Merchant Navy poor adhesion

[eastglosmog]

16 hours ago, Corbs said:

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

Agreed - definitely not a Q1, as according to this site https://en.wikipedia.org/wiki/Bulleid_Firth_Brown_wheel#/media/File:Bullied_Firth_Brown_Boxpok_wheel.JPG

where the Wikipedia photo came from, it is Merchant Navy Class  35010 "Blue Star" at the Colne Valley Railway while awaiting restoration.

[Gibbo675]

23 hours ago, PhilH said:

 

34105 on the MHR has welded wheels.

 

20 hours ago, jim.snowdon said:

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

Hi Chaps,

 

Thank you both for the information, I remember now that it has been mentioned, about the corrugated wagon wheels but I was unaware of the motor bogie wheels.

 

As you may well know, Bulleid was President of the Welding Institute and was most enthusiastic when it came to the then new technology.

 

As an asside; my experiences with Bulleid Pacifics and welding technology involved the fitting of new half sides to the fire box of 34067, I had to be very careful to remove all of the original weld material for it contained a huge amount of slag inclusion. The reason being that my welds in the new plate work had to be free of bad material so as to pass the ultrasonic test that was required for signing off according to pressure systems regulations to allow for insurance acceptance. The original welds were performed on the horizontal by manipulating the boiler and in one pass by a 4 swg electrode with the use of a backing strip. In contrast I worked in position using a cellulose root and a low hydrogen hot pass at 12 swg followed by two string bead fill runs at 10 swg and capped by a weave run again with 10 swg electrode, all low hydrogen. The capping run was applied as a weave to anneal the weld area and ground flush for the purposes of stress relief.

 

I have also weld repaired cracks in the wheels of 34067 which propagated from the root of the transition between the angled section and the large radius of the cut out. This was done with a minimal pre-heat to the weld area so that the tyres did not become loosened due to contraction and the subsequent restoration stresses.

 

Thanks again,

 

Gibbo.

[spikey]

11 hours ago, Gibbo675 said:

... I have also weld repaired cracks in the wheels of 34067 which propagated from the root of the transition between the angled section and the large radius of the cut out ...

 

Was that cracking a characteristic of BFB wheels generally, or just of 34067's?

[Mallard60022]

22 hours ago, eastglosmog said:

Agreed - definitely not a Q1, as according to this site https://en.wikipedia.org/wiki/Bulleid_Firth_Brown_wheel#/media/File:Bullied_Firth_Brown_Boxpok_wheel.JPG

where the Wikipedia photo came from, it is Merchant Navy Class  35010 "Blue Star" at the Colne Valley Railway while awaiting restoration.

Ah, thanks for that. The wheel just looks quite small without any reference to other parts. I looked at Q1s and they only have a weight on the centre driver.

Phil

[Nimbus]

On 07/04/2019 at 22:22, Dunsignalling said:

Getting back on topic, though still relating to locos making things look easy, I recall a remark in one of the books by Bishop Eric Treacy, to the effect that a Merchant Navy was the only loco he had ever observed cruising up Shap.

 

Like this?

35018 on Shap.

 

The Nim.

[Gibbo675]

10 hours ago, spikey said:

 

Was that cracking a characteristic of BFB wheels generally, or just of 34067's?

Hi Spikey,

 

It is a characteristic of wheels generally !

 

Gibbo.

[DCB]

Am I right in thinking that Bulleids pacifics had 120 degree cranks and the inside cylinder inclined by 15 degrees to give 135-105-120 degree "firing order"  It certainly sounds like it from the sounds they make.  Gresleys have to have 120-120-120 because of the conjugated valve gear and have the crank pins set to compensate for the inclination.

[30368]

Some very interesting and slightly controversial views on the Bulleid pacifics expressed, that has been the case since the 1940s.

 

A few minor historical observations that tends to colour opinions about these locomotives is simply that they operated the last main line steam service. The level of maintenance declined and many drivers (and firemen taking a turn) thrashed them since they all knew they were shortly going for scrap. That's not to say that all drivers thrashed them all the time, just more often. This, coupled with the fact that enthusiasts flocked to the Southern to take a last look probably reinforced the view that these engines slipped more than others.

 

I was lucky enough to have a footplate pass in 1964/5 as part of my training and I witnessed some of the behaviour described as well as 100 mph running memorably on Worting junction flyover. Happy days.

