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Copyright John Dunn Engineering

Welcome to the Barclay Blog.

No.8 was the last 16″ 0-4-0 saddle tank built by the Kilmarnock firm of Andrew Barclay and Sons Ltd. Works No. 2369 she was delivered new to the Scottish Region of the National Coal Board in 1955, the last brand new steam locomotive they bought.

I am lucky enough to own a 3/4 share in the locomotive and I thought people might be interested to follow the overhaul, maintenance, and day to day running of a full sized industrial “pug”.

If you are new to the site and would like to receive notifications whenever fresh posts appear please contact me through the “Replies” tab above; introduce yourself and remember to tick the relevant box!

Please feel free to contribute. I am keen to hear the experiences of anyone else who is, or has been, involved with Barclays, whether in industry or in preservation. Any relevant steam or engineering experience would be welcome, as would any constructive criticism. Photographs or information about No.8 when she was in service would be extremely useful.

Please have a good browse around and I hope you find the site interesting.

John.

Grooves & Gutters : 1. The Horns.

As far as the work on the actual axleboxes are concerned, the end is definitely in sight now. One of the jobs left to undertake is the provision of the oil-ways, grooves and gutters which allow oil to be delivered and distributed across the various bearing surfaces. There are three areas of the axlebox that require lubrication; the bearing brass, the thrust face and the horn cheeks.

This is quite a big subject and it will take two or three posts to explain what has been done and why.

On the Barclay axlebox drawing I have there is a 1/16″ x 1″ chamfer which extends across the top of each horn cheek; oil is delivered to the chamfer by oil-can and then finds its way into the gap between the two faces. I don’t have a drawing of the horns but I did see one whilst doing some research at the Archive; from memory there was a triangular shaped oil-groove cut into the top face of each horn to assist with oil retention and distribution. This arrangement is simple, practical and would have been cheap to produce. It does, however, have a definite disadvantage; any dirt and grit present on the top of the axlebox will be flushed into the gap every time oil is applied and the resulting grinding paste cannot be particularly helpful to bearing life.

Figure of Eight Oil-Grooves.

The figure of eight oil-grooves as described here. (Copyright John Dunn Engineering).

I felt that a better solution would be to introduce oil directly into the bearing, this prevents the oil getting contaminated and also tends to flush grit out rather than in. Oil will be supplied from an oil-box sited either in the cab or on the running plate. Hopefully this arrangement will be an improvement and will extend the life of the horn faces. I am certain Barclays had considered this as an option because there are signs of a similar system on the drawing I have. In this case it has been erased and I suspect a customer has asked for a modification to the “standard” at some point. To be fair, Barclays were working in a competitive market and would have been very cost conscious, they needed to make things simple in an effort to keep production costs as low as possible. I suspect anything more than “standard” would have been willingly undertaken, but at extra cost to the customer.

Trepanning the oil-grooves.

Trepanning the oil-grooves. 1/4″ wide tool ground to a radius and plunged in to depth. (Copyright John Dunn Engineering).

I wanted to make things as easy for myself as Icould so it made sense to machine the groove in the horn cheeks on the ‘boxes rather than attempting to do something with the horn faces on the locomotive. I also wanted to maximise the spread of the oil so needed to cover a fairly large area with the oil-grooves. The most practical solution seemed to be the figure of eight arrangement shown in the photographs. This arrangement was easily cut on the milling machine using a trepanning tool and it only needed one set-up; straight oil grooves which covered the same area would have needed several set-ups to get the grooves at the correct angles.

The 1/4" BSP tapped holes at the top of each horn cheek can be seen in this photograph. (Copyright John Dunn Engineering).

The 1/4″ BSP tapped holes at the top of each horn cheek can be seen in this photograph. (Copyright John Dunn Engineering).

 

 

Oil is fed to the grooves via a 1/4″ diameter hole; this, in turn, connects to a 1/4″ BSP hole which was drilled and tapped into the axlebox at the top of each horn cheek. A fitting will be screwed into the hole and this will connect to a flexible pipe which will provide the link to the copper tubing on the frames.

Keeping Up To Date.

If you’re a regular follower of the blog and would like to receive notifications when new posts appear on the site please get in touch with me through one of the “Replies” tabs at the top of a post. If you fill in the required fields and tick the relevant box you should get email notifications whenever anything new is posted.

