Rebuilding a 2½" Gauge LBSC Green Arrow

[John Baguley]

It's a long time since I've put any of my projects on the forum but recently a conversation with another member via pm's suggested that I perhaps ought to do so. Unfortunately, my own projects have fell way behind due to other commitments, other domestic jobs that need doing, and a few rebuild jobs for other people. However, now that I'm fully retired and, in theory, have more time available and also more free cash, I'm hoping to concentrate on my own stuff from now on (we'll see how long that lasts!)

Some people will know that I seem to 'specialise' in trying to turn sow's ears into silk purses (not always by choice) and this project has turned into one such episode.

Last year a member of our club at Whitwich mentioned that he had a 2½" gauge Green Arrow that had been in his shed for years and as he was having a clear-out in readiness for a house move he wanted to move it on. It had come with a 5" gauge loco that he had bought and he had no interest in 2½" gauge. He asked me if I would have a look at it for him and see what condition it was in and suggest a possible value.

I agreed and took it home. From what I could see it looked very well made but wasn't quite finished. The water feed to the boiler wasn't connected and there was no signs of a fire ever being lit in the boiler so it had obviously never been run.

The first thing I did was give the boiler a hydraulic test and found a couple of weeping stays in the firebox and a leak on the front tube plate from one of the longitudinal stays. They shouldn't be too difficult to fix as the boiler has threaded and soft solder caulked stays and a bit of Comsol should sort the leaks. I did pump it up to 160psi and it seemed ok apart from the slight weeps.

I then tried running the chassis on air but it wasn't interested at all with no signs of life. I noticed that the lubricator didn't go round which turned out to be the ratchet wheel loose on the shaft.

I reckoned that it wouldn't take too much to get it finished and running (oh, how wrong can you be!) so I had a rush of blood to the head and made him an offer for it which he accepted and that is where it all started!

Loco as bought:

I won't go into great detail about the rebuild here as it is fully documented on my website so anyone who wants to read the nitty gritty should visit that.

I decided to strip the loco completely so that I could see what was what and try and find out why it refused to run on air. The tender looked fine so that was put away for the time being along with the boiler which I will look at when the chassis is sorted and running.

The chassis was stripped down to it's component parts. A lot of the work looked very good but unfortunately, all three cylinders were a mess. and badly machined. They were also full of solid gasket goo which would partly explain why it wouldn't run on air. I decided they were beyond being salvaged and would have to be replaced with new. It seemed obvious that more than one person had built the loco, one good and the other not so. The loco had originally come with a glass display case so I wonder if it had just been finished off as a display model?

The middle cylinder was particularly bad. The ports were poorly machined and at one end the steam passage had broken through into the bore.

The mounting holes were a bit of a mess as well.

The outside cylinders were a little better but a lot of the holes for the steamchests and the cylinder mounting bolts had been drilled in the wrong place to begin with, plugged and then redrilled.

I decided to get all new castings and start again from scratch. I mentioned this to the chap I had bought the loco off and he gave me a refund for the cost of the new castings which was very good of him. He had had no idea what state the loco was in so wasn't really obliged to and I had bought it as seen.

The cylinder castings are no longer available but I was very fortunate that fellow N25GA member Dave (Davewoo on here) had a set for the middle cylinder that he no longer required and he very kindly gave them to me. The outside sets I used are for Nigel Minor and were obtained from the N25GA. The Nigel Minor steamchests caused me problems later with the exhaust passages so were not ideal.

I thought it best to start the rebuild with the frames first. It was obvious that the holes for the fixing bolts for the outside cylinders had been drilled in the wrong place to begin with as they had been plugged and redrilled, as it turns out, still in the wrong place!

Out of interest, I temporarily put the frames back together, refitted the original cylinders and measured the angles that the cylinders were inclined at. The outside cylinders should be at 1.3° and the middle cylinder should be at 7.3° to the horizontal ( I drew up a 3D model of the loco to check all the dimensions and get the cylinder angles). The righthand cylinder was at 0.4°, the lefthand cylinder was at 1.4° and the middle cylinder was at 6.3°. Slightly out!

The digital angle gauge is perfect for jobs like this.

Back to the frames and I drilled out all the original plugs, threaded the holes and Loctited in new plugs made from steel bar.

New cylinder mounting holes were then drilled using the DRO on the mill and a CAD drawing from the 3D model.

I didn't redrill the large holes for the exhaust from the outside cylinders as, although they are shown on the drawings, the exhaust goes through the wall of the steamchest and not through the frames so the holes are not needed.

