Rebuilding a 2½" Gauge LBSC Green Arrow

[John Baguley]

Part 10 - Time to finish the inside valve

As hinted at earlier, I had decided to change the way that the inside valve was driven. LBSC's method was to cut a narrow slot across the valve and file flats on either side of the valve spindle so the spindle fits the valve slot snugly and the ends of the flats drive the valve. It was a common method used by him but I don't like it at all. The area driving the valve is very small and can lead to rapid wear. Having said that, the valves on Ayesha are driven like that and still seem ok so maybe I'm overthinking it.

The main think I didn't like with this design was that there was no means to adjust the valve. LBSC suggests moving the wheels on the driving axle to get the timing right for the inside cylinder which sounds a dreadful idea to me! It would have been possible to make the fork on the end of the rod adjustable but I chose to use a threaded valve spindle driving a threaded nut so the valve can be adjusted by rotating the valve spindle.

The valve was machined just the same as the outside ones but the driving nut was threaded 5BA instead of being held by grub screws.



The valve spindle was also modified to have a threaded section.





Because I had added the threaded section to the valve spindle I reduced the end to produce a parallel surface to run in the rear boss. If I had left it threaded it would not be a very good bearing surface. This meant that the 1/8" hole that I had reamed in the rear boss was now too big so I drilled it out and tapped it 1/4" x 40 and made a bronze boss which screwed in and had a smaller hole in it.





I couldn't resist a trial assembly of the cylinders complete with valves.



I then realised that I still hadn't drilled the exhaust passage in the inside cylinder so that was the next job. This was done in a similar way to those for the outside cylinders - drill a hole so far in from the top of the cylinder and then another at an angle from the exhaust port to join up.





I've also still got to drill the steam inlet to the inside valve chest but I'll do that when we get to the steam and exhaust manifolds.

The crossheads were not yet secured to the piston rods so onto that job. I removed the pistons from the cylinders, pushed in the piston rods to the crossheads which were a reasonably tight fit and then held the piston rods in the mill whilst I drilled the holes for the taper pins.



The crossheads already had holes for the pins drilled so it was just a case of lining up the drill with the existing hole and then drilling through the piston rod. The holes were then reamed with a taper reamer to take new taper pins.

The original gudgeon pins were a real pain to fit as they had to be fitted from the back and screwed into the drop arm on the outside. The builder must have decided to do it this way as the drawings show the pins passing through the drop arms and secured by a nut on the outside. Needless to say, the heads of the pins were a bit chewed up where pliers had been used to screw them in. Putting a nut on the outside made them a lot easier to fit so I made new ones from silver steel with a longer shank and drilled out the drop arms so the pins just pushed through.



It was now time to start messing with the valve gear so I reassembled the cylinders, connecting rods and valve gear. It was obvious that there was play in various bits of the valve gear that would lead to lost motion. The bushes in the motion brackets for the expansion link trunnions were quite sloppy so I made new ones. One of the combination lever pins was a loose fit but i just replaced it with a suitable drill for the time being! I'll make a new pin later.

I also found that the motion had become quite stiff since I made the new crosshead pins (which were a better fit than the old ones) and it turns out one of the connecting rods was bent so needed straightening.

One of the things I wanted to check was the valve travel in mid gear. The calculated valve travel should be 0.117" which is interesting as that gives the valves a negative lead of -0.004" if they are made to the dimensions on the drawings. I don't think that is intentional as LBSC was a big fan of lead on his locos and I can't see him deliberately doing that. I'm going to change that by reducing the lap of the valves to give a positive lead of 0.005", my thinking being that the slight positive lead will cater for any eventual wear and any lost motion in the valve gear.

I faffed around for ages trying to measure the valve travel with calipers but it was difficult to get any consistent results. Then I thought 'you've got a drawer full of dial gauges - use one of those!



That was much easier with the gauge on the ends of the valve spindles.