I would love to hear from anyone who feels they might have something to add. Any relevant engineering experience or anything to do with steam; experiences with other locomotives, whether in preservation or otherwise; constructive criticism of anything I am doing; suggestions about how to approach a job; questions; any interaction would be welcome. Let me know what you think of the blog and please feel free to give any suggestions about how I can improve things.

All posts have to be approved and I retain the right to discard anything which I consider irrelevant or inflamatory.

Finishing the Keeps.

Finishing the keeps was a straightforward job but before I detail what was done some explanation might be useful.

Two of the axleboxes with the keeps replaced. The outside face of each keep is now set-back rom the thrust face as a result of the operations described here. (Copyright John Dunn Engineering).

Two of the axleboxes with the keeps replaced. The outside face of each keep is now set-back rom the thrust face as a result of the operations described here. (Copyright John Dunn Engineering).

When we started the axleboxes the wear on the outside faces was the same on both thrust faces and keeps. In effect, the keeps had been forming part of the bearing surface and had been taking a share of the side load on the axleboxes. I thought this was intentional and my aim was to create new faces where both the thrust face and the outside face of the keep were level with each other, thus forming a single large bearing surface. Later, when I had the opportunity to study various axlebox drawings, I began to doubt the wisdom of this assumption. My error was eventually confirmed when we got access to the relevant axlebox drawing from the Barclay Archive; the faces of the keeps were supposed to be stepped back, behind the faces of the ‘boxes.

It appears that in a lot of cases the outside face of the keep is set back, behind the outside face of the axlebox; it takes no part in the bearing action of the thrust face. I am not too sure of the reasons for this, I have one or two theories but this part of the job has shown the danger of making assumptions, so if anybody out there has the definitive answer please don’t hesitate to get in touch.

Milling the outside face of the keep. (Copyright John Dunn Engineering).

Milling the outside face of the keep. (Copyright John Dunn Engineering).

 

Anyway, back to the story! As detailed in previous posts, the keeps had been faced and bored at the same time as the axleboxes which meant the outside face was level with the thrust face and the bore was the same as that for the brass. The internal radius on the keep needed to be increased to make certain that it would not rub on the journal; the outside face needed to be reduced to achieve the required clearance behind the thrust face.

 

 

Boring out the radius to give clearance on the journal. (Copyright John Dunn Engineering).

Boring out the radius to give clearance on the journal. (Copyright John Dunn Engineering).

 

The keeps were set-up on the borer as shown in the photographs. Some shimming was necessary to get everything square and then it was a simple case of milling the right amount off the outside face. The radius was bored out and the job was finished by milling the two edges parallel and blending them into the radius. None of these dimensions is critical, they are clearances, so it was a fairly easy and quick job; in fact the setting up took almost as long as the actual machining.

 

Boring and Facing.

The left leading axlebox after the boring and facing operations had been completed. The way this was achieved is explained below. (Copyright John Dunn Engineering).

The left leading axlebox after the boring and facing operations had been completed. The way this was achieved is explained below. (Copyright John Dunn Engineering).

We were now at the point where all of the individual components which make up an axlebox had been either repaired or replaced, fitted together, assembled and we were ready to machine the bearing bores and thrust faces to size. This is a relatively straightforward operation, the crucial element is getting the bores in the right place and making sure everything finishes to the correct dimensions.

Dealing first with the bore: the vertical centre-line was set by Barclays on the drawing and, because the brasses were new and the dimension achieved the required “160º bearing”, there was no need to alter this in any way. The horizontal position was a different matter altogether; this was influenced by the work undertaken on the horns, the horn cheeks on the ‘boxes, and the need to take into account the bend in the frames. In order to get the two axles parallel and in the correct position relative to the cylinders it was necessary to bore the axleboxes slightly off centre, the actual amount varied depending on the ‘box. I would have preferred this not to be the case but I couldn’t make things work any other way; and I understand it wasn’t that uncommon on BR so I didn’t lose too much sleep over it.

The left leading axlebox set up and ready for boring and facing.

The left leading axlebox set up and ready for boring and facing. (Copyright John Dunn Engineering).