I think that will do for now as this is getting a bit long. Next time we'll start machining the new outside cylinders.

[Deleted]

This is excellent to see John, it's great to see you working on your own project and what a project, 'Green Arrow'?
It was designed by the best, in the best livery and very apt this week as the real one has just been moved to its new home for 3 years at the new Doncaster museum. The old lady has returned home.
I for one will await each update as things progress.

Regards

Pete

[davewoo]

Very pleased to see this on here John, been following your progress with the loco on the website, looks like it's going to be a lovely engine. Afraid I've pinched many of your good ideas to use in my own engine projects, the site is always a great inspiration, always interesting to see how others overcome the problems with part builds. Looks like the 2 1/2" gaugers are muscling in!

Dave

[John Baguley]

Hi Pete,

Yes, Green Arrow is one of my favourate locos. Well, anything that's LNER and green

My brother and I went to see her at the Churnet Valley Railway back in February 2008

Dave - don't worry about pinching my ideas - I've pinched plenty of other peoples!

Right - Part 2

Outside cylinders

Machining cylinders is a bit like machining wheels - ask 10 people how best to go about it and you will get 10 different suggestions!

I chose to rough machine the port face and the bolting face to make them flat and square to each other, bore the cylinders in the lathe and then return to the mill to finish the port face and the bolting face to size using the bore as the datum point.

The bolting face of the casting was rubbed on some emery paper to get it reasonably flat and also the bottom edge of the bolting face trued up with a file until that was flat. As it happens, these are really nice castings made from the original Dave Goodwin patterns and all the surfaces were pretty flat to begin with and the cored bore is accurate.

The casting was then mounted in the mill vice with the bolting face against the fixed jaw and the bottom edge of the bolting face resting on a parallel.

Note that when holding an unmachined casting like this in the vice you don't want to clamp it directly with the moving jaw. Use something soft like a piece of aluminium welding wire between the fixed jaw and the casting to even out the grip and provide a narrow point of contact. I used a piece of plastic cable tie that worked well. This ensures that the rear of the casting is held firmly and flat against the fixed jaw of the vice without being influenced by the moving jaw.

The port face was then machined to a good surface.



The casting was then flipped so that the machined port face was now against the fixed jaw of the vice and the bolting face sitting on the parallel. A light skim was taken off the outside edge of the casting. This would provide a flat surface to reference the machining of the bolting face.



The casting was then flipped 180° so that the just machined edge was now sitting on the parallel and the bolting face machined. I now had two machined surfaces at 90° to each other ready to transfer to a Keats type angle plate mounted on the faceplate of the ML7 so that I could machine the bores.

A bit of an aside here - I bought this Keats angle plate from a well known ME supplier years ago when I was machining the cylinders for my Helen Long and ruined a fabricated inside cylinder that had taken me days to make. It turned out that the Vee of the angle plate was not square to it's bolting face and the bores came out at an angle to the cylinder. I didbn't realise until it was too late.  I had made the mistake of assuming that the angle plate would be fit for purpose and accurate. Motto - always check and don't assume anything!

I did re-machine the angle plate when I last used it but decided to do it again just to make sure.

The cylinder castings were set up in the lathe and the cored hole for the bore centred using a bit of brass bar held in the tailstock. This was plenty accurate enough at this point. Remember that the port face and the bolting face would be machined again relative to the bore and there was plenty of material to come off them both so the position of the bore was not critical. Be careful not to tighten the clamp too much and distort the soft gunmetal.

This job is really fiddly as you have to loosen the bolts holding the angle plate to the faceplate and then tap it around until you get the bore centred!

The bores were then machined to the final size of 0.6875". There wasn't a lot of material to remove, only about 0.063", but fortunately the bores cleaned up well without any problems. I used a cheap carbide insert boring tool and was surprised at the excellent surface finish that it gave.



Whilst the cylinder was still in the lathe I faced across the end to make sure that the face was perfectly square to the bore. This would be the rear face of the cylinder that the rear cylinder end cover bolted to. The block was turned around and the other end faced off but not to final length yet. I would do that later.

That left me with two cylinders with the bore finished, the rear face machined and the front face rough machined.



Back to the mill then to final machine the port face and the bolting face.

I had a length of steel bar that fitted the bores perfectly so I used that as a datum to machine the port face and bolting face to the correct distance from the bore using a depth micrometer to check.



Next, I drilled and tapped the holes for the cylinder mounting bolts using the DRO to position them.

