Merchant Navy poor adhesion

[The Stationmaster]

50 minutes ago, RLBH said:

Wildly off-topic, but this must be an advantage of the induction-based cab signalling developed in the United States and used in (amongst others) Ireland - condition of the wheel/rail interface is less critical if data isn't transmitted over it.

TVM is very reliable on normal rail surfaces.  With getting on for six years of operational involvement with trains using TVM signalling I can't recall ever hearing of a loss of signal from any cause and itw as never talked about as a potential problem by any of our traction people.  But I can understand it as a potential problem for Eurotunnel for a variety of reasons.

[Fat Controller]

38 minutes ago, The Stationmaster said:

TVM is very reliable on normal rail surfaces.  With getting on for six years of operational involvement with trains using TVM signalling I can't recall ever hearing of a loss of signal from any cause and itw as never talked about as a potential problem by any of our traction people.  But I can understand it as a potential problem for Eurotunnel for a variety of reasons.

It is usually reliable, though momentary 'sudden three reds in cab' are not uncommon. One thing that does have to be monitored closely is surface rust; trains are planned to run through every point and crossing, siding etc every day, including the two Emergency Sidings.

[Pete the Elaner]

I have not seen taper boilers mentioned.

The whole purpose of these was to distribute weight differently; move some away from the leading bogie & over the driving wheels where it could be used for adhesion.

 

GWR had been using taper boilers for years but the higher cost of them created some opposition within the LMS when Stanier introduced them.

They never really caught on with SR or LNER. The tapering of Brittania boilers was quite mild (presumably due to cost-saving which became more of a priority) & these were known for slipping too.

[LMS2968]

Not really. The only use of taper boilers on the LNER was on the Pacifics and V2s, which had a trailing truck to carry the rear end weight.

 

There are many advantages  - and disadvantages - to taper boilers, but put weight over the trailing and wasn't high among the former. They reduced the amount of water, and so weight generally, concentrated the water around the firebox, which was where the heat was, and reduced the tendency to surge on braking. There is also a theory that they required less maintenance, but initial cost was higher.

[jim.snowdon]

1 hour ago, Pete the Elaner said:

I have not seen taper boilers mentioned.

The whole purpose of these was to distribute weight differently; move some away from the leading bogie & over the driving wheels where it could be used for adhesion.

 

GWR had been using taper boilers for years but the higher cost of them created some opposition within the LMS when Stanier introduced them.

They never really caught on with SR or LNER. The tapering of Brittania boilers was quite mild (presumably due to cost-saving which became more of a priority) & these were known for slipping too.

No. The whole purpose of taper boilers was to create free water circulation around the firebox without incurring a weight penalty at the front end, which always tends to be heavy due to the weight of the cylinders. The degree of taper that can be provided dimishes with the really large boilers on large cylindered locomotives, where the ability of larger boilers to cope with short term overload is a consideration.

 

40 minutes ago, LMS2968 said:

Not really. The only use of taper boilers on the LNER was on the Pacifics and V2s, which had a trailing truck to carry the rear end weight.

 

There are many advantages  - and disadvantages - to taper boilers, but put weight over the trailing and wasn't high among the former. They reduced the amount of water, and so weight generally, concentrated the water around the firebox, which was where the heat was, and reduced the tendency to surge on braking. There is also a theory that they required less maintenance, but initial cost was higher.

The LNER's use of taper boilers was linked to the use of wide fireboxes (and in turn to the largest locomotives), where a trailing truck (or radial axle in the case of the LNER) becomes a necessity as the firebox cannot be located in a practical manner over driving wheels more than about 5 foot diameter.

 

Jim

[The Johnster]

This is a very educational thread!

 

A comment, purely my own viewpoint and not to be taken as definitive or authoritative, on the subject of driving standards.  These differed noticeably between individual drivers in my time on the railway back in the 70s, on diesel traction, and the differences must have been more pronounced with steam.  The driver is tasked with stopping the train at the places and times determined in the working timetable subject to and authorised by the Rules and Regulations, but, if he's any good, does this with the least discomfort to the passengers, or the guard on a freight train, the least work for his fireman, and on some railways he got a bonus for saving coal.  The traditional way of training him for his highly skilled job was to let him spend many years firing to other drivers.