The thickness of the thrust faces was determined by a combination of things. Once again the bend in the frames was a major factor, but the amount of wear on the flange faces of both the horns and the ‘boxes, and the steps taken to deal with this, also had to be taken into account. The clearance between the axlebox and the back of the wheel is set by the thickness of the thrust face so it was important to get this correct because it affects the riding of the locomotive.

Roughing out the bore. The tool is cutting into the replacement face on the keep as well as the actual bearing surface, this gives a true circle which makes measuring easier. The keep will be bored out to give clearance in a later operation. (Copyright John Dunn Engineering).

Roughing out the bore. The tool is cutting into the replacement face on the keep as well as the actual bearing surface, this gives a true circle which makes measuring easier. The keep will be bored out to give clearance in a later operation. (Copyright John Dunn Engineering).

 

 

The various dimensions had all been calculated from the measurements we obtained a while ago (see previous posts), they had also been verified by doing a CAD drawing so hopefully they will be correct. I would have liked to have tried the axleboxes in position at this stage, this would have allowed a further check on the relative positions, but I was put-off by the logistics of humping the four ‘boxes all the way to Murton coupled with the time factor. Time will be the judge of whether this was the correct decision!

 

 

The finishing cut being undertaken on the bore. (Copyright John Dunn Engineering).

The finishing cut being undertaken on the bore. (Copyright John Dunn Engineering).

Each axlebox was placed on the horizontal borer so that one of the horn cheeks was on a pair of parallels. This face was used as the horizontal datum and it corresponded to whichever of the horn faces had been used as the datum when setting up and taking measurements on the locomotive. The vertical datum was taken as the bottom faces of the brass. The position of the centre-line of the bore was set from the datums and it was then just a case of boring the brass to the right size to give the required clearance on the journal. I had deliberately made the replacement faces on the keeps slightly undersize on the bore so it was possible to use these as a reference point to measure the diameter whilst boring the brasses; it just kept things simple!

 

Roughing the thrust face to size. (Copyright John Dunn Engineering).

Roughing the thrust face to size. (Copyright John Dunn Engineering).

 

 

Once the bore had been completed the thrust face was machined at the same setting to keep everything square. The critical dimension here was the distance from the outside face of the axlebox, an easy measurement to take.

 

 

 

 

The 'box has been turned around and the inside of the brass is being faced to size. (Copyright John Dunn Engineering).

The ‘box has been turned around and the inside of the brass is being faced to size. (Copyright John Dunn Engineering).

 

The axlebox was now turned through 180° and re-clamped on the same horn cheek as before. This was to allow the inside face of the brass to be faced to size. These were all a straightforward operation and were finished “to drawing”, i.e. 1/32″ proud of the inside face of the ‘box.

 

 

 

 

 

The next stage involves some finishing work on the keeps but I will detail this in my next post.

Re-Fitting the Keeps.

There are many designs of axlebox used on steam locomotives. The type that Barclays used on No.8 relies heavily on “fit” to retain the brass in position as has been shown in previous posts. In this instance the brass is restrained from moving from side to side by the flanges on the ends of the brass while movement in a radial direction is prevented by the bottom edges of the brass butting against the top edges of the keep. It will be appreciated that the fit between keep and brass is critical if fretting is to be prevented.

The keep retaining pins in position. (Copyright John Dunn Engineering).

The keep retaining pins in position. (Copyright John Dunn Engineering).

The keeps are held in position by two pins which pass through the sides of the ‘box and the bottom of the keep; hopefully the photographs will make this clear. In theory the holes for the pins should line up at each side of the ‘box and also be the same diameter all the way through; in practice this was not always the case. In theory the pins should pass through the perfectly lined up holes and be such a neat fit within them that they would hold the keep tight up against the brass; in practice this wasn’t going to happen either. As with most problems, there are several possible answers.

 

 

The solution adopted was simple and involved making use of the misalignment. The bottom edges of the brass were made to finish slightly lower than their designed position, thus lowering the keep slightly which placed the holes in the ‘box and keep out-of-line. An accurate, undersized pin was made and this touched on the bottom of the holes in the axlebox and on the top of the holes in the keep effectively holding everything together tightly in the manner of a wedge.

Two keeps fitted. The keep in the axlebox in the background is still proud and will be attended too next. (Copyright John Dunn Engineering).