 

Kind regards,

 

Richard B

 

 

 

 

[Gibbo675]

10 hours ago, DavidCBroad said:

Am I right in thinking that Bulleids pacifics had 120 degree cranks and the inside cylinder inclined by 15 degrees to give 135-105-120 degree "firing order"  It certainly sounds like it from the sounds they make.  Gresleys have to have 120-120-120 because of the conjugated valve gear and have the crank pins set to compensate for the inclination.

Hi David,

 

The crank axles of both Bulleid and Gresley pacifics are set at 120* with one crank offset to account for cylinder inclination, it is the angle of the cylinders that cause the staccato exhaust in both types.

 

In the case of the Bulleid the cylinders are set at 1:40 for the outside pair and 1:7.75 for the inside, the valve gear is driven by a secondary 120* crank which is fixed to the crank axle via the chains. The angles at which the offset crank throws are set, without doing any sums, may well be the angles you note above. The reason is so that each set of valve gear drives the appropriate valve in relation to the inclination of the particular cylinder and also the reason for the uneven exhaust.

 

The cylinders of the Gresley pacifics are set at similar angles but I don't know the exact figures. With the Gresley pacifics the conjugate gear is arranged to compensate for any slight difference in angle between the cylinders by way of the 2:1 levers. The 2:1 levers would only work at that ratio if all of the cylinders were on the same plane and therefore the ratio of the levers are altered to allow for the angular displacement of the cylinders where they are set differently.

 

The reason for the highly inclined inside cylinder is so that the connecting rod clears the front axle when the crank is at bottom dead centre.

 

This is the book to read, it will explain it all in matter valve gear:

 

https://www.amazon.com/Locomotive-Valves-Valve-Gears-Jacob/dp/0951936719

 

Bulleid gear is not in the book but once you understand Walschearts gear then you will understand that the secondary crank takes on the function of the more normal return crank.

 

I hope all that makes sense !

 

Gibbo.

Edited April 20, 2019 by Gibbo675
Bad grammar, again !

[PhilH]

For information.. On Bulleid pacifics cranks are set at 120-114-126 deg. 

[jim.snowdon]

2 hours ago, Gibbo675 said:

The cylinders of the Gresley pacifics are set at similar angles but I don't know the exact figures. With the Gresley pacifics the conjugate gear is arranged to compensate for any slight difference in angle between the cylinders by way of the 2:1 levers. The 2:1 levers would only work at that ratio if all of the cylinders were on the same plane and therefore the ratio of the levers are altered to allow for the angular displacement of the cylinders where they are set differently.

Actually, no. The 2:1 ratio remains unaltered, but, whilst the middle cylinder may be inclined, its valve chest is not. All of the valve gear lies in the same plane, otherwise things really do get complicated. The cylinder is inclined, and the crank position adjusted to compensate.

 

2 hours ago, Gibbo675 said:

The crank axles of both Bulleid and Gresley pacifics are set at 120* with one crank offset to account for cylinder inclination, it is the angle of the cylinders that cause the staccato exhaust in both types.

That has more to do with generously valve openings and minimal resistance to flow in the steam passages. I guess you really meant "uneven", but then, on a Gresley 3-cylinder engine, as far as the valve gear is concerned, all three cylinders are at 120 degree intervals. The shift in the crank position for the centre cylinder is simply to arrange that when the valve thinks the piston is at tdc, it actually is.

 

Jim

[The Johnster]

Thinking valves; whooda thunk it!

 

Thank you guys for these last few posts, which have been very highly educational for me.  Educational in that I've learned that I don't know as much about basic steam loco matters as I thought I did...  I had never considered that cylinder inclination made much difference beyond clearance and loading gauge issues.  If you have big cylinders with small driving wheels, like on a 9f, you need to incline them or they would be too low and wide.  I clearly need to do some thinking about this, and it's exactly the sort of mental exercise I indulge myself with when I'm trying to sleep or waiting for a bus.

[DCB]

On 20/04/2019 at 12:48, jim.snowdon said:

Actually, no. The 2:1 ratio remains unaltered, but, whilst the middle cylinder may be inclined, its valve chest is not. All of the valve gear lies in the same plane, otherwise things really do get complicated. The cylinder is inclined, and the crank position adjusted to compensate.