I was rather surprised that the results came out much better than I expected. The lefthand side gave 0.118" travel and the righthand side gave 0.113". The difference is probably due to slight differences in the lengths of the combination levers. I can live with that. I'm not making new combination levers.

I then measured the valve travel in full forward gear. The lefthand side gave 0.258" but the righthand side gave only 0.230" That could be due to the return cranks not being set exactly the same but the righthand die block seemed to be loose in the expansion link slot which would cause some lost motion.

I did some quick calculations using a spreadsheet that I designed for this purpose and if I reduce the lap of the valves from 0.0625" to 0.054" that will give a lead of 0.0045". The valve travel in full gear to give a cut off of 76% is 0.22" so we are about in the ballpark already. The ports will open by 0.056" which is just about halfway. That doesn't seem a lot but I think that's right. It's not how far the ports open it's the length of time that they are open for that matters.

I had a look at the loose die block and it was the screw that it pivots on that was a loose fit in the block rather then the die block being a loose fit in the expansion link slot. I just made a new one from silver steel.



The screws just thread into the radius rods so I made the new screw a bit longer so that it can have a locknut fitted on the other side to make sure it can't come undone. I think they should have been done like that anyway. I'll replace the screw on the other side when I finally reassemble everything.

After fitting the new screw I checked the full gear travel again and both sides were the same at 0.230". A bit different to the last result but the reverser is not a very rigid fit to the frames at the moment and tends to move backwards and forwards. It looks like the return cranks are both set spot on and the valve travel is pretty much what it should be. Good news

 

Whilst doing all this I noticed that the radius rods were hard up against the side of the slots in the motion brackets so I took the brackets off and milled the slots wider to give some clearance.



The motion seemed a lot freer after doing that.

One job that still needed doing was to make the O ring retaining caps for the bosses on the valve chests. These were a simple turning job from brass bar.



The fixing holes were drilled with the DRO in the mill. I made a simple jig for this that the covers were held to with a bolt through the valve spindle hole.





The inside valve chest still needed a threaded gland nut to retain the O ring seal for the valve spindle. That was turned from hexagon brass bar.



The outside valve spindles had been left long so now was the time to trim them to length and thread the front ends for the forks for the links that connect to the 2 to 1 levers.



I hadn't yet worked out a plan to secure the pin on the inside end of the short lever but as it happens it can't fall out anyway as it always remains inside the outside edges of the long lever so it can be left floating. Problem solved!

We are not that far of running the chassis on air now but first we need the steam and exhaust manifolds and the piston rings. Oh, and trim the valves to length. More of that next time.

John

[Deleted]

Excellent write up again sir...I'm close to this stage myself although it should have been tackled many moons ago... my valves are also overlength, along with the piston rods. At this moment in time I have no idea of how to set all of this up, well I think the piston rods should be simple enough which isn't that far away, the valves are a different kettle of fish altogether, there will be some late reading involved I'm sure.

Keep up the great work and descriptions John.

Pete

[John Baguley]

Hi Pete,

I wasn't sure about the set up of the 2 to 1 levers when it came to trimming the valve spindles. In the end I assumed that when the valve gear was at mid travel the levers should be straight across the frames i.e. at 90° to them so I shortened the valve spindles until this was the case. It seemed logical as that would give an equal swing forwards and backwards from the mid position. It seems to have worked out ok as the chassis runs very sweetly on air (spoiler alert!)

John

[lennart]

A most interesting project.

I would not have expected a 3 cylinder arrangement at all on a rather small 2 1/2" locomotive. Does a third cylinder make a noticable improvemenmt in terms of power output and smooth riding in such a small scale?

A little bit off topic:

Like you did on your Helen, the conjugated valve gear was sometimes arranged under the boiler behind the cylinders instead of under the smokebox door. At least the LNER D49 and B17 had that arrangement.

This resulted in a rather complex valve crosshead and made it necessary to kink the radius rods to clear the 1:1 and 2:1 levers.