The next photo shows how I use the drill chuck as a tap guide to get the tap nice and square to the drilled hole. The chuck is just loose enough to allow the tap to turn freely.



Next I tackled the ports. I drilled these out first with suitably sized drills to remove a lot of the metal to be milled away and then milled them to size, again using the DRO to get them exactly to the right width and spacing. The DRO makes jobs like these a doddle!





The final job for now was to drill the exhaust passage that connects to the exhaust port in the port face. Green Arrow is a bit unusual in that the exhaust cannot go through the frames due to the middle cylinder being in the way so it has to go up through the wall of the steam chest and through the steamchest cover where it connects to a manifold that goes across the top of all three cylinders. A bit of a tortuous route to say the least.

A hole is drilled in the bolting face of the cylinder part way into the casting and then an angled hole has to be drilled from the exhaust port to connect up with this. Another hole is drilled up through the edge of the port face and through the valve chest wall.

I had already drilled the hole in the bolting face when I did the holes for the fixing bolts so I had to tackle the angled hole next.
I worked out using a CAD drawing that the hole needed to be at 30° from the bottom corner of the exhaust port so set the cylinder up in the mill vice using the angle gauge to set the angle.

As the hole needed to start in the 90° corner of the exhaust port I didn't want to risk using a drill so used a 4mm endmill instead being very gentle with the feed. I carried on 'drilling' until the hole met with the hole in the bolting face.

The hole in the bolting face is tapped 1/4" x 40 and will have a brass plug fitted when the hole through to the steamchest is completed.

That's plenty for now I think. More next time.

John

[John Baguley]

Part 3

Next job on the cylinders was drilling the angled steam passages from the ends of the bore to the steam ports. It's a job that I dread, especially on cylinders this small, as it's so easy to break a drill!

From a CAD drawing I worked out that the passages needed to be at 12.2° to the port face. The cylinder was set up in the mill, again using the digital angle gauge to set the angle, and a recess milled in the end of the cylinder to provide a nice flat face for the drill to start on and also an easy entry into the bore for the steam.



Then three 2.5mm holes were carefully drilled through into the steam port. This was repeated for each end of the two cylinders. It was here that I had one of those 'Oh sh*t!' moments when my mind drifted and I turned the mill table handwheel the wrong way when milling one of the recesses and put a notch in the side of it. It's not the end of the world but really annoying!



Onto the steam chests.

As mentioned before, these turned out to be not ideal as the walls were not really thick enough to take the fixing screws at the outside and the exhaust passage on the inside edge. It didn't help the walls having quite a large draught angle on them but I got them to work.

I rubbed the top and bottom faces with a file and then on emery paper to get them so that they would sit flat without rocking.



The casting was then set in the mill with the bottom edge on a parallel and a skim taken over the top edge.



It was then flipped over and the other edge skimmed, followed by setting it up with the bottom face on parallels so I could skim the top and then flipping it to machine the bottom face.



Over to the lathe next and the angle plate again. The casting was clamped in the angle plate so that the ends and the bosses could be machined. The proper clamp for the angle plate wasn't really suitable for this job so I drilled and tapped the plate for a bolt and used a scrap of steel plate to clamp the castings in place.

I could have used the four jaw chuck for this but I thought the angle plate would be more repeatable.

Similar to the cylinders where the final machining was done using the finished bore as a datum, the steam chests would be final machined using the bosses as the datum.

Before turning the casting around to machine the other end and the other boss I needed to drill and ream the bosses for the valve spindle. Drilling the first boss was easy but the drill needed to go all the way through and drill the second boss from the inside to make sure the holes in both bosses were perfectly in line. That's easier said than done with an ordinary drill and I didn't have a spotting or centre drill long enough to do the job. I did have a search on the internet but couldn't find any long ones.

In the end, I looked through my stash of miscellaneous drills and found a brand new 3.7mm split point drill that was long enough. Hopefully, the split point would start a true hole on the inside surface of the steam chest. I didn't have any other way of doing it really so had no choice.

One thing I hadn't done when machining the outside of the steam chest was machine the inside face where the drill needed to start so I went back to the mill and did this. The drill would have had no chance of starting a true hole on a rough cast surface.



Back to the lathe and the hole was drilled with no problems but I did have to stick the drill as far out of the chuck as I dare for it to reach all the way through.



I didn't have a long enough reamer to go all the way through so the other end would have to be reamed when the casting was turned around and hope for the best that it would still line up properly.

After turning the casting around to machine the other boss I did check the drilled hole was correctly centred using the 3.7mm drill pushed into the hole and an indicator. It was slightly out so was adjusted to run true again.