 

That has more to do with generously valve openings and minimal resistance to flow in the steam passages. I guess you really meant "uneven", but then, on a Gresley 3-cylinder engine, as far as the valve gear is concerned, all three cylinders are at 120 degree intervals. The shift in the crank position for the centre cylinder is simply to arrange that when the valve thinks the piston is at tdc, it actually is.

 

Jim

 

Actually a well maintained Gresley does not have an uneven beat, it is very regular, I have video of Sir Nigel starting from Goathland NYMR with no hint of a slip and a very even beat.

The Gresley valves are at 120 degrees and all in the same plane as they have to be with Gresley / Holcroft conjugated valve gear but the middle cylinder is inclined. The WC and MN class don't have to be which is why I asked, they certainly don't sound very even to me.

[PhilH]

7 hours ago, DavidCBroad said:

 

Actually a well maintained Gresley does not have an uneven beat, it is very regular, I have video of Sir Nigel starting from Goathland NYMR with no hint of a slip and a very even beat.

The Gresley valves are at 120 degrees and all in the same plane as they have to be with Gresley / Holcroft conjugated valve gear but the middle cylinder is inclined. The WC and MN class don't have to be which is why I asked, they certainly don't sound very even to me.

Gresley pacifics definitely have a syncopated beat upon starting or with the gear well down, only evening out when the gear is pulled up. 

Not quite sure what is meant by the valves are set at 120 deg, I suppose to give valve events of 120 deg but with a middle cylinder inclination of 8 degs is why the cranks are set at 120-112-128 deg.

As the thread has now moved on to Gresley things some might find this interesting.

https://www.lner.info/forums/viewtopic.php?t=5090

Have the aspirin handy...

Edited April 22, 2019 by PhilH

[JimC]

I think the shade of Ken Cook would be holding his head in his hands at some of that. 

 

http://kesr-mic.org.uk/resources/The+Steam+Locomotive-A+Machine+of+Precision.pdf

 

Cook notes that with optical alignment and improved precision manufacturing the lifespan of WD 2-8-0 small ends was improved from 10,000 miles to 34,000.

 

 

[Gibbo675]

On 20/04/2019 at 12:48, jim.snowdon said:

Actually, no. The 2:1 ratio remains unaltered, but, whilst the middle cylinder may be inclined, its valve chest is not. All of the valve gear lies in the same plane, otherwise things really do get complicated. The cylinder is inclined, and the crank position adjusted to compensate.

 

That has more to do with generously valve openings and minimal resistance to flow in the steam passages. I guess you really meant "uneven", but then, on a Gresley 3-cylinder engine, as far as the valve gear is concerned, all three cylinders are at 120 degree intervals. The shift in the crank position for the centre cylinder is simply to arrange that when the valve thinks the piston is at tdc, it actually is.

 

Jim

Hi Jim,

 

As for the dimensions of the the 2:1 lever any slight inaccuracies that may be compounded in the building of the locomotive such as minor degrees of arc in either the building up of the crank axle, the alignment of the cylinders or even the working of the valve gear that may be compensated for in various ways. These include the drawing or jumping of rods appropriately, eccentric boring of bushes and the shimming of bearing blocks, occasionally all three.

 

I was, some twenty years or so ago, involved in an investigation as to why 60007 would not run properly in back gear, despite running fine in forward gear. It was found that there were several discrepancies in the valve gear systems on both the left and right hand side of the engine which made for compounding errors including, unequal swing of the expansion links due to incorrect back set, uneven lift to the die blocks within the expansion links and incorrect travel to the middle valve. The uneven lift to the die block meant that the valve gear could not be accurately set for the left and right hand side were effectively working at different cut offs and so the lead figures for, mid, full and working cut offs could not be accurately recorded. There was also talk that the wheels were not original to the frame set despite being appropriately stamped, possibly from 60026 but uncertain, this bore out when the front and back dead centres were trammelled out and found to be very slightly inaccurate. Having the radial alignment of the crank axle match the inclination of the cylinders is most important as the wheels would have been manufactured to the set of the cylinders within the frames at the time of building. Various modifications were made that greatly improved matters but the locomotive would still not run well in back gear although we got it timed perfectly in forward gear. The reason for setting the locomotive so is that it spent a lot of its working time in forward gear upon the main line.