 

This meant that, with minimal interference from inspectors and depending on his own enthusiasm for attending mutual improvement classes, which were voluntary and in any case more focussed on Rules and loco technology than driving technique, new drivers tended to acquire and continue old drivers' bad habits, and pass them on to the next generation.  If they were innovative enough to try a new technique of their own while being supervised in the seat during this long training period, the driver in charge told them not to and they were very strongly persuaded to do it his way.  

 

'His way' worked, of course, tried and tested over time on regularly done jobs.  But the fact that it was seldom challenged led to a stifling of innovation and a persistence of, not bad practice, but practice that could sometimes have been bettered.  

 

Modern steam drivers are different, as are their locos in some ways; their training is much more closely monitored by inspectors and be drivers who have themselves been taught by inspectors; the preservation movement is approaching it's 3rd generation of main line steam drivers and nobody who worked steam pre-1968 is in the game any more except in an advisory capacity.  The job references the old guys continually, even the loads and timings on main lines are based on the old days, but the situation is different.  The locos are, at least theoretically, in better shape, but good coal is harder and harder to come by, and the rail profile and ballasting is not set up for steam operation.  So, 'properly' taught drivers under the observation of inspectors a good bit of the time are driving locos that are in theory fully restored to main line condition, but I suspect that not all ex-Barry rebuilds withdrawn in poor condition are as good as Tornado, which is getting a bit of mileage under her now.  

 

Maintenance is rigorous, probably much more intense than in BR days, but I suspect focussed on safety issues rather than improving the efficiency or tractive ability of the loco, and locos can be set up very differently from each other to the specification of their owners or the preserved railway they mostly run on.  So, one rebuilt light pacific will fly up a bank with 11 on no problems, while a classmate with the same crew and same coal in the same conditions will struggle with 10.  Remember the criticism of Flying Scotsman last year when she embarrassed herself on the West Somerset (that was a stall, not a slip, i know, but illustrates the point; this loco was described as a bag of nails by Alan Pegler back in '63 and must have been pretty rough until her NRM rebuild; perhaps she'd have performed better in this situation in her nailbag condition).  This sort of event happened daily on pre-'68 BR and nobody commented except the signalmen and the drivers of following traffic held up by it.

 

Drivers' techniques still differ of course, and each driver has his favourite loco, that responds best to his methods, especially if he's the only one that can get much out of her.  Messroom debate on the matter is no doubt as lively as ever, and as opinionated, such is human nature, but there is a fundamental difference I think.  It is that modern driving standards are probably better than the worst of traditional ones, but unlikely to match the sheer depth of experience and knowledge of the best.  They are by and large very good indeed; driving a steam loco even at heritage railway speeds and loads is a complex and skilled job without having to react to situations at 90mph on a busy main line, but we are not really comparing like for like if we are comparing current steam operations to the old days.  

[spikey]

Well, apart from teaching me all sorts of stuff I never knew back in my 1950's trainspotting days, this thread finally got me checking out Boxpok wheels on t'internets.  And lo, from Wikipedia I learn that what I thought were Boxpok wheels aren't Boxpok wheels but are in fact Bulleid Firth Brown wheels! 

 

Not only that, but Wikipedia reckons they weigh about 10% less than a spoked wheel of the same size, which seems credible to me. What puzzles me though is this bit ... Disc wheels also distribute the weight more evenly, reducing the hammer effect on,[citation needed] and thus the damage to, the rail.  I wonder if what they're getting at with that is dynamic balance.  I can't think what else it could be, but come to that I don't really see how a disc wheel can "distribute the weight more evenly" than a spoked one simply because it's a disc wheel.

 

Any thoughts from you chaps who know what you're talking about?

Edited April 12, 2019 by spikey
typo

[IWCR]

I seem to remember reading a reference that part of the slipping problems was due to the Boxpok wheels, not due to there  stiffness but that the pockets in the design caught some of the oil coming off the motion and bearings whilst running. When stopped this would dribble from the upper pockets onto the the track.

Locos being often stopped in the same locations these got oily.

I dont know if this is true but it sounds plausible.  Probably less of a problem for preserved locos as these would do less miles and would be kept cleaner.

