Winson 5" Gauge Britannia
I've now cleaned up both combination levers and also the crosshead drop arms, the union links and the valve crossheads.
Next item on the agenda were the guide blocks for the valve crossheads. Originally these were simple blocks of brass on each end of the pin that goes through the valve crosshead fork and the combination lever. These blocks run on top of the valve guides and are retained by a metal strap on the top.
Needless to say, these were a poor fit and had been Loctited onto the ends of the pin to stop them falling out. Not a very good solution but there was nothing else to hold them in. Unfortunately, I don't have a drawing of these guide blocks but I would guess that the Spink drawings show that these blocks have a flange on the inside to hold them in place. I decided to go that route with the new ones.
I started off with some 0.5" steel bar in the lathe, drilled and reamed a 5.5mm hole in it and then parted off four slices, one for each of the four guide blocks. These were then milled to a square shape but leaving a 0.030" flange on the top and the bottom.
I was a bit worried about getting the fit right for the blocks but it went a lot easier than I thought.
The first thing was to make sure that the valve rod was located centrally in the valve liner. The valve rods were actually a really sloppy fit in the end cover of the valve chest and the gland so I made a couple of PTFE bushes that were a good fit on the valve rod and in the packing recess in the end cover. I may retain these and use them as the valve rod packing.
I also needed to centralise the other end of the rod as it could still wave about in the breeze so fitted the piston valve with the rings temporarily to act as a steady. The valve rod was also a sloppy fit in the valve bobbin but that was correct as the bobbin needs a bit of clearance on the rod to centralise itself in the valve liner. To get round this I made a thin brass bush to take up the clearance.
With the valve crosshead fitted to the valve rod and a length of silver steel through the holes of the fork I could measure the distance of the pin above the valve guide face and hence the thickness that the underside of the valve guide block needed to be.
I found that the easiest way to measure the gap was to put equal shims under each side until they were a nice sliding fit. The blocks were then milled slightly oversize and the thickness reduced a few thousandths at a time until they too were a nice sliding fit on the valve guide.
The tops of the blocks were then milled down until there was a small amount of clearance between the top of the guide block and a bit of bar placed across the valve guide top.
The last job was to mill down the front and back of the blocks to give a bit of clearance at each end of the valve travel.
Incidentally, one of the valve rods was bent on the thread that screws into the valve crosshead but I managed to straighten it out ok. I really didn't want to have to make a new one. Also, the inside arm of the lefthand valve guide was bent and had to be straightened out. It must have had quite a thump to bend it as it took a lot of effort to straighten it again.
You've probably noticed that I finished up taking the cylinders off the chassis for this job. I had tried to avoid doing this but it made the job a lot easier being able to take the cylinders into the workshop for the fitting process.
I did notice that all the cylinder fixing bolts are a very sloppy fit in the frames so I'm going to have to line the cylinders and slidebars up again when I come to refit the cylinders properly. I might even be able to get rid of that shim that I had to fit in the RH slidebar assembly.
In the last photo, I had fitted the combination lever just for show and I noticed that it won't swing back very far before the front of the oil box on the top front of the lever hits the inside of the valve crosshead slot. I can see that being a problem and could explain the bent combination levers. I may have to try and get some more back travel by a bit of judicious filing. I won't know though until all the valve gear is back together.
I've also read on the Britannia Builders website that on John's Britannia the valve guide blocks were not central in the valve guides when the valve was at mid travel. I think they were too far forward? John solved the problem by moving the expansion link brackets rearwards to shift the whole valve gear further away from the cylinders, thus moving the valve crossheads further back.
Steve Sharman also found this problem with his own build to the Spinks drawings so I'm wondering if I may have a similar problem. There will be very little clearance between the valve guide blocks and the ends of the valve guides when the valve gear is in full travel so I haven't got a lot to play with. Only time will tell!