I had already made the decision to use O rings to seal the valve spindle so each boss needed a flat bottom recess adding for the ring. It would eventually be retained by a bolt on cover made from brass bar. The recess was simply machined with a suitable size endmill.





Once the bosses were complete it was back to the mill to complete the machining of the top, bottom and sides.

To form the datum for the machining operations I put a length of silver steel through the valve spindle bore and then measured from that with a depth micrometer, as for the cylinders.

If there is a Mr. L Biggins out there, I've got your depth mic

Measuring the top and bottom faces is a little tricky as the bosses are larger in diameter than the height of the steam chest walls so stick up higher. I got around this problem by using a gauge block inbetween the mike and the surface that was being machined and allowing for the thickness of that in the measurement.

Before drilling all the holes for the fixing screws I made the steam chest covers. These are just pieces of 1/8" brass plate. No castings were harmed in the making of these! To be honest, I don't see the point of using castings for these as usually all you do is machine the casting to a flat plate anyway, unless it's a fancy shape of course.

I intend to try and round off the outside edge of the covers rather than leave them square so that they look more like those on the full size loco but the fixing screws will have to be very close to the edge of the cover because of the thin walls of the steam chest as mentioned before. I think I can get around this by deeply countersinking the outer screws.

All the fixing screws will have to be countersunk anyway as there is not enough room between the top of the steam chest and the running boards to be able to fit hex head bolts or studs and nuts.

It was now that I found the problem with the Nigel Minor steam chests with their thin walls. On the Green Arrow drawings LBSC shows the exhaust passage that is drilled through them as a 5/32" hole. The wall of the steam chest should be 5/16" but mine are only 1/4". If I drilled a 5/32" hole through the wall there would be very little surface left around the hole to make a good seal between the hole and the inside of the steam chest which will be at steam pressure.

I came up with the idea of using an elongated slot 3mm wide rather than a round hole.



This would actually give slightly more area that the original 5/32" hole and help the breathing of the cylinders a bit. I always thought that just a 5/32" hole for the exhaust would tend to restrict it's escape.

Back to the mill and the fixing holes were drilled in the steam chests and the 3mm elongated exhaust slot milled, all being done using the DRO. Can you tell I love the DRO!

This was then repeated for the steam chest covers.



Finally, the cylinders were drilled and tapped for the steam chest fixing screws.



The last job on the steam chests was to drill and tap the bosses for four 8BA bolts to secure the caps for the O rings. These were done using the pitch circle function on the DRO.



One job I still needed to do was make the brass plugs to cap off the exhaust passage on the cylinder bolting faces, fit those and then machine the oval exhaust passage through them into the hole that connects to the exhaust port.

I really should have milled those steam ports a bit deeper to get rid of the drill marks in the bottom. I've not touching them now though incase I cock them up!

That's it for today. Next - the cylinder end covers.

[steamer5]

Hi John,
I’m really enjoying your step by step guide! The end result is looking very good indeed!
Only question I have is did you consider adding a strip of brass to the inside of the valve chest to make up for the lack of material?

Cheers Kerrin

[John Baguley]

Hi Kerrin,

No, it never occured to me to add a bit of brass to the inside. That would have worked and made things a bit easier The original cylinders had a strip of brass added to the outside to make them wider to match the original steam chests!

If I had realised before I had started machining the new steam chests I could have swapped them for something more suitable but it was too late by the time I realised. It all worked out ok in the end though as you will see later when I get to running it on air.

John

[John Baguley]

Part 4 - Onward with the cylinders

I reckoned that I could get away with reusing the original cylinder end covers which would save a lot of work and preserve more of the original components.



When I measured the diameter of the spigots that fitted into the cylinder bore they were about 0.002" bigger in diameter than the bores in the new cylinders. I needed to take that tiny amount off them to make them fit but how to hold them in the lathe? I needed to get them to run as truly as possible so that the bore for the piston rod and the gland would remain concentric to the newly machined spigot. I tried holding the end cover in the 3 jaw chuck but that wasn't very successful as I could only hold it by the outer diameter of the cover and that wasn't concentric to the spigot. Using the 4 jaw would mean a lot of faffing about to get it to run true. I then wondered if it would be possible to turn a threaded spigot held in the collet chuck and screw the end cover onto that using the thread for the gland nut.



I tried it and, much to my surprise, it worked very well and the cover ran almost perfectly true enabling me to remachine the spigot to the new diameter.