 

Pete

[Gibbo675]

19 hours ago, Mike 84C said:

During my four yrs as a steam fireman on BR I experienced  GW,LM, BR stds and a very few ER types. I can say that without doubt that the GW locos had the most sensitive regulator of all, a very positve open and closure. Why BR did'nt  adopt the type is puzzling. And I will say that in general GW locos of all types were more surefooted. Black fives, class 8's slip like goodun's, 9f's inc 92203which I have fired on real freight trains, no slipping there.

  Total loss lubrication plays a huge part in plastering an engines wheels in oil and I dare say that today's drivers  display a certain amount of bravado in their handling of the engine. The engineman in the past did not have a gallery to play to. To most it was just a job but we all know the names that were the exception.

  In my memory there was nothing better than a 9f on a fitted tomato special 45/50 vans Banbury to Bordesley in under the hour. Or belting seven bells out of an 8f from Tysley back to Banbury on a coal train, sky rockets all the way up past Fosse road box, or my driver walking all round the framing on a WR 38 at night and sticking his face around the front of the cab on the way to Reading, nearly a brown trouser moment.

 One observation on firing styles, the Eastern crews seemed to do a lot of shoveling when stood waiting for their train to arrive, drinking tea and having snap, then back on, right away, a huge slip that livens up the fire, lots of smoke and blowing off in five minutes.

  Sorry this is'nt teccy with theory and calculations, which has its place, just based on my small amount of experience. Its all a bit academic really.

    Mick

Hi Mick,

 

You make some excellent points in your above piece and may I verify what you say with some reasoning.

 

In design and construction the GWR regulator is a a horizontal grid type regulator valve in exactly the same way that LMS and BR Stds are constructed. Some locomotives have vertical grid type regulators but the principle is the same.

 

The valve body is of cast iron with the main valve being of bronze, about an inch thick, mounted on top in such a way that when operated the slots in the body and valve open and allow steam. There are either three or four slots about 3/4"-7/8" bye 6"-9" long depending upon the size of the locomotive, On top of the main valve is the pilot valve this is a smaller version of what has just been described with either one or two slots about 1/4" and perhaps 3"-5" long. The pilot valve is arranged so that only it is moved bye the regulator linkage in the initial movement of the handle with the main valve being collected and actuated over the remaining travel of the handle.

 

The only difference between the GWR type and the others is that the GWR situated their regulator valves in the manifold housing in the smoke box and above it was an atomised oil feed that lubricated the sliding faces of the of the valve. In the case of the LMS and BR locomotives the regulators are atop of the main steam pipe, sometimes known as the dry pipe, and as a consequence were not fitted with an oil lubrication supply for injecting oil into the boiler would cause all manner of trouble the most prevalent being foaming which may lead to priming. It is the fact that the GWR regulators were lubricated that made them easy to operate in comparison to the other locomotives.

 

The LNER and SR used double beat type regulators in their pacifics and latterly the LNER and following on BR used Melesco poppet valve regulators on their pacifics,

 

Here is an interesting link with some good diagrams:

 

https://janfordsworld.blogspot.com/2016/09/locomotive-regulators-part-2.html

 

It would seem to me that  two of the reasons for GWR locomotives being sure footed are that they have relatively constricted steam circuits and also the cylinders were mounted horizontally which greatly reduced the ability of the piston thrust to roll the locomotive upon its springs upon starting. Any one that has ever ridden on a Crab will know all about how pronounced an effect that may be.

 

Gibbo.

[Gibbo675]

19 hours ago, Mike 84C said:

During my four yrs as a steam fireman on BR I experienced  GW,LM, BR stds and a very few ER types. I can say that without doubt that the GW locos had the most sensitive regulator of all, a very positve open and closure. Why BR did'nt  adopt the type is puzzling. And I will say that in general GW locos of all types were more surefooted. Black fives, class 8's slip like goodun's, 9f's inc 92203which I have fired on real freight trains, no slipping there.

  Total loss lubrication plays a huge part in plastering an engines wheels in oil and I dare say that today's drivers  display a certain amount of bravado in their handling of the engine. The engineman in the past did not have a gallery to play to. To most it was just a job but we all know the names that were the exception.

