After flycutting the bolting faces of the mounting lugs the top edges were milled flush with the top of the exhaust manifold and the lugs drilled and tapped 5BA for the six fixing bolts. A quick skim was taken off the top and outer face of the inlet manifold and the position of the hole to take the inlet stub marked off from the holes in the frames. This was then drilled and tapped 1/4"x40.
The cylinders were set up on the Keats angle plate as for the middle cylinder remembering to put a shim under one side to allow for the error in the machining of the angle plate. I really should have sent this back for replacement but it's a bit late now. I'll have to try and re-machine it myself somehow to square it up. The cylinders were then bored out to the final diameter of 7/8" using the 'fine feed' I had devised earlier. The piston valve bores were lapped to a fine finish using an expanding aluminium lap and grade 600 Aloxite powder. I decided that it would be a good idea to have some visual method of setting the valves so I drilled and tapped some access holes in the valve chests directly over the ports nearest the end of the chest. These enable the valves to be set by eye so that the ends of the valves line up with the edges of the ports when the motion is at mid travel. The holes will be plugged with 4BA screws after valve setting. Similar holes were drilled in the middle cylinder valve chest. The cylinders were finally drilled and tapped for cylinder drain cocks. I had already decided to fit some sort of drain cocks after getting a hot shower at the Sutton Coldfield rally recently. I will probably fit the automatic type as these need no complicated linkage to operate them and they seem to work quite well.
The cylinders were then temporarily bolted to the frames ready for the trip to Chesterfield on 2nd October.
Sunday the 2nd turned out to be a dull day weatherwise with a few showers but there was still a good turnout at the rally. This was my first visit to the Chesterfield track and I must say it is a very impressive set up. There is a raised multi-gauge track which is like a folded over figure eight with one loop inside the other with a bridge carrying one loop over the other. Because of this there are some quite severe gradients and the track is very testing for 2-1/2" locos. There is also a ground level 5" and 7-1/4" gauge track running around the raised track and facilities for O gauge and gauge 1. The only problem is that the whole site is situated amongst tall trees and everywhere tends to be damp and very slippy!
The usual Stalwarts were there with their locos (see photo section) including Peter de Salis-Johnston with his immaculate (as always!) Millenium Fay. He was particularly interested in Helen and can't wait to see her in steam (that makes two of us!!) I rashly promised that she might be ready for the Rally at Rugby in 2007! Still, I think the longest jobs are now over so that could be possible. At least I haven't got to build a tender as well.
Steve Eaton gave the boilers for Helen and the A1 the once over and gave his approval of the work so far which was good news.
Work on the cylinders continues and I am in the process of machining up the end covers which are virtually identical to those for the inside cylinder.
I've had a busy few days on the lathe turning up the cylinder and valvechest end covers and making the pistons and valve spindle assemblies. As before, the end covers are turned from brass bar and the rear covers fitted with Peek bushes. The rod seals will be 'O' rings held in place with brass cover plates. The holes for the fixing bolts were drilled in the covers using the rotary table which is much easier than marking them out. Holding the larger covers was a bit of a problem (the smaller covers were held in collets) but I've just ordered a morse taper adapter to fit the Myford chucks so that they can be easily mounted in the rotary table. This will enable larger items to be mounted on the table a lot easier as they can be gripped in the lathe chuck.
Drilling the end covers
The pistons were again turned from aluminium bronze (because I had some the right size!) and finish turned after screwing onto the stainless steel rods. When I had assembled the middle cylinder with the 'O' ring fitted to the piston I noticed that the ring tended to stick if left for a time but freed up once the piston was moved. When turning the groove for the rings in the outside pistons I checked the depth of the groove in the middle piston and found that I had not made it deep enough. This meant that the 'O' ring was being compressed too much and may explain the sticking. While the lathe was set up for machining the outside pistons I took the opportunity to deepen the groove in the middle piston to the correct depth. I've noticed that a lot of model engineers do not recommend using 'O' rings on pistons saying that they have only managed to get very short lives out of them but I am sure that is because they haven't been fitted properly using the correct size grooves. It is also no good fitting them to rough bores as that will soon shred them!
The valve spindles are 1/8" stainless but this time I made the adjustable carrier for the Peek valve from bronze instead of the brass I used for the middle cylinder. This was only because somebody recommended not using brass for any parts in contact with steam which may lead to de-zincification of the brass. I'll leave the valve carrier for the middle cylinder as it is and see what happens!
Cylinders with covers etc.
Next job to be tackled was the crossheads and slidebars. The crossheads were milled and turned from 3/4"x3/8" mild steel bar and the slidebars cut and milled from 1/8" gaugeplate as for the middle cylinder. I made the ends of the crossheads a bit fancier this time as they are in full view!