Whilst I had the cover set up like this I skimmed the bolting face and the outside edge of the cover to clean them up.

The front covers are not as critical to set up as they are only caps for the end of the cylinder so I got away with holding them by the edge in the 3 jaw chuck. This particular chuck came with my ML7 when I purchased it new back in 1973 and it's always been pretty accurate. To get the cover square I just brought up the tailstock chuck and held that against the face of the cover whilst I tightened the chuck.





The cover was then reversed so that the front face could be cleaned up.



Holding the cover this way meant that I couldn't clean up the outside edge so I machined a jig from a scrap of aluminium bar with a recess in it to take the spigot of the cover. I then fitted the cover and held it against the jig with a bit of brass bar pressed against the cover by the live centre in the tailstock. Basic pressure turning.





That was the covers cleaned up as best I could. I couldn't clean up the outside bolting face of the rear covers due to the boss for the gland and the slidebar so they will have to stop as they are.



Next job was to drill and tap the cylinders for the cover fixing bolts. The holes in the covers had already been drilled so the holes in the cylinders had to be spotted through from the covers. The holes for the front covers were not critical so long as they were somewhere near but the rear cover had to be accurately positioned to maintain the alignment of the slidebar. To do this I mounted the cylinder in the mill and found the centre of the bore with the DRO. A pointed centre was fitted in the chuck and that used to align the hole for the slidebar by winding the X axis of the mill across until the pointed centre aligned with the hole.



The cover was held firmly in position by a long bolt through the cylinder bore and the holes drilled and tapped.

The holes for the front covers were done in a similar way using the pointed centre to align the first hole in the cover. I just drilled and tapped this one hole to begin with and then fitted a bolt to hold the cover in place whilst I did the rest.



Onto the pistons and rods. The original piston and valve rods had been made from mild steel so I replaced them with stainless. Also, the crosshead end of one piston rod was bent and I had to cut the end off to remove it.

The rods were made as per LBSC i.e. the rod is fitted into a plain hole for half the thickness of the piston and threaded for the remaining half. The plain part of the hole keeps the piston aligned with the rod whereas an all threaded joint could end up with the piston not being square to the rod. In any case, the piston blanks were left oversize and final machined after fitting to the rods held in the collet chuck.



The narrow groove in the piston is for my favourate style of PTFE rings which I use and which I'll describe later. I'm not a big fan of graphited yarn or O rings for pistons.

I just made the outside cylinder rods and pistons for now. The rods were left long at this point and will be trimmed to the correct length later.



At the top is one of the old pistons which were fitted with graphited yarn.

I was now in a position to try the outside cylinders in place on the frame plates. I wanted to check the position of the outside motion brackets as I thought it highly unlikely that they would line up with the slidebars now that the cylinders were in their correct positions.



The mounting holes for the brackets lined up after a fashion ( they were considerably oversized and had obviously been filed out to make them line up) but the bolting face on the angle that held the motion brackets wasn't square and pulled the bracket out of alignment if the fixing bolts were tightened up.

So it was off to the mill to take a skim off the bolting face and make it square to the bracket.



Fitting it again showed that it might now need a shim between the angle and the frames and I spent ages faffing about trying to get it to line up correctly. At this point I didn't know how far along the slidebar the crosshead travelled so I thought it would now be a good idea to reassemble the frames and fit the driving axle and the connecting rods so that I could trim the piston rods to the correct length and see where the motion brackets really needed to be. LBSC makes no mention on the drawings or in his 'Words and music' just where the motion brackets are supposed to be located so it's a case of trial and error!

It was when I came to reassemble the frames that I found more problems. The frames twisted as soon as the bolts in the stretchers were fitted so obviously things didn't line up properly. More of that next time!

John

[John Baguley]

Part 5 - Frame problems

As mentioned in Part 4 there was definitely something wrong with the alignment of the frames when I tried to assemble them again. As soon as the screws in the trailing frame brackets or the front buffer beam were tightened, the frames twisted and would not sit flat on the surface plate. When I checked the horn slots with a square across the frames they were out of line as well. This state of affairs didn't really surprise me but it meant more work to put things right.

To try and find what was causing the problem I assembled the frames using just the pump stretcher and the front pony truck stretcher and then checked the alignment of the ends of the frames by laying one frame on the surface plate and checking across the frame ends with a square. There was a difference of 0.034" between the ends.



I then checked the hole positions for the two stretchers in the frame plates and it was apparent that the frames had not been completely drilled as a pair and the hole positions for the stretchers were different on each frame plate. Fortunately, the holes for the rear frame and for the front buffer beam seemed to be the same on both.

