LBSC Green Arrow
One of the members of our club has been clearing out some of his stuff prior to a house move and found this in the shed. He can't remember where it came from but asked me if I would have a look at it and assess it so that he could sell it. He's into 5 inch gauge so was not interested in keeping the loco.
I brought it home and gave it a looking over and a boiler test. It looks nicely made but has quite a few issues. The boiler showed no signs of being fired apart from a few bits of burnt paper in the firebox and the water feed connection to the boiler clack was only pushed in and not sealed so the loco could not have been run anyway. It only has one clack on the backhead through which both the handpump and the axle pumps feed. LBSC did give the option of using either two clacks or just the one.
The boiler test showed several leaks - a couple of very small weeps in the firebox and a bigger one from the solid longitudinal stay on the front tube plate. The firebox stays are threaded, nutted and soft solder caulked as are the longitudinal stays on the front tube plate so I thought that it would not be too difficult to repair the boiler if necessary. The superheater header had quite a bad leak and the regulator didn't seal, but again, nothing unsurmountable, I did manage to get the boiler up to twice working pressure (160psi) by continually pumping the pump on the test rig and the boiler seemed fine apart from the few leaks.
I tried running the chassis on air but with no joy. The air just went straight up the blast pipe and there was little sign of life from the chassis. Quite possibly one or more of the valves were not sealing despite squirting loads of oil into the cylinders. It looked to me as though the reverser didn't have enough travel to give full valve travel when set to full forwards or full reverse.
The lubricator didn't work. The ratchet wheel was loose on the drive shaft so didn't drive the LBSC type oscillating pump. I had a quick look at this and I found that the lubricator was jamming up due to the ram being too long which had caused the ratchet wheel to come loose on the shaft.
The handrail knobs on the boiler barrel were only glued onto the boiler cladding and most of them had become detached. They may have been soft soldered on at some time.
The springs on the safety valves looked to be too strong to blow off at the required 80psi.
The original paint job was very well done but it has suffered over the years and been touched up with a different colour green.
The loco had come with a glass display case so I suspect that someone, not necessarily the original builder, had just finished the loco as a display model.
Despite these obvious faults it looked like that the loco could be made into a nice working model and I was tempted to buy it myself. In the end, I succumbed and made an offer which was accepted. I seem to be struggling with motivation at the moment and I thought that this would be a fairly quick project to get stuck into and get back into the swing of things.
So, this will be the saga of the rebuild. I'm starting this straight away rather than leave it until later as I would like to get the loco running as soon as possible.
I've already made a start by removing the boiler and stripping down the chassis. The majority of the work done seems very good but unfortunately, the cylinders are a bit rough and I think that I may have to replace the middle cylinder at least. I may be able to salvage the outside cylinders but they are not brilliant.
The middle cylinder casting has been very poorly machined. The ports are poor and one of the steamchest fixing screws has been drilled through into the cylinder bore. Also, the centre of the cylinder bore is not in line with the centreline of the frames, which it should be, and the middle connecting rod is skewed at an angle to get it to line up. It always seems to be the cylinders that are a stumbling block for some builders.
Fortunately, the Association does have the middle cylinder castings so I think I will just order a new set and start from scratch. That is going to be lot easier than trying to salvage the original castings.
When I disassembled the cylinders there was a lot of rubbish in them and most of the steam passages were blocked by 'goo' which could have been gasket sealant or perhaps graphited yarn from the pistons. It's no wonder that it wouldn't run on air!
Progress has been a bit slower than I hoped for due to me having a bad cold for the last 10 days and not feeling like doing much. However, the chassis has been completely disassembled and stripped of paint ready for repainting and reassembly.
The frame plates proved to be a bit bodged as well with holes drilled in the wrong places, plugged and then redrilled. I should probably check the hole positions against the drawings to see if they were drilled incorrectly in the first place or had to be moved later on.
The trailing frame, front buffer beam and the other stretchers seem to be fine.
As mentioned, the middle cylinder is a mess with badly cut ports and the hole drilled into the bore. Also, the mounting holes in the 'Feet' that support the cylinder are very bad.
The threaded holes for the end covers are in different positions at each end of the cylinder. The front cover holes are ok but on the rear cover one of the holes goes straight into the steam passage and it's been bodged up with soft solder.
Fortunately, I got a message from a fellow member of the N25GA saying that he had a spare set of castings for the inside cylinder and he very kindly sent them to me. Thanks Dave!
The outside cylinders are better but I'm not happy with them so these will be replaced as well. I may as well while I'm at it.
On both the outside cylinders the valve chests overhang the outside edge of the cylinder blocks so consequently the mounting holes for the steamchests came out too close to the edge of the cylinder blocks. The builder overcame this by silver soldering a brass strip along the edge! Again, the holes for the mounting studs have been drilled in the wrong place and then plugged and moved. I'm going to have to check all these hole positions before I finally reassemble the frames and paint them. I don't want to paint the frames and then find that some of the holes need to be moved again.