In-between working on the crossheads and slidebars I've been drawing out the valve gear as it's soon going to be time to make a start on that. I had already worked out the main dimensions using the formulae in Martin Evan's book 'Model Locomotive Valve Gears' so it's just a case of drawing out all the various bits to make sure everything will fit without anything catching. The gear will be very similar to that fitted to Black Five with double sided expansion links with pivots both sides. Although more difficult to make, the link is better supported and not liable to wobble about like the single type with just one bearing. All the pivots will be made as large as possible to minimise wear and the various links and rods will be made from gauge plate. This is much stronger and harder wearing than ordinary mild steel. Don Young used to specify Chrome Vanadium steel for his valve gears and gauge plate is virtually this. The radius rod will be supported on the lifting link via a sliding die rather than just a plain pin which should wear better. This is one part of the valve gear that gets a lot of hammer in use!
For those interested the valve details are:
Inlet/exhaust ports - 3/32" wide, Lap - 1/16", Lead - approx. 0.01", Full gear travel - 5/16", Cut Off at full gear travel - approx. 84%.
I've just managed to acquire some wheel castings off Ebay which include six bogie wheel castings which may be suitable for Helen. There's another six up for grabs so if I can get those as well it may solve the problem of lack of castings from the Association.
The outside motion brackets were tackled next and are fabrications from brass sheet and 1/4" x 1/4" angle. The main 'plate' of the brackets was cut from 3/32" brass and two angles silver soldered on either side of the rear edge for bolting to the frames. The front angle is the full length of the bracket but the rear one is shorter to clear the front wheels. After fixing the angles the bolting face was trued up by flycutting in the vertical slide. The cut out to clear the crosshead was then sawn and filed to shape and two little brass blocks silver soldered in position to take fixing bolts for the ends of the slidebars. These blocks were milled to shape after fixing and drilled to take an 8BA bolt tapped into the slidebar. Another block was silver soldered at the top of the motion bracket to support the end of the inner expansion link bracket.
To make the motion brackets look more like a full size casting a strip of 1/32" brass was soft soldered around the outside edges to form a strengthening web.
Flycutting the bolting face of the embryo brackets
Finished motion brackets
Looking at the photo of the finished brackets I've just realised I've soldered the block for the inner expansion link bracket on the wrong side of the motion bracket. Oh, bother! I'll have to mill them off and put new ones on the other side.
Progress has been slow over the last week as I'm suffering from a very painful ankle injury that's proving reluctant to clear up and I'm finding it difficult to concentrate on anything. I can't stand for long periods and have to sit down to do anything. Hopefully this will sort itself out soon.
The two blocks on the motion brackets that I had put on the wrong side have been milled off and two new ones fitted on the correct side. It was not possible to silver solder these on due to the soft solder holding the brass edging onto the brackets so they were held on by a single 8BA bolt and then soft soldered to stop them coming loose.
The motion brackets were positioned on the frames by mounting the outside cylinders and then sliding the brackets over the guide bars until they were the correct distance from the cylinders. They were then clamped in postion and the mounting holes spotted through the brackets onto the frames. The cylinders etc. were then removed so that the frame holes could be drilled. I also removed the front bogie, front wheel assembly,and conjugated lever assembly to make access easier. It was then fairly easy to drill the holes in the mini-mill although the frame assembly is a bit unwieldy and difficult to hold still! The cylinders and brackets were then refitted so that the tapped holes in the slidebars for the fixing bolts that fasten the slidebars to the motion brackets could be spotted through and drilled.
The long mounting brackets for the expansion link bearings were cut from 3/32" brass. They were cut out and machined two at a time by my usual trick of soft soldering the blanks together. The inside ones are just a plain plate but the outer ones are a bit fancier with slots cut out and more brass strip soldered along the bottom edge to form a web, again to give a more realistic appearance. The outer brackets also have a 3/13"x3/16" brass block silver soldered on the inside at each end for bolting to the motion bracket at the front and the rear support bracket.The four link bearings are turned from more Peek rod and held into the brackets by four 12BA bolts.
The two outside expansion link brackets
The bracket that supports the rear end of the expansion link brackets is a simple angle bracket made up from 3/32" brass and a piece of 1/8" steel angle to bolt it to the frames. Another 3/16"x3/16" block is silver soldered on to support the inner link bracket. Again the mounting holes in the frames were spotted through from the brackets after clamping them in the correct position.