I couldn't leave things as they were as the frames need to be square for everything to line up properly. The option I chose was to plug the tapped holes in one side of the pump stretcher and the bogie pivot centre and redrill them.

I tackled the pump stretcher first. This is a solid block of brass bar that contains the two axle pumps so is quite substantial. I drilled out the existing tapped holes on one side and tapped the new holes 1/4" x 40 and Loctited in brass plugs.

I then took a skim across the face of the stretcher to level the plugs and to make sure it was square. I flipped the stretcher over and skimmed the other side. I had noticed that the sides of the stretcher were not flat before which would not have helped the squareness of the frames.

The stretcher and the bogie stretcher were fixed to one frame plate using the tapped holes that I hadn't altered and the other frame plate clamped to them with the frames sat on the surface plate to align the edges. The ends of the frames were aligned with a square. When I was happy that the frames were true and square I tightened all the clamps to hold everything securely.



The frames were transferred to the mill so that I could spot through for the new holes in the pump stretcher and drill and tap them. Holding the frames in the mill vice was fun as I had to hold them whilst trying to avoid all the clamps! I just drilled and tapped one of the holes to begin with, fitted a screw and then checked the alignment on the surface plate before doing the others.



I decided to check the fit of the trailing frames next as there are a lot of holes in their fixing angles that all need to line up correctly. The frames are bent up from one piece of steel and then have two bits of angle rivetted to them that bolt to the frames. I thought it best to check them for squareness and they were quite twisted so needed a bit of work to get them square again.
The pieces of brass angle were not square either and the distance across them was too wide. The distance across them should have been 1.9375" which is the standard width inside the frames for 2½" gauge with 0.09375" thick frame plates but it was actually 1.965". This was fortunate as it meant that I could take a skim off the angles to reduce the width and at the same time square them up.

Holding them in the vice was not practical so I clamped them vertically to an angle plate bolted to the bed of the mill. I had to do a similar job last year to the cast trailing frames for a Bonds Pacific that I have.



I could then skim the two outer faces of the angle.



I actually took a little more off to make the width across the angles match the width across the pump stretcher which was 0.010" undersize now due to me skimming the sides of that. I don't think the frames being 0.010" too narrow will matter

The trailing frames were tried in the frames but now the holes on one side didn't line up with the holes in the frames! This was probably because the trailing frames were now square which they weren't before. It seems that as soon as you put one thing right you make even more work for yourself.



Nothing for it but to plug them and drill and re tap. I found some 6BA threaded brass rod that matched the tapped holes in the angles and soft soldered short lengths into the existing holes. The excess was filed off flush.

As before, the trailing frames were fitted using the untouched tapped holes in one side, clamped in position after making sure that the main frames were still square, and then the frames clamped in the mill again to drill and tap the new holes.



I really must buy or make some little machinists jacks for supporting jobs like this that stick out of the vice. Job no. xxxxxxx !

After fitting all the screws the frames remained true and square so we are getting somewhere.



If you are wondering why the angles for the trailing frames stick out below the bottom of the frame plates it's because the frame plates are supposed to have an extension below the bottom edge at this point but the previous builder attached them as a separate piece, probably to make cutting out the frames easier.

I hadn't yet tackled the front bogie stretcher so did that next. That went in the mill to have the faces trued up. It was a little too wide but skimming the faces brought it to the right size.

When I fitted it in place all the mounting holes lined up perfectly which was a relief. No more plugged holes!

Now that I had all the major stretchers sorted out I thought it a good idea to fit the driving wheels and the coupling rods to make sure the wheels still went round.



There is a very slight tight spot at one point in the rotation but nothing to worry about. At least now the axles are square to the frames and not at an angle!

Next onto the front buffer beam. Like the trailing frames, the fixing angles were not square and parallel and they were too wide.



This was going to be awkward to hold as it had the front running boards fastened to the buffer beam and I didn't want to remove those. I needed to hold the beam vertically so I could get an endmill onto the face of the angles but the valance was in the way. Fortunately, these were only soft soldered on so I just removed them.

I used the angle plate again for this job and held the buffer beam to it with a clamp and a bolt through one of the holes for the buffers.



Not the most rigid of setups but with light cuts it worked out ok.

Fitting the buffer beam showed that a little bit needed taking out of the slots that fit over the frame plates for the beam to sit properly and two of the fixing holes on one side were very slightly out. Tightening those two screws did twist the frame by a tiny amount but I didn't think it was enough to warrant plugging and redrilling the holes.



