brake space and just leave the first class seats. 

[Davexoc]

23 minutes ago, Titan said:

 

All diesels that hauled passenger trains had to have crappy brakes.  If they used enough brake force to take full advantage of the available adhesion the tyres would overheat when trying to stop from 90mph plus. Not so much a problem for steam locos that had much bigger wheels and generally lower speeds. Hence when diesels haul passenger trains it is the coaches that help stop the locomotive.  However when hauling fitted freight, the diesel loco brakes were usually still a bit better than the wagons they were hauling, especially if it was partly fitted.  This was the reason for the passenger/freight brake changeover switch on diesel locos.  On passenger workings to avoid snatch, the train brakes would come on before the loco brakes, and for freight it was vice versa.  This is the reason that most diesel locos were restricted to 60mph light engine, and also a minimum number of coaches in tow if they were allowed to run at their top speed - I think for 100mph Deltics had to have at least six coaches behind them to provide adequate brake force, with a progressive limit on top speed the fewer coaches you had.

 

From what I remember, the changeover switch altered the application and release timings. Regardless of type, the loco brakes apply and buffer up the trailing load, faster for passenger, slower for freight. Then release is much the same, quicker release for passenger, and slower release for freight, to allow the couplings to open out and reduce snatch. If the coaches on a passenger train applied first, there would be the risk of flats on the coaches as the weight of the loco try and drag them along.

[russ p]

19 minutes ago, ianmacc said:

It was a modification to remove the standard accommodation in favour of brake space and just leave the first class seats. 

 

Did they operate in passenger service like that?

[Jeremy Cumberland]

31 minutes ago, russ p said:

 

Did they operate in passenger service like that?

Yes, the conversion was made for the Aberdeen - Inverness service. according to railcar.co.uk. There is information here: https://railcar.co.uk/type/class-120/modifications and on the photo pages here (the conversions were 51783-6): https://railcar.co.uk/images/class-120/vehicles/31

[hexagon789]

36 minutes ago, russ p said:

 

Did they operate in passenger service like that?

Yes, four were so modified and used by the ScR on Aberdeen-Inverness route.

[Gibbo675]

11 hours ago, Titan said:

 

All diesels that hauled passenger trains had to have crappy brakes.  If they used enough brake force to take full advantage of the available adhesion the tyres would overheat when trying to stop from 90mph plus. Not so much a problem for steam locos that had much bigger wheels and generally lower speeds. Hence when diesels haul passenger trains it is the coaches that help stop the locomotive.  However when hauling fitted freight, the diesel loco brakes were usually still a bit better than the wagons they were hauling, especially if it was partly fitted.  This was the reason for the passenger/freight brake changeover switch on diesel locos.  On passenger workings to avoid snatch, the train brakes would come on before the loco brakes, and for freight it was vice versa.  This is the reason that most diesel locos were restricted to 60mph light engine, and also a minimum number of coaches in tow if they were allowed to run at their top speed - I think for 100mph Deltics had to have at least six coaches behind them to provide adequate brake force, with a progressive limit on top speed the fewer coaches you had.

Hi Titan,

 

This video shews some of what you have written of,

 

 

 

Gibbo.

[rodent279]

13 hours ago, montyburns56 said:

Sarah Siddons Northwood 1972 by Trainsandtravel

 

 

You don't see brakevan tours anymore these days.

When was the last run, and is there any reason why it couldn't be done now, on the mainline (apart from the lack of brake vans)?

[rab]

17 hours ago, ianmacc said:

Looks like a lamp…

 

Assume the grain hopper is a barrier vehicle of some type?

Is the hopper actually coupled to the DMU

or are they just stored on the same track?

[Nick C]

14 hours ago, montyburns56 said:

Sarah Siddons Northwood 1972 by Trainsandtravel

 

 

The NEM pocket under the headstock is very visible there...

[ianmacc]

11 minutes ago, Nick C said:

The NEM pocket under the headstock is very visible there...

Haha now I can’t unsee it. What was he thinking painting it light grey? 
 