 

When built the 2:1 levers would be adjusted to give the correct valve travel to suit that particular locomotive, the compensations being measured in the thousands of an inch over levers that are several feet length thus compensating for two sets of compounding errors in two sets of motion.

 

 

On 22/04/2019 at 11:38, PhilH said:

Gresley pacifics definitely have a syncopated beat upon starting or with the gear well down, only evening out when the gear is pulled up. 

Not quite sure what is meant by the valves are set at 120 deg, I suppose to give valve events of 120 deg but with a middle cylinder inclination of 8 degs is why the cranks are set at 120-112-128 deg.

As the thread has now moved on to Gresley things some might find this interesting.

https://www.lner.info/forums/viewtopic.php?t=5090

Have the aspirin handy...

Hi Phil,

 

Should you look at the positions of the valve chests of either a Gresley or Bulleid pacific you will note that the valve chest of the middle cylinder is much closer to the blast pipe than the outer pair, and when running slowly there is a relative delay from the port face to the exit and chuff at the chimney compared to the middle one. On a Bulleid the port edges for the middle cylinder are about 18" from the tips of blast cap and the outer pair are approximately 10-12 feet away along a pipe with two 90* bends and an expansion bellows.

 

The radial offset of the crank is 8* from the 120* position so that the piston is at front and back dead centre when the valve opens to its full lead steam figure due to the inclination of the cylinder at 8*, the valves being timed at 120* interval per full revolution of the wheel.

 

Any questions just ask.

 

Gibbo.

[jim.snowdon]

1 hour ago, Gibbo675 said:

Having the radial alignment of the crank axle match the inclination of the cylinders is most important as the wheels would have been manufactured to the set of the cylinders within the frames at the time of building.

I'd like to see that corroborated. The cylinder blocks would have been machined on jigs to a drawing, not matched to individual crank axles, which would themselves have had their wheels fitted using dedicated machines.

 

Jim

[Gibbo675]

27 minutes ago, jim.snowdon said:

I'd like to see that corroborated. The cylinder blocks would have been machined on jigs to a drawing, not matched to individual crank axles, which would themselves have had their wheels fitted using dedicated machines.

 

Jim

Hi Jim,

 

I'm not quite sure what you want me to write so I shall simply tell you the truth of my own experience;

 

I am well aware of how to machine cylinder blocks having done so myself, it is not the machining of the cylinder block that is the difficult bit but the fastening of it into the frames into exactly the correct position and orientation that is the tricky part, I know as much for I have done that also.

 

While at Riley and Son's we had a special protractor that had an adjustable spirit level incorporated into a vernier that clamped onto the crank pin while at the same time locating into the axle centre, it was capable of measuring the radial displacement of a crank in minutes of arc in relation to the other crank pins. It was made in Paris by a specialist instrument and gauge maker and was came to us via an antiques dealer in Sandbach that contacted us asking what it was, Riley bought it on the spot giving what they asked for it. It turned out to be ex Crewe works where it was used for just the very purpose that I have described.

 

It was used when we at Riley's manufactured the driving axles including the crank axle for Tornado, when after pressing the whole together the positions of the crank pins were drilled and the crank pins shrunk into position. They were then checked and the crank pins skimmed to finish size in the correct orientation on a large boring machine somewhere In Audenshaw. I can't remember the name of the firm but they specialised in machining fabrications and castings for the oil industry.

 

When building up a crank axle you must be aware that all journals must be re-machined after being pressed together, the fitting and riveting over of the screwed keys and also that the centres must be re-addressed to compensate. The reason for this is due to distortion and minor misalignment in manufacture which was no different at Riley and Son's as it would have been in any other workshop. As Riley's did not have a crank grinder that work was undertaken by Mitchel Shackelton & Co. Patricroft. this was done to ensure that the crank throw was correct. Once the crank axle was complete, the wheels were then pressed onto the axles and proof machined before being sent for the crank pin holes to drilled and the pins shrunk into place.

 

In theory, theory and practice are the same thing, in practice however, they are not.

 

Gibbo.

[jim.snowdon]

What matters, and I doubt that any of us can answer this definitively, is what workshop practice was in a works such as Doncaster in the 1930s when they were batch building these locomotives. Modern experience is confined to dealing with locomotives on an individual basis, with very little by way of new build.

 

Jim

[spikey]

On 22/04/2019 at 13:27, JimC said:

I think the shade of Ken Cook would be holding his head in his hands at some of that. 