Two keeps fitted. The keep in the axlebox in the background is still proud and will be attended too next. (Copyright John Dunn Engineering).

 

The patterns for the brasses had been intentionally made with about 3/8″ beyond the normal “machining allowance” on the bottom edges. This gave us plenty of spare material to allow for fitting the brasses to the axlebox crowns, and the extra gunmetal on the bottom edges could be removed to achieve the correct relationship between the brass and the keep. The challenge now was to decide how much to machine off the brass to achieve the two aims, relationship between brass and keep at the same time as desired fit of pins.  

 

 

The first brass was set up on the borer and the bottom edges milled to dimensions which had been obtained by a series of calculations based on measurements obtained from the axleboxes and the keeps. In theory this should have achieved the correct off-set of the various holes but in practice, although everything was tight, the off-set was not as large as it should have been. I felt this method was too risky and did not want to take the chance of removing too much material and ending up with a loose brass. There were too many variables in the original measurements as a result of wear, distortion, misalignment etc and this was leading to errors. A good example of theory and practice not being in harmony!

Milling the bottom faces of the brass on the horizontal borer. (Copyright John Dunn Engineering).

Milling the bottom faces of the brass on the horizontal borer. (Copyright John Dunn Engineering).

The method adopted for the remaining three brasses was simpler and safer. The brass and keep were assembled in the ‘box and a rough measurement taken of the off-set of the holes. The amount to be removed from the bottom edges of the brass was calculated and they were then milled to this measurement minus something like 0.060″; in other words, the brass was still 0.060″ too long on the bottom edges. The brass was then refitted to the axlebox, the keep was positioned, and some undersized pieces of round bar placed through the holes. The round bar rested on the holes in the keep and the distance between the bar and the edge of the hole in the axlebox could be accurately measured. It was then a simple job to calculate the amount of material to be removed, reset the brass on the borer and mill off the excess material. Although this method was more time consuming and involved an extra set-up, it did prove to be more accurate and reliable.

Fitting the pins to the right leading axlebox. (Copyright John Dunn Engineering).

Fitting the pins to the right leading axlebox. (Copyright John Dunn Engineering).

 

The final part of the job involved refitting the retaining pins. These were individually turned to be a very light tap fit in the holes, this is not a big hammer job! The final job will be to mark the various pins and holes to ensure there are no mix-ups in the future.

All four axleboxes completed and ready for boring and facing. (Copyright John Dunn Engineering).

All four axleboxes completed, sitting the right way up and ready for boring and facing. (Copyright John Dunn Engineering).

 

 

 

Fitting the Bearing Brasses – 2.

In the last post I explained how we fitted the bearing brass flanges. Once this had been finished the next job was to fit the outside diameter of the brass to the crown of the axlebox, the aim being to get a reasonable area of contact between the two parts. Although the brasses have been turned accurately there is, inevitably, a certain amount of wear in the crowns due to movement of the brasses (fretting) whilst the locomotive was in service with the NCB and this is not uniform; hand fitting is the way this situation is dealt with.

A reasonable area of contact between brass and ‘box is necessary for two reasons; to stop the brass fretting when the locomotive is working and to prevent the brass distorting under the weight of the locomotive which could lead to problems with oil distribution etc.

The process involves using engineers’ blue in a more conventional manner than in the previous post.

This photograph shows the crown of the axlebox after it has been coated in engineers' blue and before the brass has been tried in place. The studs are there to maintain the sides of the 'box at the correct distance apart, this particular one has a tendency to close in slightly for some reason. (Copyright John Dunn Engineering).

This photograph shows the crown of the axlebox after it has been coated in engineers’ blue and before the brass has been tried in place. The studs are there to maintain the sides of the ‘box at the correct distance apart, this particular one has a tendency to close in slightly for some reason. (Copyright John Dunn Engineering).

The crown of the ‘box is initially coated in blue and the brass lowered into position. The brass is then tapped down with a mallet and a piece of wood to ensure that it is making as much contact as possible before being removed with the aid of a small lever.

This photograph shows the high-spots after the first trial fitting of the brass.(Copyright John Dunn Engineering).

This photograph shows the high-spots after the first trial fitting of the brass.(Copyright John Dunn Engineering).