  In my memory there was nothing better than a 9f on a fitted tomato special 45/50 vans Banbury to Bordesley in under the hour. Or belting seven bells out of an 8f from Tysley back to Banbury on a coal train, sky rockets all the way up past Fosse road box, or my driver walking all round the framing on a WR 38 at night and sticking his face around the front of the cab on the way to Reading, nearly a brown trouser moment.

 One observation on firing styles, the Eastern crews seemed to do a lot of shoveling when stood waiting for their train to arrive, drinking tea and having snap, then back on, right away, a huge slip that livens up the fire, lots of smoke and blowing off in five minutes.

  Sorry this is'nt teccy with theory and calculations, which has its place, just based on my small amount of experience. Its all a bit academic really.

    Mick

Hi Mick,

 

You make some excellent points in your above piece and may I verify what you say with some reasoning.

 

In design and construction the GWR regulator is a a horizontal grid type regulator valve in exactly the same way that LMS and BR Stds are constructed. Some locomotives have vertical grid type regulators but the principle is the same.

 

The valve body is of cast iron with the main valve being of bronze, about an inch thick, mounted on top in such a way that when operated the slots in the body and valve open and allow steam. There are either three or four slots about 3/4"-7/8" bye 6"-9" long depending upon the size of the locomotive, On top of the main valve is the pilot valve this is a smaller version of what has just been described with either one or two slots about 1/4" and perhaps 3"-5" long. The pilot valve is arranged so that only it is moved bye the regulator linkage in the initial movement of the handle with the main valve being collected and actuated over the remaining travel of the handle.

 

The only difference between the GWR type and the others is that the GWR situated their regulator valves in the manifold housing in the smoke box and above it was an atomised oil feed that lubricated the sliding faces of the of the valve. In the case of the LMS and BR locomotives the regulators are atop of the main steam pipe, sometimes known as the dry pipe, and as a consequence were not fitted with an oil lubrication supply for injecting oil into the boiler would cause all manner of trouble the most prevalent being foaming which may lead to priming. It is the fact that the GWR regulators were lubricated that made them easy to operate in comparison to the other locomotives.

 

The LNER and SR used double beat type regulators in their pacifics and latterly the LNER and following on BR used Melesco poppet valve regulators on their pacifics,

 

Here is an interesting link with some good diagrams:

 

https://janfordsworld.blogspot.com/2016/09/locomotive-regulators-part-2.html

 

It would seem to me that  two of the reasons for GWR locomotives being sure footed are that they have relatively constricted steam circuits and also the cylinders were mounted horizontally which greatly reduced the ability of the piston thrust to roll the locomotive upon its springs upon starting. Any one that has ever ridden on a Crab will know all about how pronounced an effect that may be.

 

Gibbo.

[JimC]

19 hours ago, spikey said:

[snip] Wikipedia [snip] What puzzles me though is this bit ... Disc wheels also distribute the weight more evenly, reducing the hammer effect on,[citation needed] and thus the damage to, the rail. 

 

You need to be extremely wary of Wikipedia. Articles are often maintained by a small group who may not be as knowledgable as they think they are. Any attempt to eliminate long standing myths tends to be stamped on and reverted.  Distributing the weight more evenly reducing hammer blow sounds, well, I think I'd want a citation from a knowledgable engineer before I gave it much credence.

[john new]

56 minutes ago, JimC said:

 

You need to be extremely wary of Wikipedia. Articles are often maintained by a small group who may not be as knowledgable as they think they are. Any attempt to eliminate long standing myths tends to be stamped on and reverted.  Distributing the weight more evenly reducing hammer blow sounds, well, I think I'd want a citation from a knowledgable engineer before I gave it much credence.

Agree

[jim.snowdon]

19 hours ago, spikey said:

Well, apart from teaching me all sorts of stuff I never knew back in my 1950's trainspotting days, this thread finally got me checking out Boxpok wheels on t'internets.  And lo, from Wikipedia I learn that what I thought were Boxpok wheels aren't Boxpok wheels but are in fact Bulleid Firth Brown wheels! 