As pete assumed, the reason to employ this arrangement was to eliminate thermal expansion issues. When the valve gear with the more common arrangement (under the smoke box door) is set at room temperature and the valve spindles heat up, the valve events will shift.

Just a quick calculation:

Steel has a thermal expansion coefficient of about 12*10^-6 (depending on the alloy)

Lets say that the valve gear is set at 20°C temperature and the working temperature is 200°C (temperature of steam at 200 PSI). -> 180°C difference.

It will result in an expansion of about 2,2mm per m which is even multiplied by the conjugated valve gear.

I would guess, that they allowed for that when setting the full size valve gears.

[John Baguley]

Hi Lennart,

I'm glad that you find it interesting

Three and four cylinder locos in 2½" Gauges are fairly common but space is very tight between the frames for the extra cylinders and I think the extra complexity puts a lot of bulders off.  I rebuilt a four cylinder King some years ago and that was a nightmare to work on!

I would imagine that a three cylinder engine will give more even torque that a two cylinder so it should be smoother running. I'm not sure that you would really notice it though in these small gauges. My Helen Long is certainly a smooth runner but that's quite a big loco for 2½" Gauge and it's a powerful beast with 0.875" bore cyinders

Putting the conjugated gear behing the smokebox would certainly help eliminate the expansion problems altering the valve timing. I agree that some allowance must have been made when setting the inside valves on the conventional type of conjugated gear. Maybe Pete has come across mention of this in his research?

John

[John Baguley]

Part 11 - Steam and exhaust manifolds and piston rings

The original steam and exhaust manifolds:



It would have been difficult to reuse the original exhaust manifold as that had elbows on the ends that used to screw into the old steam chest covers so I decided to make a new one from scratch. Also, the connection to the middle cylinder was just a stub that pushed into a hole in the cylinder and I wanted to replace that with a proper flanged joint.

The first job was to make some new elbows to bolt to the top of the outside steam chests and connect to the exhaust passages. I found a bit of suitable rectangular brass bar that was just long enough to get the two elbows from. It was then I realised that I needed to stock up on various materials!

The elbows were milled to shape as a pair and drilled for the fixing bolts.





I now needed to know the position of the cross pipe that connected the elbows and so made the flange that connected to the middle cylinder. That started life as a piece of 0.375" square brass with a 0.25 hole drilled through it and then everything that wasn't a flange was milled away.



I could now drill the outside elbows for the cross pipe and mill the 3mm oval slot in the flange to connect to the exhaust passage.



The cross pipe was cut from a nice piece of 0.25" brass tubing. I inherited a lot of various sized brass tubing from a friend who unfortunately is no longer with us. He used to be in the RAF as a mechanic during the war and then worked on various aircraft in his career and these brass pipes were probably oil or fuel lines of some engine or another.

I made a simple jig to hold all the bits together while they were being soldered.



The last piece needed was the blast pipe. I didn't have any suitable 0.3125" brass tube for this so used a piece of brass bar and drilled it out. The end is threaded to take the blast nozzle and the other end was scalloped with an endmill to fit over the cross pipe.



To hold the blast pipe in position and at the correct angle I used a piece of steel strip suitably bent with a hole in it that fitted over the blast pipe. The blast pipe is not at right angle to the flanges of the elbows due to the 1.3° inclination of the outside cylinders so that had to be taken into account when positioning it.



I soldered the blast pipe and the flange for the middle cylinder first. The cross pipe needed to be drilled to connect through to the blast pipe and the flange so I left the elbows until those holes had been drilled. This meant I could remove any burrs on the inside of the cross pipe before soldering the elbows.



The connecting holes were then drilled in the cross pipe.





The elbows could then be soldered on and the assembly cleaned up.



The steam manifold was a bit scruffy but could be cleaned up so I reused it. The only thing I did to it was to replace the stub pipe connection to the inside cylinder with a proper flange. Again, I made a jig to hold it all in place for soldering.



Things didn't go entirely to plan as I managed to solder the flange to the bolts holding it to the jig
Not a disaster as I just drilled the bolts out to free the assembly.