The pattern of the transferred blue on the outside diameter of the brass indicates the points of contact (high-spots) between the brass and the ‘box. These high-spots are preventing the two parts making any further contact and need to be removed if the area of contact is to be increased. You would normally use a scraper to remove high-spots but I found this an awkward way to do things on the convex surface of the brass. It was much easier to use a brand new smooth or second cut hand file; this ensured a sharp file with a safe edge to protect the sides of the flanges on the brass.

 

Part way through the process and the pattern of the blue is beginning to change, extending over a larger part of the surface. (Copyright John Dunn Engineering).

Part way through the process and the pattern of the blue is beginning to change, extending over a larger part of the surface. (Copyright John Dunn Engineering).

 

Once the high-spots have been filed off, the crown of the ‘box is given another coating of blue and the brass is again tried in place and the high-spots checked. The process is repeated over and over until the necessary fit is achieved. I was aiming for around 70 to 80% contact with the main areas being along the top and upper parts of the brass and some along the bottom edges.

 

 

 

This is time consuming, laborious, back-breaking work. The brasses weigh over 3-1/2 stones each at this stage (23kg) and they have to be lifted off the bench, carried down the ‘shop, dropped into the axlebox which is on the floor, manipulated in position, lifted back out and then returned to the bench. They are then filed and the whole process begins again, and again, and again, ad nauseum. Thankfully this stage of the work is now behind us but it has been something of  marathon.

This shows the work almost completed. There is a reasonable area of blue over the whole of the outside of the brass. A bit more work will see this one completed. (Copyright John Dunn Engineering).

This shows the work almost completed. There is a reasonable area of blue over the whole of the outside of the brass. A bit more work will see the blue spread a liitle more and that will be this one completed. (Copyright John Dunn Engineering).

I must apologise but I have neglected to take a photograph of one of the brasses with the final coating of blue on but I think the pictures give a pretty good idea of how the process evolves.

Fitting the Bearing Brasses – 1.

Even though the bearing brasses have been turned to suit each axlebox individually, they still need to be hand-fitted to ensure a proper relationship between the mating surfaces. The axleboxes are worn where the original brasses have been “fretting” and we would be extremely lucky to get the required fit with brand new brasses straight off the machine.

The flanges at each end of the brass need to be a tight fit in order to prevent any end float between the brass and the ‘box. The outside diameter of the brass needs to be in contact with a substantial portion of the crown of the axlebox to prevent any distortion whilst taking the weight of the locomotive and also to prevent any movement. This state of affairs is achieved by using files, scrapers, engineers’ blue, patience and an awful lot of time.

Right driving axlebox with the original brass fitted as a comparison. (Copyright John Dunn Engineering).

Right driving axlebox with the original brass fitted as a comparison. (Copyright John Dunn Engineering).

 

Just by way of a comparison, this photograph shows one of the original brasses in the the right driving ‘box. It’s not the best of photographs but you can see that there is 1/16″ clearance between the flanges and the ‘box and 5/64″ clearance per side (5/32″ in total); there should be no clearance at all in any of these places. There are also areas of wear along the bottom edges of the brass where it has been fretting against the keep.

 

 

The first part of the job involves establishing the correct fit between the flanges on the brass and the flange faces in the axlebox. Once this has been achieved the outside diameter of the brass can be fitted to the crown of the axlebox.

Normal practice is to apply engineers’ blue (Micrometer Blue) to the surface which is being used as a datum, the surface which is to be “fitted” is then offered up to this and points of contact are indicated by the blue being transferred from the datum to the fitted surface. The points of contact (high-spots) are removed from the fitted surface with a scraper or file, the two surfaces are then tried together again and the process is repeated until the desired fit has been obtained. In tackling the flanges we adapted the method slightly as explained below.

The insides of the flanges on the brass were coated in ink from a felt-tip pen, this was allowed to dry and then the brass was lowered into position before being tapped home with a mallet and a piece of wood. The ink coating was damaged wherever there were any points of contact. In theory any areas which were left as solid blue were therefore “high” and needed removing to allow the brass to move further into position; in practice it is not quite as simple as that! Some of the skill in this job is having the ability to read the witness marks and knowing exactly where to remove metal it, is not always as obvious as it might first appear. The aim is to end up with a light tap-fit, the outside diameter of the brass touching the crown of the axlebox and as much contact as possible over the full area of both flanges.