I wonder what the sister loco at the other end was. 
 

I also googled Sarah Siddons and she’s a famous Georgian tragedy actress!

Edited September 3, 2021 by ianmacc

[Titan]

13 hours ago, Davexoc said:

 

From what I remember, the changeover switch altered the application and release timings. Regardless of type, the loco brakes apply and buffer up the trailing load, faster for passenger, slower for freight. Then release is much the same, quicker release for passenger, and slower release for freight, to allow the couplings to open out and reduce snatch. If the coaches on a passenger train applied first, there would be the risk of flats on the coaches as the weight of the loco try and drag them along.

 

The last thing you want on a passenger train is the loco buffering up and then snapping the coupling tight when the coach brakes come on. Prior to the brakes being applied, the loco coupling will already be tight due to the springs in the buffers keeping it that way, so if the coach brakes come on first it keeps the coupling tight and there is no snatch. There will be no wheel flats either, as drivers are not in the habit of going straight into emergency application on a normal service stop, so the brakes on the coaches will only have had a gentle application before the loco brakes start to come on in proportion to that of the coaches.

Edited September 3, 2021 by Titan

[Jeremy Cumberland]

1 hour ago, ianmacc said:

I wonder what the sister loco at the other end was. 

No. 5, now in the London Transport Museum. This must have been one of its last outings. By this time, they were the only two of the class remaining.

Edited September 3, 2021 by Jeremy C

[Fat Controller]

1 hour ago, rab said:

Is the hopper actually coupled to the DMU

or are they just stored on the same track?

Similar grain wagons were still working into a mill on Birkenhead docks in the 1980s; this might be a trip working taking the unit to Horwich, or returning it.

[Wickham Green too]

Any trip to Horwich ( or elsewhere ) would have been one way at that date ! .............. oh - by the way, rab, it's an EMU !

[45125]

55 minutes ago, Titan said:

 

The last thing you want on a passenger train is the loco buffering up and then snapping the coupling tight when the coach brakes come on. Prior to the brakes being applied, the loco coupling will already be tight due to the springs in the buffers keeping it that way, so if the coach brakes come on first it keeps the coupling tight and there is no snatch. There will be no wheel flats either, as drivers are not in the habit of going straight into emergency application on a normal service stop, so the brakes on the coaches will only have had a gentle application before the loco brakes start to come on in proportion to that of the coaches.

Many diesel locos had the brake proportionality altered in that initial brake stages the train did most of the braking. As the co owner of one of these locos, the loco braking in the early stages of braking is very minimal, it is only when you drop the brake down to around 55psi/14"vac that the bogie brakes begin to bight.

 

If a a loco has been coupled up correctly there should be little or no snatch between loco and stock, the main problem comes with instanter couplings as there is always a gap between buffer faces, hence why fitted/unfitted goods timings for brake application/release are different.

[ianmacc]

7 hours ago, rodent279 said:

You don't see brakevan tours anymore these days.

When was the last run, and is there any reason why it couldn't be done now, on the mainline (apart from the lack of brake vans)?

I should think health and safety would make it about as far from suitable as it was possible to be, except maybe if you were in open mineral wagons! 
 

 

 

[DK123GWR]

47 minutes ago, ianmacc said:

I should think health and safety would make it about as far from suitable as it was possible to be, except maybe if you were in open mineral wagons! 
 

 

 

Flat wagons?

[Michael Hodgson]

If you want to run a brake van special, you need to have a supply of serviceable brake vans sitting around doing nothing else.

[rab]

Having done a brake van run on a preserved railway (25 mph max)

I don't think I'd fancy doing one in the mainline, running at the speeds needed to keep out of the way of service trains.

[rab]

7 hours ago, Wickham Green too said:

Any trip to Horwich ( or elsewhere ) would have been one way at that date ! .............. oh - by the way, rab, it's an EMU !

Sorry, never having been anywhere near an area with electrified lines, ( I've led a very sheltered life  )everything was steam or diesel to me.

[montyburns56]

 Class 123 Redbridge 1968