I decided to check the swing of the combination levers today. I made some pins for the combination lever and the union link joints so that I could assembly the combination lever etc. temporarily. I rolled the chassis back and forth on the stand and marked the extremes of travel of the crosshead on the slidebars. I disconnected the connecting rod from the crosshead so that I could just slide it up and down without having to roll the chassis. I didn't want to risk bending the combination levers again if they did foul the slots in the valve crossheads. I then refitted the drop arms to the crossheads and fitted the union links. I positioned the valve crosshead as far forward as it would go and slid the crosshead backwards as far as it would go. It would only travel about half as far back as it needed to before the oil box on the front of the combination lever hit the end of the slot in the valve crosshead. It would seem that this is indeed why the combination levers were bent backwards. When someone had tried to push the chassis along or run it on air the combination levers would have hit the end of the slots in the valve crossheads and bent them back. It would also have forced the valve crossheads upwards and caused the bent retaining bars on the valve crosshead guides and the bent valve rod.
I had to remove quite a bit from the slots in the valve crossheads before the combination levers would swing back enough to allow the connecting rod crossheads to move all the way. I did this by milling away the top end of the slots at an angle to give the necessary clearance.
There was already enough clearance in the slots for the combination levers to swing forwards. It's the oil box on the front that causes the problem with the backwards swing.
I temporarily assembled the expansion link and the radius rod on the right hand side to see what that looked like.
Much to my surprise everything seemed to line up ok and moved freely. With the radius rod in mid gear and the combination lever vertical, the valve crosshead guide blocks seemed to be pretty much central on the valve guide which is as it should be but we'll see how it is when the eccentric rod is fitted and the return crank set. One problem that I can forsee is that the top back edge of the expansion link hits the expansion link bracket before what will be the end of the valve travel in reverse. Some material has already been removed to give clearance but I think it will need more to give enough swing for the expqansion link. This doesn't seem to be a problem in forward gear though as there is plenty of clearance. Hmmm.
One thing I noticed when I was rolling the chassis along the stand was that the front coupling rod oil box hits the end of the bottom slidebar.
I hadn't noticed that before and that's with the axleboxes right at the bottom of their travel. The problem will be worse when the axleboxes are higher in the horns. The other side doesn't quite hit but it's very close. It will help if I can get rid of that shim that I fitted by jiggling the cylinder position but I may have to reduce the width of the oil boxes on the rods. Something else to sort out!
Not a lot done over the last week or so due to other things.
I decided to get the reverser and the lifting arms sorted out. The lifting arms are built up from two side plates and a central boss which is pinned to the weighshaft with a roll pin. Both of the bosses were a very sloppy fit on the weighshaft so I made some new ones. The originals were brass but I made the new ones out of steel as the arms were steel. I also decided that I would replace the roll pins with proper taper pins when the time came to refit the arms to the weighshaft.
The Spink drawings show the arms silver soldered to the boss but these are just held with a couple of bolts.
All the arms were a bit bent and battered but I managed to get them flat again and looking a bit more respectable. The sides of the slots in the lefthand arm that take the nut of the reverser were especially bent so I straightened them out, bolted both sides together and then carefully milled the slots square again taking as little off as posible. The sides are a bit flimsy anyway so I didn't want to weaken them anymore.
The Spink plans show the reverser nut with a pin either side of it with two steel dies that run in the slot. The Winson affair was just a groove turned in each end of the nut which was machined from brass bar. I decided to use the proper die blocks as shown on the drawings as that is a much better arrangement. The pins on the original nut were a sloppy fit in the lifting arm slots to begin with and I had made the slots slightly wider now when milling them true. To modify the nut I just held it in a collet in the lathe and machined the ends down to 0.1875" diameter. The dies were made from 0.3125" square steel bar and drilled and reamed 0.1875" diameter to fit the pins on the reverser nut and then two sides milled down to fit the slots in the lifting arms. The die was then sawn off leaving a flange to hold them in place. The rough sawn flange was then milled down to 0.020" so that the dies and the nut would fit between the arms of the lifting arm.
The result was much nicer than the original.
I would have liked to have made a new nut altogether as it's not a good fit on the screw but it's a lefthand thread and I don't have any lefthand taps. I didn't fancy trying to screwcut a new one.