The last photograph shows a flange part way through the fitting process. The damaged areas of ink can be seen.

Witness marks on one of the bearing brass end flanges. (Copyright John Dunn Engineering).

Witness marks on one of the bearing brass end flanges. (Copyright John Dunn Engineering).

Turning the Axlebox Brasses

The outside diameters of the remaining three axlebox brasses have now been turned using the horizontal boring machine. The process is fairly straightforward, hopefully the explanation and photographs will make things clear.

The casting before setting up on the machine. The milled end-face described in the text can be seen as can the rough nature of the casting. (Copyright John Dunn Engineering).

The casting before setting up on the machine. The milled end-face described in the text can be seen as can the rough nature of the casting. (Copyright John Dunn Engineering).

The brasses were previously milled to establish faces on both ends and on the bottom “joint” which butts against the keeps when everything is assembled; these faces are all flat and at 90 degrees to each other. The brass is bolted onto a large box angle plate on the borer using these faces to set-up to. Various parallels, clamps and packing pieces are used to make the set-up as rigid as possible. The facing head is then set up so that it is in the centre of the finished diameter.

The machining process is fairly straightforward and can be broken down into a number of stages. The central portion is roughed out first, this involves using left and right handed tools to remove the material up to the inside faces of the end flanges. Next, the flanges are roughed out.

Rough turning the central portion of the brass. (Copyright John Dunn Engineering).

Rough turning the central portion of the brass. (Copyright John Dunn Engineering).

Finish turning the central portion, the flanges have been rough faced and will also be finished at this setting. (Copyright John Dunn Engineering).

Finish turning the central portion, the flanges have been rough faced and will also be finished at this setting. (Copyright John Dunn Engineering).

 

The central portion is then finished from approximately the centre line back to one flange using a right hand knifing tool, the first flange is then faced to finish using the same tool. The central portion is next turned to finish in the opposite direction using a left hand knifing tool and the second flange faced to finish. The distance between the two flanges is critical as this affects the end float (or lack of it!) on the brass when it is inserted into the ‘box so this dimension was made about 0.003″ small to allow for fitting.

 

Turning the outside diameter of the first (inside) flange. (Copyright John Dunn Engineering).

Turning the outside diameter of the first (inside) flange. (Copyright John Dunn Engineering).

 

 

The next stage involves machining the outside diameter of the flange nearest to the facing head. The centreline of this is pitched 5/8″ higher than the centreline of the central portion so the borer is adjusted accordingly. The flange is then roughed and finished to diameter.

 

 

 

The brass has now been set up to allow the second flange to be turned. (Copyright John Dunn Engineering).

The brass has now been set up to allow the second flange to be turned. (Copyright John Dunn Engineering).

 

The casting is now taken off the machine and de-burred before being mounted back onto the box angle plate, this time it is turned through 180 degrees to allow the second flange to be turned. The facing head is set on centre, raised by 5/8″ to achieve the off-set, and the second flange machined in exactly the same way as the first, a series of roughing and finishing cuts.

 

 

 

One awkward bit of this job was deciding on a method of determining the radius of the crown of the axlebox on the face which mates with the brass; because it is a semi-circle there is nothing to use as a surface to measure from if an inside micrometer is used. We took a machinist’s ground parallel of known length and thickness and placed it across the crown of the ‘box. Using a depth micrometer, measurements were taken from the top of the parallel to the top of the radius at the outside, centre and inside of the axlebox. With some maths and a formula it was possible to work out the radius using the measurements we were in possession of. It was then a simple case of deciding the best radius to machine the brass to in order to achieve the correct fit between brass and ‘box.

All turning finished and ready for trying in the axlebox. (Copyright John Dunn Engineering).

All turning finished , the brass is ready for trying in the axlebox. (Copyright John Dunn Engineering).

Axlebox Brass – Fitting.

Over the winter we will concentrate on the axleboxes and the brasses, work that can be done in the workshop where we will not be affected by the vagaries of the british climate.

The brass "as turned" and before fitting. The flanges can clearly be seen. (Copyright John Dunn Engineering).

The brass “as turned” and before fitting. The flanges can clearly be seen. (Copyright John Dunn Engineering).