I did play about a bit more trying to stop the slight twisting caused by the front buffer beam and eventually I bit the bullet and did plug the holes and re tap them!

There is still the stretcher that supports the 2 to 1 lever assembly for the valve gear and a simple square stretcher to support the end of the inside slidebar but we'll deal with those later on. For now the frames are sorted and next time we can carry on with the cylinders.

John

[Deleted]

excellent work John and your very clear descriptions should help anyone who finds themselves in a similar situation when taking on a part built model.
Great stuff...

Pete

[John Baguley]

Thanks Pete

It can be very frustrating carrying on where someone else left off. Sometimes you get lucky, sometimes not. Either way, it's nice to get these projects sorted and running like they were supposed to. It can sometimes involve more work than starting from scratch though!

I don't know when this particular loco was started but I try and keep in mind that the builder probably would have only had access to very limited machinery and hand tools and quite possibly never done any engineering work before. We've got it easy nowadays with good tools and machinery available at very reasonable costs and most people have a relatively well equiped workshop compared to years ago.

I often think that LBSC made it all look too easy and many builders found themselves out of their depth. Just look at the number of part built locos etc. that appear on Ebay where the builder probably gave up. So long as they got some enjoyment out of it though, that's all that matters

John

[Deleted]

Mar 1, 2021 12:34:23 GMT John Baguley said:

Thanks Pete

It can be very frustrating carrying on where someone else left off. Sometimes you get lucky, sometimes not. Either way, it's nice to get these projects sorted and running like they were supposed to. It can sometimes involve more work than starting from scratch though!

I don't know when this particular loco was started but I try and keep in mind that the builder probably would have only had access to very limited machinery and hand tools and quite possibly never done any engineering work before. We've got it easy nowadays with good tools and machinery available at very reasonable costs and most people have a relatively well equiped workshop compared to years ago.

I often think that LBSC made it all look too easy and many builders found themselves out of their depth. Just look at the number of part built locos etc. that appear on Ebay where the builder probably gave up. So long as they got some enjoyment out of it though, that's all that matters

John

yes, I've experienced that with 4470, talking of part built models... not sure if any good to you or not but there's currently a 2 1/2" gauge Flying Scotsman tender with 2 days to go, some bids already placed. I did look at your website and couldn't see a tender for your FS so thought I'd mention it, just in case it's of use.

regards

Pete

[John Baguley]

Yes, the tender is in my watch list

I've already got the wheel castings and the horns and axle boxes for mine though. I think the Ebay one is the Bassett Lowke version or at least the chassis is. Shame about those ugly rivets.

There's a Green Arrow chassis for sale as well that's supposed to have run on air. I don't think I want another one though. I'll have had enough of Green Arrows by the time this one is finished! I've got far too many projects already anyway

John

[John Baguley]

Part 6 - Back to the cylinders

Back to trimming the piston rods. I fitted the righthand cylinder to the frames along with the connecting rod, the crosshead and the piston. At this point the piston rod was just pushed into the crosshead. It will be drilled and reamed for a taper pin to secure it later.



I determined how much needed to be taken off the end of the piston rod by careful measurement and a calculation so as to leave an equal gap at each end of the cylinder when the piston was at each end of it's stroke. It needed shortening by 0.158" so that was removed by mounting the piston and rod in the collet chuck in the lathe with the piston behind the collet and the rod sticking out. Fortunately, there was enough room behind the collet for the piston.

This process was repeated for the lefthand cylinder.

Time to try the motion brackets in place. The righthand bracket had already had the mounting face trued so that it was square to the frames and it fitted quite well now.



However, the holes in the brackets were greatly oversize for the 6BA fixing bolts. They had obviously been filed out to get them to match up with the tapped holes in the frames. These tapped holes had been plugged and redrilled at some point so obviously someone else had had problems!

I decided to silver solder some steel plugs into the existing holes in the brackets and redrill them for 5BA bolts. I thought that 6BA was a bit flimsy considering the forces on the motion bracket caused by the expansion link. In fact, the whole motion bracket seems very flimsy to me and I could see it flexing in service (My fears were justified when later on I ran the chassis on air and the brackets did flex quite a bit). If building one from scratch I think I would beef up the brackets and the method of mounting them to the frames.

Once the bracket mounting holes had been plugged and redrilled I had to plug and redrill the holes in the frames to make sure they lined up properly. Actually, what I did was drill out the existing plugs in the frames and fit new ones.