I thought I had better try the lifting arm and reverser screw in place before I went any further and that's when I found out that the reverser screw doesn't line up with the nut!
The screw lines up vertically but it's too far from the frames by about 0.125". Several rude words later and I noticed that the screw is not parallel to the bolting face of the main bracket, in fact it's miles out!
I set the bracket and screw up in the mill vice and compared the axis of the screw with some gauge blocks and you can see how far it is out of line. I checked it with my Wixey Digital Angle Gauge and it's 1.9° out of true.
The hole for the rear bearing bush has obviously been drilled in the wrong place and needs to be moved by about 0.125". I'm not sure if there is enough meat on that part of the bracket to do that easily. I may have to move the front bush as well to get the screw to line up properly. More problems!
I decided to just move the rear bearing to begin with and see how everything lined up after that. I knocked the rear bush out and Loctited in a plug turned from aluminium bar. I also knocked out the front bush so that I could drill through the hole.
The bracket was then set up in the mill vice and the front bush hole centred using a DTI as per normal practice.
The idea was to then redrill the hole for the bottom bush in the correct position and refit the bush. All went well until I was using a 7mm drill and then the Loctited in plug broke loose. To be honest, I half expected this to happen and I should have known better! The 7mm hole only left a crescent shaped piece of the plug remaining and there wasn't enough contact area left to hold it in place. The plug really needs to be of a large enough diameter so that the new hole doesn't break through the edge of the plug and weaken it.
So, I started again using a larger 10mm diameter plug. The hole in the bracket was now oval shaped so I had to enlarge it with an endmill rather than try to drill it out to 10mm which would have been a bit tricky to do.
The new 10mm plug was then Loctited in place.
I then repeated the process of drilling the new hole and finished it with an 8mm drill to take the bush. It all went ok this time!
I temporarily assembled the reverser and bracket and fitted it back on the chassis to see how everything lined up.
The reverser screw could still have done with going over a bit further but that would have meant moving both of the bushes rather than just the one. It does just line up with the nut but the outside lifting arm is touching the inside of the slot in the bracket. I think it will be ok though.
I'm not sure yet how well the lifting arm lines up with the radius rod. I've only got the lifting link assembled with some of the old pins which are a very loose fit in the opened out holes and I think that the lifting arm could do with moving inwards by maybe 0.063". I'll check it when I make and fit the new pins for the link. If it does need to go over a bit then I think the easiest way of doing that is to machine some off the bolting face of the bracket and move the whole assembly nearer the frames. Hopefully, it may not come to that.
You may notice that I've drilled and tapped the end of the reverser screw to take a bolt and washer. This is to control the end float of the screw in the bracket. Originally the end of the screw was cross drilled to take a split pin and there was a lot of end float in the screw which caused the lifting arms to move up and down quite a lot. There seems very little play between the reverser nut and the screw so hopefully that will be ok.
I've been plodding on and doing bits when I can inbetween sorting the workshop out a bit more. I'm still trying to find storage for all the tools that I keep buying!
I decided to have a look at the problem of the front coupling rod oil boxes fouling the end of the slide bars. It looked as though I could get away with milling a bit off the end of the slidebars so took them off and put them in the mill vice. I managed to take 0.030" off the ends of the slidebars and at the moment it looks as though this will do the trick. If the oil boxes still foul when the springs are depressed then the only thing to do will be to reduce the size of the oil boxes.
The next job was to machine the weighshaft to the correct length (I had left the ends over long when I made it). I fitted the weighshaft to the chassis, loosely fitted the lifting arms on each end and et them find there own position on the shaft. I then measured the amount that the ends of the shaft stuck out past the lifting arms and made a note of how much needed to be taken off to leave the end of the shaft about 0.030" past the lifting arms. The excess was turned off by putting one end of the weighshaft in the lathe chuck and supporting the other end with the fixed steady.
Whilst the lifting arms were off the shaft I decided to drill and tap the boss for a 6BA grub screw. I could then use that to lock the lifting arms to the weighshaft when the time came to drill and ream for the taper pins that would hold the arms to the shaft. The grub screws would stop anything moving. It would be a bit of a disaster if one of the arms moved and they finished up out of line!