 

I previously started machining the brass which will be fitted into the left leading axlebox and it has progressed to the stage where the outside has been turned on the horizontal borer; the photographs of this are not brilliant so I will post some better ones when a start is made on the remaining brasses. I wanted to check the fit of this brass within the ‘box before I did any work on the other three, mainly to ascertain whether there were any snags which might be avoided at an earlier stage.

 

 

Not a good picture but you can just see the marks on the gunmetal where the keeps were rubbing. These were removed by filing and scraping. (Copyright John Dunn Engineering).

Not a good picture but you can just see the marks on the gunmetal where the keeps were rubbing. These were removed by filing and scraping. (Copyright John Dunn Engineering).

To start with the fit of the keep within the ‘box was assessed. It is important to make sure this is correct because the keep can force the sides of the ‘box out wider than they should be which might affect the fit of the brass within the ‘box as well as the clearances between the ‘box and the horns. The fit of the keeps had been checked at an earlier stage but the new thrust faces have been attached since then; as it happened the gunmetal on the thrust faces needed a bit of attention with files and a scraper to achieve a decent fit.

 

 

 

I made a series of measurements to check whether the sides of the axlebox were closing in when the keep was removed, again, this may have an effect on the fit of the brass. The sides were moving in slightly, by about 0.004″, so we used a couple of pieces of stud-iron to jack the sides into their proper position, these will be left in place throughout the fitting process.

The start of the fitting process. The sides of the box are held apart by some stud-iron and the brass has been placed into position. There is still a large gap at the crown and this will close up as the job progresses. (Copyright John Dunn Engineering).

The start of the fitting process. The sides of the box are held apart by some stud-iron and the brass has been placed into position. There is still a large gap at the crown and this will close up as the job progresses. (Copyright John Dunn Engineering).

Satisfied with all the above, we moved onto the actual fitting operation. The outside diameter of the brass had been machined to a series of dimensions which had been obtained from the axlebox ( I will explain how I did these in a later post); the distance between the flanges on the brass was made a couple of thou smaller than the distance between the mating faces on the axlebox to allow final fitting. It is important that the brass has no end float and these flanges are the way this is prevented.

The excess material on the flanges was gradually removed using a scraper until we had a decent fit. The brass needs a light tap with a soft mallet to bed it into position but is not that tight that you can’t get it out again! Once down it was checked with engineer’s blue to make sure that it was making contact over the majority of the crown of the ‘box, this is to ensure that there will be no distortion once the ‘box is supporting the weight of the locomotive.

The left leading box with the brass and keep fitted. Requires the joint between keep and brass milling back to size and then boring. (Copyright John Dunn Engineering).

The left leading box with the brass and keep fitted. Requires the joint between keep and brass milling back to size and then boring. (Copyright John Dunn Engineering).

 

The final photograph shows the brass fitted into the axlebox with the keep replaced. We still need to machine away some of the joint face on the brass to allow the keep to enter fully into the box but this will be done at a later stage. For now I am happy with the method and we can concentrate on the final fitting of the remaining three keeps and the turning of the rest of the brasses.

Horn Flange Faces- 2.

Having got to the point where we had manufactured the new flange faces for the horns the rather obvious next step is to fix them into position onto the locomotive. They have all been individually made to achieve the correct side-to-side clearances between the axleboxes and the horns; each face had been stamped to identify where it was meant to go.

One of the new flange faces after fitting. (Copyright John Dunn Engineering).

One of the new flange faces after fitting. (Copyright John Dunn Engineering).

 

The process was relatively straightforward but time consuming. The plates were held in position and an assessment made; inevitably they required some attention with a file to allow them to sit snugly. Once this had been achieved they were screwed into place and another check made. If everything was correct then the screws were removed one at a time, the screw and the female thread in the horn were thoroughly de-greased and then the screw replaced with the addition of some thread locking compound.

 

 

The finished flange face after blending the join with the horn cheek. (Copyright John Dunn Engineering).

The finished flange face after blending the join with the horn cheek. (Copyright John Dunn Engineering).

 

 

The new flange faces had intentionally been made slightly wider than needed to allow them to be dressed back to achieve a neat join with the horn cheeks. This involves the use of an angle grinder to rough the edge down followed up by files and emery to achieve a decent joint. I have managed to get the left driving horns finished but unfortunately the weather has beaten us for this year so the others will have to wait until the Spring now.