I put the manifold in place on the cylinders and marked out the positions of the screws that held it to the outside steam chest covers, removed the covers and drilled and tapped them for 7BA screws.



I then spotted the holes in the inside cylinder for the fixing bolts for the flange and drilled and tapped those. I also drilled the hole in the inside steam chest for the steam inlet.

I still had to drill the steam inlet holes in the outer steam chest covers. It wasn't a case of simply drilling a hole midway between the fixing holes as the inlet holes didn't line up with the bolt holes. So, I made a template from paper by covering the flange with black Sharpie and then pressing the flange onto the paper. That left an outline of the flange and by lining up the bolting holes on the steam chest covers I could spot the hole for the steam inlet.



By this time I had decided to use O rings to seal as many of the connections as possible to avoid using gaskets. With this in mind I counterbored all the round holes to take a 0.070" section Viton O ring.





I would have liked to have used similar O ring seals for the exhaust connections on the outside steam chests but didn't consider it possible at the time because of the oval holes. However, the next day I wondered if I could use a thin section O ring for the exhaust connections and get them to conform to the oval hole. I looked through my collection of O rings and found some 1mm section rings that were just the right diameter to fit. All I had to do was machine a recess around the oval holes with a 5mm endmill.



The rings fitted perfectly



As this had worked out well I decided to fit them to the steam chests as well. I had been concerned that the area around the oval passages in the steam chest was quite narrow and there was the possibility that a gasket would leak or blow out between the exhaust and the high pressure steam in the steam chest.

The top of the steam chest wall was quite narrow to take the O ring counterbore so I put it in the underside of the steam chest cover instead. There was plenty of thickness to have a counterbore either side of the cover. The bottom of the steam chest wall was thicker (the walls tapered) so I did machine the counterbore in that.



All the connections now had O ring seals. I will still use a gasket on the steam chest covers so they can be removed easily for setting the valves but the steam chests will probably be sealed to the cylinders with Loctite 574 flange sealant or similar.

Back to the valves now and trimmimg them to final width. That was just a case of putting them in the mill and taking a bit off each side. The valves were a bit flimsy now with having all the slots milled in them and I was worried about distorting them if I was a bit heavy handed when clamping them in the mill vice. To avoid this I fitted some gauge blocks in the slot for the valve rod that were a nice tight fit and they would stop the valve being crushed.


The sides were trimmed to size using a micrometer to get the lands either side of the exhaust cavity equal and to the right width.



That's the valves finished so all we need now are some piston rings.

These are my pet design PTFE rings which consist of two thin rings side by side in the piston groove. The rings are split and gapped and then installed with the gaps at 180° so there is no leakage of steam.

The PTFE bar was chucked in the lathe, faced off, drilled and bored and then machined to diameter. The bores are 0.6875" diameter so I machined the outside of the bar to 0.70" so that the rings would be compressed when fitted in the bore. The bore was machined to 0.450" to give some clearance on the bottom of the piston grooves which were 0.4375" diameter. When I later came to fit the rings I found that I hadn't made the bore big enough and they wouldn't compress enough to fit. I should have gone back and read my notes instead of doing it off the top of my head!



This was the first time that I had tried using the polished carbide inserts for aluminium and non ferrous metals and I'm a convert to them. I recall that JasonB mentioned them on the Model Engineer forum some time ago and I've been meaning to try them ever since. They are razor sharp unlike the ordinary carbide tips and give a really good finish. They made a really good job of machining the PTFE.

I parted off 8 rings (six for the pistons and two spares for cock ups) at 0.065" wide. The ring grooves are 0.125" wide so that left a few thou to take off the thickness of the rings to fit them to the grooves. I finish them by rubbing on fine emery paper.

To make holding the rings easier for finishing I made up a 'holder' from a scrap of brass bar. It just has a spigot on the end that is a snug fit in the bore of the rings.







Using the holder gives nice even pressure over the surface of the ring and helps to keep the ring parallel. If you try holding the rings with your fingers they can finish up all shapes.