The time had come to put all the valve gear together and check that we could get the correct valve travel without anything hitting something else.
I started with the left hand side and made a temporary eccentric rod which was merely a length of steel bar with a hole at each end the correct distance apart. According to my calculations the original eccentric rods are too long so would give incorrect valve events.
The photo above shows the right hand side of the loco but, as mentioned above, I did the lefthand side first, mainly because that side has the reverser.
I then had to set the return crank to give the correct throw. The return cranks on the loco are shorter than those on the drawings for some reason so the throw will be different. I can't see the throw mentioned on the drawings but according to my valve gear simulation the return crank throw needs to be 0.5". The easiest way to set this is with some sort of a jig but at this time I was only interested in getting a rough setting to check the clearances on the valve gear.
I set the cranks using a flat plate clamped to the building stand and a square sitting on this plate resting against the side of the return crank pin. When the wheel was rotated and the pin at it's greatest travel on each side, I just put a mark on the plate where the edge of the square came to and then measured the distance between the marks.
This gave a result good enough for what I wanted at this point in time. Before doing all this I had jacked up the chassis on a couple of blocks of wood so that I could rotate the wheels easily without having to roll the chassis up and down the stand.
According to my calculations, the valve gear travel needs to be 0.690" to suit the dimensions of the ports and the lap required to give the new lead of 0.020". Say 0.700" to be on the safe side. This assumes that the ports open fully which would give a theoretical cut off in full gear of 81%. This could be reduced to say 75% without a problem.
It was obvious when I put the reverser in full forward gear that the valve crosshead guide blocks would hit the rear ends of the guides way before that sort of travel could be achieved. There was plenty of clearance at the front end of the blocks. I decided that the easiest way around this was to remove the blocks and machine some off the back edge of them. I set them up in the mill and removed 0.030" off them and then refitted them. This time it was possible to get a valve travel of 0.720" before anything touched so that side looks good to go.
I had the same problem with the right hand side and I did the same to the valve guide blocks on that side i.e. machine 0.030" off the rear ends of the blocks.
A month since the last update but I have been working on the Brit on and off.
I had another session of measuring up the valve gear, particularly the position of the weighshaft. After much fiddling about I decided that the original position was pretty much spot on and agree with the Spink drawings so I've put the expansion link brackets back where they were. Unfortunately, someone before me had elongated all the mounting holes to move them further back so I've had to fit washers under the heads of the bolts to cover up the mess. Ideally, the brackets could do with a couple of dowel pins to fix their position but it would be very difficult to do that without stripping the frames and I do not fancy doing that!
It seems that the original eccentric rods are actually the correct length after all so they don't need to be altered. I may just try cleaning them up and see what they look like.
I decided that it was time to get it back together so that I could try running it on air. I finished off the new pins for the valve gear and fitted them all apart from those in the end of the eccentric rods. I've still not decided whether to make new eccentric rods and return cranks but will do so after the chassis is running on air.
The new valve gear pins are just hollow pins made from 5.5mm silver steel and secured with a 5BA bolt through them, a couple of washers and a nut on the back. You could machine the hex heads of the bolts round and fit them with a dummy taper pin and they would look just like the ones on the full size loco but I'm not going to go to all that trouble. If the loco was mine then I probably would do that but they don't look too bad as they are.
I pondered about the way to secure the long pin that goes through the valve rod crosshead and has the guide blocks on each end. On the Spink drawings the combination lever is drilled and tapped for a small grubscrew that locks onto the pin and holds it in place. I decided to do the same although I was concerned that it would weaken the combination lever at that point. Hopefully it will be ok. I've got to get some shorter grubscrews as the ones that I had are much too long. You can just see it sticking out in the photo above. The drawings show the pin in the top of the combination lever also held with a grubscrew but I decided to stick with a hollow pin and securing bolt.
Next on the agenda were the piston valves. As mentioned before, I hate the way of adjusting the valve using two nuts either side as it's a right pain to do it. Instead, I altered the valve so that all the adjustment can be done from the front end of the cylinder just by removing the front valve chest cover.