You can't get the proper Green Arrow outside cylinder castings anymore but I've got a set of Nigel Minor castings which hopefully will do the job. I'm hoping to be able to reuse all the cylinder end covers and probably the pistons but we will see when the time comes.
I'm still not sure what's gone off with this loco. There is definitely two different standards of workmanship so it does seem probable that one person started it but someone else finished it. Hopefully, we won't find too many more disasters during the rebuild!
Not much practical done again but I have compared the frames to the drawings. They tie up reasonably well so the cylinder mounting holes must have been drilled incorrectly to begin with and then altered.
LBSC's description of positioning the outside cylinders is not very clear and to me it reads as if the outside valve spindles are horizontal instead of being inclined at an angle. It says - 'Firstly the correct position of the outside cylinders is with the valve spindles level with the horizontal centre of the slot for the "two-to-one" Gresley gear in the front end of the frames, the centre line of the bores passing through the centre of the driving axle; with the boxes blocked up to running position ' I presume it actually means that the line of the valve spindles should pass through the centre point of the slot.
This means that the 2 to 1 levers to drive the inside valve should also be inclined but the description doesn't make that clear and the drawings show the levers and the mounting stretcher as being horizontal. LBSC does mention loosely clamping the 2 to 1 stretcher in place and checking for free movement before drilling the mounting holes in the fixing angles so that would allow for everything to be inclined I suppose. I haven't checked the stretcher though to see if it is horizontal or if it is indeed inclined.
I had a look at Martin Evans' drawings for his 5 inch gauge Green Arrow and according to those the outside cylinders are inclined at 1 in 32 and the inside cylinder at 1 in 7.6. The valve chest of the inside cylinder is at an angle to the cylinder though so that the inside valve spindle is on the same plane as the outside ones. I can see it being fun to get everything lined up properly on reassembly!
LBSC mentions that due to the different inclination of the inside cylinder and the outside cylinders the inside crank will not be at 120° to the outside cranks (which it won't be) and it will be necessary to 'adjust' the angle of the crank when finally setting the valve gear for the inside cylinder. That sounds a dreadful way to do it and I'll have to come up with something a bit more scientific! It should be easy enough to calculate the correct angle for the inside crank and set that to begin with. It's quite possible that the crank will not be set properly as built and I'll have to reset it anyway.
Not much done again due to having to organise the N25GA stand at the Model Garden Railway Show last weekend which went on despite the current Coronavirus madness and hysteria. Visitor numbers were down by 50% compared to last year which was to be expected.
I've been 3D modelling the front end of the loco to try and get some accurate positions for the cylinders and the 2 to 1 gear that drives the middle valve.
I'm now happy with the result so I've got something better to work from than the LBSC drawings. The 3D model shows that the dimensions of the 2 to levers are not actually correct. The righthand end of the long lever lines up with the valve rod ok but the lefthand end of the short lever sticks out too far so it doesn't line up with the lefthand valve rod. You can see that in the picture above. The inside end of the short lever nearly lines up with the middle valve rod but not exactly. I guess LBSC made the dimensions of the levers to 'whole' fractions to make it easier to make.
To see how the original cylinders fitted compared to the 3D model I temporarily bolted the frames back together and fitted the cylinder blocks. I then measured the angles of the cylinders compared to the frames using a digital angle gauge which gave some not unsurprising results!
The 3D model gives an angle of inclination for the outside cylinders of 1.27° and 7.27° for the inside cylinder. In 'real life' the lefthand cylinder had an inclination of 1.0° and the righthand cylinder had an inclination of only 0.4° which was way out. The middle cylinder was a bit more tricky to measure but I used a parallel inside the bore and that gave an inclination of 6.3°. The inside cylinder has got a flat machined on the top which I thought might be parallel to the bore but it isn't! Hence the use of the parallel in the bore. All the valve spindles need to be parallel of course to line up correctly with the 2 to 1 lever assembly.
I'm beginning to think that the best way forward is to fill in the existing cylinder mounting holes in the frames and then redrill them to match the holes given by the 3D model. Then, if I accurately position the cylinder mounting studs according to my model, the cylinders should all be in exactly the right place. This will mean that I will no doubt have to reposition the stretcher that carries the 2 to 1 lever pivot and probably the outside motion brackets as they will be in the wrong place to match the new position and angles of the cylinders. A lot of work I didn't want but at least it will be right when I've done it.
Not much done in the workshop recently. I've been making the most of the dry sunny weather to catch up with some much needed work in the garden.
Last night I made a start on repositioning the cylinder mounting holes in the frames. It would have been easiest to simply weld up the existing holes and start again but I don't have any gas for my MIG welder and don't know anyone local with a TIG welder which would have been better. My original idea was to silver solder in some steel blanks but I am a bit concerned that heating the frames to silver solder may cause some distortion. I think I will just tap some oversize holes and screw and Loctite in some tight fitting plugs. All but one of the existing holes are miles out of position and have been filed all shapes to allow the cylinder studs to fit!