 

Not only that, but Wikipedia reckons they weigh about 10% less than a spoked wheel of the same size, which seems credible to me. What puzzles me though is this bit ... Disc wheels also distribute the weight more evenly, reducing the hammer effect on,[citation needed] and thus the damage to, the rail.  I wonder if what they're getting at with that is dynamic balance.  I can't think what else it could be, but come to that I don't really see how a disc wheel can "distribute the weight more evenly" than a spoked one simply because it's a disc wheel.

 

Any thoughts from you chaps who know what you're talking about?

Wiki did at least get it right as regards the wheels being a Bulleid-Firth Brown design, very different to a Boxpok wheel. However, their references to weight distribution and hammer blow are way off beam. The objectives of the BFB wheel are to reduce weight (more importantly, unsprung weight, as it is that that damages the track) and to provide even support to the tire. This is also why the later LMS and the BR wheels had a really substantial triangular section rim. The flatter rims on earlier wheels flexed a little between the spokes, with the result that tyres occasionally worked loose or slipped.

Hammer blow is a direct consequence of the compromises between balancing the rotating parts (easy) and the reciprocating parts (not so easy, especially on two cylindered locomotives), and nothing to do with the design of the wheels.

 

Jim

[The Johnster]

It is not difficult to balance rotating mass, that is, the wheels, cranks, crankpins, coupling rods and so on, with balance weights on the driving wheels and counterbalances for the internal cranks of inside cylinders, and as the forces increase identically in the rotating mass and the counterbalancing with increased speed of rotation, it can be done pretty accurately and effectively. 

 

Hammer blow is nothing to do with this, although the ‘stiffness’ of the wheels will affect the ride if the loco and may exacerbate or ameliorate it.  Hammer blow is caused by reciprocating mass, the stuff that goes to and fro rather than round and round.  This is the pistons, piston valves if there are any, and crossheads.  And then there’s the connecting rods.  These take some of the reciprocating load at the crosshead end and become rotating mass at the crank end. 

 

Hammer blow, unsurprisingly given what it is called, manifests itself as a physical shock throughout the loco and at the railhead, and is A Bad Thing that has caused many a CME to look old and grey before his time.  While the rotating mass maintains the same speed, reciprocating mass stops dead for a nanosecond (or we’ll say it does to stop my brain hurting) at the end of it’s stroke, accelerates until it gets to the middle, then decelerates to stop at t’other end before reversing itself and repeating the move. 

 

So, we have stuff going round and round all at the same speed, and stuff going to and fro at all sorts of different speeds, the latter being impossible to balance and easier to increase than it is to reduce.  The difference has to escape the system somewhere and does so in this violent way. 

 

This is is my very limited layman’s understanding of a very complex engineering issue; I am sure there are many contributors here who can explain it better than my inane ramblings!

 

A steam locomotive in motion moves, like god, in all sorts of mysterious ways, not all of them in the same direction or speed and not all of them intended...

[LMS2968]

Hammerblow is the result of the attempt to balance the reciprocating masses, mostly the pistons, piston rods, crossheads, about half the connecting rods and, depending on the valve gear, union links and half the combination levers. All these move backwards and forwards and so have momentum in that plane, meaning they don't want to stop at the end of each stroke. What stops them are, in order, the wheels via the crankpins, the axleboxes, and the horn guides in the frames so the reciprocating forces are fed into the loco structure, causing heavy knocks, possible damage and, in extreme cases, can result in derailment.

 

To help alleviate these reciprocating imbalances, weights over and above those required to counteract the rotating masses are incorporated in the driving and coupled wheels so that they are acting in the opposite direction of the reciprocating forces and so reduce what is fed into the frames. This is all very well in the horizontal plane where they and the reciprocating forces cancel each other out, but as the wheels are rotating, these portions of the balance weights also have a vertical component, which the reciprocating masses do not possess. These vertical forces are therefore not balanced and try to lift the wheels as they are on the rising part of the their' revolution and then push downwards as the wheels comes around to the downwards part, thereby decreasing and increasing  the vertical force (weight) that the wheels are exerting on the rails each revolution, effectively acing like a hammer striking downwards.

[Corbs]

Here's a question; how are Bulleid-Firth Brown wheels made lighter than spoked ones? I was quite surprised to learn this, as to look at them, they look like a larger amount of metal.