The original cast iron bobbins were reused and drilled and reamed 0.375" all the way through. Both ends were then tapped 7/16" x 26 tpi to take brass end caps that hold the PTFE valve heads in place. The valve floats on a brass sleeve which is threaded to accept the valve rod. All you have to do to adjust the valve is screw the sleeve up and down the thread on the valve rod and secure it with a locknut. All this can be done from the front end of the valve chest using a couple of tubular box spanners.
The bobbins needed a little bit of machining to adjust the seat for the PTFE heads. The heads needed moving closer together by machining a bit off the outside edges of the centre flanges on the bobbin. This is because I will be increasing the lap of the valves to reduce the excessive lead given by the original design. I also machined a groove in the seat for the PTFE heads in order to fit an O ring. This is merely to make sure that the heads seal to the bobbin okay and not to try and expand the PTFE ring.
On final assembly I'll use Loctite on the brass end caps to make sure that they don't come undone and also the nut on the end of the sleeve that the bobbin floats on. That needs to be adjusted so that the bobbin can float up and down but with no end to end play.
I've still got the PTFE heads to machine for the other valve. I would have done them all tonight but Mr Bozo paid a visit. When I was machining the PTFE for the first two heads I make a cock up and machined the diameter too small!
I think that once they are all done I will machine some oil grooves in the heads to help retain some oil.
Tonight I machined the remaining two valve heads and turned some oil grooves in all of them.
That's the new valves finished so they can be assembled on the valve rods now and fitted to the cylinders.
I haven't had a lot of workshop time over the last two weeks but I've assembled all the valve gear and refitted the valves. I've just fitted temporary eccentric rods for the time being and have got the chassis to run on air. The lefthand side runs very well but the righthand cylinder has a very bad blow all the time. I took the valve bobbin out again and inspected it and the rear valve head had some quite deep scores in it. I suspected that the ports, which are only drilled holes, had some burrs on the edges so I polished the liner bore with some 1200 grit carborundum paper wrapped around a suitably sized wooden handle. I then made a new PTFE head and refitted the valve but the blow was just the same as before. I began to suspect that the valve liner was not sealing in the cylinder block and air was leaking between the inlet and the ports. I made up a plug with two O rings on it to seal the liner bore either side of the inlet, fitted that and air still came out of the front ports which it shouldn't have done. I also blocked the inlet by sticking my finger in the bore and holding it over the inlet hole in the liner but air still came out of the front ports. I'm rapidly reaching the conclusion that it is indeed the liner not sealing into the cylinder block and allowing air to leak around the outside.
The problem now is how to remove the liner. The Spink drawings show the liner to be in two halves pressed into the cylinder block but were the Winson cylinders done the same? There is a grubscrew at each end of the liner bore that is obviously meant to secure the liner and I've removed those but the liner still won't budge. If the liner is pressed in then it's going to be a sod to remove it again. It's possible that the liner is Loctited in in which case heating the cylinder may loosen it.
I'm sure that in the Winson Black Five kits the liners did not come fitted to the cylinders and the builder had to fit them. I think that the liners had O rings in grooves machined in the outside to seal them to the block. Are these the same? If so. maybe the O rings were damaged when the liners were fitted. I think that was a common problem with the Black Five cylinders. Unfortunately, the only build log for a Black Five disappeared off the web some years ago so I can't have a look. The later ModelWorks Britannia definitely came with the liners already fitted to the cylinders so the Winson ones may have also.
More fun and games!
I asked about how the liners might be fitted on the MECH forum and the concensus was that the liners were in two halves and glued in place with Loctite or similar.
With that in mind I put the cylinder block in the oven at 250°C for about 10 minutes. After that, the two halves of the liner were quite easy to remove. I don't recomend using the domestic oven for this job unless you live on your own! The smell of burning oil is not to everyones taste!
There is not much evidence of sealant on the liners so I can see why they were leaking. I don't know what Winsons actually used but it went brown and gooey when it was hot.