 

http://kesr-mic.org.uk/resources/The+Steam+Locomotive-A+Machine+of+Precision.pdf

 

What a wonderful read!  Thank you very much JimC for posting the link.

 

"There was a good amount of subterfuge in the olden days for making lines appear to run true ..."

 

That started my day with a smile

 

Anyhow, this whole thread is fascinating, so do please keep it going gentlemen!

 

Edited April 24, 2019 by spikey

[JimC]

The last paragraph is an amusing snipe at the BR standards isn't it!

[The Johnster]

The ghost of Ahrons yet walked; a locomotive was still being judged on appearance rather than more practical considerations.  I wonder what Cook thought of the Ivatt pacifics, with no curve between the footplate and buffer beam plate at the front and cabs perched merkan style on straight footplate at the back.  I rate them the best looking of LMS pacifics, and the Peppercorn A1s the best LNER look, but I am a child of the 1950s and this is my taste.  

 

Some Ivatt designs and their BR standard derivates combined high pitched boilers and running plates with small wheels, and looked a bit ungainly from a broadside perpsective, and my view was that the angled drop plate at the front of BR standards was ugly, but I by and large liked looking at them.

[rogerzilla]

The SR Class V (Schools) is probably worse for slipping.  As everyone probably knows, it is the most powerful British 4-4-0 and this asks a lot of the four driving wheels.  The factor of adhesion (weight on drivers divided by theoretical tractive effort, and not coincidentally the inverse of the coefficient of friction on a dry rail) is less than 4, which is something designers usually try to avoid.   The 3-cylinder design helps smooth out the power compared to a 2 or 4*-cylinder locomotive but a Schools Class can still slip wildly and lose half its fire up the chimney before the driver gets it back under control.  Having said that, starting any express locomotive is difficult compared to a tank engine with all wheels driven.

 

*almost all 4-cylinder engines have pairs of cylinders in phase with each other so they can use only two sets of valve gear and simple rocking levers, although the Lord Nelsons have them at 135 degrees.

 

[brianusa]

As a layman on such matters, it always appeared odd to me that while the lighter WC/BBs slipped, the extra weight of the MNs didn't seem to make any difference.

        Brian.

[Right Away]

11 hours ago, rogerzilla said:

The SR Class V (Schools) is probably worse for slipping.  As everyone probably knows, it is the most powerful British 4-4-0 and this asks a lot of the four driving wheels.  The factor of adhesion (weight on drivers divided by theoretical tractive effort, and not coincidentally the inverse of the coefficient of friction on a dry rail) is less than 4, which is something designers usually try to avoid.   The 3-cylinder design helps smooth out the power compared to a 2 or 4*-cylinder locomotive but a Schools Class can still slip wildly and lose half its fire up the chimney before the driver gets it back under control.  Having said that, starting any express locomotive is difficult compared to a tank engine with all wheels driven.

 

*almost all 4-cylinder engines have pairs of cylinders in phase with each other so they can use only two sets of valve gear and simple rocking levers, although the Lord Nelsons have them at 135 degrees.

 

The design of the Schools has been well documented in many publications and like almost every steam locomotive built, will continue to fuel interesting arguments. The alignment of the London to Hastings road was predominant in the decision to have a short wheelbase and a 4 coupled arrangement.  However whether the engines would have fared better wth their 21 ton axle loading over smaller driving wheels* , eg maybe 6' 0", will forever be another subject to muse. The increase in nominal tractive effort would not have necessarily reduced any slipping propensity; indeed it can make things worse. It was stated many years ago by an eminent locomotive engineer that an engine's capacity to boil water is tantamount to its success or failure and in that respect the Schools excelled.

Throughout their working lives, testaments from footplatemen have generally shown favour to the design (with the exception perhaps of the lower cabside cutouts of the first ten and the bruised heads that could result!)

 

Fortunate to have travelled behind several examples - both small chimney and Lemâitre fitted, in the late '50s and early '60s, they always appeared capable with 10 or so bogies on the excursion traffic to the South Coast. Oh, to have experienced them in Kent or on the Pompey and Bournemouth roads when in their prime.

 

* The solitary Nelson with 6' 3" drivers by all accounts made little difference compared to the other class members and was deemed in some quarters to be less popular with the crews.