I thought that I may as well use the DRO on the mill to get the new holes accurately positioned but first I needed to enlarge the existing holes to fit the oversize plugs. The frames were bolted together as a pair and then clamped to the mill table with the bottom edge, which seems to be straight, parallel to the X axis of the table. I then established a datum point using the axle centre of the middle set of horns and took dimensions of the new cylinder mounting holes from that. I already had the 3D drawing for the frame plates so I could just take the X and Y co-ordinates of the holes from that.
It would have been impossible to just drill the holes oversize and get them accurately positioned because of the irregular shapes of the existing holes plus they were so far out of position. The drill would have just tried to follow the existing holes and they would have ended up in the wrong place again. Instead I first used a 4mm carbide endmill to produce a new centre hole in the correct position and then I will increase the diameter of the endmill used until I have a true hole that can be tapped for the plugs.
Yes, I know that the 'exspurts' say that you shouldn't hold endmills in a drill chuck but so long as you are careful and only take light cuts then there is no real problem, certainly for what I am doing here. Not ideal but it works. Just don't try it in a chuck that doesn't have a drawbar to stop it pulling out of the spindle. That is asking for trouble.
What actually happened was that I had intended to use the collet chuck but found that I would have had to lower the mill head for the endmill to reach which would have lost my datum point and I would have had to start again. That's the big problem with a round column mill. One day I will come up with a way to keep the head alignment when the head is raised and lowered. There are plenty of good ideas out there for doing that.
I am probably going to have to go up to at least a 6mm endmill to get some of the existing holes cleaned up so some of the plugs are going to have to be something like 1/4 x 40 or 9/32 x 40.
Tonight I carried on and finished drilling out the holes for the cylinder mounting studs. I ended up having to go larger than originally thought and the blanking plugs will now have to be 3/8 x 40. I mentioned earlier that the holes had already been filled and redrilled before and whoever did it must have thought the same as me as their plugs were also threaded into the frames.
After using the 4mm endmill I went up to 5mm but that didn't clean the holes up so went up to 6mm When I tried drilling the holes to 6mm diameter I broke through the sides of the original plugs and they came loose so I had to drill larger to get back to sound metal. After the 6mm endmill I changed to an 8mm spotting drill as these are short and stubby and less likely to wander.
The holes were then drilled out to 8.9mm (or letter S for us imperialists) which is the tapping size for 3/8 x 40. The tap was initially held in the mill chuck which was turned by hand to get it started straight and then finished with a tap wrench. I didn't fancy trying to power tap it!
Incidently, there is a spare hole in the middle of the top two cylinder mounting holes. This is shown on the frame drawing and is supposed to be for the exhaust from the outside cylinders but because the middle cylinder is in the way it can't be used and the exhaust has to come out of the top of the steam chests. LBSC obviously never altered the drawings to delete it.
Note the little plastic squeezy bottle with the blunt hyperdermic needle on the end in the photo. I saw some YouTubers using something similar for applying cutting oil etc. and got half a dozen off Ebay. They are brilliant for applying just the right amount of oil just where you want it without waste. Much better than an oil can or a brush for jobs like this.
One thing I haven't mentioned is that the horns for the centre driving axle boxes don't line up when the frames are bolted together but the other two for the leading and trailing axles do. You can see it in the first picture. If you look closely there is a step between the inside faces of the top and bottom horns. I had a look at the driving axle assembly and one of the axle boxes is bored off centre, hopefully to correct the error in the horns. We'll see when I put it back together!
I've now made and fitted the steel plugs to screw into the frames.
I threaded a length of 0.375" mild steel bar for a couple of inches in the lathe using the tailstock die holder and then partially parted off a slice 0.125" long leaving about 0.08" dia. in the middle. This left the slice still attached to the rest of the bar and made it easy to thread it into the hole in the frame after applying Loctite 603. The bar was then bent from side to side until it broke off. The bar was then returned to the lathe, the little pip faced off and another slice partially parted off as before. This was repeated for all ten holes in the frames.
The frames are 0.09375" thick so the slice protrudes slightly from each side of the frames and when the Loctite has had 24 hours to cure properly I'll mill the excess off as close to the surface of the frames as I can and finish with emery paper.
While I was filling the cylinder mounting holes I thought that I may as well fill in the redundant exhaust holes as well. These had been drilled 0.375" dia. already so I drilled and tapped these for 7/16 x 40.
Once the new cylinders are mounted I am probably going to have to do a similar job to reposition the mounting holes for the outside motion brackets as they will be in a different position to before.
The plugs have been finished flush with the frames and the new cylinder mounting holes drilled, hopefully in the right place this time!
I think the next job will be machining the new outside cylinder blocks.