I'll give the liners and the bore in the cylinder a good clean up and see what the fit is like. If it's not too bad I'm going to machine grooves in the outside of the liners and fit Viton O rings before putting the liners back. The liners are plenty thick enough to take a 0.070" O ring. They shouldn't leak then!
After cleaning up the liners and the bore in the cylinder I tried the liners in the bore and they are a pretty sloppy fit with about 0.008"/0.20 mm clearance. I guess that the clearance was maybe deliberate (rather than poor machining!) to give room for the adhesive/sealant. If Loctite had been used then too small a gap could have made fitting the liners difficult. The time that Loctite takes to go off depends on the joint gap. Too small and the Loctite may have grabbed before the liners were fully home and positioned. A larger gap would give more time to get the liners in the right place.
I ordered some 1.78mm section O rings to fit to the liners and those arrived this morning. I've also ordered some more Loctite as I'm running low. I haven't made my mind up which one to use yet. The ideal one is probably 638 as that is designed to work with gaps up to 0.25mm but it sets very quickly which will leave me little time to fit the liners. I also thought of using 290 which is a high strength thread locker. This has a much longer setting time. It is also a wicking grade i.e. very thin so I could fit the liners and then add the Loctite 290 afterwards when it would wick into the gaps around the liners. The O rings will take care of the sealing so the Loctite only has to hold the liners in place. There's also the two grub screws which would help do that as well. In any case, I've ordered some Loctite 638 and 290 to keep my options open. I may use both!
When I put the post on the MECH forum, several people said that I ought to take the opportunity to square off the ports to improve the exhaust release. After some consideration I've decided to do that and also open up the steam ports in the cylinder block which at the moment are just a single drilled hole. The only thing is that I will have to do the same to the other cylinder which hasn't given any problems!
Most people suggest just filing the ports square which would no doubt work fine. However, I preferred something a bit more accurate so milled them using the rotary table and the DRO. Besides, I hate filing!
I held the liners in the rotary table and used that to position the ports and then milled the ports square with a 2mm carbide endmill using the DRO for the measurements. Quite easy really and I was surprised how accurately the original round ports had been drilled! I had to hold the endmill in the drill chuck as I don't have a small enough collet but it's fine so long as you only take light cuts.
Holding the rear half of the liner was a bit precarious as you can see from the above photo. I could only hold it by the very end otherwise the drill chuck fouled the 3 jaw chuck. Unlike the Spink/Perrier liners, these have the valve liner and the guide machined from one piece so they are a bit awkward to hold in a chuck.
The next job is to machine some grooves to take the O rings. That's just a simple job in the lathe using a parting tool. There's just about room to fit an O ring between the ports and the exhaust outlet and plenty of room to fit one, or even two, between the ports and the steam inlet.
I think that when I come to refit the liners I may have to make a close fitting mandrel to make sure that the two halves of the liner are perfectly in line. I've noticed that the bores of the liners are not exactly concentric with the outside diameter so that could cause issues if I just push the liners in without something to line them up.
I decided to do some work on the steam passages before finishing off the liners.
The original passages from the ports to the end of the cylinder are just drilled holes of 3.5mm diameter which is much too small really so I decided to enlarge them.
Before I did that though I decided to machine some grooves in the wall of the valve liner bore to help the steam flow from the ports to the steam passages. Originally the drilled hole for the passages just came through the wall of the liner bore and that was it.
I machined these grooves using a Woodruffe cutter in the mill as that seemed to be the easiest way. I lined up the top of the cutter with the top of the cylinder and then dropped it down by the required distance to line the grooves up with where the ports in the liner will be when the liners are refitted. The cutter was then fed into the wall of the cylinder to make a semicircular groove 0.125" deep. They should make the steam flow a bit less tortuous.
Next I enlarged the passages. There is not a lot of room to make the cutout in the end of the cylinder much wider without encroaching on the end cover bolts but I managed to widen it by 0.1" with an endmill. Holding the cylinder at the right angle was a bit interesting but I managed it with an angle plate and some G clamps!
I then opened the original hole up with a 4mm endmill and also extended it sideways to 8mm wide.