The rings were sized until two of them were a nice fit side by side in the ring groove. They were then split and gapped by cutting a small segment out with a sharp knife.



The size of the gap is not really critical so long as there is a small gap when the ring is fitted in the bore. It's just to leave a bit of room for expansion.

The rings fit easily over the outside of the piston. They may distort a little but they will soon be pressed back into shape when fitted in the bores.

It was when I tried to fit one of the pistons into the bore that I realised I hadn't left enough clearance in the bore of the ring. Oh bother! or words to that effect. I couldn't remachine the rings as they were too thin to hold now. I didn't want to have to make another set either so I cheated and put the pistons back in the lathe and machined the grooves 0.005" deeper!

It was a devil of a job trying to get the pistons and rings into the bores due to all the steam passages on the ends so I made a piston ring compressor from another scrap of brass.

This is just bored to the diameter of the cylinder bores and has a taper lead in machined on one end. I just pushed the piston into the 'compressor, held it on the end of the cylinder and pushed the piston through into the bore.

You can see the small gap in the ring in the above photo.

I was hoping that we would get to the exciting bit this time but that will have to wait until next time now

John

[Deleted]

Mar 6, 2021 23:50:25 GMT John Baguley said:

Hi Lennart,

Putting the conjugated gear behing the smokebox would certainly help eliminate the expansion problems altering the valve timing. I agree that some allowance must have been made when setting the inside valves on the conventional type of conjugated gear. Maybe Pete has come across mention of this in his research?

John

I do recall reading something about setting the valves but can't remember where? I had a quick browse through RCTS 2A which gives some insight. There is one passing comment on a problem with a loco which may have been due to the valves being set when cold? No further details but seems like some allowance was made. Most have probably read about the middle cylinder doing most of the work and suffering most damage/wear. I wonder if they know by how much? The 3 cylinders were pretty even at slow speed and high cut-off but at high speed and cut-off down to 15% the middle cylinder was doing most of the work, in fact it's power output could be something like 70 % higher than the weakest L/H cylinder, the R/H cylinder power was somewhere near the middle of the other two. Gresley made many changes to try and balance things out, involving different lap or lead setting between the 3 cylinderd. Later a special set of valve piston rings were fitted just to thr middle cylinder in an attempt to balance the valve events. Lots of interesting experiments were carried out on the pacifics, even into the late 30's.
Eddie will probably be able to give the real story.

Pete

[Deleted]

I've done a little more reading, in particular, words written by Holcroft on his meeting with Gresley to discuss the then planned conjugated valve gear and its design.
Holcroft was in favour of placing the gear behind the cylinders, Gresley at this time was not ( he later did), here's some of what Holcroft wrote.

Quote:
" I pointed out that the setting of the inside valve would be affected by the lengthening by heat of the outside valve spindles and that the gear would have to be dismantled before it was possible to withdraw piston valves or inside piston. Gresley thought that the lengthening of the spindles would be offset by making the allowances for it when setting the valve. As to removal of piston valves for examinations, he was prepared to uncouple the connections to the spindles and to lift the combination bodily out of the way. This was how matters were left"

end quote:

So I think it's safe to say that some maths/trial and error was involved as to what to set the valves at when cold?

Pete

[John Baguley]

Part 12 - Running on air and sorting out the valve gear.

The cylinders were given a good clean in the ultrasonic cleaner to get rid of all the swarf and rubbish in all the drillings etc. and the valves and port faces lapped to a nice finish using 1200 grade carborundum paper and WD 40. The cylinders were then assembled and oiled and fitted to the frames. I used Loctite 574 on the cylinder end covers and the steam chest to cylinder joints but used a paper gasket for the steam chest cover joints so they were easily removable to adjust the valves. I'm not sure that the 574 was such a good idea as it seems to set quite hard and I may have a job getting the cylinders apart again if/when I need to!