The lefthand bracket was tackled next and, like the righthand one, needed the bolting face skimming to get it square to the frames. Before going any further I thought that it would be a good idea to check that both motion brackets were in the same position on the frames.

The vertical position of the brackets is determined by the end of the slidebar which fits into a slot in the bracket but I thought that I would check that anyway. I used a surface gauge with the frames sat on the surface plate to compare the height of the bush for the expansion link trunnions.



Both bushes were within about 0.010" of each other and that was good enough for me.

The longitudinal position of the bushes was determined by putting a bit of rod in the bushes and measuring the distance of the rod from the front ends of the cylinders.

This showed about a 0.030" difference between the two sides. I had already fixed the righthand side so moved the lefthand side to match it. As mentioned before, LBSC gives no position for the motion brackets on the drawings so it's anyone's guess where exactly they are supposed to be.

Of course, the mounting holes did not line up with the holes in the frames now



More plugging and redrilling! (I must have got something wrong with this as later I found out that the lefthand bracket was still in the wrong position and I had to move it again!)

Time to look at the front stretcher that supports the 2 to 1 lever assembly. This stretcher is not exactly horizontal but has to be angled to match the inclination of the outside cylinders so that the levers are in the same plane as the valve spindles. How to set the angle?

I fitted the steam chests and put lengths of 4mm silver steel through the bosses and used those as a datum to set the angle of the stretcher. The stretcher was held in place with just one screw in the righthand frames so that it could be angled up and down.



A steel rule was then clamped to the dummy valve spindles. That gave me a reference surface to work to. I would have preferred to use something a bit thicker but there wasn't room to get anything else through the cut outs in the frames.



I found that one of my gauge blocks was just the right thickness to fit between the top of the stretcher and the underside of the ruler. Putting a clamp across the 'sandwich' held the stretcher at the correct angle. The stretcher was actually too low compared to my 3D model but I could compensate for that later by adjusting the height of the pivot for the 2 to 1 lever assembly. It couldn't go any higher anyway otherwise it would have been higher than the bottom of the frame cut outs.



To my surprise the second mounting hole in the righthand frame lined up perfectly! I wasn't expecting that. However, neither of the holes in the lefthand frame lined up. Yet more plugging, redrilling and retapping was needed.

Finally, apart from the stretcher for the inside slidebar that was the frames sorted (or so I thought at the time!)



With the frames sorted it was time to bite the bullet and tackle the inside cylinder. I wasn't looking forward to this as it's a very awkward shape to hold due to the port face being at a 6° angle to the cylinder bore. The cylinder has to be inclined at 7.3° so that the piston rod will clear the front driving axle but the valve spindle has to line up with the outside valve spindles which are angled at 1.3° so it can be driven by the 2 to 1 lever assembly. Also, the cylinder is supported by two 'legs' to the righthand frame only rather than being a solid block.

Where on earth do you start with a casting like that!

I decided to get some flat datum surfaces to work from by first rough machining the port face and the 'feet' of the mounting legs. The port face as cast was very rough so I filed it to get it as flat as I could and then rubbed it on emery paper on the surface plate to finish it off. The casting was then clamped in the mill vice by the ends with the port face sitting on parallels. I could now true up the feet until they were flat and level.



The casting was then clamped to the mill table with the feet on the surface of the table so that I could machine the portface.



Why does the camera always make milled surfaces look absolutely awful! The finish was actually pretty good.

With two good surfaces now I could hold the casting in the vice again and take a skim off the top surface of the casting that aligns with the steam chest. I made the assumption that this surface would be more or less at the correct angle to the cylinder bore and just set it level with the Wixey angle gauge.



I then flipped the casting over, set the just machined edge on a parallel and machined the bottom. I took the minimum from both faces to just clean them up so that I didn't machine into the ends of the cylinder.



Time to get creative but more of that next time

John

[springcrocus]

Sorry, John, late to the party. Some really nice work on display here and also good to see alternative used tooling like the Keat's plate being used.

Regards, Steve

[Deleted]

Great work John...for some reason 9 of the pictures aren't showing for me, I can see the first and last 4, the rest are broken? I'll take another look later when on the PC, perhaps it's something with my phone?
Keep the updates coming, very informative...

Kind regards

Pete

[stevep]

Same with me.

[Deleted]

yep, can't see with the PC either...

Pete

[John Baguley]

Whoops, they worked last night when I posted them I'll look into it.

John

[John Baguley]

Ok, not sure what went wrong there but I've reposted the photos and it seems to work ok now

John