It's still a bit on the small side but it will have to do. I've increased the area by a factor of three so it will at least be a lot better than it was. I'll take the sharp corners off before I refit the liners to streamline the steam flow a bit.
On with the liners!
I set the liners up in the four jaw in the lathe to machine the grooves for the O rings. Getting the front liner to run true was fairly easy using a DTI on the bore.
Two grooves were then machined in the liner using a parting tool. The data from the PolyMax website (where I usually get my O rings) gave a groove width of 2.4mm for the 1.78mm O rings and one of my parting off tools had a width of 2.3mm so I considered that near enough.
I machined one groove inbetween the ports and the exhaust outlet and the other between the ports and the steam inlet.
The rear liner was a bit tricky as I couldn't hold it easily with the bore outwards because of the attached valve crosshead guide so I had to hold it by the very end, as when I milled the ports on the rotary table. I took pot luck by taking out the front liner by loosening jaws 1 and 2 on the four jaw and then rechucking the rear liner and retightening jaws 1 and 2, hoping that it would still run reasonably truly. It seemed to work out ok.
I did make a Mr Bozo mistake with the depth of the grooves. When I first machined the grooves I made them a bit too shallow and when I tried them in the cylinder block with the 1.78mm O rings fitted, they seemed too tight. I machined the grooves a bit deeper but went too far and they were then too loose! Fortunately, I had also bought some 2mm section O rings and they saved the day.
I tried a couple of dry runs fitting the liners with the O rings installed but both times the O rings got damaged when they passed over the exhaust port and the steam passages. It didn't help not being able to use any lubricant on the rings which would have stopped the Loctite bonding. I tried smoothing the sharp edges with a small grinding stone in the dremel but the same thing still happened. I think this was the problem that builders of the Black Five found. Suddenly, I came up with the idea of inserting a strip of very thin brass shim into the cylinder bore to cover the passages when the liners were fitted and this worked ok, although the shim took some effort to remove once the liner was in place.
I fitted the rear liner first as that is the most tricky to get right. Not only does it have to go into the bore the correct depth, it has to go in so that the valve crosshead guides are lined up correctly to the cylinder block.
I decided against using the Loctite 638 which would need to be smeared on the liners when they were fitted but instead opted to use the 290 which could be added after the liner was fitted and lined up properly. I had visions of the 638 grabbing before I had got everything lined up properly and ruining the job. To satisfy myself that the 290 would give a strong enough bond I did an experiment fitting a 6mm nut to a bolt using the 290 and there is no way that it could be removed without heating it.
So, the rear liner was fitted, lined up and then the 290 liberally squirted on the joint between the liner and the end of the bore in the cylinder. The 290 is so thin that it wicked instantly into the gap around the liner and filled the gap all the way up to the first O ring. Once that had had chance to go off, I added some more onto the end of the liner inside the bore. That secured the inside end of the liner.
The front liner was then fitted in a similar way, the 290 added inside and outside and any excess cleaned off with paper towels.
I was concerned that the bores in the two liners would not line up correctly without using a close fitting mandrel through them but they seem to be fine.
I'm going to leave the cylinder for 24 hours to allow the Loctite to cure fully then I'll fit the two grubscrews at each end of the liners that will lock the liners in place, although I very much doubt that they will ever move now. The only way that the liners will move now is if the cylinder is heated up to about 250°C to soften the bond.
I did have to redrill and tap the holes for the two grubscrews as the original positions lined up with one of the O ring grooves in the liner and I didn't want the grubscrews to clamp down on the O ring and distort it, compromising the seal. I just moved the holes closer to the end of the cylinder and the old holes will be blanked off with a bolt cut off flush.
Next job is to refit the cylinder to the chassis and try it on air again. Then I'm going to have to repeat the whole thing with the lefthand cylinder! That should go a lot quicker now that I know what I'm doing and have got the setups sorted out.
Just a brief update today.
I refitted the cylinder to the chassis and ran the chaassis on air. Everything was perfect with no leaks anywhere. Success!
I've now also completed rebuilding the second cylinder and that's ready to go back onto the chassis.