The valve gear was all refitted and the outside valves set roughly by eye so that the ports just cracked open when the pistons were at dead centres. However, there is no way to see the inside valve so it's a case of guess and play with it when the chassis is running. I did wonder if it would be possible to drill and tap two 'sighting' holes in the bottom of the inside steam chest but I don't think you would be able to see much if you did.

Time for a test run on air. I didn't want to use my big noisy compressor but I do have a small airbrush compressor. It's not got much capacity but I thought I would give it a try. The motion is not very free at the moment so I didn't hold out much hope.

It did show some encouraging signs when the wheels were turned by hand but there were quite a few leaks from the steam chest covers and the screws attaching the steam inlet flanges. A bit more grunt on the steam chest cover screws and some threadlock on the flange screws sorted that. After playing with the setting of the inside valve I eventually got it to run quite well in forward gear. It was alive!

There was no reading on the pressure gauge on the compressor so it can't have been running on much pressure. I took a shaky video of it running here:



There's a bit of a knock in the video which I thought was the axle boxes rattling in the horns but I later found out that it was the inside connecting rod big end bushes loose on the crank pin. My suspicions about the motion brackets not being sturdy enough proved correct as they flexed quite a lot while the chassis was running.

It wouldn't run in reverse gear at all however. It just made half a revolution and stopped. The valve timing was obviously way out in reverse although near enough in forward gear.

My first thought was that the crank for the inside cylinder was not quartered correctly relative to the outside cranks and so the timing for the inside valve was not correct in reverse. Because of the 6° inclination of the inside cylinder to the outside cylinders, the cranks were not all set at 120°. The outside cranks should be at 120° but the inside crank is at 114° to one outside crank and 126° to the other.



I decided to remove the crank axle and try and measure the angles of the cranks somehow.

When quartering wheels I normally do them between centres in the lathe with accurate blocks under the crankpins to set the crankpins in their correct positions. That should work in reverse I thought - set the axle between centres and then measure the crankpin heights with gauge blocks. Once I had the dimensions I could do a CAD drawing and determine the angles.

A few photos to show the set up:

The axle was set between centres in the lathe. The centre in the headstock end is the same diameter as the outside crankpin i.e. 0.25". A square is then clamped to the cross slide touching the centre and the crankpin positioned so that touches the square as well. That crankpin is now set vertically inline with the axle and we can call that the zero point.



The height of the middle crankpin from the top of the cross slide was then measured using gauge blocks.



This was repeated for the other outside crank.



I must admit that I find using gauge blocks extremely fiddly and it would have been a lot easier to use a height gauge and plenty accurate enough.

The last thing was to measure the height of the lathe centre from the top of the cross slide. I had already got this actually from previous set ups.

I now had all the dimensions I needed to make the CAD drawing and work out the angles between the cranks. I'm sure that the angles I got are not as accurate as they seem due to measuring errors etc. but they will be close enough.

I was very surprised but very pleased to see that the angles were virtually spot on to what they should be. Whoever made this crank axle and fitted the wheels obviously knew what they were doing.



The only thing I did notice and I don't think it affects anything is that the cranks are set up with the lefthand crank leading whereas the convention is to have the righthand crank leading. I won't tell the rivet counters if you won't!

So, the problems with reverse running were not due to errors in the crank axle. I decided to take some measurements from the frames to see where the expansion link trunnions were in relation to the driving axle and then put the results into the simulator. That should help determine what the problem is.

The measurements were carried out in the mill again using a pointed centre and the DRO.



I did also measure the position of the weighshaft but that's not critical to the valve timing in this case.

This is when I found out that the lefthand motion bracket was still in the wrong place. The horizontal distance between the lefthand expansion link trunnion and the axle was 0.060" less than the righthand one. The vertical positions were pretty much the same.

Whilst the frames were set up in the mill I measured the throw of the return cranks and they were both the same at 0.232". I also measured the lengths of the eccentric rods.