Trial assembly of the motion brackets and expansion link brackets
I received an interesting email the other day from Denis McAllister in Australia who has been gathering information on Helen Long with a view to building a 5" gauge version. He's following this construction series with interest and I've promised him a set of drawings when they are complete. Helen should make a really powerful loco in 5" gauge!
I can't believe it's coming up to a year since I first started work on Helen! How time flies when you're enjoying yourself!
I thought I would tackle the outside connecting rods next and get those out of the way. Making coupling and connecting rods is not one of my favourite jobs as they seem to take ages. It would be a lot quicker to use laser or waterjet cut blanks I suppose and I will probably do that for Simplex.
The connecting rods are quite long (5-3/4" between centres) and were rough cut from a piece of rusty 1/4"x 1" steel bar as that was the only 1/4" thick steel I had that was wide enough. The rust was only on the surface and cleaned off with a wire brush. To save marking out I used my usual trick of printing out a template onto thick paper and sticking it to the steel with double sided tape. The rods were then cut out with a hacksaw and the two bearing holes drilled 1/4" diameter. The two rods were then fastened together with a couple of 1/4" bolts and the profile finished by milling the straight edges in the lathe and filing the rounded ends using filing buttons (as done for the coupling rods).
The two rods were then seperated and machined seperately to reduce the thickness to 3/16" between the big and little ends.This was done by reducing each side of the rod by 1/32". Working on both sides of the steel helps to equalise the stresses in the steel and stop any warping that might occur if only one side is machined. The outside face of each rod was then fluted with a 3/32" wide Woodruff cutter for appearances sake. As mentioned above, it would be better to flute both sides but fluting one side is bad enough, never mind both! The rods were then cleaned up using a little drum sander in the Dremel. These sanding drums are excellent for jobs such as this.
Trying the connecting rods for size
Final jobs on the rods are to drill out the big ends to 5/16" for the big end bushes, fit the small end bushes, and drill oil holes in the big and small ends. I used aluminium bronze for the inside big end bush, mainly because it has to be split to fit on the crank, but I will try Peek for the outside big ends to see how it will stand up to the load. I'll stick with bronze for the small end bushes I think as the load on these will be quite high.
The big end and small end bushes were turned up, pressed into place, and then reamed to final size. The small end pins (gudgeon pins?) were made from 3/16" dia. silver steel turned down at one end and threaded 5BA to take the retaining nut. The same nut will also retain the droplink when made.
The connecting rods were then fitted in place and the piston rods cut down to the right length to give equal gaps at each end of the cylinder at each end of the stroke. The rods were made a tight fit in the crossheads and will be finally secured with a 3/32" taper pin. As mentioned previously, I am not keen on the idea of screwing the rod into the crosshead as it is difficult to make sure that it goes in square.
At this point the motion has become quite stiff to turn and obviously some fine adjustments to the bearing fits etc. are needed to free everything up. I think the best thing to do now is to dismantle the cylinders etc. and then refit everything a bit at a time complete with 'O' rings and gaskets, checking fits as I go along. Before that though there are a few more bits such as the inlet and exhaust manifolds that need to be made so that the cylinders can be fitted and left in place until the final strip down for painting (which will be done after steam testing of the completed loco).
Next item therefore was the steam inlet manifold to distribute the steam to the three cylinders. I had decided previously not to use outside steam pipes to feed the outside cylinders due to the difficulty of connecting them up inside the smokebox, replacing these with a central manifold under the smokebox saddle.
The two inlet stubs which screw into the blocks on top of the outside cylinders were simple turning jobs from brass bar drilled through 5/32" with a groove at the larger end to take an 'O' ring to seal the stub into the main manifold.
The two steam inlet stubs fitted to the outside cylinders
The manifold itself is built up from various bits of brass bar silver soldered together. The main 'cross tube' into which the two outside cylinder stubs fit was made from 7/16" bar drilled right through 5/16". Into this is soldered a vertical stub which will extend into the smokebox and to which the main steam pipe from the superheaters will be connected. The stub will be sealed to the smokebox bottom by a shaped washer and a nut. To one end of the cross tube and facing forwards is another stub for connection of the steam pipe for the middle cylinder. Finally, a 3/16" threaded stub was fitted to the bottom of the vertical stub and facing to the rear for the oil feed from the mechanical lubricator. This feeds the oil into the steam before it enters the manifold and hopefully this will ensure that all three cylinders will get their fair share of the oil!
Main steam manifold in position
I've now got to think about the exhaust manifold which is going to be a bit of a nightmare I think! There's not a lot of room to play with to get any bends in and also three pipes have to be combined into one before going through the bottom of the smokebox to the blast pipe. The pipes also have to clear the valve rod and the steam pipe for the inside cylinder. Hmmm.
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