(I presume the one in the pic is on a rebuilt light pacific due to the presence of the balance weight)

 

 

Also, Boxpok for comparison:

[Mallard60022]

Is your first pic from a Q1 by any chance? Looks a bit small for a Spam.

Phil

[spikey]

13 hours ago, LMS2968 said:

To help alleviate these reciprocating imbalances, weights over and above those required to counteract the rotating masses are incorporated in the driving and coupled wheels so that they are acting in the opposite direction of the reciprocating forces and so reduce what is fed into the frames. This is all very well in the horizontal plane where they and the reciprocating forces cancel each other out, but as the wheels are rotating, these portions of the balance weights also have a vertical component, which the reciprocating masses do not possess. These vertical forces are therefore not balanced and try to lift the wheels as they are on the rising part of the their' revolution and then push downwards as the wheels comes around to the downwards part, thereby decreasing and increasing  the vertical force (weight) that the wheels are exerting on the rails each revolution, effectively acing like a hammer striking downwards.

 

Thank you sir for that explanation.  One thing's for sure - whoever did the calculations for the balance factors certainly knew what he was doing!

[The Stationmaster]

On 12/04/2019 at 20:04, Gibbo675 said:

Hi Mick,

 

It would seem to me that  two of the reasons for GWR locomotives being sure footed are that they have relatively constricted steam circuits and also the cylinders were mounted horizontally which greatly reduced the ability of the piston thrust to roll the locomotive upon its springs upon starting. Any one that has ever ridden on a Crab will know all about how pronounced an effect that may be.

 

Gibbo.

Don't forget also that some GWR 4-6-0s had compensating levers between the springs although Collett reportedly dropped them from c.1930 (according to Holcroft).  They don't appear on any drawings which I can find of a 'King' but they are definitely present on early 'Castle' drawings and the 'Stars' and 'Saints' also had them.

[JimC]

5 hours ago, The Stationmaster said:

Don't forget also that some GWR 4-6-0s had compensating levers between the springs although Collett reportedly dropped them from c.1930 (according to Holcroft).  

 

They were removed from all the locomotives that had them. New spring designs were fitted instead. 

[Corbs]

6 hours ago, Mallard60022 said:

Is your first pic from a Q1 by any chance? Looks a bit small for a Spam.

Phil

Don't think so, looks like a wide firebox top left of pic?

[jim.snowdon]

20 hours ago, Corbs said:

Here's a question; how are Bulleid-Firth Brown wheels made lighter than spoked ones? I was quite surprised to learn this, as to look at them, they look like a larger amount of metal.

(I presume the one in the pic is on a rebuilt light pacific due to the presence of the balance weight)

 

 

Also, Boxpok for comparison:

The back of a BFB wheel looks just like the front, except displaced by half a "spoke". The wheel centre is effectively a corrugated plate, which can be made relatively thin for its strength. The Boxpok and others are still pretty substantial castings.

 

Jim

[Gibbo675]

9 minutes ago, jim.snowdon said:

The back of a BFB wheel looks just like the front, except displaced by half a "spoke". The wheel centre is effectively a corrugated plate, which can be made relatively thin for its strength. The Boxpok and others are still pretty substantial castings.

 

Jim

Hi Jim,

 

There was a least one full set of wheels that were fabricated from flame cut steel pressings which were welded around a boss and within a rim onto which the tyre was shrunk.

 

Gibbo.

[PhilH]

57 minutes ago, Gibbo675 said:

Hi Jim,

 

There was a least one full set of wheels that were fabricated from flame cut steel pressings which were welded around a boss and within a rim onto which the tyre was shrunk.

 

Gibbo.

 

34105 on the MHR has welded wheels.

Edited April 15, 2019 by PhilH

[jim.snowdon]

3 hours ago, Gibbo675 said:

Hi Jim,

 

There was a least one full set of wheels that were fabricated from flame cut steel pressings which were welded around a boss and within a rim onto which the tyre was shrunk.

 

Gibbo.

There were, although by their numbers, they were still experimental. The 4DD emu sets were built with welded wheels on the motor bogies and, from what I can recall, suffered problems early on to the extent that they had to be replaced. Bulleid also experimented with corrugated plate wheel centres for wagons. 

 

Jim