Armed with this information I set the valve gear up in the Wallace simulator and the results were pretty terrible. It proved that if you set the valves for forward running, they were miles out in reverse. That's why it wouldn't run in reverse. The problem was the lengths of the eccentric rods. They were too short. Taking the righthand side as an example, the eccentric rod is 2.412" long but it needs to be 2.490" long, a difference of nearly 0.080". That may not seem a lot but it makes a huge difference to the equality of the valve timing between forward and reverse.

To put things right I had to first move the lefthand motion bracket and then either modify the eccentric rods or make new ones.

Moving the motion bracket was fairly easy - drill out the plugs in the frames, fit new ones and redrill the mounting holes.

At this time I really didn't fancy making new eccentric rods so, at least for the time being, I modified the existing ones. I cut the return crank ends off them, scalloped the end with an endmill and silver soldered on a new end using a jig. this extended them by the required 0.080". The new end was just a disc turned from steel bar. If I decide to keep these modified rods I will fit bronze bushes.





Time for another test run. I had to reset the valves as the positions would have altered due to the longer eccentric rods and moving the lefthand motion bracket but after a lot of fiddling about with the inside valve setting I got it to run nicely in forward gear. The moment of truth and I put it into reverse. Yay, it ran perfectly! Problems solved

Another couple of videos:





Unfortunately, the driving wheels are a bit wobbly on the axles but I don't think I am going to touch them. It would mean taking the wheels off, boring and bushing them and then refitting them. I really don't want the hassle. I've had enough hassle with this rebuild so far

There were just a few little jobs to do now before stripping the chassis for final cleaning and painting.

I think I mentioned that the reverser moved about on it's fixing screws. It was held by two 6BA screws that also held the rear drag beam to the trailing frame and the holes in the reverser stand were far too big. I replaced the two screws with 5BA ones which fitted better and also added two 7BA screws. It's now rock solid.



The reach rod was 0.125" too short as well and mid gear on the lifting arms didn't coincide with mid gear on the reverser. I cut the existing end off and bolted on an extension piece rather than have to make a new reach rod.

I wasn't happy with the motion brackets flexing like they did so added a block to them and added a bolt through the end of the slidebar into this block. That should make them more rigid.



I mentioned that there was play in the big end bearing on the inside connecting rod. I thought it was the split bush that was a loose fit on the crankpin and was going to make a new one but it turned out to be the bolt that secures the end cap to the connecting rod that was a loose fit. It wasn't pulling the end cap up tight to the end of the rod so I made a new one that was a good fit and that cured it.

Finally, I had to fettle the running boards so that they fitted over the steam and exhaust manifolds. They have a cut out over the cylinders and a cover silver soldered on that goes over the manifolds and hides them. The steam manifold must be a bit further forward than it was before and the running boards fouled them and wouldn't sit down properly. I managed to grind some more out of the cut outs without breaking through the covers and eventually got them to fit.





Unfortunately, the builder has silver soldered the front centre running board to the outside ones which makes them awkward to handle. I may separate them to make access easier to the lubricator which sits behind the front buffer beam.

Well that's it, we are up to date with the project. It's all stripped down again now ready for cleaning and painting. I have to admit that I hate painting and can't work up much enthusiasm for it but it's got to done. From now on, updates will be much less frequent as work will be done at my normal slow pace!

John

[timb]

Fantastic John, amazing what can happen when you know what you are doing! The beat of the engine sounds good and even, both directions - Well Done Sir!

Now I know where to come for help setting up my Baker gear!

Tim

[Deleted]

Brilliant work John... your experience makes it sound easy to sort out, as my knowledge is today I'd be lost. Let's hope my learning catches up before I get to this stage, it hasn't got very long.

Keep up the great work sir...

Pete

[iant]

Very good John. I've been following this with great interest and I'm sure I'll come back and read through it again in the future.

Thank you for sharing.