It was a bit of a struggle to get the liners out of the cylinder block this time as they were a much tighter fit in the bore in the block. That's probably why the liners in this cylinder didn't leak. I finished up having to carefully knock them out with a brass rod when they were hot, managing to burn my finger in the process!
The clearance between the liners and the bore is only 0.003" this time as opposed to 0.008" for the other cylinder. This smaller clearance meant that I couldn't use the brass shim to protect the O rings when refitting the liners so I had to make sure that there were no sharp edges that might cut the rings. I also made the rings a looser fit in the cylinder bore but still tight enough to give a seal. Both liners seemed to go back ok fortunately.
With using the loctite 290 there is probably no need for the O rings to actually seal but at least they centralise the liners in the cylinder bore before the Loctite glues them in place.
Nearly two weeks since the last update but I haven't been idle. All the work on the chassis is now completed and it's ready to go back to the owner.
The second cylinder was refitted and everything seemed ok. After a bit of fiddling with the valve timing the chassis runs quite well in forward gear but not so good in reverse. It does run ok in reverse but it needs a bit more pressure to run smoothly. As most drivers never run in reverse anyway, I'm not too bothered about it.
Once the cylinders were sorted all that was left to do were the return cranks and the eccentric rods.
The return cranks were not brilliant. They were too thin to fit properly on the end of the crankpin and one had had the slot extended very roughly with a hacksaw. The eccentric rod pins were pretty rough so they were removed with heat as they had been Loctited in.
I really didn't want to make new ones so set about tidying the original ones up.
I drilled and reamed the crankpin hole to a larger size and then turned up two top hat shaped bushes to fit into the enlarged bores to bring the bores back to size and also make a boss to increase the thickness of the return crank where it fitted on the crankpin. These were then silver soldered in place.
At the same time I filled in the rough slot in the bad crank.
The return cranks were actually lopsided as neither the crankpin bore or the bore for the eccentric pin had been drilled on the centreline of the crank.
I roughly remachined the outside shape in the mill using the rotary table and the final finishing was done by filing and sanding. The slots were then recut with a slitting saw and new eccentric rod pins machined and pressed in with a bit of Loctite 638 to make sure they didn't move.
I decided to also drill and tap the boss for a 6BA grubscrew to lock the return crank in position on the crankpin once the cranks were in their final position. The two bolts through the crank hold it pretty securely but the grubscrew will make sure that it won't move again. The idea is to put a dimple in the crankpin once they are correctly set by drilling through the hole for the grubscrew and then locking the grubscrew up tight.
To set the return cranks to the correct throw I made up a very simple jig from a piece of round bar with a centre turned on the end and a piece of flat bar with two holes in it. The two holes were drilled and reamed in the mill using the DRO to get the distance apart correct (0.5"). One hole was reamed to fit the round bar and the other reamed to fit over the eccentric rod pin of the crank.
To use the jig the return crank is fitted loosely onto the crankpin, the flat bar fitted onto the eccentric rod pin and held with a nut and the pointed bar slid through the flat bar until it touches the wheel centre. The return crank is then adjusted until the point on the round bar fits into the countersink in the end of the axle and the return crank bolts tightened up.
The return crank is now set to the correct throw.
Last, but by no means least, the eccentric rods themselves were cleaned up. I had intended to replace these but decided that they weren't as bad as I first thought and could be made to look reasonable with a bit of work. They were tackled in the same way as the other motion rods i.e. with sanding drums in the Dremel, files and carborundum paper. They are not perfect but quite presentable from a distance.
The original ball bearings in the ecentric rods were pretty rough so I replaced them with some with rubber seals which should keep the muck out of them. They should have brass covers over them which I presume the owner has.
Then it was just a case of putting back a few bits that I had taken off such as the cylinder drain cocks. The operating mechanism for these is not brilliant and the levers that operate the cocks are way too flimsy and I can see them getting bent very easily. They were pretty mangled when I got the chassis! They really need replacing with something more substantial but they work ok.
Well, that's this job done hopefully and I can't say that I will be sorry to see it gone. It's been a lot more work than I expected and I've spent far too much time on it.