Regards,

IanT

[osiris09]

This is a great project and really interesting reading. The only thing I will say though is about wobbly wheels. I was rebuilding my pamela that I purchased and after a successful steam test at home took it to the local track to see how it would perform. That's when I found wobbly wheels don't like points or corners as every time the wobble went wide it jammed the loco on the track. I had to bore and rebush 🤦‍♂️

Keep up the good work and looking forward to learning more from your postings.

[John Baguley]

Mar 8, 2021 10:16:08 GMT osiris09 said:

This is a great project and really interesting reading. The only thing I will say though is about wobbly wheels. I was rebuilding my pamela that I purchased and after a successful steam test at home took it to the local track to see how it would perform. That's when I found wobbly wheels don't like points or corners as every time the wobble went wide it jammed the loco on the track. I had to bore and rebush 🤦‍♂️

Keep up the good work and looking forward to learning more from your postings.

That's a good point. The back to backs of the wheels is a bit oversize as well which won't help. It would have been useful to have been able to take the chassis down the track and push it around to check that. I think I'll put the wheels sets back in the lathe and see just how wobbly they are. I may have to adjust them after all.

I worked on a 3½" Gauge Princess Royal some years ago and when I took it down the track for a test run it really struggled to get around. It turned out that the wheels were so over gauge that they were jamming between the rails. I had to take all the wheel sets out and remachine the flanges to thin them down. They were too thick anyway so that wasn't a problem.

Thanks for all the comments chaps. I'm glad that people have found it interesting

John

[johnd]

Really enjoy reading your posts John.
Always seem to find something new, have learnt a lot from your detailed builds.
Keep it coming.

Daggers

[coniston]

Excellent work John, will follow the rest as and when it happens with great interest.

Chris D

[John Baguley]

I put the driving wheels back in the lathe between centres last night and gave them a spin. There is a definite wobble but it's not as bad as appears on the videos. I think a lot of the apparent wobble is due to the axle moving from side to side as the wheels rotate. There is quite a lot of clearance between the backs of the wheels and the axle boxes due to the back to back distance being more than it should be. Hopefully I can get away with leaving the wheels alone as there still seems plenty of clearance between the wheel flanges and a bit of track that i've got.

John

[osiris09]

Good to hear. Mine was wide + a wobble up and down + a wobble side to side. I think if i remember correctly, i was getting 1-2mm difference between top and bottom and this combined with the back to back being to far apart, any time i looked at a corner it jammed or the front bogie would ride up and derail.

Look forward to the next update.

[runner42]

Mar 10, 2021 1:26:04 GMT John Baguley said:

I put the driving wheels back in the lathe between centres last night and gave them a spin. There is a definite wobble but it's not as bad as appears on the videos. I think a lot of the apparent wobble is due to the axle moving from side to side as the wheels rotate. There is quite a lot of clearance between the backs of the wheels and the axle boxes due to the back to back distance being more than it should be. Hopefully I can get away with leaving the wheels alone as there still seems plenty of clearance between the wheel flanges and a bit of track that i've got.

John

John,

I am sure you are aware of the issue of excessive side to side clearance that allows the axles to float. It could cause some rotating parts, valve gear etc to come in contact with fixed to chassis parts and cause a lock up, particularly when negotiating the curves. If this is a potential problem and you don't want to excessively rework the chassis then you could fix collars on the axles abutting the axles boxes to stop this movement. Make them in two halves and screwed together just like the two halves of an eccentric strap on an axle pump, but pinned to rotate with the axle.

Brian

[John Baguley]

Hi Brian,

It only seems to be the crank axle that has the excessive clearance but I agree that it's not good to have this, certainly not on the crank axle as it could cause excessive wear on the connecting rod bearings and valve gear. The axle boxes are the type with just a flange on the outside so what I could do is solder a shim onto the outside face of the horns to move the axle boxes further out and take up the clearance. I've got some thin bronze sheet that would do the job nicely. The frames are in bits now so it's the ideal opportunity to do this.

Actually, looking back, some of the frame stretchers were too long making the frames wider than they should have been. Now that I've remachined them the frames are narrower than before so that won't have helped the situation.

John